Construction and Building Materials最新文献

The evolution of rust layers and degradation of mechanical properties of Q420B steel used for the construction of ultra-high voltage (UHV) transmission towers were investigated through accelerated wet/dry cyclic corrosion test (CCT). After 135 cycles of CCT, the corrosion of Q420B low alloy steel was divided into three distinct stages. Initially, the corrosion rate rose, then declined, and finally stabilized, with turning points of 45CCT and 105CCT respectively. Corrosion rates were influenced by the morphology of the rust layer and the evolution of its phases. The internal rust layer containing β-FeOOH, a strong oxidative corrosion product with a tunneling structure, significantly accelerated the corrosion rate of Q420B steel in coastal environments. In the initial corrosion stage, strong oxidizing products facilitated the cathodic process. As corrosion proceeded, the thickening rust layer and increasing α-FeOOH content in the middle to late stages impeded the cathodic/anodic process. Furthermore, the mechanical properties of the specimens showed a significant decline after wet/dry cyclic corrosion. The material failure occurred at the turning point between the second and third stages of corrosion evolution, 105CCT, marked by a 7.55 % weight loss. Elongation was the most susceptible to corrosion, with the degradation patterns of plasticity and strength following linear and quadratic functions, respectively. The inhomogeneous corrosion component had a more pronounced effect on the mechanical properties of the specimen during the CCT. However, the protective rust layer served to moderately slow down the deterioration of mechanical properties. This study provides a reference for predicting the performance degradation of UHV transmission tower components in coastal environments.

Acid rain corrosion is a critical factor contributing to the increased susceptibility of concrete pavements to cracking and reduced service life, raising significant safety concerns. This research aims to investigate the acid rain corrosion resistance and purification performance of geopolymer recycled pervious concrete (GRPC) with top-bottom interconnected channels under acid rain soaking and spraying simulation tests. The impacts of acid rain exposure on the compressive strength, permeability coefficient, mass loss, neutralization depth of GRPC, and the pH value of percolating acid rainwater were analyzed. The results proved that GRPC exhibited excellent resistance to simulated acid rain with a pH of 4.0. Furthermore, employing a combination of sodium hydroxide and sodium silicate as alkali-activators provided the optimal acid rain corrosion resistance. Additionally, in the early stage of acid rain exposure, acid rain was neutralized by the sodium carbonate formed through efflorescence. While in the middle-later stage, the migrating alkaline substances in GRPC matrix directly neutralized the pH of acid rain. Notably, after 28 days of simulated acid rain spraying, GRPC maintained its ability to purify the acid rain flowing through its channels, successfully raising the pH from 4 to a range between 7 and 8, demonstrating an effective acid rain purification capability. In conclusion, GRPC can transform the efflorescence issue in concrete into an effective means to counteract acid rain corrosion, thereby equipping concrete pavements with the dual advantages of alleviating urban waterlogging and resisting acid rain corrosion. This renders GRPC a promising avenue for both academic research and practical engineering applications.

Bio-based materials have attracted much attention because their application in the construction field is conducive to energy saving and emission reduction. In this paper, a bio-based composite phase change material (CPCM) was prepared by utilizing pitaya peel as a bio-based material, MXene quantum dots (MQDs) as a modified material, and polyethylene glycol (PEG) as a phase change medium. MXene quantum dots dispersed in the pitaya peel-based porous carbon skeleton enhanced the three-dimensional thermal conductivity network of the porous carbon skeleton somewhat improved the thermal conductivity (0.676 W/mK) of the polyethylene glycol/MXene quantum dots-modified pitaya peel-based porous carbon foam (PPF) composite phase change material (PEG/PPF@M). It is worth noting that PEG/PPF@M has excellent thermal stability and its enthalpy is basically unchanged after 100 cycles, which proves the recyclable stability of PEG/PPF@M in practical applications. PEG/PPF@M has great potential for thermal management of buildings and electronic components. Overall, a novel multifunctional CPCM was prepared in this study using a simple process method, which can not only be applied in electronic products to improve the service life of electronic components, but also in the field of construction to realize energy saving and emission reduction, as well as the recycling and reuse of waste.

