The particle size distribution and surface characteristics of admixtures play a crucial role in enhancing the early strength and reducing the rebound rate of shotcrete. In this study, a slag-based composite powder coated with nano-silica fume was synthesized using silica fume (SF) and ground granulated blast furnace slag (GGBFS) as raw materials. The effects of this composite powder on the rheological and mechanical properties of cement-based materials were systematically investigated. The results demonstrated that when the SF content reached 50%, the composite powder exhibited excellent overall performance. It improved the early compressive strength of cement-based materials by more than 9%, while maintaining stable long-term strength. Compared to the direct incorporation of SF into cement slurry, the initial yield stress of the slurry increased by 32%, while the plastic viscosity decreased by 9.8%. When the slag composite powder content was 8%, the 1-day compressive strength of shotcrete increased from 10.9 MPa to 16.4 MPa, and the rebound rate dropped significantly from 26.1% to 7.3%. These findings provide valuable insights for promoting the large-scale, cost-effective application of novel micro-nano composite admixtures. Additionally, this study offers a sustainable approach for the comprehensive utilization of industrial solid waste in alignment with the “dual carbon” strategy.

With the development of technology, the application of a large number of electronic devices has led to a sudden increase in electromagnetic radiation risks, posing a threat to information security, military security, and ecological security. Building absorbing materials can effectively reduce electromagnetic radiation hazards and are of great significance for the sustainable development of ecological civilization. This article takes cement-based absorbing materials as an example to summarize the current development status and research shortcomings of cement-based absorbing materials from the perspectives of the loss mechanism of electromagnetic waves by absorbing agents (resistance type, dielectric type, magnetic loss type) and the structure of cement matrix (layered, periodic, porous). It also looks forward to the future development direction of such materials, providing reference for the development of ideal absorbers.

Magnesium phosphate cement (MPC) is used in saline soil areas due to its high performance and good erosion resistance, but due to its high brittleness, a large number of microcracks will appear during long-term use of the project, thus affecting the durability and service life of the MPC structure. Basalt fiber (BF) as a new type of fiber was added to MPC to further improve the application effect and tensile properties of MPC in saline soil region. Therefore, freeze-thaw accelerated tests were carried out by adding different volume dosage of BFRMPC in composite salt solution (3% Na₂SO₄+5% NaCl) to reveal the corrosion deterioration mechanism of BFRMPC with the help of XRD, SEM-EDS energy spectroscopy analysis, and low-field nuclear magnetic resonance (NMR) technique of the microfabricated pore structure. The test results show that under the environment of composite salt freezing and thawing coupling, the incorporation of BF can significantly strengthen the corrosion resistance of MPC, and the incorporation of 0.09% by volume of BF makes the most obvious improvement in the strength of MPC and the lowest degree of corrosion. At the same time, the addition of BF attenuates the degradation of the pore space after the erosion of the cement, and the percentage of the gel pores increases by 5.74% and the percentage of the large pores decreases by 26.38% compared with that of the ordinary MPC. The percentage of large pores is reduced by 26.38%.

Rubber particles have good energy absorption and deformation ability. The incorporation of rubber particles into cement base can effectively improve the toughness of the material, and enhance the freezing resistance, cracking resistance, impact resistance and other properties of cement base. However, because rubber particles are a kind of hydrophobic substance, the interface bonding force between rubber and cement slurry is weak, and the strength of cement-based materials is decreased. Therefore, chemical and physical modification of rubber cement-based materials is studied. The results show that the modified rubber can enhance the properties of cement-based materials in two ways. First, the modifier can improve the hydrophilic of rubber by dissolving the impurities on the surface of rubber particles and forming a film on the surface. Second, the modifier reacts with the hydration product to form an effective chemical cross-link, so that the rubber particles form a close connection with the cement slurry. At the same time, it is found that rubber particles and fiber polymers have synergistic effect on the strengthening and toughening of cement-based materials.

The research on high-performance cementitious composites has received much attention. Nanomaterials are excellent in promoting cement hydration, enhancing the densification of cement microstructure, as well as improving the mechanical properties and durability of cementitious materials, which can give the cementitious materials a variety of functionalities and reduce the amount of cement added. In this manuscript, the effects of different dimensions of inorganic nanomaterials on hydration, microstructure, mechanical properties and durability of cementitious materials are systematically sorted out from the mechanistic level of the materials, and the research direction of inorganic nanomaterials modification of cementitious materials in the future is proposed.

