Frontier Research on High Performance Concrete and Mechanical Properties

Basalt fiber has excellent quality, and adding appropriate amount of basalt fiber into concrete can enhance the mechanical properties and durability of concrete. Basalt fiber concrete has a broad development and application prospect. This paper summarizes the research progress of basalt fiber concrete in recent years and its application in water conservancy projects, analyzes the reinforcement mechanism of basalt fiber in concrete, and puts forward some suggestions for further research and development of basalt fiber concrete.

The encased concrete in a composite bridge with corrugated steel web (CSW) is a critical structure to improve the stability of the web and relieve the stiffness difference between the composite girder and intermediate crossbeam. This study aims to investigate the effects of the encased concrete on the mechanical behaviors of composite girder bridges with CSWs. The finite element model of a rigid frame bridge is established, the calculation method of the shear force sharing ratio of the encased concrete is proposed, and the effect of the length and thickness of the encased concrete is analyzed. The results show that the encased concrete was under compression in longitudinal direction, while vertical tensile stresses occur near the transition section between pure CSW and the composite web. The encased concrete shares 65–90% of the total shear force, and the shear force sharing ratio increases with the increase of the concrete thickness. Increasing the length of the encased concrete reduces the deflection of the girder and pre-compression stress of the top concrete slab. All the findings of present study may provide reference for the design of composite girder bridges with CSWs.

In this paper, taking an extra-high arch dam as an example, the simulation of the stress, deformation and overload failure of arch dam is carried out to investigate the effect of the shear strength of contraction joints on the safety of the arch dam based on the nonlinear trial load method. The numerical simulation results show that the overload safety factor of the arch dam decreases significantly with the decrease in shear strength of contraction joints. The maximum tensile stress of the arch dam is reduced when the shear strength of the contraction joints is reduced by 30% compared to the strength of the dam material. The results provide a reference for the design of the mechanical properties of the contraction joints.

In order to improve the bearing performances of bored cast-in-place piles in soft soil area, an end-side association post-grouting technology is proposed. Based on one highway bridge project, the composite post grouting and O-cell pile testing method on one cast-in-place concrete piles S1 are performed to study their bearing deformation characteristics and the improving effect of pile tip resistance and pile side frictional resistance. The research shows that pile side grouting has improved the mechanical characteristics of pile-soil interface and the pile tip grouting could strengthen pile end soil. The strengthening effects of pile shaft resistance in silty clay are in the range of 1.49–1.60 and the strengthening effects of pile tip resistance in gravel with clay is 1.71. End-side association post-grouting technology can effectively increase the axial bearing capacity of bored piles in soft soil and reduce the pile top settlement.

Massive slope engineering exists in large water conservancy projects. The artificial and natural rock slopes are high and steep with diverse lithologies, and the stability and safety of high slopes are the guarantee for the overall project to be effective. This paper presents a parameter inversion procedure for rock slopes based on statistical regression models using monitoring data and coupled analysis of seepage and stress. It is applied to the intake slope of a hydropower station in Southwest China. The results show that based on the strength parameters from inversion, the relative error between the measured and calculated displacement of the monitoring points is less than 4.55% under the water level rise and fall inversion conditions, and less than 4.01% under the validation condition, meeting the requirements for engineering applications. The slope stability safety factor meets the requirements specified in the regulations. The inversion procedure proposed in this paper can provide reference for the determination of high slope strength parameters in this project and other projects.

In order to study the influencing factors and variation patterns of the creep performance of prestressed concrete, the creep deformation of concrete specimens caused by long-term constant pressure and the instantaneous elastic deformation at the initial moment of applying this load were measured through experiments. The creep coefficient is mainly related to water reducing agents and additives, and the creep coefficient of concrete with single addition of fly ash at the same age is higher than that of concrete with double addition of fly ash and slag micro powder. Therefore, current research has not revealed the variation pattern of creep in prestressed concrete structures and the mechanism of its impact on prestressed relaxation. The measurement values of concrete creep and elastic modulus provided in this paper can be used as a reference for engineering construction control.

Performance tests were conducted on concrete with different infiltration crystallization dosages. The influence of the dosage of permeable crystallization on the mechanical properties and durability of concrete is analyzed. The results show that infiltration crystallization has a significant improvement effect on the mechanical properties and durability of concrete. When the infiltration crystallization dosage is 1.2%, the increase in compressive strength, tensile strength, and compressive tensile elastic modulus of concrete reaches its maximum. When the infiltration crystallization dosage is 0.6%, the increase in the ultimate tensile strain value of concrete reaches its maximum. When the infiltration crystallization dosage increases within the range of 0–1.2%, the water seepage height and quality loss rate of concrete decrease to varying degrees, and there is a different degree of improvement compared to the dynamic modulus. The research results can provide reference for the mix design and engineering application of permeable crystalline concrete.