Salt storage asphalt pavement can effectively alleviate the problem of pavement snow and ice in winter, and ensure the driving safety and transportation capacity. Salt storage type snow melting and ice suppression materials are the key to the function of salt storage asphalt pavement. The purpose of this paper is to develop a snow-melting and ice suppression aggregate with outstanding sustained release performance by coupling the orthogonal test and response surface method. Three process variables, such as adsorption time, concentration of snow-melting salt solution and mass ratio of porous aggregate to snow melting salt, were optimized by orthogonal test and response surface method. Then, the preparation process of salt storage aggregate was determined by adsorption performance test. Finally, the physical and mechanical properties, slow release performance and ice melting performance of the slow-release salt-storage snowmelt aggregate were tested. The results showed that the optimum preparation process of salt-storing aggregate was the adsorption time of 12 h, concentration of snow-melting agent solution of 30 %, and mass ratio of snow-melting salt to salt-storing carrier of 0.5:1. The optimum mass ratio of salt-storing aggregate to wrapping material (phenolic resin) was 1:2.5. The salt release amount of the slow-release salt-storing snowmelt aggregate at 180 min was about 43.75 % lower than that of the unwrapped salt-storing aggregate. At the same time, 5 g of slow-release salt-storing snow-melting aggregate had a melting ice amount of 0.9 g at a temperature of −5°C. In addition, the slow-release salt-storing snow-melting aggregates wrapped with different proportions of asphalt could release salt, and its conductivity was at least 1200 μs/cm in the stable stage.

In this paper, an experimental study is conducted to gain insight into the bond behavior of ribbed fiber-reinforced polymer (FRP) bar in FRP-confined concrete. Various parameters, including the ratio of concrete cover to bar diameter, concrete strength, and FRP confinement level, are considered in this study. The test results demonstrate the effectiveness of FRP confinement in changing the bond failure mode of FRP bar from the concrete splitting to the pullout and improving bond ductility and strength. The bond response of ribbed FRP bar in FRP-confined concrete is characterized by three distinct stages: uncracked stage, cracking enhancement stage, and cracking degradation stage. The bond mechanism within each stage is elucidated. The study reveals that the normalized bond strength is distinctly influenced by the ratio of concrete cover to diameter and FRP confinement level, while concrete strength exhibits a negligible impact. Finally, the study proposes a novel model for predicting the bond strength of the ribbed FRP bar embedded in both unconfined and FRP-confined concrete.

Today, with the increase in population, the amount of energy consumption has increased; as well, high-level construction in urban areas has increased. In this regard, the shading of tall buildings has further increased energy consumption. The present research provides a solution to reduce energy consumption associated with buildings lighting by introducing new techniques associated with casting light transmitting concrete. For this purpose, 4 mixing designs are presented as, 1- reference concrete (Ref), 2- light-transmitting concrete based on plastic optical fibers (B1), 3- light-transmitting concrete based on ribbed resin rods (B2), 4- composite based on tempered glass waste and epoxy resin (B3). Since the samples are used as external walls, first the mechanical characteristics were investigated and then with the aim of assessing the effect of using the materials on energy consumption, a building was modeled with Design Builder software. Considering the results, samples B1 and B2 provided acceptable compressive strength in terms of structural performance. However, regarding tensile strength, only sample B1 can be used in the structure. In sample B2, the cost of consumables has decreased by 86.5 % compared to sample B1, which can be more suitable for non-structural applications. Compared to other samples, sample B3 has been associated with a 26 % decrease in volumetric mass and a 10-fold increase in light transmission; in addition, it has better efficiency than glass, which can replace glass windows. In general, all samples are more suitable for cold climates and are not recommended for hot climates. The north and south walls are more suitable for the use of samples.

Since bamboo possesses an extremely high weight-strength ratio, excellent flexibility, and a unique round structure, this fast-growing and abundant biomass has been thought of as a promising alternative to building materials, especially plastic pipes. However, the inherent limitations, including poor water resistance, transverse mechanical weaknesses, and low mildew resistance, hinder its application. Composite bamboo with resins could effectively improve the above problems, but resin modification methods that have been traditionally used fail to achieve strong interfacial bonding with the bamboo substrate, which could not meet the requirements for high performance in harsh conditions. This study treated round bamboo with limited delignification and acetylation. The limited delignification treatment promoted lateral impregnation of the epoxy resin into the round bamboo substrate and maximized retention of the performance advantages of round bamboo. The treatment also provided more reaction sites for acetylation. The acetylation treatment enhanced interfacial adhesion between the cured epoxy resin and the round bamboo substrate. Due to this tighter connection from both physical structure bonding, the as-prepared bamboo-based/epoxy resin composite pipes exhibited excellent mechanical performance, with a tensile strength of 3.89 MPa in the hoop direction, 74.69 MPa in the longitudinal direction, and a ring stiffness of 50.26 kPa. This study prepared a sustainable and high-strength candidate for plastic pipes through a low-carbon, energy-saving, and emission reduction method, which brought new perspective for achieving the goal of carbon neutrality.