Calcined kaolin can effectively improve the mechanical properties of epoxy resin cement-based materials. Experiments show that calcined kaolin can greatly improve the early flexural and compressive strength of epoxy resin cement-based materials, when the kaolin content is 30%, the flexural and compressive strength of modified epoxy resin cement-based materials are increased by 134.28% and 106.25%, respectively. When the kaolin content is less than 30%, the modified epoxy resin cement-based material has secondary flexural strength, and the residual rate of flexural strength is greater than 50%. According to the influence of different kaolin content on compressive strength, flexural strength and secondary flexural strength of modified epoxy resin cementitious materials, a multi-strength combination index ratio optimization method suitable for different stress characteristics of structural engineering was proposed, and the optimal kaolin ratio under different maximum tensile stress and maximum compressive stress combination conditions considering the influence of secondary tensile strength was obtained, which provided a theoretical basis for the preparation of kaolin modified epoxy resin cementitious materials with different stress characteristics in different parts of different structures.

Graphene oxide (GO) has promising applications in improving the microstructure and mechanical properties of cementitious materials due to its excellent properties. However, the enhancement effect of GO is largely dependent on its dispersion in the cement matrix. This paper summarizes the research results of GO in cementitious materials in recent years, focusing on the review of GO dispersion methods, dispersion mechanisms, and the corresponding mechanical property improvement mechanisms, comparing the advantages and disadvantages of different GO dispersion methods, and analyzing the effects on the microstructure and mechanical properties of cementitious materials before and after GO dispersion. The problems of the current research are pointed out, and an outlook on future research trends is provided, aiming to provide a basis for subsequent GO in cementitious materials for stable applications, in order to promote the preparation of highly functionalized GO cementitious composite reinforced materials.

Graphene oxide (GO), as a derivative of graphene (G), has excellent mechanical properties and thermal conductivity similar to graphene, and its hydrophilic functional groups make it easier to disperse in water and combine with cement-based materials. A large number of studies have shown that adding GO into cement matrix can not only enhance the mechanical properties and durability of cement matrix, but also enhance the electromagnetic shielding properties and thermal conductivity of cement matrix, which provides the possibility for the development of multifunctional and intelligent concrete. Focusing on the application of GO mixed with other functional fiber materials in cement-based materials, this paper briefly describes the performance characteristics and structural characteristics of GO, thus indicating the breadth and scope of its application in cement-based materials, emphatically summarizes the research on the dispersion of GO and the working performance, hydration process, mechanical properties, durability and functional properties of GO mixed with fiber cement-based materials, and looks forward to the future research direction of GO mixed with fiber cement-based materials.

This study employs copper mining wastewater (CMw) as mixing water to prepare alkali-activated fly ash/slag (AAFS) cementitious material, aiming to expedite the resourceful utilization of CMw. The influence of varying CMw dosages on the setting time, hydration characteristics, hydration products, pore structure, and compressive strength of AAFS was investigated through this study. The results indicate that the incorporation of CMw in AAFS slightly prolongs its setting process while slightly promoting the hydration process of AAFS. This phenomenon is attributed to the acidity of CMw, residual organic reagents, and metallic ions present. By adding varying amounts of CMw, the gel pores of AAFS continue increasing, while the transitional pores gradually decrease in volume. The compressive strength exhibits a trend of initial enhancement followed by a slight reduction. When the CMw dosage reaches 50%, the compressive strength of AAFS shows the greatest improvement, with increments of 12.23% (3 d), 21.07% (7 d), and 16.74% (28 d), respectively. These research findings offer new insights and references for the resource utilization of copper mining wastewater.

As one of the important internal curing agents for cement-based materials, inorganic/organic composite water absorbing materials, which has hydrophilic groups and three-dimensional network structures, exhibits excellent water absorption, water retention, and water release properties. By introducing inorganic/organic composite water absorbing materials into cement-based materials, their water absorption and release characteristics can automatically adjust the internal relative humidity of cement-based materials, promote hydration reactions, reduce self shrinkage and early cracking of cement-based materials, and thereby improve mechanical properties and durability. The preparation methods, structural characteristics and absorption/desorption behavior of inorganic/organic composite internal curing materials (CICA) were introduced. The impact on the hydration process, microstructure, macroscopic properties and durability of cement-based materials were summarized. The development prospects of CICA in concrete applications were prospected, providing theoretical guidance and technical reference for the application of CICA in cement-based internal curing.

In this study, the mixing mode and content of fly ash and slag were set as variables, and 24 groups of C30 recycled coarse aggregate concrete (RAC) were designed. The compressive strength of RAC was studied. The experimental results show that when adding fly ash or slag independently, the compressive strength of RAC increased firstly and then decreased with the mineral powder content, and the improvement of compressive strength of RAC of slag was significantly better than that of fly ash at the same content. If one of them was kept at 20% when added together, the cubic and axial compressive strength increased firstly with the other mineral powder content and then declined with its increase. Moreover, the compressive strength of RAC was higher when fly ash and slag were added together than independently. The compressive strength of RAC had an obvious size effect. The strength conversion coefficient (η) of cubic and axial compressive strength of RAC increased with the growth of fly ash or slag content when adding independently, while kept stable at 0.85 ± 0.02 when adding together. A modified formula for η of RAC under different conditions of fine mineral admixtures was established, and the verification showed good agreement. Therefore, in actual engineering, the content of fly ash and slag is recommended mixed and its content is suggested within 25%.