In this paper, the effect of CFRP reinforced in different ways on the mechanical properties of WFRC columns is investigated by using numerical simulations. By studying the stress cloud, hysteresis curve, skeleton curve and energy dissipation performance, the development of seismic performance of WFRC columns reinforced by CFRP was investigated. The results show that the damage patterns of CFRP-reinforced specimens are basically the same as those of unreinforced specimens, but the seismic performance is slightly improved.

In order to investigate the sensitivity of influencing factors of rock-socketed piles’ vertical bearing capability. The field static load test of embedded rock piles was performed in the article, and the pile-soil interaction model was built using ABAQUS software. The orthogonal test is properly designed to examine the sensitivity of the influencing elements of embedded rock piles by varying the relevant pile, pile side soil and bedrock parameters. The conclusions are as follows: (A) From large to small, the following factors have varying degrees of influence on the bearing capacity of rock-socketed piles: rock internal friction angle, pile diameter, rock elastic modulus, pile elastic modulus, rock poisson's ratio, soil density, soil thickness, rock-socketed depth, rock friction coefficient, rock cohesion, pile density, soil poisson's ratio, soil friction coefficient, soil elastic modulus, rock density, soil cohesion, pile poisson's ratio and soil internal friction angle; (B) Rock internal friction angle, pile diameter, rock elastic modulus, pile elastic modulus, rock poisson's ratio, soil density, soil thickness, and depth of the rock-socketed piles all have a greatly significant impact on the vertical bearing capacity of these piles. The bearing capacity of rock-socketed piles is significantly impacted by the rock friction coefficient and rock cohesiveness. The research results can provide a basis for the design of rock-socketed piles and the prediction of bearing capacity of rock-socketed piles.

The concrete with different fibre and ratio can lead to different performance. This paper studies the mechanical properties of concrete by changing the ratio of PVA fibre and steel fibre. Three kinds of ratio of the PVA fibre and steel fibre are studied. They are 0% PVA fibre and 0% steel fibre, 0.25% PVA fibre and 0.75% steel fibre, 0.5% PVA fibre and 0.5% steel fibre. The compressive strength, flexural strength, bending toughness are tested. The test result shows that the compressive strength of the P0.25S0.75 increases. While the group of P0.5S0.5 shows a little range of decreasing. The 28d flexural strength of P0.25S0.75 and P0.5S0.5 increases 2.3 and 30.2% respectively. The loading-deflection curves of P0.25S0.75 and P0.5S0.5 all appear strain harden property. By the mixing amount of the PVA fibre increasing, the cracking strength and limitation bearing ability can all be enhanced. The areas under the curve enlarge and the toughness of the concrete are enhanced. The bending toughness of P0.5S0.5 is much better than the P0.25S0.75 but the difference is not very large.

Through reading and integrating a large amount of literature, this paper innovatively proposed a new method of making transparent concrete. On this basis, we added fly ash and slag powder to replace cement according to different volume ratios, and developed four new types of green self-compacting transparent concrete with different mix ratios. By testing the compressive strength, tensile strength, elastic modulus and thermal conductivity of these concrete, found that according to (20%, 20%) added fly ash and slag powder cement instead of new green self-dense light transparent concrete in all aspects of the best performance, test results show that the 28 days compressive strength of 36.2 Mpa, 28 days of tensile strength 4 Mpa, 28 days of elastic modulus of 27.1 Gpa. This new type of green self-dense transparent concrete not only has high compressive strength, tensile strength and elastic modulus, but also has excellent transparent thermal conductivity. The experimental results show that the average illumination of four self-dense transparent concrete of 25W bulb is 152XL, and the average illumination of 40W bulb is 246XL and the average temperature is 32.125 ℃. In addition, the photothermal conductivity of the four different mix ratios showed good consistency, indicating that the addition of fly ash and slag powder has no negative impact on the light transmittance of the transparent concrete. This new type of transparent concrete not only has high mechanical properties, but also has good transparent thermal conductivity, which has wide application prospects and provides reference for subsequent research and application.

Pipe cooling is an important measure for controlling the temperature in mass concrete structures, so it is one of the key problems to specifically simulate the effect of the cooling pipes in temperature field analysis. Because the size of cooling pipe is quite small from that of mass concrete structure, its exact simulation is the focus of simulation calculation. In this paper, a new method called SEM (superposed element method) is proposed to analyze the temperature field of mass concrete with cooling pipes in it. First, the structure is divided into two independent meshes. One is the global mesh without cooling pipes, and the other is the local mesh of the cooling pipes together with its adjacent region. Then the elements within the local mesh is treated based on FEM, and the two independent meshes are coupled together through the coupling surface by the coordination of heat conduction. Finally, using the SEM proposed in this paper, the numerical model with a single pipe was analyzed and the calculation precision was validated. The convenient process of grid discretization and good performance in both precision and efficiency show the feasibility of the new method in engineering application.