Conventional curing agents are associated with environmental impacts when treating Zn²⁺contaminated soils. To overcome this limitation. In this study, we study a new type of MgO-CSB curing agent. Namely, corn stover biochar is modified with activated MgO. Modification of corn stover biochar using activated MgO, and carbonation curing was adopted to solidify/stabilize the Zn²⁺contaminated soil. The curing efficacy of Zn²⁺contaminated soil under modified mass ratio, Zn²⁺ concentration, carbonation time, and curing agent incorporation was investigated. The findings indicate that the optimal adsorption efficiency was attained following the co-pyrolytic modification of activated MgO with corn stover biochar at 700°C. The optimal modified mass ratios for curing were found to be 1:1, 1:2, and 2:1 at Zn²⁺ concentrations of 0.1 %, 0.5 %, and 1 %, respectively. At a lower Zn²⁺ concentration, peak carbonization intensity is achieved at 0.5 hours, while at a 1 % Zn²⁺ concentration, peak intensity is reached at 1 hour. The deformation modulus of the cured soil increases as the curing agent dosage increases and the soil aggregates become denser. SEM results show that: The carbonization and curing reaction products are mainly nesquehonite and Mg (OH)₂. The internal structural damage of the cured soil was aggravated by the increase in Zn²⁺concentration, and the generation of nesquehonite and Mg (OH)₂ was inhibited; The carbonation time was extended to 1 h and the soil structure stability was enhanced.

Graphene oxide (GO) has shown promise in improving concrete strength. Despite its frequent use in cement composites, its effect on concrete properties is less explored. The influence of GO on concrete remains unclear due to various interactions among constituents such as GO type and percentage, Superplasticiser (SP) type and percentage, dispersion technique, and curing age. Therefore, making prediction of compressive strength using simple mathematical formation is challenging. This study represents the first-ever attempt at developing a comprehensively validated machine learning model to predict GO-concrete's compressive strength characteristics by considering all key variable parameters. A comprehensive laboratory experiment program was conducted to collect the data required for training the machine learning (ML) models. Once the ML models were trained, they were used to predict the relationship of each of those input variables towards the compressive strength properties. Four machine learning models—(a) multiple linear regression (MLR), (b) k-nearest neighbour (KNN), (c) random forest (RF) and (d) extreme gradient boost (XGB)—were utilised to model the relationship between input parameters and compressive strength. Also, explainable machine learning (XML) methods were employed to elucidate the impact of mixed constituents on the compressive strength of GO concrete. The results from test predictions showcase that the XGB has attained a coefficient of determination (R²) of 0.981, coefficient of correlation (R) of 0.99, mean square error (MSE) of 0.9, mean normalised bias (MNB) of 0.004, scatter index (SI) of 0.2 with mean absolute error (MAE) of 0.8 MPa for the predictions, outperforming the remaining models. XML highlighted the true impact of GO and the remaining variables, emphasising that the presence of GO significantly improves compressive strength. The optimum GO content and optimum superplasticiser content observed from the experimental work agreed with results obtained from the XML analysis, showing the consistency of the explanation with the experimental results. This implies the superiority of using XML methods in concrete mix design applications in industry.

Snow and ice on the pavement surfaces in winter seriously threaten the traffic safety. This study prepared high-elastic/salt-storage (HESS) asphalt mixtures containing rubber particles (RP) and self-developed salt-storage fillers to improve deicing performance in various aspects. Specifically, the RP was incorporated into the asphalt mixture by replacing 1 %, 2 %, and 3 % of fine aggregate by mass and the self-developed salt-storage filler was incorporated into the asphalt mixture to replace 25 %, 50 %, and 75 % of the mineral filler by equal volume. Hydrated lime was used as a mineral filler to enhance the asphalt mixtures’ water damage resistance. The pavement performance of HESS asphalt mixtures was first studied. The pull-out and fall ball impact tests were designed to investigate the composite deicing effect of RP and salt-storage filler on the asphalt mixtures. A self-designed rainfall simulation test was used to assess the long-term deicing performance of HESS asphalt mixtures. Results showed that the incorporation of RP improves the high-temperature stability and low-temperature crack resistance of the mixtures, but negatively affects their water damage resistance. The RP content should not exceed 3 % to guarantee water damage resistance. Due to combining effects RP and salt-storage fillers, the deicing performance of HESS asphalt mixtures has been improved by 15.9 % and 10.6 % as compared to the addition of RP and salt-storage fillers separately. It is recommended to replace the fine aggregates with the RP at content of 1.5–3 % by mass and 60–75 % mineral filler with the salt-storage filler by volume.