Reactive Cement Research Articles

Impact of Physical Processes and Temperatures on the Composition, Microstructure, and Pozzolanic Properties of Oil Palm Kernel Ash

In recent decades, the global use of ashes derived from agro-industrial by-products, such as oil palm kernel shells, which are widely cultivated in Colombia and other tropical regions of the world, has increased. However, the application of these ashes in engineering remains limited due to their heterogeneity and variability. This study utilized scanning electron microscopy (SEM) to assess the influence of calcination temperatures, ranging from 500 °C to 1000 °C, as well as the physical processes of cutting, grinding, and crushing, on the silica content of the studied ashes. Specifically, the sample labeled M18A-c-m-T600°C-t1.5h-tr1h, which was subjected to a calcination temperature of 600 °C and underwent cutting and grinding before calcination, followed by post-calcination crushing, exhibited the highest silica concentration. Complementary techniques such as X-ray fluorescence (XRF) and X-ray diffraction (XRD), were applied to this sample to evaluate its feasibility as an additive or partial replacement for cement in concrete. XRF analysis revealed a composition of 71.24% SiO2, 9.39% Al2O3, and 2.65% Fe2O3, thus, meeting the minimum oxide content established by ASTM C 618 for the classification as a pozzolanic material. Furthermore, XRD analysis confirmed that the sample M18A-c-m-T600°C-t1.5h-tr1h is in an amorphous state, which is the only state in which silica can chemically react with calcium hydroxide resulting from the hydration reactions of cement, forming stable cementitious products with strong mechanical properties.

Self-healing performance of silica nanoparticle-infused concrete based on microbial mineralization

This study investigates the effects of incorporating two substances–expanded perlite as a carrier for bacteria and nanosilica–into cement mortar. The objective of this study is to evaluate the effect of the dosage of these two substances on the strength and self-healing properties of mortars. The strengths of the specimens at different curing ages are tested using a pressure-testing machine and recorded. Additionally, precracks are introduced into the specimens. The cracks and their healing products are observed via electron microscopy, scanning electron microscopy, and X-ray diffraction to validate the experimental results. The results show that the self-healing agents agglomerate at the cracks and trigger a metabolic reaction, thus resulting in the formation of numerous calcium carbonate precipitates that sealed the cracks. Therefore, the addition of self-healing agents significantly improves the self-healing properties of the cement mortar. The nanosilica facilitates the hydration reaction of cement in mortar. Additionally, nanosilica undergoes a pozzolanic reaction with calcium hydroxide, which consumes calcium hydroxide and generates hydrated calcium silicate to fill the pores. Consequently, the incorporation of an appropriate amount of nanosilica effectively enhances the strength of the cement mortar. Therefore, simultaneously incorporating self-healing agents and nanosilica while controlling the dosage provides a new approach for optimizing both the mechanical properties and self-healing performance of concrete.

Research and prediction of early-age loads in double-block ballastless track structure

Considering the hydration reaction of cement, a finite element model(FEM) of the coupling of temperature and humidity field and chemical field in the early age of the double-block ballastless track structure was established, and a field monitoring test on the early age of track slab was carried out with the newly constructed Fuzhou-Xiamen high-speed railway line as a case to verify the correctness of the FEM. Based on the official meteorological data from China Meteorological Administration (CMA) and the FEM, the dataset of vertical temperature and humidity gradients in the early age of the track slab was constructed, and five machine learning training models, namely, machine learning (MLR), multivariate polynomial regression (MPR), support vector regression (SVR), random forest (RF), and gradient boosted regression (GBR), were adopted to train the temperature gradient model and humidity gradient model for the early age of the track slab. The research results show that: (1) under the combined effect of solar radiation, convective heat transfer, radiative heat exchange and the cement hydration reaction, the temperature loading leads to the susceptibility of the sleepers to diagonal cracking; the humidity loading leads to transverse cracking in the center region of the surface of the track slab; (2) the finite element model with a higher accuracy provided the training dataset for the machine learning model. According to the Spearman correlation coefficient, the input features of the temperature gradient model and the humidity gradient model are determined, respectively; (3) Five ML methods were used to train the temperature gradient model and humidity gradient model, both of which demonstrated good generalization ability with a coefficient of determination(R2) greater than 0.85. Among these methods, GBR and SVR exhibited the best performance; From the perspective of MAPE value, the prediction effect of the temperature gradient training model was better than that of the humidity gradient training model; (4) The curing method and the average value of the relative humidity were the important input features influencing the training models for the temperature and humidity gradient loads, respectively. This finding provided an important guideline for the construction of ballastless track structures.