In order to improve the shortcomings of airport pavement repair mortar, such as high brittleness and poor bonding performance, a kind of quick mortar was prepared by using waterborne epoxy resin (WER), polypropylene (PP) fiber and sulfoaluminate cement (SAC), and its working performance, mechanical properties, damping properties and sulfate corrosion resistance were studied. The results show that PP fiber and WER can significantly improve the toughness and bonding properties of the quick repair mortar, making the 2 h compressive and folding strength and bonding strength of the quick repair mortar reach 22.3, 5.1 and 3.7 MPa respectively, meeting the requirements of civil airport specifications, and improving the damping performance and sulfate erosion resistance of the quick repair mortar.

In order to study the cementitious material suitable for high concentration waste tailings mortar backfill, the rheological properties of mortar under different fly ash content were tested by the expansion degree test, and the applicability of the test method was analyzed. The results indicate that the correlation between the degree of expansion and the L-tube model test is 0.985, indicating that the degree of expansion can be used as a pre test for L-tube to synergistically characterize the rheological properties of mortar. The yield stress of the mortar mixed with 10% fly ash decreases by 13.06%~24.74%, the strength increases by 40% in 3 days, and 9.9% in 7 days, fully exerting the comprehensive effect of solid waste. As the content of fly ash gradually increases, the ion concentration of the slurry gradually decreases, leading to an increase in the repulsive force between the cementitious particles and more dispersed particles. At the same time, the cumulative amount of 3 d hydration heat release of the slurry with a 10% content of fly ash is 261.696 J/g, which increases by 2.9%, and the porosity decreases by 4.02% by 15.15%. The "rolling ball" characteristic of fly ash to some extent improves its flowability and enhances the strength of the hardened body.

With P.O 42.5 sulphoaluminate cement as the base material, sulphoaluminate high performance cement concrete was prepared by adding S105 slag with different doping amounts to the concrete. The effect of S105 slag doping amount on the lattice structure, microstructure, mechanical properties, frost resistance, and chloride ion diffusion performance of concrete was studied. The results showed that the addition of appropriate S105 slag accelerated the hydration reaction of concrete, increased the uniformity and density of hydration gel, and reduced the occurrence of holes and cracks. With the increase of S105 slag doping amount, the compressive strength, flexural strength, and splitting tensile strength of concrete showed a trend of first increasing and then decreasing. After 28 d of curing, the compressive strength, flexural strength and splitting tensile strength of concrete with a 30wt% content of S105 slag reached their maximum values, which were 47.4,10.4 and 2.59 MPa, respectively. The addition of S105 slag reduced the chloride ion diffusion coefficient of concrete. After 28 d of curing, the minimum chloride ion diffusion coefficient of concrete with a 60wt% content of S105 slag was 1.35×10^-8 cm²/s. The addition of S105 slag improved the frost resistance of concrete. After 90 freeze-thaw cycles, the maximum compressive strength of concrete with a 30wt% content of S105 slag was 35.1 MPa, and the minimum compressive strength attenuation was 25.95%.

In this paper, Ca(OH)₂ was used to replace the raw material MgO in magnesium silicate base cementing material with different mass ratios, and its fluidity, setting time and compressive strength were tested. The influence mechanism was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS), thermogravimetric analysis (TG-DTG) and mercury injection test (MIP). The results show that Ca(OH)₂ can significantly increase the fluidity and compressive strength of magnesium silicate based cementitious materials, and shorten the setting time. The results of XRD, SEM-EDS, TG and MIP showed the reason for the improvement of compressive strength. Ca(OH)₂ reacted with silica fume to form C-S-H gel, and promoted the hydration of MgO, improved the hydration degree of magnesium silicate based cementative material, and significantly reduced its porosity.

Carbon nanotubes are a new type of material with excellent properties, and their incorporation into cementitious materials can improve the microstructure and durability of the material. This paper reviews the research progress on the effect of nucleation, filling and bridging properties of carbon nanotubes on the microstructure and carbonation resistance of cementitious materials, and discusses the mechanism of the effect of the doping amount, dispersion method and length-to-diameter ratio of carbon nanotubes on the carbonation reaction of cementitious materials. The analysis shows that carbon nanotubes promote the hydration of cement by nucleation, increase the hydration product Ca(OH)₂, increase the alkalinity of the matrix and slow down the carbonisation, and optimise the pore structure of the material and the compactness of the interfacial transition zone by combining the filling and bridging effects, inhibit the formation of microcracks and prevent the infiltration of CO₂, thus optimising the microstructure of cement-based materials and enhancing their anti-carbonisation properties. Finally, the problems of the current research are analyzed and the prospects of its research are given.