The exploitation and utilization of river sand along the SGR Phase II A Project in Kenya was rare. This work aims to explore the effect of the machine-made sand rate on the compressive strength, workability, and impermeability of sleeper concrete. The research demonstrated that the 28d compressive strength (46.30 MPa) of sleeper concrete (KD-45) were the optimal when the machine-made sand rate in the sleeper concrete was 45%. These results indicated that the compactness of the KD-45 was improved, leading to an increase in compressive strength. The slump (175 mm) and extensibility (455 mm) of the sleeper concrete KD-45 were the highest as the machine-made sand rate was 45% in the sleeper concrete. This result proved that the workability and flowability of KD-45 pre mixed sleeper concrete were excellent. The electrical flux (840 °C) of KD-45 was lowest when the machine-made sand rate in the sleeper concrete was 45%. This phenomenon demonstrated that the ability of sleeper concrete KD-45 to resist chloride ion penetration was higher compared to other sleeper concrete. These properties meet the requirements of C40 sleeper concrete. Therefore, this work presents novel insight on the performance improvement of sleeper concrete based on the machine-made sand rate.

Metal connectors are important load-bearing components in precast concrete insulated sandwich wall panels, and their tensile capacity need to be determined through testing. Due to the variety of connector styles and different anchoring structures, this article focuses on the commonly used single-pull and double-pull test methods, using typical specifications of pin connectors and flat connectors for tensile testing, and considering the influence of different constraints on the single-pull test method. By comparing the failure modes, tensile strains and tensile capacity of the connectors, the study shows that using the double-pull test method to test metal connectors results in more stable and safer test results, and it is recommended to prioritize this method.

To systematically investigate the durability performance of coal gangue pervious concrete (CGPC) under acid rain environment, various factors are taken into account, including designed porosity, acid rain pH value, and erosion time. These factors affect the mass, compressive strength, and permeability coefficient of CGPC. Moreover, the research delves into the erosion mechanism of acid rain. The results indicate that the compressive strength of CGPC shows an initial increase followed by a subsequent decrease under acid rain environment. The permeability coefficient slightly decreases in the early stage of acid rain erosion, followed by an increase in the later stage. In the acid rain, the reaction between $${\text{SO}}_{{4}}^{{2 - }}$$ SO 4 2 - and Ca2+ generates expansive products such as gypsum. Initially, these products fill the pores, increasing the structural density. However, as erosion progresses, the continuous accumulation of gypsum leads to the formation of expansive microcracks, resulting in a reduction in strength.

Cement concrete is widely used in various levels of highways, and it is prone to diseases such as cracking, potholes, and local collapse during operation. The maintenance and repair of existing cement concrete has become an important task in the daily operation and maintenance of roads and bridges. However, traditional cement-based repair materials have problems such as long maintenance periods and low bonding strength with existing concrete. In view of this, this article proposes an early strength and high ductility cement composite material, aiming to achieve good curing age, compressive performance, and relatively low price. The compressive performance tests of a new type of composite material were conducted to study the effects of PVA fiber content, fly ash (FA) content, and sand cement ratio on the axial compression performance. The results show that the FA content is 50wt.% When the PVA fiber content is around 2% and the sand cement ratio is 0.36, the compressive performance of early strength and high ductility cement composite materials at different ages is better. Under optimal mix ratio conditions, the axial compressive strength of early strength and high ductility cement-based composite materials at 2 h, 1 day, 3 days, and 28 days reaches 18.1, 27.5, 34.4, and 37.6 MPa; The peak strain at each age is greater than 0.5%.

The Hong Kong–Zhuhai–Macau Bridge immersed tube tunnel project is the only deep buried and large siltation immersed tube tunnel in the world. There is no similar case in the world. Its stress deformation characteristics are different from those of conventional shallow buried tunnels. According to the traditional design method of immersed tubes, there will be a series of problems. To address these issues, a semi rigid pipe joint scheme between rigid and flexible pipe joints has been proposed. By comparing the forces acting on the joints with traditional types of pipe joints, the mechanical mechanism of semi rigid immersed pipe structures has been revealed. Compared with flexible immersed pipe structural systems, it improves the load-bearing capacity and water tightness of the segment joints, reduces the internal force of the immersed pipe structure, reduces the risk of concrete cracking, and solves the technical problems of deep buried large sedimentation immersed pipe structures. This can provide reference for similar projects.