Setting reaction of a olivine-based Mg-phosphate cement

The cementitious properties of natural Mg-rich olivine when reacted with a phosphoric acid solution are investigated, as a function of acid concentration and liquid/solid mass ratio. The obtained cements are composed of residual olivine crystals and amorphous silica nanoparticles dispersed in a dense and compact newberyite (MgHPO4∙3H2O) matrix. The latter was mostly formed by packed micrometric tabular crystals, although evidence of the presence of a fraction of amorphous MgHPO4 was also found. Water content in the raw mix was observed to play a pivotal role on the reaction pathway, either promoting porosity or hindering the crystallization of the products. Up to 57 % of olivine reactivity, whose dissolution was promoted by the curing temperature (60 °C) and low pH, was achieved. All in all, these results indicate that the industrial mineral olivine may serve a viable source of Mg for the production of phosphate cements.

Low-grade fly ash in portland cement blends: A decoupling approach to evaluate reactivity and hydration effects

Fly ash with low glass content is often prohibited from use in concrete due to the low reactivity and/or the inclusion of contaminants. However, the scarcity of high-quality fly ash promotes the evaluation of the feasibility of using fly ash with low glass content (e.g., low-grade fly ash) in concrete. This study proposes a decoupling method to quantitatively estimate the degree of reaction of fly ash with extremely low glass content, which partially replaces cement, and the degree of hydration of the hosting cement, simultaneously. The estimation is derived from the contents of calcium hydroxide and chemically bonded water in hydrated binary cement pastes, which can be determined by thermogravimetric analysis-based experiments and theoretically validated stoichiometric parameters. The results exhibit that the fly ash tends to retard the early-age hydration of cement but promotes its later-age hydration, resulting in a higher ultimate degree of reaction of cement than the reference paste. The microstructural and porosity evaluation shows that the fly ash, though has relatively low degrees of reaction due to its low glass content, can result in a more tortuous pore network of the hydrated pastes, which could be potentially more resistant to the penetration of water and aggressive chemicals.

New Methodology for Evaluating Strength Degradation from Temperature Increase in Concrete Hydration under Adiabatic Conditions

Cement-based construction materials, commonly known as “cement concrete”, result from the hydration reaction of cement, which releases heat. Numerous studies have examined the heat of cement hydration and other thermal properties of these materials. However, a significant gap in the literature is the assessment of the impact of the hydration temperature on the material’s strength, particularly compressive strength. This work presents an experimental methodology that consistently estimates the temperature evolution of a mixture used to manufacture concrete or mortar during the first hours of Portland cement hydration. The methodology aims to ensure results that correspond to an infinite medium (adiabatic conditions), where there are no heat losses to the surroundings. Results obtained under adiabatic conditions (simulating an infinite medium) indicate that a ready-made mortar (Portland cement: sand: water; 1:2.5:0.5) can reach temperatures of approximately 100 °C after 48 h of hydration. Under these conditions, compressive strength decreases by up to 20%.

Phase evolution and heavy metal solidification of cement desulphurized electrolytic manganese residue composite cementitious system under steam curing conditions based on thermodynamic simulation

The mechanical properties and microstructure of desulphurized electrolytic manganese (D-EMR) cement mortar under steam curing at 80 °C for 7 h and 7 days and standard curing for 3 days and 28 days were studied. The hydration products, microstructure and pore distribution were studied by Quantitative X-ray diffraction analysis (QXRD), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), thermogravimetric-differential thermal analysis (TG-DTA) and backscattered electron (BSE). At the same time, the evolution of hydration products with age and the existence form of heavy metals under different curing conditions were simulated by GEMS thermodynamics. The results show that steam curing can promote the hydration reaction of cement and the secondary hydration of D-EMR. With the extension of steam curing time, the mechanical properties of the early stage are significantly improved. At a D-EMR content of 15 %, the compressive strength of D-EMR cement mortar after steam curing for 7 days is 1.15 times that of the control group under the same conditions, and the content of calcium hydroxide (CH) is 65.91 % of the control group. Steam curing can significantly improve the degree of C3S hydration of cement clinker and the secondary hydration of D-EMR, and increase the degree of polymerization of hydrated calcium silicate (C-S-H) gel. In addition, thermodynamic simulation showed that when the pH value was greater than 7.5, Mn2+ was mainly stable in the form of Mn(OH)2, MnOOH and Mn3O4, and there was no leaching risk. This will provide theoretical support for the use of D-EMR as a new type of supplementary cementitious material (SCM).