Highland barley straw ash (HBSA) prepared by calcination and grinding under certain conditions is an active admixture of biomass silicon source, which will affect the mechanical properties of magnesium oxychloride cement (MOC). In order to study the influence of HBSA added into MOC on its mechanical properties, MOC mortar specimens with different HBSA content were tested for flexural and compressive strength under dry and saturated conditions respectively. Strength loss rate and softening coefficient were used to characterize the degree of mechanical property damage of MOC in saturated conditions. The pore structure of MOC mortar specimens was tested and characterized by low field nuclear magnetic resonance technology and gas adsorption method. The results show that MOC with 5% HBSA has the highest flexural and compressive strength in dry and saturated conditions, while MOC with 10% HBSA has the lowest strength loss rate and the highest softening coefficient in saturated conditions. When the content of HBSA is 10%, the proportion of harmful pores and multi harmful pores in the pore structure of MOC is significantly reduced, and the most probable pore diameter is reduced, which optimizes the pore structure of MOC and enhances the mechanical properties in saturated conditions.

In order to improve the low hydration activity and insufficient strength of fly ash concrete, graphene toughened fly ash concrete with excellent mechanical properties and durability was prepared by adding graphene to fly ash concrete. The influence of graphene content on mechanical properties, hydration reaction and wear resistance of fly ash concrete was analyzed. The results showed that the addition of graphene accelerated the hydration reaction, shortens the time of hydration induction period, increased the rate of hydration heat release during the induction period, reduced the time when the rate of hydration heat release reached the peak, increased the amount of hydration products in concrete, and improved the structural compactness of concrete. With the increase of graphene doping, the compressive strength, flexural strength and deflection of concrete increasd first and then decreased. The compressive strength and flexural strength of the concrete with 0.05 wt% of graphene content reached the maximum, which were 44.32 and 5.96 MPa, respectively, which were 12.89% and 10.78% higher than that of pure concrete. The maximum deflection value of 0.05 wt% graphene doped concrete was 7.1 mm, and the deformation resistance was improved. With the increase of graphene doping, the wear amount per unit area of concrete decreased first and then increased slightly, the concrete with 0.05wt% of graphene content had the minimum abrasion loss of 1.13 kg/m², and the abrasion resistance was the best.

Cement matrix intermixed with microcapsules were taken as the research objects. Micromorphology, particle characteristics and repair characteristics were characterized by ESEM, LA and LSM, respectively. The recovery rate of strength was utilized to characterize the ability of secondary repair. The result shows that there are average holes in the wall of the slow-release microcapsules with the characteristics of slow release and multiple release. The surface of ordinary microcapsules with the characteristics of rapid release and rupture release is rough and easy to rupture. The application of hybrid microcapsules to cement-based materials can complement advantages of the two kinds of microcapsules. As a consequence, primary strength recovery rate of cement matrix intermixed with microcapsules was 28.72 % higher than that of single-doped slow-release microcapsules, and the secondary strength recovery rate was 252.34 % higher than that of single-doped ordinary microcapsules. Cement matrix intermixed with self-healing microcapsules has the ability of rapid repair and can achieve secondary repair. The secondary repair was mainly slow-release microcapsules.

Fly ash, slag powder, and metakaolin were used as the main raw materials to prepare the binary alkali-activated cementitious materials, and the compound alkali-activated cementitious materials with different proportions were corroded in 5% (NH₄)₂SO₄ solution for 120 days by different immersion methods. The preparation scheme was optimized by measuring its mechanical properties. Then scanning electron microscopy (SEM) was used to analyze the erosion mechanism of different ratios. Results show that the optimal ratio of fly ash-slag powder (FA-SP) is 2:3, and the strength loss is serious under semi-immersion with a large number of cracks and salt crystal. The optimal ratio of metakaolin-slag powder (MK-SP) is 1:1, which has stable structure, unapparent difference in appearance between the semi-immersed group and the full-immersed group. It has good resistance to sulfate corrosion and less erosive by NH⁺₄.

Calcium carbonate whiskers can effectively improve the compressive properties of cement-based composites at room temperature, but the effect of calcium carbonate whiskers on the compressive properties of cement-based composites after high temperature is not clear. In this paper, the compressive properties of calcium carbonate whisker reinforced cement-based composites with different volume contents (0%, 0.5%, 1%, 2%) were studied at room temperature and 200 , 400 , 600 and 800 ℃ respectively. The test results show that the compressive strength and compressive toughness of the specimens increase first and then decrease with the increase of whisker content at room temperature, and the compressive performance of the material mixed with 1% calcium carbonate whisker is the best. The compressive strength and compressive toughness of the material at 200 ℃ are significantly higher than those at room temperature. When the target temperature exceeds 200 ℃, the high temperature has an obvious deterioration on the compressive performance of the material, and its compressive strength and compressive toughness continue declining. There is no obvious difference in the compressive performance of each group after 800 ℃, but under each target temperature, calcium carbonate whisker can improve the compressive strength and compressive toughness after high temperature. It shows that the addition of calcium carbonate whisker plays a positive role in improving the compressive properties of the material after high temperature.

