Polylactic acid (PLA) is a biomaterial widely used as an alternative to petroleum-based polymeric matrices in plastic components. PLA-based biocomposites reinforced with lignocellulosic waste are currently receiving special attention owing to their mechanical properties, low toxicity, recyclability, and biodegradability. The influence of the percentage of waste on their properties and resistance to degradation are some of the points of great relevance. Therefore, a series of PLA-based biocomposites containing different percentages of olive pits  were manufactured and characterized both (a) immediately after manufacture and (b) after one year of storage under environmental conditions. The results obtained were analyzed to evaluate the influence of the incorporation of olive pits on the resistance to degradation , mechanical properties , structure , morphology  and water absorption capacity of the manufactured materials. PLA degradation, corroborated by Differential Scanning Calorimetry (DSC), FT-IR, and XRD, resulted in a decrease in tensile and flexural strengths and an increase in the tensile and flexural moduli. This trend was maintained for the biocomposites, confirming that reinforcement promoted the PLA degradation. Globally, 140 million tons of fossil-origin polymers are generated annually. The production of this type of plastic results in a large amount of wastage. In 2050, the annual production of 850 million tons of this waste is estimated . HoweverThe introduction of reinforcements of lignocellulosic origin is a practice for improving the mechanical, physical, and thermal properties of PLA without compromising its design and manufacturing capacity . In addiOlive pit (OP) is the most abundant residue in olive oil production . TypicalNumerous elements can participate in the decomposition of PLA, including enzymes, water, ultraviolet radiation and microbes ,14. UndeMaterials derived from nature, such as PLA and lignocellulosic reinforcements, are more sensitive to degradation processes than conventional plastics . Some liThe removal of polymer-based materials after their useful life is a key factor in reducing the environmental impact of bioplastics, such as PLA . TherefoThe main novelties of this research work are the following: (a) the study focused on the analysis of the influence of the percentage by weight of OP on the degradation process of the materials as a consequence of their storage for one year in controlled environmental conditions of temperature and humidity; (b) a single range of sizes of the OP particle were considered, specifically that resulting from the milling process, leaving out the size classification process and simplifying the number of steps to obtain the composites; (c) additional additives were used to improve processability and phase compatibility, with the aim of making the manufacturing process and biocomposites more efficient; (d) the range of percentages by weight of OP of the manufactured biocomposites was twice as wide as that reported by other researchers; (e) in addition to the mechanical and morphological properties of the biocomposites, their thermal, structural and water absorption properties were analysed.The OP was supplied by local suppliers located in Jaén Province (Spain). It was received once the process of obtaining olive oil was carried out, containing remains from the end of this process, such as rests of pulp and olive skin.3, a melt flow index of 35 g/10 min at 190 °C and 2.16 kg load, and a glass transition temperature (gT) of 55–60 °C. Two additives were used: (a) BYK P-MAX, a process additive based on a fatty acid ester  as a powder, and (b) Excellor PO1020, an additive with a high level of maleic anhydride grafting (MAPP) in the form of pellets .Ingeo™ Biopolymer 3251D PLA was supplied in pellet form by NatureWorks . As indicated by the manufacturer, the material has a density of 1.24 g/cmThe OP received was subjected to successive washing cycles to eliminate non-valuable components (pomace and olive skin remains) and was dried in an oven at 60 °C. After drying, the samples were shredded using an ultra-centrifugal mill ZM 200  to obtain the final OP with a suitable particle size range. This equipment achieved an adequate reduction in the size of the OP particles in a single pass by means of a rotor-ring sieving system. Specifically, a stainless steel ring sieve with a pore size of 0.5 mm was used. A rotation speed of 18,000 rpm was used to obtain a 0.5 L sample after 5 min of grinding.−1. The chemical composition of the OP, in terms of cellulose, hemicellulose, and lignin, was determined by following the methodology proposed by Browning [2 flow to obtain the weight loss curve  and its derivative .The particle size of OP was determined by using a Mastersizer 2000 particle analyzer . To study morphology, Scanning Electron Microscopy (SEM) was performed using JSM 840 equipment  that operated at a voltage of 15 kV. To identify the main chemical functional groups, attenuated total reflection (ATR) analysis was performed in conjunction with Fourier Transform Infrared Spectroscopy (FT-IR) using Vertex 70 equipment . FT-IR spectra were recorded in the wavenumber range of 4000–400 cmBrowning . After hTo determine the influence of the OP on the properties of the PLA matrix, a series of biocomposites was manufactured with different percentages of reinforcement . All biocomposites were manufactured with 1.5% wt. of BYK and 4% wt. of PO1020. The influence of these additives on a thermoplastic matrix has been previously studied [To identify the effect of the OP on the degradation of the PLA and its properties, all the manufactured biocomposites were subjected to a degradation process for one year. The denomination of the biocomposites after the degradation process (PLAD-based biocomposites) is presented in Prior to manufacturing the biocomposites, the conditioned OP was dried in an oven at 65 °C for 24 h to remove moisture. PLA pellets were dried at 60 °C for 10 h using a KKT 75 dryer . Finally, the compounding process was carried out on a Mini E-Lab 22 extrusion-pelletizing production line  to obtain biocomposites in the form of pellets. The parameters of the compounding process are listed in Inside the extruder, the melting processes of the polymeric matrix and the additives and their intimate mixing with OP particles take place in zones I–VI. This is achieved by means of an adequate selection of the temperatures of each one of the zones, speed of rotation of the screws and suitable feeding of the components. The polymer-based materials are fed and advanced through the extruder chamber as a result of the rotation of the screws at the same time that they begin to melt. Once melted, the configuration of the screws allows an intimate mixture of the fluid phases between them and with the solid particles of OP, so that at the end of the residence time of the components inside the extruder chamber a proper mixing of the components makes it possible to obtain a biocomposite thread ready to be granulated and transformed into pellets at the output of the equipment.The required test specimens were obtained using injection molding technology in a Victory 28 injection machine , removing moisture from the pellets in a KKT 75 dryer  under the following conditions: 60 °C for 10 h. The dimensions of the three different types of specimens obtained were according to the ISO 527-2, 178 and 179-1 standards, respectively, to guarantee suitable characterization of the materials in terms of tensile, flexural, and impact strength properties ,22,23.The biocomposites were mechanically characterized in terms of their tensile, flexural, and Charpy impact strength properties. Tensile and flexural properties were determined according to ISO 527-2 and 178 standards, respectively, using a 10 KS universal testing machine . A Charpy Impact Meter Izod IMPats 2281  was used to determine the Charpy impact strengths of the different materials according to the ISO 179-1 standard.−1 was used in the spectral range of 400–4000 cm−1, again applying ATR methodology to obtain the FT-IR spectra of the different samples. A Bruker Platinum diamond glass ATR accessory with stainless steel glass holder and pressure control was used. FT-IR spectra were thoroughly analyzed to determine the main chemical bonds present in the biocomposites as well as the changes, in terms of chemical bonds, of the material as a consequence of the degradation process. The crystalline structure of the biocomposites was determined by XRD using the same equipment and methodology described in FT-IR and XRD analyses were performed for the structural characterization of the manufactured biocomposites. A Tensor 27 FT-IR spectrometer  with a resolution of 4 cmCI) calculated using Equation (1).A1715 and A974 are, respectively, the absorbances at 1715 and 974 cm−1 of the samples analyzed, and which are due to the carbonyl groups present [The degradation of the material was quantified by means of the comparative analysis of their Carbonyl Indices ( present .c) was determined by immersion. Specimens with dimensions 80 mm × 10 mm × 4 mm were immersed in distilled water at 23 °C, as described in the ISO 69 standard [m1 is the initial mass of the specimen before immersion (mg), and m2 is the mass of the specimen after being subjected to the immersion process defined in the ISO 69 standard.The water absorption capacity  was calculated using Equation (3):mH (J/g) is the enthalpy of fusion of the analysed material, calculated as the area contained in the section of the curve corresponding to the peak of the endothermic melting process; ΔmcH (J/g) corresponds to the enthalpy of fusion of 100% crystalline PLA (93.7 J/g) [f is the weight fraction of the polymer matrix (PLA or PLAD) in the biocomposite.The thermal stability of the manufactured materials was determined by DSC using a Mettler Toledo 1 Stare System . The crystallinity and thermal transitions were analyzed in the temperature range of −30 °C to 350 °C, with a heating rate of 5 °C/min and an ultra-high purity N3.7 J/g) ; and f iThe particle size distribution of the conditioned OP samples used as reinforcements in PLA matrix is shown in Images obtained from the morphological analysis of the OP particle surfaces at different magnifications are presented in The moisture, ash, cellulose, hemicellulose, and lignin contents of the OP samples are listed in The results corresponding to the thermal properties of the OP obtained from the TGA curves are shown in According to the study by Yang et al. (2007), the thermal decomposition of hemicellulose mainly occurs in the range 220–315 °C, whereas cellulose degrades between 315 °C and 400 °C. However, the thermal degradation of lignin occurs in a wider temperature range (160–900 °C) since it exhibits slow degradation kinetics . These fm), tensile stress at break (σb), maximum tensile strain (εm), yield strain at break (εb) and Young’s modulus (Et). In general, the introduction of OP into the PLA matrix had a very significant influence on the mechanical properties of the manufactured biocomposites. σm decreases when incorporating OP, this effect being greater as the percentage by weight of OP in the material increases, going from 53.16 MPa for PLA to 11.92 MPa for PLA-40OP, that is, a decrease of 77.6%. The behavior of σb is very similar due to the lack of compatibility between the OP and the polymer matrix, which