Injectable bone cement based on magnesium potassium phosphate and cross-linked alginate hydrogel designed for minimally invasive orthopedic procedures

Bone cement based on magnesium phosphate has extremely favorable properties for its application as a bioactive bone substitute. However, further improvement is still expected due to difficult injectability and high brittleness. This paper reported the preparation of novel biocomposite cement, classified as dual-setting, obtained through ceramic hydration reaction and polymer cross-linking. Cement was composed of magnesium potassium phosphate and sodium alginate cross-linked with calcium carbonate and gluconolactone. The properties of the obtained composite material and the influence of sodium alginate modification on cement reaction were investigated. Our results indicated that proposed cements have several advantages compared to ceramic cement, like shortened curing time, diverse microstructure, increased wettability and biodegradability and improved paste cohesion and injectability. The magnesium phosphate cement with 1.50% sodium alginate obtained using a powder-to-liquid ratio of 2.5 g/mL and cross-linking ratio 90/120 of GDL/CC showed the most favorable properties, with no adverse effect on mechanical strength and osteoblasts cytocompatibility. Overall, our research suggested that this novel cement might have promising medical application prospects, especially in minimally invasive procedures.

High performance CaCO3-based composites using sodium tripolyphosphate as phase controlling additive: Bamboo fiber driven high strength development

Due to the limited carbonation degree caused by the surface densification of carbonated products, the development of high-strength carbonated composites remains challenging. In this work, bamboo fiber (BFs) is utilized as a reaction reinforcing agent along with sodium tripolyphosphate (STPP) as a CaCO3 phase controlling additive to prepare high-strength bamboo fiber reinforced carbonated wollastonite composites (BFRCWs). The phase composition and microstructure are systematically investigated by multiscale physicochemical analysis, followed by the determination of macro properties and volume deformation. Results indicate that BF and STPP have a synergistic effect on the microstructural formation and macro performance of BFRCWs. STPP-treated BF (ST-BF) can serve as an internal curing agent and the porous structure of BF provides more channels for ion and CO2 transport, whereas CaCO3 phase composition and cementitious behavior is modified by STPP. The addition of ST-BF, particularly for long fibers, accelerates the carbonation reaction, resulting in an increased ratio of poorly crystalline CaCO3 and a refined pore structure. With increasing ST-BF dosage (0–3 vol%), the cementitious reaction is enhanced, but excessive fibers (3 vol%) incorporation introduces additional porosity, consequently reducing compressive strength. The desired pore structure with the optimal 2 vol% ST-BF (3–6 mm) shows the highest strength of 103.5 MPa at 28 days.

Effect and mechanism of activators on the properties of Yellow River sediment/fly ash/cement-based alkali-activated cementitious materials used for coal mine filling

Preparing Yellow River sediment/fly ash/cement-based alkali-activated cementitious materials for coal mine filling can realize the large-scale consumption of Yellow River sediment and reduce the cost of coal mine filling materials. This paper studied the effects of Ca(OH)2, NaOH, and water glass on the properties of coal mine filling materials. Adding activators Ca(OH)2, NaOH, and water glass can improve the compressive strength and shorten the setting time of the filling materials. NaOH and water glass can also significantly reduce the bleeding rate. The mechanism of activators' influence on the mechanical properties of filling materials was explored based on XRD, TGA, FTIR, MIP, and SEM. The alkaline environment provided by NaOH and Ca(OH)2 accelerated the hydration reaction of cement, and the SiO32- from the hydrolysis of water glass can bind to Ca2+ to form C-S-H gel. The co-mixing of water glass and NaOH can make fly ash and Yellow River sediment's active components react more fully, generating more C-S-H and C-A-S-H gels. This can refine the pore size distribution of the filling materials, reduce the content of harmful pores, make the matrix dense, and improve the filling materials' working and mechanical properties. When the NaOH is 0.5 wt%, and the water glass is 13 wt%, the strength of the filling materials prepared by compound doping was the highest, and the working performance met the requirements. The results had broad application prospects and economic value, contributing to ecological and environmental protection and sustainable development.