In order to study the shear performance of single spigot shear connectors when applied in practical engineering, the shear performance research is carried out with the engineering background of a waveform steel web steel-mixed girder bridge under construction in a certain area, using the finite element modeling method to establish a local model in the connecting part of the steel box girder and the concrete plate, and combining with the practical engineering to carry out the simulation launching test of the spigot connectors and comparing the results of the load displacement curve with the classical theoretical curve, the results match well and verify the modeling correctness. The results of load displacement curve are compared with the classical theoretical curve, and the results are in good agreement, which verifies the correctness of modeling. On this basis, the influence of steel strength and concrete strength on the shear performance of the peg is investigated, and it is found that the shear capacity increases with the increase of peg strength and concrete strength, and the peg strength has a greater influence on the shear capacity than the concrete strength.

The surrounding rock of large underground engineering projects is often composed of hard rock, and defects such as mineral particles and micro-cracks in the hard rock, significantly affect the mechanical properties of the rock. To investigate the influence of micro-crack distribution on the mechanical behavior, damage evolution, and fracture mechanism of rock, a numerical simulation model of basalt with single crack was established using the particle flow code PFC2D, based on the widely distributed cryptocrystalline basalt in the Baihetan Hydropower Station. In this study, the laws of crack initiation, propagation, and connection in the basalt under loading were deeply studied; the influence of different crack angles on the deformation and strength of the rock mass was discussed; the evolution characteristics and fracture mechanism of the whole process of the basalt under different confining pressures were revealed. The results of this study are significant for further studies into the mechanical properties characterizing fissured rock masses, as well as providing guiding principles for the design of cavern support.

The phenomenon of concrete cracking is a major problem plaguing the engineering community, and one of the major factors causing cracking is temperature loading, while thin-walled concrete, such as hydraulic tunnel lining and other similar projects, makes the impact of this phenomenon more prominent due to its special structure and role. To address this problem based on the concrete temperature field theory, combined with the three-dimensional finite unit method of temperature control methods in engineering analysis and research, it is concluded that surface water conservation and water cooling can effectively reduce the base temperature difference to reduce the temperature stress; early low temperature water flow may cause excessive temperature gradients, resulting in large temperature stress; surface insulation layer can be applied to effectively mitigate the rate of temperature drop and environmental temperature changes on the concrete.

The artificial cemented granular particles were prepared to simulate the rockfills, and conventional triaxial drainage tests were conducted to explore the mechanical properties of granular materials under different confining pressures. Furthermore, the results were simulated based on the discrete element method. Test results from the laboratory tests indicated the nonlinearity of this materials’ strength envelope. The particle flow method could be used to simulate the stress–strain and volumetric deformation properties of artificially prepared granular materials. By the simulation, the number of failure bonds and the variation of the displacement field during the test process were recorded, visually displaying the microscopic displacement and fragmentation of the internal particles.

Concrete is a typical heterogeneous and multiscale material, and the macro-mechanical response is affected by the meso-scale geometric structure and mechanical parameters. Based on the continuum-discontinuum element method, this study conducts the numerical simulation and quantitively studies the change trend of macro-mechanical response with the different mesoscopic heterogeneity. First, a full-time numerical simulation is conducted, and the elastic modulus and cohesive strength at the meso-scale are assumed to obey the Weibull distribution. Then, the change trend of macro-mechanical parameters is studied. Finally, the change trend of crack evolution characteristic is studied. The results show that the macro-elastic modulus and macro-peak stress gradually increase with the increase of shape parameter k, and the growth rate of macro-mechanical parameters gradually decays. The difference in the shape parameter k causes the value of crack ratio to change, while the change trend of crack ratio-strain curve is similar. As the shape parameter k increases, the final value of crack ratio first decreases and then increases, and the final value of crack ratio when k = 15 is the smallest.

Aiming at the problem of weakening mechanical properties of conventional concrete due to damage, the present paper studies the effect of nano-active powder on the splitting strength of concrete before and after damage. The nano-active powder concrete was prepared by adding 1.5%, 2.0% and 2.5% nano-silica (NS) and nano-zirconia (NZ) respectively. Through the splitting test before and after the damage of the sample, the self-healing performance of the sample was studied with the recovery rate of the splitting strength as the index. The results show that nano-active powders NS and NZ can increase the splitting strength and its recovery rate. Compared with the control group concrete, the addition of nano-active powder effectively improved the recovery rate of concrete splitting strength, and the optimal content of nano-active powders NS and NZ are 1.5% and 2.0%, respectively. This study deepens the understanding of mechanical properties of nano-concrete.