gives rise to the agglomeration phenomena of small-sized OP particles that become stress concentrators [m was also observed, going from 6.45% (PLA) to 1.66% (PLA-40OP), which indicates that the incorporation of OP gives rise to increased brittleness. Nevertheless, certain percentages of OP in the material generated an increase in Et, which was almost 30% higher than that of pure PLA when 15% OP was incorporated into the PLA matrix.ntrators . A decrem, εm and Et, respectively, was assumed to be due to hydrolysis of ester bonds, especially in the amorphous regions of PLA, which governs the degradation mechanism of PLA by environmental exposure [t as a consequence of the degradation process also occurred. Nevertheless, there was an increase in σm in PLAD-based biocomposites compared to PLA-based biocomposites, which was due to the higher crystallinity of the biocomposites after the degradation process [After the degradation process, a slight decrease in practically all the tensile properties of the PLA was observed. Karamanlioglu and Alkan (2019)  also repexposure . In the  process .fm), flexural strength at the breaking point (σfb), deformation at the point of maximum flexural strength (εfm), flexural strain at the breaking point (εfb), and flexural modulus (Ef). The incorporation of OP particles had an effect on the flexural behavior of the materials, similar to the effect on the tensile behavior; that is, it produced a decrease in the values of flexural strength and deformation, this effect being greater as the OP percentage increases. The values of σfm and εfm decreased by up to 56.4% and 64%, respectively, compared to those of pure PLA with 40% wt. of OP. This behavior is attributed to poor interfacial adhesion between the hydrophilic reinforcement and the hydrophobic polymer matrix [r matrix . The incr matrix . Furtherr matrix . Neverthr matrix . FinallyThe decrease in the mechanical properties of OP composites with respect to pure PLA has been observed when other thermoplastic matrices such as polystyrene , recycle−1, corresponding to –OH groups. A second, of medium intensity, is located around 1270 cm−1, which is associated with the stretching of the C-H bonds. Both bands identified the functional groups present in cellulose [−1 was attributed to the vibration of the glycosidic bond (C-O-C) superimposed with the stretching vibrations of the C-OH bond present in cellulose, hemicelluloses, and lignin [ellulose . The strd lignin .−1, stretching of the CH group; (b) 1746 cm−1, stretching of the C=O group [−1, deformation of the CH bond; and (d) 1452 cm−1, a peak generally associated with the presence of lactic acid [−1 were attributed to the stretching of –C-O-C. The absence of bands in the region attributed to –OH bonds (around 3350 cm−1) was also observed, indicating that the number of –OH groups present in the material was very poor [−1 were attributed to the amorphous and crystalline regions of the polymer, respectively [The PLA spectrum identified bands associated with the most representative functional groups of the polymer matrix: (a) 2995 and 2945 cm=O group ; (c) 145tic acid . The peaery poor . The peaectively .−1, due to the stretching of the ester bond, and (b) at 1750 cm−1, attributed to the stretching of the carbonyl group [−1 decreased in amplitude because degradation began in the amorphous region, increasing the crystallinity of the final material. Although the PLA samples were under environmental conditions, the FT-IR of the PLAD indicated signs of hydrolysis of the ester bonds, which is in agreement with what was reported by other authors who indicated that, in the degradation process of semicrystalline PLA, the ester bonds in amorphous regions were initially affected [The FT-IR spectrum of PLAD showed a significant increase in the intensity of the peaks located at (a) 1180 and 1082 cmyl group . The peaaffected .The PLA degradation mechanisms are shown in −1 are representative of the -CH group present in cellulose, hemicellulose, and lignin. The band around 700 cm−1 is associated with the stretching vibrations of the C-O group present in lignin [−1 were observed due to the vibration of the carbon skeleton (C=C) of the benzene ring on the molecular structure of the lignin present in the OP [n lignin . In addin the OP .−1, which are associated with the -OH stretching vibrations of the OP reinforcement used [Both the PLA-based and PLAD-based biocomposite spectra present broad bands located between 3100 and 3600 cm2 and therefore the formation of new C=O groups [The CI was calculated as a measure of the degree of degradation of the PLA and biocomposites. O groups .In the case of the materials that incorporated OP, the presence of particles mixed with the polymer matrix was observed c,e, as wPLAD-based biocomposites reported higher water absorption values of up to 18% for the PLAD-40OP sample compared with 12.14% for the PLA-40OP sample.In composites of OP with other polymer matrices such as PVC , the samgT), crystallization temperature (cT), melting temperature (mT), ΔmH, and cW of all the materials studied. When OP particles were introduced, there was a decrease in the cW values of the PLA-based biocomposites with respect to pure PLA. This was because the OP hindered the mobility of the PLA chains, preventing the formation of crystals [cW value of 47% for pure PLA to 30.42% for PLA-15OP. A similar effect was observed for PLAD-based materials. The hydrolytic process, initiated when the diffusion of water to the amorphous zones occurs, also contributed significantly to the increase in cW of PLAD with respect to PLA [cW values than PLA-based biocomposites, which is not only due to hydrolytic degradation but also to its synergistic effect with the OP particles that allows the alignment of the PLA chains and their rearrangement into a more stable crystalline structure [gT and mT compared to PLAD-based materials. This decrease was due to the loss of molecular weight after degradation [cT shifted towards lower temperatures due to chain scission [crystals ,44 from t to PLA . Regardiradation . This efradation . FinallytE of almost 30% was observed. The degradation led to significant decreases in the tensile properties of the biocomposites; nevertheless, an increase in mσ occurred because of the increase in the crystallinity of the biocomposites. The trend in the behavior of the materials in terms of flexural properties turned out to be similar to their tensile behavior. As for the impact resistance, there was an even more noticeable decrease due to the lack of adhesion between the phases and degradation.The introduction of OP into the PLA matrix affected the mechanical properties of the manufactured biocomposites, similarly to other biocomposites reinforced with OP using a different polymer matrix. The tensile strength and elongation decreases when OP was incorporated; nevertheless, an increase in 2 and therefore the formation of new C=O groups.The FT-IR spectra and diffraction patterns confirmed the degradation and changes in the crystalline structure of the materials originating as a consequence of the storage conditions. The analysis of the CI values indicated that the degree of degradation of the biocomposites was much greater than that of virgin PLA; however, the degradation of the biocomposites reached a lower degree as the percentage of OP increased, probably because the OP prevented the flow of OSEM images of the fracture surface of the impact-tested samples confirmed the increased presence of a layered texture in the degraded materials and the lack of interfacial bonding, resulting in low stress transfer and corroborating the loss of mechanical properties.c than PLA in the first 24 h, equilibrating from that moment on in the following hours of immersion. In turn, virgin materials showed less c than biocomposites, with c being higher as the percentage by weight of OP increased, which confirmed that OP favors water absorption. PLAD-based biocomposites reported higher c values than PLA-based biocomposites, with the influence of degradation being important, although less significant than OP weight percentage.PLAD presented a significantly higher cW of the PLA-based biocomposites with respect to pure PLA, mainly due to the greater difficulty of movement of the PLA chains. A similar effect was observed for PLAD-based materials. The hydrolytic process also contributed significantly to the increase in cW of PLAD with respect to PLA. PLAD-based biocomposites also presented higher cW values than PLA-based biocomposites, which was not only due to hydrolytic degradation but also to its synergistic effect with OP particles, allowing the alignment of the PLA chains and their rearrangement into a more stable crystalline structure. PLAD-based materials showed a slight decrease in gT and mT compared to PLAD-based materials due to molecular weight loss after degradation. cT was shifted towards lower temperatures due to chain scission.The OP particles caused a decrease in


The particle size of microemulsion acid is smaller compared to emulsified acid. At 60 °C, the mass transfer coefficient of microemulsion acid is 3.2 × 10−8 cm2/s, which is one order of magnitude less than that of emulsified acid. Microemulsion acid shows good solubility performance in dissolving organic and inorganic scales, and the comprehensive solubility of mixed scales can reach 98.28%. The stronger scale solubilization ability and lower acid-rock reaction rate enable microemulsion acid to form a thin and straight main wormhole, thus enhancing the acidizing and plugging removal effect. This study can solve the problem of poor hydrochloric acid solubilization ability of microemulsion acid to a certain extent, which provides theoretical and data support for the research and development of microemulsion acid and the efficient plugging removal technology for carbonate reservoirs.Matrix acidification is one of the most effective stimulations to dissolve scales and remove damage in carbonate reservoirs. However, existing acid systems are difficult to dissolve organic and inorganic scales simultaneously, and complex multi-stage alternative injection often introduces new precipitation and damages the reservoir. Here, based on the retardation ability of emulsified acid and the stable structure of microemulsion, an oil-phase solvent was preferably selected, and the surfactant and cosurfactant were optimized to prepare an acid-in-oil type microemulsion acid capable of dissolving both organic and inorganic scales and high solubilizing for hydrochloric acid. Based on the rotating disc experiment, scale dissolution experiment and acid driving experiment, the acid-rock reaction kinetics, scale dissolution ability and acidizing and plugging removal performance of microemulsion acid in a carbonate reservoir were systematically studied and compared. The results show that Solvesso 150 (aromatic solvent) has the advantages of low toxicity, high flash point and high-scale dissolving ability. At NP−4: OP−10: A (cosurfactant) = 3:3:4, the microemulsion acid system has the strongest ability to solubilize hydrochloric acid and can solve the problem of low H Scaling in the production process of carbonate reservoirs has always been an important issue affecting production and development efficiency ,2. Matri+ in the microemulsion acid to enhance the ability to remove the plugging and dissolving scale.Microemulsion