A rare presentation of bone cement implantation syndrome as hypertensive anaphylaxis: A diagnostic and management dilemma.

Bone cement implantation syndrome characteristically involves acute alterations in the function of respiratory and cardiovascular systems. We present a case report of cement reaction with unusual presentation, that is, hypoxia, hypertension and tachycardia. A 74-year-old hypertensive male on regular medications sustained a slip and fall, presented with a right intertrochanteric neck of femur fracture, now posted for cemented hemiarthroplasty. Intraoperatively, after applying bone cement, the patient developed sweating, dyspnoea, bilateral wheezing and tachypnoea and desaturation of up to 80%-84%. Respiratory symptoms were associated with tachycardia (140-160 bpm) and hypertension (220/110 mm Hg). The surgeon was alerted about the event, the patient was reassured, and respiration was assisted with positive pressure ventilation with supplementation of 100% oxygen. Several mechanisms have been proposed, such as the toxic effect of systemically absorbed methyl methacrylate, exothermic reaction, fat and marrow embolism, high marrow pressure during cementing and anaphylactic reaction. The administration of adrenaline, which can worsen the clinical picture, is the mainstay in managing anaphylaxis. The association of hypertension and tachycardia with bone cement implantation syndrome, previously not reported, can have distinct pathomechanisms and cause a diagnostic and management dilemma.

Temporal effects on the micro- and nano-structural cement-slag pastes subjected to microwave curing over 7 years

This study examines the changes in the micro- and nano-structures of microwave-cured cement and slag pastes over 7 years. The properties of aged samples were compared with those of young pastes made from the same mixtures. Both young and aged samples were analyzed by XRD, DTA-TG, SEM-EDX, and Solid-state MAS NMR of 29Si and 27Al. It is found that, in addition to the usual components (C-S-H, calcium hydroxide, monosulfoaluminate, trisulfoaluminate, and hydrotalcite-like phases (HT)), the aged samples contained calcium magnesium aluminate hydrate and gibbsite (AH3). Over time, some HT or AH3 integrated into the C-S-H nanostructure as additional layers. These findings suggest that microwaves accelerate the general hydration processes in cement due to thermodynamic effects and selectively activate reactions in the aluminate components. This discovery highlights the potential for using microwaves to manipulate cement reactions.

Pemanfaatan Abu Cangkang Kopi Sebagai Substitusi Semen Untuk Bahan Beton Ringan Menggunakan Bahan Tambah Sikament NN

The chemical reaction of cement and water produces compounds that are alkaline and react with various acids so that they can reduce the quality of concrete. To minimize this effect, pozzolanic materials need to be added. Organic pozzolan materials such as coffee shell ash waste can be used as material for making lightweight foam concrete which can be applied to non-structural buildings such as lightweight bricks. This research was conducted to see the effect of coffee shell ash substitution for cement on the properties of fresh concrete and the mechanical properties of lightweight foam concrete and to find the most optimal substitution composition for coffee shell ash for cement as well as lightweight foam concrete with FAS 0.5. Substitution of coffee shell ash for cement weight was carried out with variations of 0% BBN, 5% BBAAK1, 10% BBAAK2, and 15% BBAAK3 using 1% superplasticizer additive. The test object used is a cylinder with dimensions of 15 cm x 30 cm. The number of test objects used was 24 pieces. Tests for compressive strength and split tensile strength were carried out at the age of 28 days. The results of compressive strength tests carried out at 28 days for the lightweight foam concrete variations BBN, BBAAK 1, BBAAK 2 and BBAAK 3 were respectively 15.29 MPa, 12.21 MPa, 18.29 MPa and 19.52 MPa. The greater showing variation in the percentage of coffee shell ash substitution used, the greater the resulting compressive strength and split tensile strength values. This is because Sikament NN also plays a role in increasing the compressive strength of concrete

Regulation of osteogenesis and angiogenesis by cobalt, manganese and strontium doped apatitic materials for functional bone tissue regeneration