With the acceleration of urbanization, the output of construction sludge and waste mud is increasing. Its transportation cost is high and there are potential safety hazards. Therefore, it is necessary to seek effective disposal and utilization methods. Aiming at the silt soil with high water content, the developed YB100 powder curing agent was used to improve the properties of silt soil, and the effects of dynamic properties and water stability of the cured soil were studied by curing agent dosing, surrounding pressure, and dynamic stress ratio. The microstructure of the cured soil was analyzed by SEM scanning electron microscopy to reveal the curing mechanism. The results showed that: the dynamic elastic modulus of the cured soil specimens increased from about 60 MPa to about 150 MPa when the amount of curing agent was increased by 0, 2, 4 and 6%; with the increase of curing agent content, the damping ratio changed less during vibration and the curve was flatter; after 24 h of water immersion, the dynamic elastic modulus of the specimens decreased by about 15–20% and the damping ratio had some growth, and with the dynamic stress ratio. With the growth of dynamic stress ratio, the weakening of dynamic elastic modulus of the specimen is not obvious, and the change of damping ratio weakly decreases less; SEM photos show that the cured soil particles are agglomerated, and the pore space is greatly reduced, because the curing agent produces hydration reaction with water in the silt soil, and the resulting gelling material improves the strength of the soil, and at the same time the complexes generated by the reaction with the soil strengthen the stability of the soil.

A new method to obtain the distribution of rock stone in RSM subgrade by high density resistivity surveys is proposed. Using image processing technology, the true resistivity image could be transformed to a vector format which can imported into finite element software. The finite models of RSM subgrade are established based on the vector image. The RSM subgrade bearing capacity and differential settlement under foundation’s load are analyzed. Numerical analysis result shows that the bearing capacity of RSM subgrade is bigger than the soil subgrade. The differential settlement is effected mainly by subgrade stiffness under two corners of the foundation and the location of the interface of rock and soil.

At present, the engineering properties of unsaturated soil have been studied intensively in the soil mechanics community. The shear strength of unsaturated soil is particularly important for the engineering properties of soil. In this study, GDS unsaturated back pressure shear apparatus (UBPS) is employed to control the matrix suction to 50 kPa to conduct the direct shear test of consolidation and drainage on the unsaturated soil and the unsaturated fiber soil. Through the analysis of the test data, the fiber material is found to be able to improve the shear strength of unsaturated soil when controlling the matrix suction, but the improvement effect is not as good as in the case without considering the matrix suction. It can be concluded that the matrix suction is an important factor that must be taken into account in soil improvement engineering since most soils are unsaturated under natural condition.

In geothermal energy development, high-temperature rock mass will go through the process of water cooling. It is of great significance to study the physical and mechanical characteristics and microstructure of high-temperature rock after water cooling for the long-term stability analysis of underground engineering. Based on this, the surface characteristics, mass, and volume variation of sandstone cooled by water at high temperatures (100, 200, 400, 600, 800, and 1000 °C) were investigated. Using the Rock Top multifield coupling tester, a series of axial compressions and longitudinal wave velocity tests of the sandstone after a high temperature-water cooling treatment are performed. The microstructure characteristic obtained by X-ray diffraction and scanning electron microscope was studied, and the effect of high temperature-water cooling behavior on the mechanical properties of sandstone was investigated. The results show that: (1) The mass loss rate, volume expansion rate and peak strain of sandstone increase with increasing temperature, while peak strength decreases gradually. When the temperature exceeds 400 °C, the physical and mechanical parameters of sandstone change markedly. (2) When the temperature is less than 400 °C, corresponds to the compressive and line-elastic phases, the stable crack propagation phase, the rapid crack propagation phase and the destructive phase during the failure process of sandstone, the wave velocity of sandstone are steadily increasing, oscillating, and sharply decreasing, respectively. While the temperature is below 1000 °C, the wave velocity of sandstone is oscillation increases, slows down and drops sharply, respectively. (3) When the temperature is below 400 °C, the mineral content of sandstone varies less. While the temperature exceeds 400 °C, there is an overall increasing trend in the sodium feldspar content of sandstone. (4) The increase in temperature promotes the development of pore fractures within the sandstone, especially at higher temperature states where microcracks expand along the intergranular to form microcrack networks, leading to an increase in the scale and number of defects such as fractures within the sandstone.

Engineering practice indicates that the use of bentonite support fluid in borehole may significantly reduce the pile bearing capacity. To estimate the reduction quantitively, the static load test in field was performed on two kinds of piles with and without bentonite fluid, i.e., the slurry displacement (SD) pile and continuous flight auger (CFA) pile. Test site was selected in Huangpu District of Guangdong, and two CFA piles and one SD pile were installed. Sensing technology of ultra-weak fiber Bragg grating was applied to measure the soil-pile interface behavior, with a series of sensors attached to the longitudinal steel bar. Evolution of shaft resistance with the static load was thereby captured. Test results show that the bentonite support fluid reduces the shaft resistance by 52 and 61% in granitic residual soil and completely decomposed granite soil, respectively. Field excavation suggests that the reduction is attributed to the existence of residual bentonite layer between the pile concrete and soil, instead of the filter cake formed by bentonite filtration.

The layer bonding performance is very vital for the utilization of hydraulic engineered cementitious composites (HECC). The layer bonding performance involves the interlayer performance of HECC and HECC, and the layer performance of HECC and normal mortar (NM). The bonding strength of the untreated layer is very low, only half of that of the whole specimen without layer. Based on the fact, this article proposes three different improvement measures to improve the bonding performance of the layers: pickling surface, using interface agents, and using high-speed stirring devices to stir layer. The layer bonding performance is tested by the layer flexural strength. The test results show that: muriatic acid and acetic acid pickling can improve the interlayer bonding performance by 10% to 30%, while citric acid will reduce it by more than 90%; different interface agents have different improvement effects, among which The epoxy resin mortar interface agent has the most obvious improvement effect, reaching 44.9%; high-speed stirring of the layer eliminates the layer in a certain sense, improving the layer bonding performance by 349%, and has the most obvious effect among all methods.

Soil erosion is one of the most serious problems that threaten the safety of embankments and earth-rock dams. When water flows through the base soil, fine particles subjected to hydrodynamic action will be washed away, which will lead to internal erosion of the embankment project. The inverted filter structure is one of the effective methods to eliminate or reduce the risk of infiltration and erosion, with a history of nearly a century of engineering practice. This article is based on the three-dimensional LBM-DEM fluid solid coupling simulation method. By setting different particle size ratios and hydraulic gradients in the filter medium, the particle contact erosion and subsequent migration and transportation of fine particles in the filter layer structure were comprehensively reproduced, verifying the effectiveness of traditional empirical formulas. This study demonstrates the effectiveness and feasibility of the three-dimensional LBM-DEM coupling method in practical engineering applications from a microscopic view, laying the foundation for the next large-scale simulation of embankment filter layers and the revelation of microscopic mechanisms.

Luminescent concrete is based on ordinary concrete, in which zinc sulfide luminescent material is added to make ordinary concrete with luminescent function of concrete, and its mechanical properties are greatly affected by the dosage of luminescent powder and mineral admixture. In order to study the mechanical properties and optical properties of luminescent concrete, luminescent concrete composite adding different dosages of fly ash and slag powder compressive test and flexural test, obtained different fly ash and slag powder dosage of luminescent concrete compressive strength and flexural strength with the curing time of the change curve and based on this proposed luminescent concrete compressive strength and flexural strength of the correction coefficient, for the subsequent light-emitting concrete. The research and engineering application of luminous concrete provides theoretical basis.

In order to obtain epoxy concrete that can adapt to different strengths and different environmental conditions, this paper innovatively constructed a new type of accurate epoxy concrete mix calculation logic and calculation method through literature investigation, analysis, and test, which can make the process of calculating epoxy concrete mix ratio more concise and precise. In this paper, a new type of epoxy concrete mix with a strength class of C30 is designed, which can provide a reference for engineers and technicians to design accurate epoxy concrete mix better. It also provides some reference value for improving the mix ratio design method and engineering application of epoxy resin concrete.

This paper investigates the cracking prevention and control of concrete engineering in ultra-high altitude areas. Combined with the hydration-temperature-humidity-constraint coupling model, the cracking risk assessment of bridge piers under extreme environment was carried out. The effect of deformation compensation crack control in concrete cracking risk control was revealed. Finally, the concrete cracking risk was assessed after long-term temperature changes. The results show that wind speed, air temperature, light, humidity and freeze–thaw greatly affect the cracking control of concrete. The cracking risk in the surface layer of the bridge piers is maximum around 2–4 days. The maximum cracking risk coefficient is between 0.6  and  0.95. And the risk of core cracking increases progressively after 14 days. When the HME-V® crack-resistant product is added, the unit expansion deformation of concrete increases during the temperature rise phase. Furthermore, the unit volume shrinkage is decreased during the temperature drop phase. A significant deformation compensation is produced. The risk of early and long-term cracking in the core and surface layers of the concrete structure is significantly reduced. The effect of crack control is remarkable. In summary, pre-cracking control in the surface layer of bridge piers is crucial. The risk of long-term cracking in the core is significantly higher than that in the early stage, and long-term cracking control should also be emphasized.

In order to improve the strength and permeability of coal gangue pervious concrete, an optimized mix design was conducted. An orthogonal experiment was employed to study the variations of compressive strength and permeability coefficient of coal gangue pervious concrete under the influence of aggregate particle size, water-cement ratio, designed porosity, and dosage of permeable admixture. After obtaining a relatively optimal mix proportion, further discussions were carried out by restricting the values of compressive strength and permeability coefficient to determine the appropriate range for the excess paste content ratio, total porosity, and effective porosity, resulting in the determination of the optimal mix design. Results indicated that the compressive strength reached its maximum at an aggregate particle size of 9.5–16 mm, with minimal impact on the permeability coefficient. As the water-cement ratio increased, the compressive strength gradually increased, while the permeability coefficient slightly decreased within the range of 0.25–0.29, and decreased by 60% within the range of 0.29–0.31. With the increase of designed porosity, the compressive strength gradually decreased, while the permeability performance gradually enhanced.

Cement concrete is widely used in pavement, bridge decks and expansion joint anchorage zones. It is prone to cracking, potholes, spalling and other diseases during use. Cement-based repair materials generally have problems such as a long curing period, low bonding strength with existing concrete, and insufficient mechanical properties. Given this, this paper proposes an early-strength high-ductility cement composite material with the goal of short curing age, excellent tensile mechanical properties and relatively low price. The tensile mechanical properties of the composite material at different ages were tested, and the tensile constitutive model of the composite material was proposed. The results show that when the fly ash content is about 50 wt.%, the PVA fiber content is about 2%, and the sand-binder ratio is 0.36–0.50, the tensile properties of the early strength high ductility cement composite material at each age are better. Under the condition of optimum mix ratio, the tensile strength of 1, 3 and 28 d of early strength high ductility cement-based composites reached 4.58 MPa, 4.67 MPa and 4.64 MPa respectively, and the strain corresponding to 0.8 times of peak stress in softening section could reach 2%.

In order to develop a synchronous grouting material with good comprehensive performance, this paper selected cement, fly ash, mineral powder and slag by orthogonal experimental design method to carry out the proportioning test research, which provided the most suitable slurry proportion for engineering construction. The effects of group proportioning on fluidity, compressive and flexural strength, impermeability and volumetric stability were investigated. The results show that the increase of mineral powder content improves the fluidity performance of the system; the slurry nodules with high cement dosage have higher mechanical properties and impermeability; the secondary hydration of fly ash plays a slower role, so it reduces the early strength of the material and increases the late strength; the slag reduces the impermeability and drying shrinkage of the nodules. The research focuses on the characteristics of synchronous grouting in a subway station construction project in Qingdao. It investigates the mechanical and engineering properties of a new type of material and applies it to the field of engineering control. To some extent, this material can replace cement and effectively prevent tunnel water leakage, reduce operation and maintenance costs, and extend the operation and maintenance cycle, showing significant potential for widespread application.

Aiming at the characteristics of structural backfill engineering, combined with the backfill performance requirements of subway stations, and taking backfill material fluidity, crystalline body strength, seepage resistance and volumetric stability as the main assessment indexes, a self-compacting and high seepage-resistant backfill material has been researched and prepared by taking the bulk solid waste cinder slag and fly ash as the main raw materials, blast furnace slag powder as the dope, and cement as the curing component. Compared with traditional backfill, the material has self-leveling characteristics and good backfill uniformity. The 28-day compressive strength of the material can reach 10.2–21.3 MPa, which exceeds that of C10 concrete. The material has good seepage resistance, seepage pressure up to 0.7–0.8 MPa, good volume stability, 28 d shrinkage rate of 10–4 orders of magnitude. The research results were applied in the backfilling project of Xintun Station of Qingdao Metro Line 6, which showed excellent mobility, greatly saving construction cost and time, and the test results met the project requirements. This study takes into account the requirements of material performance and the proportion of solid waste mixing, and under the premise of meeting the engineering requirements of backfill materials, it can effectively absorb fly ash, slag and other bulk solid waste, and has achieved good economic and environmental benefits.

BFRPs has the advantages of light weight, corrosion resistance and good durability compared with steels, which is expected to solve the above problems when applied to shield tunnelling segments. In this study, the preparation process of basalt fiber-reinforced polymer (BFRP) bar reinforced shield tunnelling segment (BSTS) is described in detail against the background of shield tunnelling segment actually used in engineering. In order to investigate the blast resistance performance of the BSTS under blast loading, the test process is simulated using LS-DYNA finite element analysis software. The results show that the main damage modes of BSTS under proximity blast loading can be categorized as cratering, cracking, spalling and rupture. With the decreasing Scaled distance, the top surface blast crater is expanding, and the concrete on the back surface is further spalling, showing more obvious local damage characteristics. Provide reference for the design of shield tunnel lining structure's anti-explosion performance.

This study investigated the loading mechanism of SPFRC shear walls by conducting low-cycle repeated loading tests on two steel-polypropylene hybrid fiber reinforced concrete (SPFRC) shear walls and one reinforced concrete (RC) shear wall. Furthermore, this study analyzed the impact of fiber content and axial compression ratio on the failure mode, shear carrying capacity, ductility, and energy dissipation capacity of the shear walls. The test results show that hybrid fibers effectively restrain the development of cracks in shear walls, and improve the shear carrying capacity, deformation capacity, and energy dissipation capacity of the shear walls. Considering the contributions of hybrid fibers, horizontal and vertical distributed steel reinforcement, concrete diagonal struts, and concealed columns to shear carrying capacity, a calculation formula for the shear carrying capacity of SPFRC shear walls has been established based on the truss-diagonal brace mechanism. This formula has been validated using data from this study and relevant domestic literature. The average ratio of measured shear carrying capacity to calculated values is 1.01, with a standard deviation of 0.17, indicating a good agreement between them.

The dynamic response of concrete components under blast loading is of great military and social importance. Based on the continuum-discontinuum element method and fluid–structure coupling algorithm, the dynamic response of concrete slab is simulated and analyzed. First, a full-time numerical simulation is conducted. Then, the displacement and crack characteristics of concrete slab are analyzed quantitatively. The result indicates that the displacement is distributed in a circular pattern, and the maximum value is located at the center of concrete slab. The crack ratio increases gradually with the growth of time, while the growth rate is not a constant value. The fracture type of concrete slab includes tensile fracture and shear fracture, the interface at the center mainly undergoes shear fracture, and a small number of interface on the outside of cracked region suffers tensile fracture.

Columns are the main load-bearing elements in many structures, but with the advancement of service time, damage to reinforced concrete columns before reaching their design service life occurs from time to time. In this experiment, the cumulative damage of reinforced concrete short columns is investigated by using the research method of proposed static structural test. Through the low-week fatigue proposed static test of reinforced concrete short columns, the changes in the process are analyzed, and the changes in physical quantities such as cracks, strains, and deflections are recorded to study the shear damage characteristics of fatigue of reinforced concrete short columns, the damage mechanism, and the mechanical properties of the members such as the load carrying capacity after the damage.

In order to improve the energy dissipation effect of the connection components of steel truss joints and optimize the arrangement of the components, a new replaceable component railway pier structure was proposed, referring to the transmission tower structure. The new pier consists of four pier columns and the steel truss connection system between the columns. Based on the OpenSees platform, a dynamic analysis model of the new railway pier was established. 56 seismic records were input, and incremental dynamic analysis (IDA) was carried out to investigate the damage evolution law of the connection components and the influence of component yielding on the stress of the rebar in the middle and bottom of the pier. The results show that the steel truss connection system yields in a row and consumes energy in a graded manner. The yielding order of the second and third rows of the steel truss connection system is always in the forefront. The second and third rows are the main energy-consuming rows, followed by the fourth, fifth, and sixth rows, and finally the seventh, eighth, and first rows, with the first and eighth rows being less likely to yield. The outer chord members in each row yield first, followed by the inner chord members, and the vertical and diagonal members are less likely to yield. The yielding of the pier columns occurs after the yielding of the chord members of the steel truss. The yielding of the outer chord members in the steel truss connection system has a certain inhibitory effect on the stress increase of the rebar in the pier columns and at the bottom of the pier, and the inhibitory effect on the bottom of the pier is better than that in the middle.

In our country, there are 60 billion square meters of existing leasable area, reactive powder concrete (RPC) has the characteristics of high toughness and high strength-to-weight ratio. RPC strengthened concrete (RC) forms RPC-RC structure, it is an important way for sustainable development of civil engineering to improve the anti-explosion ability of building structure while strengthening and reforming the structure. The dynamic response and damage assessment methods of RPC-RC columns subjected to blast loading are not clear. In order to solve this problem, the dynamic response of RPC-RC column under blast loading is simulated by using LS-DYNA finite element software, the Pressure-Impulse curve of RPC-RC column is established by using simplified numerical method, and the parameters of Pressrue-Impulse curve are analyzed. Finally, based on the results of parameter analysis, the formulas for calculating the overpressure asymptote and impulse asymptote are obtained, and the damage assessment method for RPC-RC columns is established.