acid comprises three parts: acid phase, oil phase and surfactant. Most scholars believe that according to the continuous phase and dispersed phase classification, microemulsion can also be similarly divided into the following three categories: acid-in-oil type, acid-in-oil type and double-continuous type . The str+ mass transfer rate of hydrochloric acid. One is to increase the viscosity of the acid solution, thereby reducing the diffusion rate of H+ [. The second is establishing an isolation layer on the rock’s surface to isolate the contact between H+ and carbonate minerals [+ in the acid-rock reaction, thereby reducing the acid-rock reaction rate [+ and rock, reduces the mass transfer rate of H+, and then reduces the acid-rock reaction rate [There are two main ways to slow down the Hte of H+ ,11. The minerals . Howeverminerals . The aciion rate . The Almion rate  study shion rate . The aciion rate . Differeion rate . HoweverThe technology of scale dissolution and plugging removal in oil and water wells are mainly based on an acid system with additives, which is suitable for the demand of plugging removal in oil and water wells caused by inorganic scale, clay particles, serious corrosion and other factors ,20. It c+ mass transfer rate without the need to add other additives that can remove organic and inorganic scales in one step. For the microemulsion acid system, the kinetics of the acid-rock reaction, scale dissolving ability and plugging removal performance in this study.To solve the problem of removing organic and inorganic mixed scale damage and plugging removal by acidizing technology in carbonate reservoirs, this study optimizes the oil-soluble reagent, optimizes the ratio of surfactant and cosurfactant, and prepares a new microemulsion acid. The microemulsion acid significantly improves its solubilization ability to hydrochloric acid. It has a very low HMost organic plugging in the oil field is composed of asphaltene and paraffin. The experiment uses the high-purity asphalt block to simulate the organic scale. The organic solvent is preferably selected from four solvents: diesel, xylene, cyclohexane, and Solvesso 150 .m1) of about 2.5 g was made using a mold, as shown in m2. The formula for calculating the dissolution rate of asphalt is as follows. To clarify the ability of the oil phase solvents to dissolve asphalt at different temperatures, the water bath temperature in the experiment was changed to obtain the dissolution rate of the oil phase solvents at different temperatures.To reduce the influence of surface area on the dissolution rate, spherical asphalt samples with the same surface area were prepared. After the asphalt oil bath was dissolved, the asphalt ball with a mass , nonionic surfactant OP−10 (S2) and cosurfactant (A). Therefore, the ratio of S1:S2 and the ratio of S:A must be optimized.The alcohol used in the experiment is octanol and isopropanol. The surfactants are non-nonionic NP−4 (nonylphenol polyoxyethylene ether) and OP−10 (dodecylphenol polyoxyethylene ether). The oil phase is S150 (aromatic solvent). Acid is 37% hydrochloric acid standard solution. The S + A (surfactant + cosurfactant) phase of the pseudo-ternary phase diagram of the microemulsion acid system consists of nonionic surfactant NP−4 (S1 + S2) were fixed, the mass ratio of the two surfactants (S1:S2) was changed, and then added to the beaker on the magnetic stirrer. The hydrochloric acid was added while stirring, and the phase change was observed. Before hydrochloric acid was added, the solution in the beaker was the oil phase. With the gradual addition of hydrochloric acid, the solution changed from the oil phase to the microemulsion phase. When hydrochloric acid increased the solubilizing ability of microemulsion relative to hydrochloric acid, the solution became two-phase. When the phase state was not single-phase, the addition of hydrochloric acid was stopped, and the maximum amount of hydrochloric acid solubilized under the surfactant ratio was recorded. The ratio of S1 and S2 was optimized according to the mass fraction of hydrochloric acid in the liquid (WHCl). After determining the ratio of S1 and S2, according to the same method, the mass of the oil phase (O) and the ratio of surfactant phase S were fixed, and the ratio of S:A was optimized by changing the total mass of the two surfactants (S) and the mass ratio of the cosurfactant (A).At room temperature, the oil phase (O) mass, cosurfactant (A) and the total mass of the two surfactants  + 44% oil phase (Solvesso 150) + 20% acid phase (37% hydrochloric acid).The effect of hydrochloric acid on the single-phase microemulsion region was studied by a pseudo-ternary phase diagram. The impact of deionized water and 37% hydrochloric acid on the system was studied. It can be seen from + in the microemulsion acid and the retardation mechanism of the acid system were explored.In addition to removing scale, microemulsions can chemically react with the rock minerals of carbonates after entering the reservoir. The comprehensive plugging removal of microemulsion acid to enhance hydrocarbon flow capacity includes plugging removal and reacting with a rock to enlarge the pore structure. The acid-rock reaction rate determines the effective distance of acidizing, which determines the change in permeability and conductivity of the reservoir after acidizing. It ultimately determines the effect of matrix acidizing . A large+ concentration were prepared to compare the difference in acidizing mechanism between conventional acid system and microemulsion acid. The formulation of the emulsified acid in this work is 30% oil phase (93% S150 + 7% EEA) + 70% acid phase, in which EEA is the surfactant.The rock samples used in this study are Indiana limestone outcrops, and non-clay and clay mineral X-ray diffraction (XRD) analysis was performed. The results are shown in The rotating disk reactor is the most commonly used test equipment, which can be used to test the microemulsion acid system in this study. According to the mass transfer theory of rotating disks, applying a rotating disk reactor is very reliable under clear conditions, and the influence of reaction kinetics and mass transfer motion can be studied completely . The rot2 was added to increase the pressure. The acid in the liquid storage vessel was transferred to the reaction vessel at a pressure of 1 MPa, and the overall pressure was increased to 7.5 MPa. (2) The control panel set the rotational speed to start the experiment. After the experiment, the acid was sampled from the sampling memory immediately, and the samples in the first few seconds were discarded to eliminate the influence of the residual liquid in the sample chamber. (3) 1 mL of acid sample was collected every 10 min 5 times. (4) After the reaction, the core was removed, and the spent acid on the surface was washed with deionized water. The core was placed in an oven at 105 °C for 24 h and weighed.The experimental steps are as follows: (1) the core was fixed in the reaction vessel using a polytetrafluoroethylene thermoplastic pipe, and the liquid storage vessel containing the acid liquid was preheated. The inert gas N2+ concentration and reaction time in two kinds of acid solution. It can be seen that the mass concentration of Ca2+ is linear with time, so the following equation can be used to calculate the mass transfer rate of H+ [Emulsified acid similar to the structure of microemulsion acid was prepared. Three rotational speeds of 100, 800 and 1800 r/min were used to compare the retarding ability of microemulsion acid at 60 °C. The reaction of hydrochloric acid and carbonate rock in the rotating disk is violent, and the core falls off during the reaction process. Therefore, hydrochloric acid is not recorded for comparison. The microemulsion and emulsified acid have a slow reaction rate at 100 rpm, which is lower than the range of the burette, and the fitted linear error may be large. te of H+ .(2)Jmt=K is the consistency coefficient, ρ is the acid density, dr is the diameter of the rotating disc, ω is the rotation rate of the rotating disc, and n is a power-law index.Were 2+, and the relationship between acid-rock reaction rate and rotational speed was plotted .The dissolution rate of carbonate minerals was calculated by Ca plotted . Overall+ mass transfer coefficient of two acid systems at 60 °C. For the H+ mass transfer process, the limitation of the microemulsion structure of the acid-in-oil on the H+ mass transfer rate is stronger than that of the emulsified acid. The mass transfer coefficient of microemulsion and emulsified acid are 3.2 × 10−8 cm2/s and 5.7 × 10−7 cm2/s at 60 °C, respectively. The mass transfer coefficient of microemulsion acid is more than one order of magnitude smaller than that of emulsified acid. It can be clarified that the mechanism of microemulsion acid reducing the acid-rock reaction rate is similar to that of emulsified acid. The acid liquid is wrapped by the external oil phase to reduce the diffusion rate of H+, and the microemulsion acid has a more stable structure than the emulsified acid, further reducing the diffusion rate. Therefore, the retarding performance of microemulsion acid is stronger than that of emulsified acid.2+ concentration and reaction time during the reaction of microemulsion acid at different rotational speeds. At all rotational speeds, the Ca2+ concentration increased with the increase of time, and the Ca2+ concentration was linear with time. The most important thing is that the concentration of Ca2+ increases significantly with the increase in rotational speed, which is consistent with the results of Taylor‘s study [‘s study . This shThe pollutants in oil and water wells can be divided into organic deposition scale and inorganic deposition scale. Organic sediments are mainly composed of paraffin and asphaltene in crude oil. Inorganic sediments are mainly due to the corrosion of pipelines and equipment, forming iron scales such as iron hydroxide and ferrous hydroxide precipitation. In addition, when the injected water is incompatible with the formation water, inorganic scales will be produced .