Under loading and environment, the cracking will easily occur and reduces the durability and strength of the structure concrete. Inspired by the capsule-based self-repairing system, a self-healing system of repairing agent to be encapsulated in the porous lightweight aggregates that are used as carriers was proposed. In the paper, the recent progresses of lightweight aggregates self-repairing cementitious materials are reviewed and the rupture mode of inorganic porous lightweight aggregates and the mechanism of repairing agent to be released are described. The mechanical properties and durability of the cementitious matrix are compared before and after the repairing process and the evaluation methods of crack-repairing degree and repairing efficiency are also discussed. Finally, the key problems and the research direction of lightweight aggregate self-repairing cementitious material are summarized.

Based on orthogonal tests comparing 16 groups of C30 fibre self-compacting recycled concrete, the effects of polyvinyl alcohol fibre (PVA), steel slag stone, fly ash and wrapped slurry recycled aggregate on the mechanical properties of fibre self-compacting recycled concrete were investigated. The results show that fly ash has a significant effect on compressive strength, splitting strength and bending strength, with a maximum increase of 34.4%, 21.6% and 16.9% respectively. PVA has a certain effect on splitting strength, with a maximum increase of 9.1%. Steel slag stone and wrapped slurry recycled aggregate have no significant effect on all three strengths, but steel slag stone has a higher significance on splitting and bending strength than wrapped slurry recycled aggregate, and the opposite for compressive strength. The efficacy coefficient method was used to score the four factors, and the optimum ratio was obtained as 1vol% PVA, 10wt% steel slag stone, 30wt% fly ash and 50wt% wrapped slurry recycled aggregate. The results of other scholars' studies were introduced, and a non-linear regression analysis was carried out on the mechanical test data. The new conversion equation obtained was well correlated and had some reference value. Suggestions are made for the industrial production of the cladding process.

To produce high-strength prefabricated building materials and reduce their CO₂ emissions, a low calcium CO₂ sequestration binder (LC-CSB) is prepared by calcining industrial raw materials limestone and sandstone at 1 275 ℃. The influence of cement-sand ratio (1∶0, 1∶1, 1∶2, 1∶3) on the carbonation degree and the early carbonation hardening performance of LC-CSB mortar is investigated, and the XRD, TG-DTA, FT-IR, SEM, nano-indentation and mercury intrusion porosimeter are used to study the evolution of mineral composition, porosity and micromechanical properties at the interfacial transition zone between carbonated LC-CSB paste and siliceous river sand aggregate. The results show that with the decrease of cement-sand ratio, the carbonation degree of LC-CSB increases significantly. While the compressive strength of the mortar is the highest at the cement-sand ratio of 1∶1, the compressive strength reaches 46.9 MPa after 24 h of carbonation curing. The carbonation-hardening properties of the mortar decrease with the continued decrease of the cement-sand ratio, which might be related to the enrichment of calcium carbonate crystals in the interfacial transition zone.

In order to study the effects of ultrafine fly ash and recycled fine aggregate on the performance of ultra-high performance concrete (UHPC), the compressive strength, tensile strength and microstructure of UHPC studied by workability test, axial tensile strength test, axial compressive strength test and scanning electron microscopy(SEM). The UHPC strength prediction model based on the influence of ultrafine fly ash and recycled fine aggregate established. The results show that the UHPC expands and flows well, the compressive strength decreases and the tensile strength presents an upward trend with the increase of ultrafine fly ash contentThe compressive strength of UHPC could be improved to 115.36 MPa when ultrafine fly ash content is less than 10%. With the increase of recycled fine aggregate content, the working performance of UHPC becomes worsen, but the compressive strength and tensile strength increase gradually. SEM test that fly ash Ca(OH)₂ to produce more C-H-S gel, making the structure more dense internally. Based on the improved theoretical model of compressible stacking, a UHPC strength prediction model of ultrafine fly ash modified reclaimed fine aggregate established.

