Journal of Materials in Civil Engineering

Steel fiber is the most widely used type of fiber in concrete because of its advanced and economical manufacturing facilities, reinforcing effect, and ability to cope with changing environmental conditions. The use of steel fiber in concrete can reduce the amount of reinforcement used and increase the crack resistance of concrete, which extends the service life of concrete structures, reduces the frequency of maintenance and repairs, and consequently lowers energy consumption and emissions. Many studies focus on the postcracking behavior of steel fiber–reinforced concrete (SFRC). However, it is also crucial to examine the precracking behavior of SFRC at early age. A temperature stress test machine (TSTM) was used to investigate the autogenous shrinkage (AS), tensile creep (TC), and cracking behavior of hooked-end SFRC (HSFRC) at early age under uniaxial constant restrained condition. Analysis and experimental findings demonstrated that (1) the addition of steel fiber increased the splitting tensile strength and modulus of elasticity of HSFRC. The 1-, 3-, and 7-day splitting tensile strength and modulus of elasticity increased with an increase in curing temperature. However, a decrease was observed at 28 days as the curing temperature increased; (2) increasing steel fiber content had a significant influence on reducing TC and AS of HSFRC. TC and AS of HSFRC increased with increasing curing temperature; and (3) early-age cracking potential of HSFRC decreased as steel fiber content increased. Increased curing temperature resulted in a concomitant elevation in the potential for early-age cracking in HSFRC.

Wax warm additives are widely used in asphalt mixture production due to their energy savings and low cost. However, the compatibility problem between waxes and asphalt binders leads to wax precipitation and asphalt low-temperature cracking. Plasma treatment technology can modify the surface of waxes. In this study, plasma technology was used to modify Fischer Tropsch (FT) wax surfaces, linear aliphatic hydrocarbon wax, and two plastic cracking waxes. The effects of waxes on the high-temperature performance, fatigue performance, low-temperature physical hardening, and wax precipitation temperature of asphalt binders were evaluated by the multistress creep recovery (MSCR) test, linear amplitude sweep (LAS) test, extended bending beam rheometer (ExBBR) test, and dynamic shear rheometer (DSR) viscosity test. In addition, the effect of plasma treatment on waxes in terms of low-temperature physical hardening and wax precipitation temperature was explored. The results showed that the effect of waxes on the high-temperature properties of asphalt binders was related to wax type, dosage, and stress level. Within the allowable dosage range, waxes improve the fatigue properties of asphalt binders. After plasma treatment, the surface roughness and activity of waxes were increased, resulting in the alleviation of physical hardening of waxed asphalt binders and a decrease in wax precipitation temperature. Among them, plastic cracking waxes were more sensitive to the plasma treatment technique.

The creep of bamboo scrimber is an important factor to be considered in engineering applications. Simply using the creep test method not only consumes a lot of time and money, but also cannot be extended to the full stress level. Therefore, in this paper, the short-term creep tests of bamboo scrimber under different stress levels (30% and 40%) and ambient temperatures (30°C–70°C) were carried out. The multicomponent Kelvin-Voigt model and generalized Maxwell shear relaxation model of bamboo scrimber were established. The Maxwell-3 shear relaxation model was used as the constitutive model of bamboo scrimber, and the creep finite-element model of bamboo scrimber under parallel-to-grain compression was established, which verified the creep constitutive model of bamboo scrimber. The results showed that the shear relaxation modulus exhibited a significant decrease during the unstable creep stage, reaching a maximum reduction of 62.0%. It showed nonlinear for the effect of ambient temperature on the compression creep of bamboo scrimber, and the creep rate near the glass transition temperature was significantly higher than that at other temperatures. The fitting coefficients, $R$-square of creep compliance models, were sorted as KV-4 and $\mathrm{KV}\text{-}5>\mathrm{KV}\text{-}3>\mathrm{Burgers}>\mathrm{KV}\text{-}2$. The fitting coefficients, $R$-square of the generalized Maxwell model of shear relaxation modulus, were sorted as Maxwell-4 and $\mathrm{Maxwell}\text{-}3>\mathrm{Maxwell}\text{-}2>\mathrm{Maxwell}\text{-}1$. The simulated creep displacement error of the two specimens was 2.8% and 0.1%, respectively, which verified the accuracy of the numerical simulation method. The paper proposed creep behavior and a constitutive model for bamboo scrimber under parallel-to-grain compression, which holds significant theoretical implications for its widespread application.

In this paper, a novel pervious concrete (PC) has been proposed, which combines a high-strength self-compacting concrete matrix with artificial pore channels, to prepare a novel self-compacting recycled pervious concrete (NSRPC) with vertically and uniformly distributed pore channels. Then, an analysis was conducted to assess the flexural performance, permeability, and resilience to rainstorm of NSRPC after flexural fatigue load, which was carried out to ascertain the fluctuations in strength and drainage efficiency over the anticipated service life. The experimental results of NSRPC with porosity levels of 0.28%, 0.56%, 0.84%, and 1.12% show that the reduction in rainstorm will first decrease and then increase with the increase of fatigue cycles. After ${2\times 10}^5$ fatigue cycles, the corresponding NSRPC flexural strength was 5.9, 5.6, 5.4, and 4.5 MPa, respectively, and the ultimate displacement decreased by 20.2%, 25.1%, 28.0%, and 33.1%, respectively. After ${2\times 10}^5$ fatigue cycles, NSRPCs still demonstrate good storm waterlogging resistance under 20-, 50-, and 100-year rainstorms. The maximum water retention dissipation rate of NSRPC can reach $0.13\mathrm{mm}/\min$, and the maximum water retention depth is less than 2.5 mm. Additionally, the permeability coefficient of NSRPC remains almost unchanged with an increase in fatigue cycles. When the permeability coefficient is greater than $4.5\mathrm{mm}/\mathrm{s}$, the depth of stagnant water remains almost constant with the increase of the permeability coefficient. The research in this project provides a new material and direction for the study of pervious concrete to control rainstorms and waterlogging.