+ concentration. The experimental conditions were 90 °C, and the reaction time was 4 h. After the reaction, the reaction was filtered and dried at a low temperature for 24 h to weigh and measure the mass after the reaction. The reaction amount and dissolution rate were calculated by weighing before and after.The inorganic scale sample used in the experiment is a mixture of Indiana core and iron hydroxide powder. The organic scale sample used in the experiment is high-purity asphalt. The experimental solution was 20 g of HCl, S150, emulsified and microemulsion acid with the same HThe experimental results of inorganic scale dissolution are shown in It can be seen from + concentrations. The experimental conditions were a 90 °C water bath reaction for 4 h. After filtration and drying, the mass after the reaction was weighed to obtain the dissolution rate of the mixed scale.According to the method of making an organic scale, the organic and inorganic scales are mixed to make a mixed scale. The experimental solution was HCl, S150, emulsified and microemulsion acid with equal HIt can be seen from To explore the dissolution mechanism of microemulsion acid for mixed scale, The research on the acid-rock reaction mechanism of carbonate rocks has been relatively mature. Acid-etched wormholes can greatly improve the flow conditions of low-permeability reservoirs and improve the effect of acidizing stimulation. The development conditions of wormholes are related to the acid system and the optimization of stimulation parameters in carbonate acidizing. Therefore, investigating the change in the morphology of the acid-etched wormhole after acidizing can provide theoretical conditions for on-site acidizing stimulation. To ensure the effect of acid etching wormhole, it is necessary to have oil dissolve and remove the organic scale. Therefore, the microemulsion acid can achieve the effect of acid etching wormhole and dissolving asphalt at the same time.2 solution to damage the core, and then 15% sodium hydroxide solution is injected in reverse alternately to simulate the damage of iron scale to the core. After simulated iron scale damage, the core is put into a beaker, and the mass ratio of asphalt to heptane solution is 1:1. The specific damage process can refer to Wang‘s research [The experimental material uses 10.5% FeclThe experimental steps are as follows: (1) Preheat the equipment and intermediate container to 90 °C, place the core in the core holder; (2) Put the configured acid into the intermediate container and empty the pipeline air; (3) The confining pressure is slowly loaded to 2 MPa, and the confining pressure value is always greater than the core inlet pressure of 1.5~2.0 MPa during the experiment; (4) Driving the treatment fluid until the breakthrough pressure drop becomes 0, and recording the relevant data such as leak off, breakthrough volume and breakthrough pressure; (5) CT scan was performed on the core after acidizing to observe the morphology of the wormhole and analyze the acidizing effect.The experimental results show that different acid treatment solutions can form acid-etched wormhole es to relieve the mixed scale damage of carbonate rock core to a certain extent. The HCl treatment solution can only dissolve the inorganic scale. It can be observed from the surface of the inlet end that the amount of asphalt adhesion after emulsified acid and microemulsion acid treatment is significantly reduced .bt is the acid consumption when the wormhole breaks through the core outlet (PVbt = acid consumption/pore volume). When the propagation distance of the wormhole is the same, the amount of acid used in HCl is the most. The amount of acid used when HCl breaks through the core outlet is 7.12 PV. The amount of acid used when the microemulsion acid breaks through the core outlet is the lowest at 5.14 PV. The acidizing effect of different acid fluids on carbonate rock cores after mixed scale damage is shown in The experimental data and results of the acid-driving experiment are shown in (1)+ concentration.Solvesso 150 with low toxicity, flash point of 69 °C and ability to dissolve scale of 0.0441 g/min at 90 °C was selected as the oil phase. The ratio of surfactant and the ratio of surfactant to cosurfactant were optimized according to the ability to solubilize HCl. When NP−4: OP−10: A = 3: 3: 4, the system had the strongest ability to solubilize hydrochloric acid, which solved the problem of low H(2)−8 cm2/s at 60 °C, which is one order of magnitude smaller than that of emulsified acid. It is limited by the mass transfer process in the acid-rock reaction.The particle size of microemulsion acid is smaller than that of emulsified acid in the external oil phase, further reducing the diffusion rate. The mass transfer coefficient of microemulsion acid is 3.2 × 10(3)Microemulsion acid shows good dissolution performance in dissolving both organic and inorganic scales, and the combined solubility of mixed scales can reach 98.28%. The stronger scale dissolving ability and lower acid rock reaction rate enable microemulsion acid to form a thin and straight main wormhole, thus enhancing the acidizing and plugging removal efficiency.Based on the retarding ability of emulsified acid and the stable structure of microemulsion, this study optimizes the ratio of surfactants and cosurfactants by optimizing the oil phase reagent. It prepares an acid-in-oil microemulsion acid that can dissolve organic scale and inorganic scale simultaneously and has a high solubilization ability for HCl. The acid-rock reaction kinetics, scale dissolving ability and plugging removal performance of microemulsion acid in carbonate reservoirs were systematically studied, and the following conclusions were obtained.


The development of the quality and commercial value of poultry meat is related to the formation of visible quality defects (hemorrhages) in muscles during the first stage of production (stunning). The production of meat with an unusual appearance for the consumers affects their purchasing decisions and, consequently, the company’s economics. The aim of this research was to determine the possibility of reducing visible quality defects  in commercial turkey carcass elements  using an alternative device (AD) for the electrical stunning of animals in comparison to the quality effects obtained using the conventional device (CD) in plant X. The factors differentiating the experiment were the electrical current frequency  and process time (9 and 18 s). The increase in electrical current frequency used in the alternative device stunner (own construction) resulted in changing the percentage share of defective turkey meat production. The greatest reduction of minor and severe meat defects and improvement of its quality were obtained for the alternative device at f = 800 Hz and t = 9 s—considered optimal for specific industrial conditions. Extending the time of stunning turkeys to 18 s had a positive effect on visible quality defects in the evaluated commercial elements of the carcass; however, its application in practice will depend on the efficiency of the slaughter line of the plant. A comparative analysis of the results of the impact of the frequency of electric current in the alternative device and plant X on the improvement of meat quality showed a justified need to commercialize the research results and replace the device currently used in the plant with an alternative one. The increased awareness of meat producers regarding factors and processes that induce defects of poultry meat has urged the management of processing plants to undertake actions aimed at meat quality improvement. Diminished meat quality and commercial value of poultry meat are mainly related to the occurrence of meat quality defects in the form of extravasations—hemorrhages ,2. They Despite the innovative actions undertaken, scientists are still conducting research on improving the efficiency of existing slaughter lines and optimizing the electrical parameters of stunning devices for animals. It has been demonstrated that the use of low frequencies of electrical current 50 and 100 Hz) in the stunning process of turkeys contributed to an increase in the number of hemorrhages and bone fractures, whereas the use of higher frequencies (500–1500 Hz) contributed to faster bleeding, a lower number of bone fractures, and of resultant extravasations on the skin and in pectoral major muscles ,9,10. Wh0 Hz in tConsidering the ambiguous character of the effects of technical and technological parameters of the water bath stunning process on the quality of poultry meat, research was carried out to determine the possibility of reducing visible quality defects  in commercial elements of turkey carcasses  using an alternative device for stunning animals compared to the qualitative effects obtained using a conventional device in plant X. The factors differentiating the experiment were the frequency of the current used in devices  and the process time (9 and 18 s). The aim of this research was also to indicate the optimal parameters of an alternative device for electrical stunning of turkeys, guaranteeing high-quality meat.➢The alternative device, AD ,16—recta➢The conventional device, CD (plant X equipment)—manufactured in The Netherlands: sine wave AC b, f = 50Experimental material included heavy-type turkey toms type BIG-6. The birds were transported in cages with vehicles from production farms to a slaughterhouse in northeastern Poland. To ensure a comparative experimental design at each stage of the study, the birds subjected to experimental and control slaughter originated from the same supplier and were unloaded manually from the same vehicle. The industrial process of stunning in water-bath, supervised by the veterinarian, was carried out on-line using:The current values (250 and 400 mA) used during the research were in accordance with the requirements of Council Regulation (EC) 1099/2009 . The alt✓Stage I, optimization of stun parameters using an alternative device: frequency (f)—125, 400, 800, and 1600 Hz for 9 and 18 s. Raw material was from supplier 1 .✓Stage II, comparison of stunning using two devices: alternative device  and conventional device, f = 50 Hz. Raw material came from supplier 2 .The study on the impact of an alternative device for stunning turkeys on the reduction of quality defects  of meat was carried out on the automatic slaughter line (yield 1000 birds/h) in two stages:The quality of the supplied raw material was classified on the basis of the company’s quality assessment protocol for live turkeys, in which the percentage of birds that died during transport, the degree of their plumage, and weight diversity were estimated.At each stage—for each device, frequency, and time—the research was carried out on a batch of 100 birds. Turkey carcasses were air-chilled with water spray  and subjected to industrial cutting for the culinary parts ca. 24 h after slaughter.Meat quality defects were evaluated by a five-person panel on 30 of 100 randomly selected commercially valuable parts of carcasses, i.e., m. pectoralis major (fillet), m. pectoralis minor (loin), and m. biceps brachii (wing). The methodology of quantitative evaluation of quality defects in meat were developed, taking into consideration some quality problems occurring in the slaughterhouse. The evaluation of the meat quality defects was based on two main criteria: (1) small hemorrhages, ø < 19 mm—minor defects (MD) and (2) large hemorrhages, ø > 20 mm—severe defects (SD). Meat defect was defined as the percentage of meat with small or large hemorrhages. Such an evaluation enabled us to determine the high-quality (premium) meat rate—expected by consumers ,18.Main effects ANOVA were used to assess the influence of traits  on the dependent variable .The basis for the implementation of the first stage of the research was literature data and the results of our own research ,20, whicThe results of the evaluation of quality defects of meat from turkey toms stunned with an alternative device for 9 s showed that the use of f = 125 Hz affected the occurrence of minor quality defects  in the majority of the evaluated elements (97%). The greatest degree of their occurrence (73%) was observed in the wings. In loins and fillets, minor defects were present at the level of 47%. Severe defects (large hemorrhages) were observed in 50% of the evaluated meat elements. The most severe quality defects were again observed in wings (33%), fillets (30%), and the least in loins (17%)—The use of f = 400 Hz resulted in the appearance of the highest percentage of minor (MD) and severe defects (SD) of meat in wings and fillets, which was MD: 30 and 20% and SD: 