Strontium, cobalt, and manganese ions are present in the composition of bone and useful for bone metabolism, even when combined with calcium phosphate in the composition of biomaterials. Herein we explored the possibility to include these ions in the composition of apatitic materials prepared through the cementitious reaction between ion-substituted calcium phosphate dibasic dihydrate, CaHPO4·2H2O (DCPD) and tetracalcium phosphate, Ca4(PO4)2O (TTCP). The results of the chemical, structural, morphological and mechanical characterization indicate that cobalt and manganese exhibit a greater delaying effect than strontium (about 15 at.%) on the cementitious reaction, even though they are present in smaller amounts within the materials (about 0.8 and 4.5 at.%, respectively). Furthermore, the presence of the foreign ions in the apatitic materials leads to a slight reduction of porosity and to enhancement of compressive strength. The results of biological tests show that the presence of strontium and manganese, as well as calcium, in the apatitic materials cultured in direct contact with human mesenchymal stem cells (hMSCs) stimulates their viability and activity. In contrast, the apatitic material containing cobalt exhibits a lower metabolic activity. All the materials have a positive effect on the expression of Vascular Endothelial Growth Factor (VEGF) and Von Willebrand Factor (vWF). Moreover, the apatitic material containing strontium induces the most significant reduction in the differentiation of preosteoclasts into osteoclasts, demonstrating not only osteogenic and angiogenic properties, but also ability to regulate bone resorption.

Effect of MgO-based expansive agent on strengths, volume stability, and microstructures of C80 SCC in steel tube arch

In order to meet the requirements of concrete filling, vibration, and pumping during the construction of the concrete-filled steel tube (CFST) arch bridge, the C80 expansive self-compacting concrete (SCC) is prepared using the absolute volume method. This research investigates the effects of MgO-based expansive agent (EA) and water-to-binder ratio (w/b) on the fresh properties, mechanical properties, autogenous shrinkage, and creep behaviors of expansive SCC. The microstructure of expansive SCC is analyzed by scanning electronic microscopy (SEM) and nuclear magnetic resonance (NMR). Results show that, as the MgO-based EA content increases from 5 % to 10 %, its effect on fresh properties of SCC is negligible. The addition of EA retards the hydration reaction of cement at early ages, thus delaying the strength development. However, the long-term mechanical strengths of the SCC are enhanced, due to the expansion product refines the microstructure at later ages. Moreover, the 14-day autogenous shrinkage of SCC with 10 % EA content is eliminated and shows the micro expansion (155.3 με). The microstructural analysis shows that the porosity of SCC with 10 % EA content is 1.8 % while the pore throat below 0.1 μm accounting for 55 % and the pore size above 30 μm is negligible. This research reveals the mechanism of the effects of MgO-based EA and w/b on the volume stability of the SCC, facilitating the application of expansive SCC in CFST composite structures.

Magnesium Potassium Phosphate Cement for Encapsulation of Ash from Burning Radioactively Contaminated Wood

When wood from Chornobyl radioactively contaminated forests is burned in the Incinerator created in the Chornobyl zone under support of the European Commission, ash with a high content of Cs radionuclides is formed. Recently, magnesium potassium phosphate cements (MKPC) have been proposed as an effective alternative to Portland cement-based protective matrices. In this work, MKPC compositions were optimized for laboratory-scale encapsulation of inactive model ash, used as surrogate of the radioactive ash. The influence of the MgO/KH2PO4 ratio and the amount of added model ash on the temperature and setting time of the MKPC paste were determined. The compressive strength after 28 days of MKPC curing without ash was 22.7 MPa. After adding 20 wt.% model ash, the compressive strength of the MKPC matrix was 34.5 MPa, 40 % model ash was 23.4 MPa and 60 % model ash was 8.3 MPa. Thus, the accepted amount of the added ash that does not initiate the essential strength decrease of the MKPC matrix is 40 %. X-ray diffraction analysis of the MKPC matrix with 40 % model ash shows the presence of the main phase – K-struvite MgKPO4·6H2O. In addition to K-struvite, there are peaks of unreacted MgO and compounds such as calcite CaCO3, quartz SiO2 and potassium chloride KCl, which are parts of the model ash. It has been shown that ash components such as hydroxyapatite Ca5(PO4)3(OH) and calcium oxyphosphate Ca4(PO4)2O are involved in the formation reaction of phosphate cement and it contributes to increasing of the permissible amount of ash encapsulated into the MKPC matrix. SEM images of MKPC samples demonstrate a dense structure with well-connected ash particles. The leaching behavior of the MKPC matrices and their thermal stability were also assessed using immersion tests and thermogravimetric analysis, respectively. The Cs leaching rate of 1.2×10-4 g/cm2·day from the MKPC matrix containing 40 % MA is lower than the rates typical for cement waste forms. The obtained results demonstrate the possibility of using new magnesium-potassium phosphate cement as a matrix for the encapsulation of ash from the combustion of radioactively contaminated wood in the Chornobyl zone.