The emergency repair and maintenance of important infrastructure in cold winter require the use of high early strength repair materials that can quickly set and harden under severe cold and no maintenance conditions. Magnesium phosphate cement (MPC) is often used to prepare rapid repair materials, but its early mechanical properties are significantly reduced in severe cold environment. The influences of highly active magnesia whiskers on the early hydration characteristics, mechanical properties and hydration products of MPC cured at (-20±2)℃ are studied. The results show that magnesia whiskers hydrate rapidly and significantly increase the initial temperature of MPC slurry at (-20±2)℃. The peak temperature rise of MPC with the content of magnesia whiskers of 1% to 3% reaches 60 to 70 ℃, and the 2 h compressive strength and 2 h flexural strength reach 25.4 and 6.6 MPa, respectively. The rapid hydration of magnesia whisker promotes the smooth progress of acid-base reaction of MPC, and the struvite produced by the rapid hydration of magnesia whiskers acts as a crystal seed to induce crystallization, which promotes the early hydration of MPC and the growth of struvite crystal, so that MPC still has high early strength even in severe cold environment.

As a new type of cementitious material system, the low-calcium cementitious material system can react with carbon dioxide to produce stable calcium carbonate and highly polymerized silica gel, which is in line with the current policy guidelines of the cement industry requiring CO₂ emission reduction. In order to better understand the low-calcium cementitious materials system, this paper reviews the carbonation reaction process of low-calcium cementitious materials, analyzes the influence of different factors on the CO₂ uptakes ability of this system, and the related hardening properties of the carbonation hardened pastes, and presents the prospect of the subsequent development of low-calcium cementitious materials.

In this paper, the effects of nano-TiO₂ (NT)/styrene-acrylic emulsion (SAE) composites on strength and impermeability of cement-based materials are studied, and the underlying mechanism is analyzed through their influences on the hydration characteristics and microstructures of hardened cement pastes. Results show that mix SAE and NT could significantly improve the early strength degradation and hydration delay caused by mix SAE alone, reduce the total pore volume, and the amount of harmful and much harm pores, refine the pore structure, and increase the hydration degree of cement clinker and the polymerization degree of C-S-H gels, so as to improve the strength and anti-permeability. Such results have some guiding significance for the composite application of nanoparticle/polymer in cement-based materials.

In view of the problem that the pit repair materials of asphalt pavement are difficult to repair in rainy season or have poor stability and durability after repair, a rapid repair material, waterborne epoxy resin-emulsified asphalt-cement (EAC), with high early strength and high stability is designed by combining waterborne epoxy resin, cement cementitious materials and emulsified asphalt in this study. The influence of waterborne epoxy resin content on mechanical properties and pavement performance of rapid repair material is investigated. Besides, the micro-structures are tested and analyzed by XRD, SEM and IR tests. Results indicate that the addition of waterborne epoxy resin can slightly reduce the 2 h strength of EAC rapid repair material, but can significantly increase its later strength. The high temperature resistance, low temperature resistance and moisture susceptibility are improved as the content of waterborne epoxy resin increasing in a certain range. The microscopic test results show that waterborne epoxy resin can delay the hydration process of cementitious materials and the crystallization of CH. The compactness of EAC rapid repair material can be improved by introducing an appropriate amount of waterborne epoxy resin.

Aftermelting at high temperature and water quenching and quenching, lead-zinc smelting slag will form glass form materials. It has certain activity under alkaline conditions and can be used to produce building material admixtures and cementing materials. Lead-zinc slag ecological cementitious material is successfully prepared by using lead-zinc slag as main raw material with a small amount of bischofite, calcium based solid waste and cement as activator. The mechanical properties and hydration products of cementitious materials are analyzed by electronic universal testing machine and X-ray diffraction (XRD). The mechanical properties of cementitious materials are studied by orthogonal test. The microstructure and morphology of the hydration products are analyzed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry (MIP). The results show that when the content of bischofite is 3 wt%, the total content of solid waste is 70 wt%, the water cement ratio is 0.4, and the content of calcium based solid waste is 16 wt%, the prepared lead-zinc slag ecological cementitious material has the best performance. The 28 d compressive strength of cementitious material reaches 9.73 MPa, and the water cement ratio is the first factor affecting the compressive strength. XRD analysis shows that the cementitious materials are polymerized to form the structure of - Si-O-Si-. SEM analysis shows that the hydration products of cementitious materials present honeycomb structure, which stimulates the potential hydration activity and improves the mechanical properties of the materials. FT-IR analysis shows that the Si-O bond is gradually polymerized into Si-O-Si bond, and the degree of polymerization of silicon oxygen tetrahedron in C-S-H increases. MIP analysis shows that the pore size of cementitious material is small, and the structure of hardened body is dense and the strength is high.

The coal gasification slag is used as fine aggregate to replace natural sand aggregate for preparing cement mortar. The physical and mechanical properties and microstructure development of coal gasification slag cement mortar are researched. The interface reaction mechanism between coal gasification slag and cement paste is analyzed by scanning electron microscope, energy dispersive spectrometer and mercury intrusion porosimeter. The results show that the mechanical strength of coal gasification slag cement mortar is lower than that of natural sand cement mortar before 28 days, but it continues increasing after 28 days and exceeds that of natural sand cement mortar. Additional Ettringite and C-S-H gel generated by the interface reaction of coal gasification slag aggregate under the activation of cement paste, which reduces the porosity of cement mortar and enhances the bonding performance between coal gasification slag aggregate and cement paste in cement mortar, are responsible for the continuous increase in the later mechanical strength of coal gasification slag cement mortar.