23 and 15%, respectively. The smallest defects were found in the loins (3%) with only small hemorrhages (less than 20 mm), and large hemorrhages were not observed. In addition, the extension of stunning time of the turkeys had a negative impact on the occurrence of minor quality defects (MD) in wings—40%, and loins—23%. The smallest defects (MD—7%) were found in fillets. Considering the above, it was found that increasing the frequency (125–400 Hz) in the alternative device affected the reduction of minor and serious defects in meat, in general, and in the individual carcass meat elements .The application of f = 800 Hz resulted in the occurrence of the largest minor and severe quality defects in wing muscles (33 and 13%) and fillets (17 and 10%). With the extended time of stunning (18 s), the share of small and large hemorrhages in the evaluated elements was lower than when using the standard time (9 s). In wings, it was 20 and 10%, respectively, and in fillets, 13 and 7%. It was also observed that the time of stunning had no effect on the defectiveness of loins, which are the most delicate and the most expensive commercial elements of poultry meat. A comparison of the evaluation of meat quality defects conducted for turkeys stunned with an electrical current used at the frequencies of f = 400 Hz and f = 800 Hz shows that increasing the frequency in this range resulted in a decrease in the percentage share of assessed carcass elements with severe quality defects, especially after stunning for 9 s . It is wThe application of a higher current frequency (f = 1600 Hz) for 9 s resulted in an increase in the production of defective carcass elements compared to the quality of meat produced using f = 400 Hz and f = 800 Hz. The evaluation of meat defects (minor—MD and severe—SD) indicated that the frequency of 1600 Hz had the most adverse effect on loin defects  and fillets , which are the most commercially valuable. Comparing the impact of stunning using an alternative device (own construction) at f = 400 Hz and f = 1600 Hz for 9 s, it was observed that the MD of fillets, regardless of the size of hemorrhages, was at a similar level of 20%, but SD was slightly lower—15%. In the wings, both minor and severe qualitative defects were at the level of 15%—The elongation of stunning time from 9 to 18 s had a positive effect on meat quality defects; however, the application of such a long stunning procedure is feasible only in processing plants with a low-yield slaughter line ,14. In ap = 0.25 and p = 0.21 is > α = 0.05), it was assumed that the variances in the studied groups are homogeneous. This means that the mean values of small hemorrhages . The qualitative factor—elements of the carcass—however, did not significantly affect the occurrence of minor and severe quality defects .The results of the analysis of variance  confirmeResults of measurements performed at the first stage of the study demonstrated that the lower percentage of visible quality defects (minor and severe) of commercial elements of meat carcasses was achieved upon the use of the frequency of f = 800 Hz, whereas the greatest one—upon the use of f = 125 Hz . ObtaineConsidering that in the first stage the greatest reduction of meat quality defects was demonstrated with the use of an alternative device with f = 800 Hz, the statical analysis confirmed the significant impact of the current frequency on the occurrence of hemorrhages. The second stage compared the impact of two types of devices, alternative and commercial, on the occurrence of these defects in meat obtained from low-quality raw material (from supplier 2). Taking into account the aspect of the type of device and the value of low and high frequencies of the electrical current allowed us to determine their impact on the efficiency of high-quality meat production (without defects) in the research.The research carried out in this area showed that the elements of carcasses of turkeys stunned using a conventional device with f = 50 Hz were characterized by the greatest defects. Most minor defects were observed in loins (90%) and in wings (65%), while severe defects (difficult to remove and costly) were also found in loins (40%). In fillets and wings, SD defects were at the levels of 20 and 15%, respectively. The use of f = 800 Hz in an alternative device  also confirmed the occurrence of meat defects at the lowest level compared to the defects occurring with the conventional device (f = 50 Hz). The least severe quality defects for manufacturers, in the form of large hemorrhages, occurred with the use of the alternative device. The level of defectiveness of the loin produced was 25%, and in the case of fillets and wings, it was only 10% .p = 0.39 and p = 0.37 > α = 0.05) in relation to the type of device and elements of the carcass were authorized by the Levene significance test. The obtained results of statistical calculations  affected the occurrence of both large  of this factor was obtained in relation to the occurrence of large hemorrhages in meat—p = 0.11) but comparable to the level of influence of the type of device. The mean values of large hemorrhages in fillets and wings differed significantly from the values in loins , economic indicators , and the natural environment (waste).


The softening coefficient of P15R45 with a 45 wt.% recycled fine powder content can reach 1.06, which is 26.2% higher than P35R25 with a 25 wt.% recycled fine powder content. The synergistic work reduces the negative impact of delayed AFt and improves the mechanical stability of the geopolymer.Geopolymer prepared from solid waste is a high value-added means. However, when used alone, the geopolymer produced by phosphogypsum has the risk of expansion cracking, while the geopolymer of recycled fine powder has high strength and good density, but its volume shrinkage and deformation are large. If the two are combined, the synergistic effect of the phosphogypsum geopolymer and recycled fine powder geopolymer can realize the complementarity of advantages and disadvantages, which provides a possibility for the preparation of stable geopolymers. In this study, the volume stability, water stability and mechanical stability of geopolymers were tested, and the stability synergy mechanism between phosphogypsum, recycled fine powder and slag was analyzed by micro experiments. The results show that the synergistic effect of phosphogypsum, recycled fine powder and slag can not only control the production of ettringite (AFt) but also control the capillary stress in the hydration product, thus improving the volume stability of the geopolymer. The synergistic effect can not only improve the pore structure of the hydration product but also reduce the negative impact of calcium sulfate dihydrate (CaSO Slag contains a large amount of active CaO, which is the main source of Ca2+ in the system. The 4]5−, [SiO4]4− and Ca2+ participate in a series of hydration reactions, generating CSH, CASH, NASH and other hydration gels and AFt crystals [The main chemical component of phosphogypsum is crystals ,62,63,64The main hydration reactions involved in the phosphogypsum and recycled fine powder-based multi-source solid waste geopolymer can be abbreviated as Formulas (7)–(10).σ, porosity P, pore saturation S and AFt generation determine the volume stability of geopolymers. According to the analysis in P and pore saturation S. When the slag content is fixed, with the increase in phosphogypsum content, the amount of recycled fine powder will be reduced accordingly. On the one hand, with the increase in phosphogypsum content, the concentration of 2+ in the system promotes hydration reactions (7) and (10) to the left, and more CSH gel and AFt crystals are generated  and (10) within the system will proceed to the left, whereas the reactions of Equations (8) and (9) are suppressed. The final manifestation is an increase in the generation of CSH and AFt and a decrease in the generation of CASH and NASH. It should be noted that the active component of slag is much higher than that of phosphogypsum and recycled fine powder, so an increase in slag will lead to a significant increase in CSH cementation. In addition, 2+ will lead to more AFt generation, but it will not lead to a sharp increase in AFt generation [According to the analysis in neration . AccordiAccording to the analysis in (1)The combined action of phosphogypsum, recycled fine powder, slag and other multi-source solid wastes can not only control the generation of AFt crystals but also control the capillary stress inside the matrix by adjusting the pore structure of the matrix, thus improving the volume stability of phosphogypsum and recycled fine powder-based multi-source solid waste geopolymers, reducing its volume deformation, and avoiding the expansion and damage of geopolymers. The volume of specimen P35R25 slightly shrinks without any risk of expansion or damage. Meanwhile, the 154-day volume change rate of specimen P35R25 decreased by 66.4% compared to that of specimen P0R60, and its 28-day volume change rate was 10.7% lower than that of specimen OPC.(2)The synergistic effect of phosphogypsum, recycled fine powder and slag promotes the generation of more CASH and NASH hydration gels, improves the pore structure of the matrix and reduces the negative impact on the matrix, thus improving the water stability of phosphogypsum and recycled fine powder-based multi-source solid waste geopolymer. The water stability of mortar specimen P15R45 is the best, with a softening coefficient of 1.06, which is 26.2% higher than that of mortar specimen P35R25.(3)The synergistic effect of phosphogypsum, recycled fine powder and slag reduces the negative impact of delayed AFt and improves the mechanical stability of the geopolymer. The 118-day standard curing compressive strength  of mortar specimen P15R45 decreased by only 2.3% compared to its 28-day compressive strength, whereas its 118-day water-curing compressive strength  increased by 18.2% compared to its 28-day compressive strength.(4)Microscopic analysis shows that phosphogypsum can promote the generation of more hydration products, especially AFt, which has an important impact on the pore structure and volume change of the slurry. Both phosphogypsum and recycled fine powder in geopolymers do not completely react, and the unreacted phosphogypsum particles and recycled fine powder particles not only have an important impact on the compactness of the matrix structure but also affect its stability. Recycled fine powder can promote the generation of hydration products, such as CASH and NASH, from geopolymers, improve the compactness of the slurry and enhance its stability. When the content of phosphogypsum increases, the content of recycled fine powder decreases, and the compact structure of the geopolymer slurry is destroyed, thereby becoming loose and porous.The stability and synergistic mechanism under the combined action of multi-source solid waste, such as phosphogypsum, recycled fine powder and slag, were studied. Based on these results and analyses, the following conclusions are obtained:To sum up, geopolymers have excellent stability due to the combined action of multi-source solid waste, such as phosphogypsum, recycled fine powder and slag. The contents shown in this study can be used as an effective method to change hazardous materials into green building materials and reduce harm to the environment.