Crack resistance, permeability, and microstructural analysis of recycled aggregate concrete with SAP

High shrinkage and cracking performance are among the main problems that hinder the wide application of recycled aggregate concrete (RAC). To analyze the influence trend and mechanism of superabsorbent polymers (SAP) on the crack resistance of RAC, the effects of the recycled coarse aggregate (RA) content and SAP content on the crack resistance of RAC were studied via a slab cracking test. Moreover, the compressive strength, chloride permeability, pore distribution, and microstructure of the concrete in each mixture were also tested. The results showed that the incorporation of RA will have a negative impact on the crack resistance of concrete. The greater the amount of RA, the shorter the initial cracking time of the concrete, and the larger the crack width and area of the concrete. The initial cracking time, maximum crack width, and cracking area of the RAC tended to decrease with increasing SAP content. However, the crack resistance of the RAC does not seem to change much when the SAP content exceeds 0.3%, and even the local cracks in the slab specimens of the RAC increase in size. NMR and SEM analyses revealed that the water absorption-release and microreservoir characteristics of SAP affect the degree of the hydration reaction in the early stage, alleviate the internal drying of concrete, reduce shrinkage and inhibit the development of inner cracks, and effectively reduce the cracking sensitivity of RAC. This process can continuously provide water for the hydration reaction of cement when the SAP releases water in the later stage of curing, optimize the pore structure of the recycled concrete system, enhance its compactness, and improve its compressive strength and impermeability.

Analysis of cementitious pore solutions with very high time resolution by coupling cross flow filtration and ICP-OES

Pore solution analysis is a powerful tool for understanding reactions that occur during the cement hydration. Crossflow filtration of cement paste provides more detailed insight into reactions and reaction pathways compared to standard methods for gaining pore fluid. In particular, the large time resolution for the analysis enables the characterization of fast processes like adsorption kinetics and hydration reactions of aluminate phases in unprecedented detail. A direct comparison of the crossflow filtration results with those obtained using a filter press showed no significant difference in pore solution composition. With this method, it is possible to analyze the complex reaction patterns of cementitious reactions in great detail during the first minutes of hydration. This is especially important for chemically admixed systems.

Monitoring the hardening process of cemented soil with polymer optical fibre

Cement-soil can effectively improve the mechanical characteristics of soft soil and reduce the deformation of foundations through the physical and chemical processes of cement hydration. After mixing cement with soft soil, the hydration reaction of cement consumes a certain amount of water, which leads to a decrease in the water content. The early strength of cement-soil refers to the undrained shear strength within a few hours of mixing. The initial setting time of cement-soil can reflect its early strength development. In this study, polymer optical fibre (POF) sensors are used to visually monitor the early strength of cement-soil with different cement contents; the monitoring results show that the POF sensor can effectively visualize the hydration process of cemented soil. The cement-soil hydration process is divided into three stages: the initial setting time of the cement-soil is 13-15 h, and the final is 33-41 h. Furthermore, the cement content significantly influences the initial and final setting times of cement-reinforced soil. As the cement content increases, the initial and final setting times of the cement–soil decrease. This study proposes a new method for monitoring the strength of cement-reinforced soils.

Study on Influence of Mechanical Properties of Concrete based on Microbe Supported in Slag

Concrete material with its own excellent properties, plays a vital role in the construction industry, the annual production of about 10 billion tons, which makes concrete become second only to water, the world's second largest amount of material. However, in the actual service process, all kinds of buildings will be affected by their own and environmental factors, concrete is easy to crack, which affects the mechanical properties of concrete decline, this paper in slag as a carrier of microorganisms on the basis of adding nano-SiO2 in ready-mixed concrete, studied its 3d, 7d, 14d, 28d compressive strength changes. The results show that the strength of concrete can be improved by adding the right amount of nano-SiO2. The addition of nano SiO2 can promote the hydration reaction of cement, resulting in more hydration gelling products of concrete, thus reducing the porosity of concrete and improving the compressive strength of concrete. The results of this study provide an important reference value for the practical application of microbial concrete self-healing.