Geopolymer is a new green cementitious material,which has many excellent properties in mechanical properties and durability,but also has some shortcomings.It is a feasible way to overcome the disadvantages of geopolymer by using the advantages of nano materials.In this paper,the influence of nano materials blending geopolymer on the workability,mechanical properties and durability of the mixture was systematically described.The influence mechanism was summarized and the existing problems of nano modified geopolymer were discussed.The future modification research may include revealing the influence mechanism,focusing on the compatibility and synergy between nano materials and other components,accurately designing and developing nano core-shell particles suitable for geopolymer reaction system,and quantificationally evaluating the dispersion of nanoparticles in aqueous solution and colloidal environment.Improving the modification efficiency of nano particles provided a reference for the future research on nano modified geopolymer.

X ray diffraction (XRD),Fourier transform infrared analysis (FTIR),scanning electron microscopy (SEM),mercury intrusion test (MIP) and nuclear magnetic resonance (NMR) were used to study the influence mechanism of chloride ion on sulfate ion in alkali activated polymer.The test shows that when the content of sodium sulfate was constant,the unconfined compressive strength of polymer 28d decreased with the increase of sodium chloride content.Chloride could inhibit the formation of ettringite (AFt) in fly ash base polymer,and sodium chloride solution mixed with paste could rapidly generate Friedel salt (FS).With the continuous increase of NaCl,micro cracks increased,pore diameter increased and pore volume increased.The strong peaks in the NMR spectra gradually moved to the right.The structure of the silicon oxide polyhedron network of the fly ash vitreous body was partly increased without decreasing the Q0 of the oligomeric silicon tetrahedron structure,and the Q4 of the tetrahedral structure of the high silicon polysilicon increased.The chloride ion in the fly ash based geopolymer had a certain inhibitory effect on sulfate ion.

According to certain proportion, multilayer graphene/cement composite was prepared. The morphology and structure of multilayer graphene were analyzed by SEM and XPS. The influence of the amount of multilayer graphene on the mechanical properties of the composite was studied by the compressive/flexural strength test. The influence of adding multilayer graphene on the resistance and varistor performance of the composite was discussed by conducting property test and varistor performance test, and the influence of hydration time on the resistance performance of the composite was analyzed. The results showed that the microstructure of multilayered graphene was multilayer stacking, and the ratio of C to O in multilayer graphene was about 4.5. Adding appropriate amount of multilayer graphene could improve the mechanical properties of the composite significantly. Adding multilayer graphene could increase the compressive strength and bending strength of the composite by 30.1% and 11.6% respectively. With the increase of cement hydration time, the electrical resistance of the composite increased, but with the increase of the content of multilayer graphene, the electrical resistance of the composite decreased. When the content of multilayer graphene was less than 1.2 wt%, the content of multilayer graphene had little effect on the electrical resistance of the composite. When the content of multilayer graphene increased from 1.2 wt% to 1.6 wt%, the electrical resistance of the composite decreased significantly with the increase of fraction. When multilayer graphene was added to cement, the changed degree of resistance (R-R₀)/R₀ of the composite would be increased, making it to have pressure-sensitive property. When the amount of multilayer graphene was 1.6 wt%, the pressure-sensitive property of the composite was the best.

The cement-based composite (GNP/CBC) with different GNP content was prepared by ball milling with multilayer graphenenanoflakes (GNP) as reinforcement.The microstructure of the composite was characterized by field emission scanning electron microscopy and X-ray diffraction. The thermoelectric properties of the composite were studied by four probe conductivity meter, differential scanning calorimeter, Fourier infrared spectrometer and Hall effect tester.The results showed that the conductivity of the composites increased with the increase of GNP content. When the GNP content was 20wt% at 70 °C, the highest conductivity was 16.2 S/cm, and the maximum power factor was 1.6μW/(m·K²).The Seebeck coefficient of the composite increased with the increase of temperature. When the GNP content was 15wt%, the maximum Seebeck coefficient of the composite was 34 μV/K, the maximum Hall coefficient was +0.842 cm²/C, and the maximum quality factor was 1.44×10^-3.The cement-based composite (GNP/CBC) could be potentially applied to indoor climate improvement of buildings and mitigation of urban heat island (UHI) effect.