Sulfates and chlorides are absent, while the insoluble residue portion for natural diatomite is 1.54% and 1.92% for calcined diatomite, values comparatively lower than the standardized 3%. On the other hand, the results of the chemical analysis of pozzolanicity show that the samples studied behave efficiently as natural pozzolans, both in a natural and calcined state. The mechanical tests establish that the mechanical strength of the mixed Portland cement and natural diatomite specimens (52.5 MPa) with 10% PC substitution exceeds the reference specimen (51.9 MPa) after 28 days of curing. In the case of the specimens made with Portland cement and calcined diatomite (10%), the compressive strength values increase even more and exceed the reference specimen at both 28 days (54 MPa) and 90 days (64.5 MPa) of curing. The results obtained in this research confirm that the diatomites studied are pozzolanic, which is of vital importance because they could be used to improve cements, mortars, and concrete, which translates to a positive advantage in the care of the environment.The object of this work is to study and characterize diatomites from the southeast of the Iberian Peninsula to establish their character and quality as natural pozzolans. This research carried out a morphological and chemical characterization study of the samples using SEM and XRF. Subsequently, the physical properties of the samples were determined, including thermic treatment, Blaine particle finesse, real density and apparent density, porosity, volume stability, and the initial and final setting times. Finally, a detailed study was conducted to establish the technical properties of the samples through chemical analysis of technological quality, chemical analysis of pozzolanicity, mechanical compressive strength tests at 7, 28, and 90 days, and a non-destructive ultrasonic pulse test. The results using SEM and XRF show that the samples are composed entirely of colonies of diatoms whose bodies are formed by silica between 83.8 and 89.99% and CaO between 5.2 and 5.8%. Likewise, this indicates a remarkable reactivity of the SiO Gerengi et al.  and CaO were determined by Equations (1) and (2), respectively.The purpose of the chemical analysis of pozzolanicity (CAP) is to determine the pozzolanic capacity of the samples using the Standard UNE-EN 196-5:2011 . This an−] is the concentration in hydroxyl ions (mmol/L).[OH3 is the volume of the hydrochloric acid solution (0.1 mol/L).V2 is the factor of the hydrochloric acid solution (0.1 mol/L).f[CaO] is the concentration of calcium oxide (mmol/L).4 is the volume of EDTA solution used in the titration.V1 is the factor of the EDTA solution.fMechanical compressive strength test at 7, 28, and 90 days:In this paper, the mechanical behavior was studied in 6 mortar specimens made by a mixed formulation of diatomite in its natural (NDT) as well as calcined (CDT) states, each partially replacing Portland cement (PC) in proportions of 10, 25, and 40% . AdditioTest to determine ultrasonic pulse velocity in mortar specimens:This method was developed to determine the propagation time of ultrasound waves as well as the ultrasonic pulse velocity (UPV) on mortar specimens made with mixtures of NDT/PC and CDT/PC, as well as the reference mortar specimen (RMS). The steps followed comply with the guidelines in the Standard UNE-EN ISO 16810 . To deteEquation (3) was used for the calculation of UPV:D is the distance measured in km.T is time measured in µs.The values of the UPV are expressed in km/s.* .2 (83.8%) and CaO (5.2%) is noted as the most abundant major compounds in the composition of the sample. On the other hand, the SiO2-to-Al2O3 ratio is extremely high, while compounds such as sulfates and chlorides are well below the thresholds indicated in the standard. Loss on ignition (LOI) indicates a strong tendency of the sample for absorption and desorption and evident behavior as an open system. According to the data shown in 2 (89.99%), followed by CaO (5.80%). According to these results, it seems that the original sample is of high purity [2 (89.44%), it is certain that almost all the silica present in the sample can react in the solution. In the same way, the reactive CaO has reacted almost in its entirety, as can be seen when compared with the original content of the total CaO. The contents of Al2O3, MgO, and Fe2O3 are low and confirm that it is a typical diatomite; however, the average content of these compounds calculated for 15 different deposits in the Russian Federation [2O3 (6.05%) and Fe2O3 (2.56%) in these deposits, with MgO values (0.84%) being slightly comparable with those calculated in this research ; however, unlike diatomite in its natural state, CDT shows low values of reactive CaO, which could be interpreted as a direct consequence of the heating process during which a part of the CaO could be recombined, forming calcium silicate, which is more stable and unable to react. This same calcination process also seems to produce a slight increase in insoluble residues, which could be considered reaction products with an inert nature. The drastic drop in LOI values indicates that virtually all volatile matter has been ejected from the sample during the calcination process [The chemical composition of the calcined diatomite (CDT) sample does not show great differences in relation to NDT, but the SiOs et al. , have sh process .3, could make these materials suitable substitutes for Portland cement during the manufacture of cements with additives, pozzolanic cements, mortars, and concrete.According to the results discussed, the two samples meet the qualitative and technological requirements to be considered for use as pozzolans . The lowAt 8 days of testing a, all anAt 15 days b, the poSome authors, such as Tironi et al. , have emA detailed analysis of According to Based on the above criteria and the data contained in 1 is the mechanical compressive strength (MPa) of mixed mortar specimens produced according to NDT/PC and CDT/PC formulations.V2 is the mechanical compressive strength (MPa) of reference mortar specimens.V(%) is the percentage factor with a value of 100%.f* RAI ≥ 75% .According to the data shown in Analysis of the 28-day estimate reveals not only an unavoidable increase in resistant activity but also that the NDT-10% and CDT-10% samples exceed 100% of the RAI, while the CDT-25% sample now reaches a RAI equal to 80%. After 90 days of curing, in addition to the three samples indicated above, the NDT-25% sample has exceeded the lower limit of the RAI. The conclusions obtained through this analysis allow us to confirm once again the pozzolanic behavior of the samples analyzed.2 content. Some authors, such as Presa et al. [These arguments establish that the factors depend on the chemical and physical properties of diatomites, mainly porosity, particle size, and total and reactive SiOa et al. , not onl2 and reactive SiO2, porosity, absorption capacity, tendency to loss on ignition, and the active surface of diatomite particles.The samples of diatomites studied, both in their natural (NDT) and calcined (CDT) states, behave similar to typical natural pozzolans; the features that potentially affect this fact are: their chemical composition, mainly the high contents of total SiO2 after heating.Pozzolanic reactivity visibly increases after calcination of the diatomite, which may be due to an increase in the degree of porosity of the sample and an increase in amorphous silica from total SiOThe presence of NDT and CDT provides effective volume stability to mixed mortar paste and considerable durability to hardened specimens.The setting start and final times of the paste of mortars containing NDT and CDT tend to increase relative to the fresh mortar reference, especially when the portion of diatomite is between 25 and 40%; however, these values are drastically reduced when the proportion is 10%.The mechanical resistance to compression increases visibly between 7 and 90 days of curing, mainly in those specimens that contain NDT and CDT at 10 and 25%. In some cases, these increases exceed the value of the mechanical compressive strength of the reference specimen. This same trend has been determined with the calculation of the Resistant Activity Index.Specimens made with NDT and CDT slow down the rate of the ultrasonic pulse through the specimens, which can be a direct consequence of the high silica content and porosity of the sample, factors that produce a strong acoustic impedance. This characteristic could be a predictive factor when formulating lighter mortars and concretes with insulating properties, both thermal and acoustic.Now that the results of this research have been stated and discussed, the following conclusions are established:


Neurogenic cervical spondylosis [cervical spondylotic radiculopathy (CSR)] accounts for ~50–60% of all types of cervical spondylosis, and its incidence is the highest among all types of cervical spondylosis.The present study aimed to investigate the clinical efficacy of the Qihuang needle in the treatment of senile cervical radiculopathy.A total of 55 elderly patients with neurogenic cervical spondylosis were randomly divided into the general acupuncture group (27 cases) and the Qihuang acupuncture group (28 cases). The treatment given to these patients lasted for three sessions. The VAS scores and the Tanaka Yasuhisa Scale scores were compared before the treatment, after the first treatment, after the first session, and at the end of the session.The basic data of the two groups before the treatment showed no difference. The VAS scores in the mackerel acupuncture group decreased significantly, whereas in the Tanaka Kangjiu Scale scores, the efficiency rates of the first and second courses of treatment increased significantly.The Qihuang needle therapy is recommended for the treatment of cervical spondylosis of the nerve root type. The said therapy is characterized by selection of fewer acupoints, a quick operation time, and no needle retention. Neurogenic cervical spondylosis [cervical spondylotic radiculopathy (CSR)] accounts for ~50–60% of all types of cervical spondylosis, and its incidence is the highest among all types of cervical spondylosis  and takes the theory of meridians and internal organs of Chinese medicine as the basic guiding theory. Due to a lighter stimulation of acupuncture for elderly patients, fast operation, no stagnant needle retention, and avoiding the discomfort caused by the long-term fixed positioning of elderly patients, the clinical effect of Qihuang Acupuncture Therapy is good. In this study, a kind of Qihuang Acupuncture Therapy was used to treat CSR, and satisfactory clinical efficacy was achieved.P > 0.05)  and the general acupuncture group (27 cases) according to the random number table method. There were no differences in gender ratio, age, and disease duration between the two groups ( > 0.05) . The ethThe inclusion criteria for the present study were as follows: (1) those who met the relevant diagnostic criteria in the “Expert Consensus on the Standardization of Diagnosis and Treatment of Cervical Spondylosis of the Nerve” . Operation procedure: The patient was asked to lie prone with a soft pillow on the chest and the hands were folded in front of the forehead to fully expose the skin of the neck and neck. After the aforementioned needle points were sterilized, the needles were inserted according to the conventional acupuncture method (attention paid to the angle and depth of needle insertion at Fengchi Point). After the needle pricking sensation was experienced by the patient, the needles were retained for 30 min and the said procedure was performed once in every 10 min. The course of treatment: 5 consecutive days of treatment is a course of treatment. After a two-day rest after each course, the second course of treatment was continued for a 3-course treatment .The patients were treated with ordinary acupuncture, and the acupuncture points were selected according to the “Tenth Five-Year Plan” National Planning Textbooks for ordinary higher education. Acupoint selection: GB20, Neckjiaji, BL10, GB21, SI3, LI4, and TE5. Needle size: 0.30*40-mm disposable sterile acupoint needle . Operation procedure: The patient was placed in a prone position with a soft pillow on the chest and the hands were folded in front of the forehead to fully expose the skin of the neck and neck. The operator disinfected both the hands and the skin of the treatment site, the left thumb was positioned on the point, the index and the middle fingers were placed on both sides of the point, the Qihuang needle was held, and the needle was flown (inserted) into the skin quickly. After insertion, the thumb and forefinger were used to push the needle body slowly. The depth of the needle was ~25–35 mm according to the patient's body weight. First, the infusion method, with the needle tip straight to the bone surface, was used, and the needle handle was gently shaken in small increments for ~5 s. Then, the needle handle was gently swung at an angle of 15° along the longitudinal axis of the body to perform Hegu thorn needling. The needle was then fed forward and backward or left and right at an angle of 15° to 20° from the original direction, with a light and small swing of the needle handle for ~10 s. The operation time of each point was ~15 s. After the local soreness and swelling became prominent, the needle was quickly removed, and the sterile dry cotton ball was pressed for a few moments. The course of treatment: 1 day off after the first treatment, a second treatment on the third day, then a 2-day break, and a third treatment on the sixth day. Then, a day of rest was taken when a course of treatment was completed. The aforementioned three sets of acupoints were used alternately, and 3 weeks of treatment constituted a course of treatment. The same clinician does acupuncture for all patients.The patients were subjected to Qihuang needle therapy, and the acupoints were selected. The first set of acupoints was C6 Jiaji point, IL5; the second set was C4 Jiaji point, LI14; and the third set was the extra point-Jian qian, TE4 (affected side). Needle size: 0.5(1) The VAS score  test, and the rank-sum tests were performed for comparisons between groups. An unpaired t-test was used for comparison between groups and a paired t-test was used for intra-group pre–post comparisons. Single-ordered rank information was gathered by applying the chi-square (χ2) tests. A rank-sum test was used for collecting rank information. A value of P < 0.05 suggests that the difference was statistically significant.SPSS22.0 software was used for data statistics. Variance analysis, t-test, the chi-square (χP > 0.05). Compared with the ordinary acupuncture group, the VAS scores in the Qihuang needle group decreased significantly after the first treatment, after the first session, and at the end of all sessions (P < 0.05). It showed that the treatment using a Qi Huang needle could effectively improve the VAS scores of patients and has a certain therapeutic effect  scores showed no significant difference between the two groups before treatment (c effect .P > 0.05). Compared with the general acupuncture group, the VAS scores in the mackerel acupuncture group increased significantly after the first treatment, after the first session, and at the end of all sessions (P < 0.05). It was shown that Tanaka Yasuhisa Scale scores could be effectively improved in patients with Tanaka Yasuhisa Scale scores and showed a certain therapeutic effect  (The effectiveness rates after one course of treatment were 28.57% (8/28) and 14.81% (4/27) for the Qihuang acupuncture group and the general acupuncture group, respectively, and 50.00% (14/28) and 22.22% (6/27) after two courses of treatment, respectively. The effectiveness rates of the first and second courses of treatment in the Qihuang acupuncture group were higher than those in the general acupuncture group. The duration of treatment was significantly shorter in the Qihuang acupuncture group than in the control group ( < 0.05) , 2 (EffiCure rates were 85.71% 24/28) and 66.66% (18/27) in the Qihuang acupuncture and moxibustion and general acupuncture groups, respectively. Therefore, the clinical efficacy of the acupuncture group was better than that of the general acupuncture group , 4. It s/28 and 6Professor Chen Zhenhu pioneered the Qihuang acupuncture. The common clinical pain treatment of Qihuang acupuncture is based on the Five Body Structure Theory of the “Spiritual Book.” According to this theory, the body is composed of five bodies: skin, veins, tendons, flesh, and bone, and most of the pain symptoms originate from lesions of these five bodies. This has led to an insight into meridian-tendon differentiation-acupuncture point selection for acupuncture treatment.“Ancesrtal sinew mainly binds bones and benefits organs.” The meridian sinew system is an external connection system, in which the Qi of the 12 meridians gathers the remaining muscles and joints. It connects the limbs and joints, constrains the bone, maintains the whole body, and governs the movement. Therefore, for the common clinical neck, shoulder, waist, and leg pain, the Qihuang needle therapy mostly uses the theory of meridian sinew as the basic guiding factor Chen, . For cerQihuang acupuncture believes that acupuncture's basis for treating diseases is the unblocking meridian–regulating Qi–harmonizing yin yang Chen, . The so-In theory, Qihuang acupuncture still uses the TCM meridian and acupoints and acupuncture theory, but it has carried out innovative reforms in needling instruments. Professor Chen studied the characteristics of the nine needles in depth and made the needle tip of the Qihuang needle oval to “make it easier to dredge the meridian Qi between the muscles” without hurting the muscles. The needle tip has expanded the sensation of the points in depth, thus enhancing the “DeQi” effect. At the same time, the hollow structure of the needle body of the Qihuang needle increases the hardness of the needle body, which is beneficial for acupuncture manipulation of the needle handle to be transmitted to the needle tip through the needle body to achieve the effect of “Qi to the lesion.” Therefore, the design of the needle tool fully reflects the “necessity of stab and the effect of Qi.”There are few literature reports on treating cervical spondylosis with Qihuang needle therapy, which is mainly used for treating chronic pain in the shoulder, the waist, and the knee and muscle soft tissue lesions. Zhang et al.  reportedvia the effect of Hegu thorn  for the publication of any potentially identifiable images or data included in this article.JY and HH were major contributors in writing the manuscript. JS and CH collected the patient data. KZ and ZC performed both surgeries and followed up the patients. RZ and JL realized the scarcity of the two cases, did literature searches, and revised the manuscript. All authors read and approved the final manuscript.


In order to improve the resource utilization of recycled concrete powder (RCP), this study aimed to investigate the effect of RCP admixture, curing age, and alkali excitation on the strength of RCP concrete. In addition, the pore structure characteristics of RCP concrete were analyzed in combination with low-field NMR. Furthermore, a gray predictive GM  model was established to predict the mechanical properties of the concrete based on the pore structure parameters, especially the compressive and flexural tensile strengths. The results of the study indicate that the mechanical properties, namely compressive strength and flexural strength, of RCP concrete exhibit an initial increase followed by a subsequent decrease with increasing RCP content at 3 d, 7 d, and 28 d curing ages. In particular, the concrete exhibits the highest mechanical properties when the RCP content reaches 10%. As the curing age increases, the RCP gradually achieves full hydration, resulting in further refinement of the concrete pores and a denser structure, which subsequently improves the mechanical properties. In addition, the strength growth rate of alkali-excited recycled concrete (ARC) showed a continuous increase, indicating that alkali excitation increasingly improved the mechanical properties of the concrete. Furthermore, the study accurately predicted the mechanical properties of RCP concrete by using GM  prediction models for its compressive strength and flexural tensile strength using pore characteristic parameters. Since the beginning of the 21st century, there has been rapid global urbanization, resulting in significant amounts of construction and demolition (C&D) waste . For exa2, Al2O3, and CaO and exhibits properties typical of supplementary cementitious materials (SCM), such as the micro-aggregate filling effect and the volcanic ash effect. Ma [2 content increases. Consequently, the compressive strength decreases as the RCP content increases.The processing of C&D waste can result in the production of recycled aggregate through a series of treatments. Although the performance of recycled aggregates may not be equal to that of natural aggregates, by improving the crushing process, surface treatment, and matrix modification, as well as adjusting the matching ratio, recycled aggregate concrete or mortar can still meet the design requirements. This has been demonstrated in previous studies ,10,11,12fect. Ma  has showfect. Ma ,19 arguefect. Ma  shows thfect. Ma ,22,23,24fect. Ma  shows thConcrete is a complex and heterogeneous multiphase material that forms numerous pores during the setting and hardening process. These pores have different morphologies, complex structures, and a wide range of sizes. At present, there is limited research on the pore structure of concrete after the addition of RCP. Most scholars ,27 have At present, there is relatively little research on the relationship between pore structure parameters and mechanical properties after the incorporation of RCP concrete. In addition, the investigation of the laws and quantitative relationship between pore structure and mechanical properties of RCP concrete under the influence of alkali excitation is particularly lacking. Therefore, this research focuses on the use of RCP derived from C&D waste in the resource recovery process. It aims to investigate the effect of replacement rate and curing age of RCP as well as alkali excitation on the mechanical properties of concrete. In addition, low-field NMR analysis is used to investigate the pore structure characteristics of the concrete. A GM  gray prediction model is then established to correlate the mechanical properties of the concrete with the pore structure parameters. The primary objective of this study is to increase the resource utilization rate of RCP while reducing the environmental pollution associated with traditional cement production. This research has strategic significance for China’s building materials’ industry to achieve the “double carbon” goal  and effe2, CaO, and Al2O3. In addition, the mineral fraction of RCP was examined using an X-ray diffractometer (XRD) and the results are shown in P.O42.5 ordinary silicate cement supplied by Jidong Cement Co., Ltd.,  was used in the test. In the experiment, ordinary river sand with a grain size ranging from 0.15 mm to 5 mm was used as the fine aggregate. The sand is properly graded