In this paper, two series of quick-setting 3D printing cement-based materials were prepared with fast hard sulphoaluminate cement and ordinary Portland cement as basic cementing materials, supplemented by water reducing agent, coagulant and volume stabilizer, etc., in order to achieve rapid printing. The experimental results show that the prepared quick-setting 3D printing cement-based material could control the setting time within 5-20 min. The printed specimen had good construction performance with the overall deformation less than 5% and the lowest deformation less than 10%. The printed specimen had early and late strength, and the simulated print sample strength loss rate did not exceed 15%, meeting the requirements of architectural 3D printing materials for work performance and mechanical properties.

Graphene oxide(GO) surface contains a large amount of oxygen-containing groups, which is of good hydrophilicity. It is a new type of nano-carbon material that affects the shape and aggregation state of cement hydration products. In this paper, multilayer GO and water were mixed to form GO dispersions by ultrasonic dispersion. The autogenous shrinkage of fresh cement paste with different GO content was tested and its pore structure was characterized by nitrogen adsorption method. The results showed that the incorporation of GO increased the free water in the gel pores and accelerated the hydration rate of the cement. The autogenous shrinkage increased as the GO content increased. It was deduced from the hysteresis effect that GO made the pores inside the cement paste develop into a slit. The pore distribution was analyzed by the BJH method of Kelvin equation to explore the regulation mechanism of GO on autogenous shrinkage. It was found that GO could refine the internal pore diameter. The large capillary pores inside the cement slurry were transformed toward the small capillary pores, which led to an increase in capillary pore pressure, thereby increasing the autogenous shrinkage of the cement-based composite material.

The optimal mix proportion of basalt PVA hybrid fiber cement-based materials was determined, and the durability of basalt PVA hybrid fiber cement-based materials was compared with common C40 concrete under the same conditions. The results showed that the mass loss of basalt PVA hybrid fiber cement-based materials was less than 1.5% after 300 freeze-thaw cycles, while that of ordinary C40 concrete was close to 5% in less than 150 freeze-thaw cycles. The permeability coefficients of 28 and 56 days of hybrid fiber cement-based materials were 53% and 26% of that of ordinary C40 concrete. Hybrid fiber cement-based materials had strong permeability resistance, and the permeability resistance gradually increased with age. When the carbonation time was less than 28 days, the carbonation depth of hybrid fiber cement-based materials was greater than that of ordinary C40 concrete, but when the carbonation time was 56 days, the carbonation depth of hybrid fiber cement-based materials was 90% of that of ordinary C40 concrete. The electric flux of hybrid fiber cement-based materials in 28 and 56 days was 65% and 49% of that of common C40 concrete, respectively. The chloride resistance of hybrid fiber cement-based materials was significantly higher than that of common C40 concrete. The durability indexes of basalt PVA hybrid fiber cement-based materials were better than that of common C40 concrete.

To investigate the effect of calcium carbonate whisker on the mechanical properties of steel/PVA hybrid fiber reinforced high ductility cementitious composites (HyFRHDCC), 2% volume content of cheap calcium carbonate whisker was used to replace the dosage of fibers. The compressive and tensile properties of HyFRHDCC with different fiber content were studied. The microstructure of HyFRHDCC was observed by scanning electron microscope. The results showed that the addition of calcium carbonate whisker could improve the tensile strain and pre-peak compressive toughness of HyFRHDCC. The usage of 2% calcium carbonate whisker in 1.5% PVA + 0.25% steel fiber HyFRHDCC could improve the tensile properties of the specimens. When the dosage of PVA fiber was reduced to 1%, HyFRHDCC exhibited a significant strain softening behavior. Micromorphology analysis found that calcium carbonate whisker could improve the strain hardening behavior of HyFRHDCC through microscopic mechanisms such as crack deflection, whisker pull-out and crack bridging.

The effects of calcium ammonium nitrate on the fluidity, setting time, compressive strength, electrical resistivity, internal temperature, heat of hydration, hydration products and pore structure of calcium sulfoaluminate cement pastes at room temperature and the mechanism of enhancing strength at early age were investigated. The results show that the initial fluidity of cement paste was obviously increased, the setting time was significantly shortened, and the compressive strength was significantly increased at 6 h, 1, 3, 7 and 28 d when the dosage of calcium ammonium nitrate increased from 0 to 5%. The occurring time of the peak was accelerated for the curve of rate of electrical resistivity versus time, and for the curve of internal temperature of cement paste, the internal temperature of cement paste was gradually increased, and the peak time of internal temperature was advanced. When the dosage of calcium ammonium nitrate was below 2%, the exothermic rate of cement hydration obviously accelerated, the accumulated heat at 1 d increased slightly, and the formation rate and content of ettringite increased. The dosage of 2% of calcium ammonium nitrate could significantly reduce the average pore radius, the total pore volume and porosity. Calcium ammonium nitrate could obviously enhance the hydration process and early-age strength of calcium sulfoaluminate cement, so it could be used as accelerating admixture.