and has a fineness modulus of 2.7. The coarse aggregate used was machine crushed stone with continuous grading from 4.75 mm to 26.0 mm. Detailed performance indices of the sand and coarse aggregate are shown in 2+ content, analytically pure Ca(OH)2 was used as a chemical exciter, specifically selected to stimulate the activity of the RCP , produced by the Tianjin Beichen Fangzheng Reagent Factory . A high efficiency polycarboxylic acid water reducer was used to achieve a water reduction rate of approximately 30%.In order to increase the OH concentration of the slurry and to replenish the Ca2 was selected as the activator, and the RCP was used to replace the cement at replacement rates of 10%, 20%, and 30%, respectively. The details of the mixes are listed in Based on the Technical Guidelines for Construction of Highway Cement Concrete Pavements (JTG/TF30-2014) , the oriThe procedure commenced with an initial blending of sand and coarse aggregate within a mixer for a duration of 2 min. Subsequently, cement and recycled micronized powder were introduced sequentially and mixed for 2 min to achieve homogeneity. Following this, a composite of water reducer, exciter, and test water was meticulously prepared and then introduced into the mixer for a 2-min cycle. Finally, the meticulously blended concrete was poured into molds with precision. The molded concrete specimens were then subjected to 2 min of controlled vibration on a vibrator, followed by the meticulous removal of excess mixture using a trowel, thereby ensuring strict adherence to the specified specimen dimensions.In accordance with the Test Methods of Cement and Concrete for Highway Engineering (JTG 3420-2020) , the dimIn accordance with the Test Methods of Cement and Concrete for Highway Engineering (JTG 3420-2020) , the speT2 relaxation value by the action of external gradient field, so that the water molecules in the magnetic field and the gradient field produce nuclear magnetic resonance phenomenon. According to the change of T2, a certain calculation and inversion are carried out to determine the pore structure characteristics in concrete.The principle of the low-field NMR instrument is to convert the energy change signal of water molecules at resonance into the T2 can be expressed by Equation (1) [The relaxation time tion (1) :(1)1T2=1TB2—the volume relaxation time of the fluid and S—pore surface area, V—pore volume, and TD2—diffusion relaxation time of fluid.In the formula: TB2 and TD2 can be ignored in saturated structures [In this experiment, saturated specimens are used, and ructures . AssuminG—pore shape factor, assuming that the pore structure is an ideal sphere, then G is 3 and r—is the aperture.In the formula: r can be determined from the T2 value measured by the low-field NMR instrument .When The specimen for this experiment has a cylindrical shape with a diameter and height of 50 mm. After reaching the specified curing age, the specimen is removed for vacuum saturation. The concrete specimen is first subjected to vacuum saturation for 8 h using a vacuum saturation device to ensure complete saturation. The specimens are then soaked in water for 24 h. The samples are then removed from the water saturation apparatus, wrapped in plastic wrap, and immediately placed in a pre-prepared water tank. Before the low-field NMR test is performed, the low-field NMR instrument is calibrated. The excess water on the surface of the plastic film is wiped off, and the samples are carefully positioned in the low-field NMR system for testing . The low2 and Al2O3 in RCP react with Ca(OH)2 to form cementitious products such as calcium silicate hydrate (C-S-H) and calcium aluminate hydrate (C-A-H). These products effectively fill the internal pores of the concrete, improving its compactness and promoting strength development [2, resulting in a reduction in the formation of hydration products such as C-S-H. Furthermore, the excess amount of RCP fills concrete microcracks without undergoing secondary hydration reactions, thereby weakening the mechanical properties of the concrete.The mechanical properties of RCP concrete and ARC at different curing ages are shown in elopment . Second,elopment , which delopment , resultielopment . Secondl2 is beneficial in stimulating the activity of RCP, thereby improving the mechanical properties of the concrete. The addition of Ca(OH)2 primarily increases the OH concentration in the slurry, which facilitates the formation of free unsaturated reactive bonds on the surface of RCP in an alkaline environment. As a result, the degree of polymerization of the SiO2 and Al2O3 network aggregates decreases, increasing their reactivity with the active components in the liquid phase of the system. Moreover, this process leads to an increased production of cementitious products, which ultimately stimulates the activity of the RCP and improves the mechanical properties of the concrete. Ca(OH)2, as an activator, introduces a significant amount of Ca2+ ions, replenishing the CaO content in the RCP and promoting the formation of silicate and other cementitious materials. Meanwhile, Ca(OH)2 can react with active SiO2, Al2O3 in a large amount of aluminum-silica glass in the RCP in a volcanic ash reaction to produce C-S-H and C-A-H with higher strength and water hardness.It can also be seen from 2 itself has certain cementing properties, but its solubility is low, resulting in insignificant early strength growth of the concrete. With the prolongation of the curing time, a large amount of Ca2+ and the rest of the active substances in the system were dissolved, and a large amount of calcium aluminate and some gelatinous substances were formed, which led to the improvement of the late strength of the system [The growth rates of ARC over RCP concrete mechanical properties at the same RCP loading and curing age are shown in e system .2S and C3S. The increased hydration results in the generation of a significant volume of C-S-H and C-A-H, which effectively fills the concrete pores and reduces the porosity of ARC [The variation patterns of RCP concrete and ARC porosity with RCP dosage at 28 d maintenance age are shown in y of ARC . Both RCy of ARC . On the y of ARC . In addi2, is not readily soluble in water, which hinders its ability to dissolve rapidly during the early stages of the hydration reaction [The variation pattern of porosity in NC, RC-1, and ARC-1 with curing age are shown in reaction . Over tiThe pore size distribution curves of concrete containing different amounts of RCP at a curing age of 28 days are shown in 2, the excitation of the secondary volcanic ash reaction of RCP leads to the formation of C-S-H gel. This reaction not only increases the strength of the concrete, but also effectively fills the internal pores, leading to an increase in the proportion of harmless pores and a decrease in the proportion of multiple harmful pores. As a result, the pore size distribution is significantly improved.According to the classification of pore classes in concrete by Wu , differeThe pore size distribution curves of NC, RC-1, and ARC-1 at different curing ages are shown in The pore size distribution trends of NC, RC-1, and ARC-1 at each curing age are shown in Determine the order of fundamental parameters:The relationship between the mechanical properties of RCP and fine-scale pore structure characteristics was investigated using gray correlation entropy analysis ,48,49. Tn = 7, m = 2, and l = 5.The mechanical properties of recycled powder concrete, denoted as 2.Dimensionless processing of data in each series:3.Calculate the absolute difference between the reference sequence and the comparison sequence.4.Determine the maximum and minimum values of the absolute difference, denoted as:5.Computing the number of correlation coefficients.6.Calculate the gray relation entropy.7.Calculate the gray entropy correlation grade.iY, and porosity, harmless pores, less harmful pores, multiple harmful pores, and harmful pores were selected as the comparison sequence jX. The parameter sequences are shown in The data of NC, RC-1, RC-2, RC-3, ARC-1, ARC-2, and ARC-3 specimens at the age of 28 d of maintenance were used as the basis for the theoretical calculation of the gray entropy correlation. Compressive strength and flexural tensile strength were selected as the reference sequence Based on From 8.Determine the system characteristic data sequence A and the sequence of related factors as:The gray prediction model is generated by accumulating the original series once so that the discrete data have a certain regularity, and the differential equation for the newly generated series is the GM prediction model, which is calculated using the least squares method to obtain the relevant parameters of the model . The GM 9.Find its corresponding once accumulated generating sequence (AGO).10.A is the immediate neighbor of B to generate a sequence of mean values.11.Establish the GM  model.Through the gray relational entropy analysis, the functional relationship between the system characteristic data sequence and the related factor sequence is established. The data of the top three pore characteristic parameters  and mechanical properties  of RCP concrete are used as the modeling set, and the data are substituted into the GM  gray prediction model. The compressive strength prediction model of RCP concrete is obtained by the Equations (11)–(15):Flexural tensile strength prediction model:After the GM  gray prediction model was established, the reasonableness of the model simulation and prediction performance was evaluated using accuracy tests such as the mean relative error and the posterior difference ratio . The criThe error test of the GM  prediction model of compressive strength and flexural tensile strength of RCP concrete is With the increase of RCP, the mechanical properties of concrete first increased and then decreased. When a reasonable amount of RCP (10%) is added, the secondary hydration reaction and micro-aggregate filling effect of RCP are beneficial to reduce the porosity of concrete and improve the mechanical properties of concrete. Excessive incorporation of RCP (30%) will cause the porosity of concrete to increase and the compactness to decrease, thereby reducing the mechanical properties of concrete.2 is beneficial to stimulate the activity of RCP, improve the pore size distribution of concrete, reduce the porosity, and improve the compactness, thus improving the mechanical properties of ARC. As the curing age increases, the RCP is fully hydrated, the pore size in the concrete is further refined, the structure becomes denser, and the mechanical properties are improved. At the same time, the effect of alkali excitation on the mechanical properties of concrete becomes higher and higher.The incorporation of 2.5% Ca(OH)The compressive strength and flexural tensile strength of RCP concrete are in the same order of gray entropy correlation degree of each pore characteristic parameter of low-field NMR, that is, harmless pore > porosity > multiple harmful pores > less harmful pore > harmful pore.The average relative errors of the GM  model for predicting the compressive strength and flexural strength of RCP concrete are 1.519% and 1.423%, respectively, and the accuracy is level 2. The posterior error ratios are 0.189 and 0.255, respectively, and the accuracy is one level. The established predictive GM  model can accurately predict the mechanical properties of RCP concrete.In this paper, the GM  prediction model is established by studying the compressive strength and flexural tensile strength of RCP concrete and analyzing the pore structure characteristics by low-field NMR. The main conclusions are as follows: