Case Studies in Construction Materials最新文献

The coffee industry is known to generate voluminous amount of waste during its production process. Different types of waste such as coffee hush ash and spent coffee ground, to name a few, have been extensively researched as a substitute in the construction industry. However, the utilization of coffee husk as a substitute for construction materials has seen limited exploration. In particular, there are no studies which investigate the utilization of waste coffee husk (WCH) in alkali-activated bricks. Therefore, in this research WCH was employed as a substitute to sand in alkali-activated bricks. Alkali-activated bricks were synthesized with ground granulated blast furnace slag (GGBFS), fly ash (FA), sand, and sodium silicate solution (SS). Sand was replaced with WCH at replacement rates of 0 %, 5 %, 10 %, 15 %, 20 %, and 30 % by volume. The developed bricks were evaluated for strength, density, water absorption, porosity, and efflorescence. Additionally, structural and morphological characteristics of bricks were assessed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and Scanning electron microscopy (SEM) analysis. The results indicate that bricks with WCH improve the compressive strength with a maximum value of 15.7 MPa, and reduce the density with a minimum value of 1509 kg/m³ for composites with 30 % WCH, respectively. The water absorption and porosity of bricks increased with incorporation of WCH due to porous structure of WCH. The physico-chemical analysis of the bricks shows effective geopolymerization in the composite system with WCH, and further the bricks with 30 % WCH depict thermal stability with insignificant weight loss at 575 ℃. Finally, the composites with 30 % WCH classify as good quality bricks as per IS 1077: 1992 specifications, and this will improve practical feasibility of such materials in the construction industry.

The escalating demand for methods to diminish cement usage without compromising the strength and durability of concrete mixtures has led to an intensified exploration of alternative mixture ingredients. Nano silica has emerged as a prominent supplementary cementitious material, recognized for its capability to partially substitute cement. Despite this potential, there was a gap in the literature on the effects of nano silica on the concrete’s fresh and hardened properties, particularly when used in conjunction with silica fume. This gap motivated the current investigation, aiming to capture and compare the effects of incrementally substituting silica fume with nano silica in self-consolidating concrete (SCC). For this purpose, four nano silica dosages—1%, 2%, 3%, and 5%— were considered as replacements for silica fume. A range of experiments, including slump flow, T50 time, and L-box tests, were conducted to assess the workability of the developed SCC mixtures. Subsequent analyses focused on key mechanical attributes, including the static modulus of elasticity, compressive strength, and tensile strength. The research further encompassed water absorption, penetration depth, and electrical resistivity evaluations to understand the durability characteristics of the developed mixtures. The scanning electron microscopy (SEM) analyses complemented these tests, offering a microstructural perspective to further explain the outcomes. This investigation’s findings offer novel insights into leveraging nano silica’s distinctive properties to achieve the desired SCC properties while reducing the environmental impact of this class of mixtures.

The use of high-strength concrete (HSC) in constructing high-rise reinforced concrete buildings and their deep foundations is becoming more popular because of the significant reduction in member size and, thus, self-weight in structural members. However, the higher cement content in HSC may result in increased heat of hydration and autogenous shrinkage, growing concerns about forming early-age cracks in HSC structural members. This case study assessed the early-age cracking of HSC in bored pile construction of high-rise buildings. A nonlinear transient coupled thermal-mechanical response analysis was performed to evaluate the potential of early-age cracking caused by the heat of hydration generated in the HSC using ABAQUS and two subprograms, USDFLD and UEXPAN. A 3-D finite element model was developed considering thermal effects, time-dependent evolution of early-age strength and stiffness of HSC, crack strain development, autogenous shrinkage, and stress-relaxation in the analysis. Field measurements were carried out on a 3-m diameter bored pile constructed using Grade C50/60 HSC (f_ck,cube = 60 MPa) for a high-rise building project in Hong Kong to evaluate the validity of the numerical model. Optical fiber sensors were used to monitor the temperature changes of the pile for approximately 380 hours after casting. The temporal and spatial temperature distributions measured in the field measurements agree well with the simulations. Large thermal gradients and high tensile stress zones were observed across the horizontal cross-sections of the pile, resulting in the formation of vertical annular cracks. Based on the results of the analysis, the maximum crack widths were predicted and compared with the durability crack width limits.

The application of non-metallic glass fiber-reinforced polymer (GFRP) bars as embedded reinforcement in reinforced concrete (RC) has been of great interest among researchers and practicing engineers alike, owing to its properties such as high strength-to-weight ratio and corrosion resistance. This study investigated the long-term performance of ribbed (RB) and sand-coated (SC) GFRP bars embedded in concrete columns exposed to harsh seawater conditions for approximately 20 years. The bars extracted from the concrete elements were tested to evaluate strength retention based on ASTM standard transverse and interlaminar shear strength tests. After the long-term field exposure, the ribbed and sand-coated GFRP bars exhibited 82.5 % and 79.4 % transverse shear strength retention, and 84.4 % and 78.1 % interlaminar shear strength retention, respectively, which corresponds to approximately 5 months of exposure in the accelerated solution specified by ACI 440.3R-12 guide. Scanning electron microscopy analyses revealed the extent of damage in the fibers, the matrix, and their interface, which validated the degradation in the mechanical strength of the exposed GFRP bars. Finally, correlations between long-term and accelerated exposure test conditions were developed to predict transverse and interlaminar shear strength in the field based on laboratory conditioning investigations.

Clogging in permeable asphalt pavements compromises their functional properties. Understanding clogging characteristics and developing appropriate maintenance methods is crucial. This study integrates indoor accelerated clogging simulations with Grey Relational Analysis to investigate the factors influencing clogging behavior. Computer tomography scanning and seepage model simulations are utilized to examine the distribution of clogging materials, seepage properties, and changes in pore parameters in permeable asphalt mixtures before and after clogging. Additionally, variable frequency vibration tests are conducted to evaluate the impact of vibration frequency on clog removal efficiency. Findings show that the cementation hardening effect of clay progressively seals pores, with sand particles of 0.15 mm diameter exerting the most significant influence on clogging. Wet-dry cycles lead to an accumulation of clay cementation, resulting in a 26.1 % and 72.4 % decrease in pore channel length and volume, respectively, at depths of 0–4.2 cm. The area within this depth range is most prone to clogging, increasing pore tortuosity. Seepage behavior is primarily determined by several main interconnected pores. Vibration test outcomes indicate that frequencies between 100 and 400 Hz are optimal for disrupting cementation blockages.

The role of chemical components is pivotal in determining the rheological and adhesion performance of asphalt binders. In this study, the saturate, aromatic, resin, and asphaltene (SARA) components were directly blended with the original asphalt in specific proportions, enabling a direct assessment of their influence on critical asphalt properties. Various tests, including frequency sweep, temperature sweep, and multiple stress creep and recovery tests, were conducted, followed by the utilization of master curves to analyze the rheological properties of SARA-doped asphalt. Additionally, binder bond strength tests were performed to evaluate the adhesion properties of SARA-doped asphalt binders. The research outcomes revealed that the complex modulus, rutting factor, creep and recovery behaviors increased with higher asphaltene and resin proportions, while diminishing with elevated saturate and aromatic proportions. Analysis of the Glover–Rowe (G-R) parameter variation indicated that increasing the proportion of aromatic and saturate components can enhance cracking resistance, with the aromatic component playing a particularly significant role in this enhancement. Furthermore, augmenting the proportion of heavy components was found to enhance the adhesion performance between asphalt and commonly used aggregates. Notably, the pattern of interfacial failure transitioned from cohesive failure to adhesive failure gradually with rising proportions of heavy components.

Rock asphalt (RA) has gradually been recognized as a green and efficient asphalt modifier. However, the weakness of low-temperature performance and fatigue resistance for RA modified asphalt limited its application and popularization in asphalt pavement. To overcome the above shortcomings, this study aimed to synergistically apply devulcanized rubber powder (DRP) with American rock asphalt (ARA) for asphalt modification. Multiple experiments such as dynamic shear rheology (DSR) and bending beam rheology (BBR) were conducted to evaluate the rheological properties and road performance of composite modified asphalt (CMA). Cigar tube test (CTT) was applied to assess storage stability of CMA. In addition, Fourier transform infrared spectrometer (FTIR) and microscopic test (MT) were used to investigate the modification mechanisms. The results showed that CMA modified by DRP and ARA exhibited comparable storage stability, low-temperature performance and rutting resistance as SBS modified asphalt. ARA tended to cause aging problems of asphalt, but the addition of DRP effectively improved the aging resistance performance of modified binder blends, especially long-term aging resistance. The mixing of DRP, ARA and base asphalt is a physical process without chemical reactions. Even though the ash in ARA slightly lowered its storage stability, it significantly improved dispersion and homogenous interface of DRP in asphalt.

Semi-flexible pavement is a new type of pavement technology with excellent mechanical and road performance. Grouting materials play a crucial role in filling and reinforcing semi-flexible pavements as an important component. In this study, based on sulphoaluminate cement, the effect of mineral admixtures on rheological properties of grouting materials was studied by introducing rheology. High-performance grouting materials for semi-flexible pavements were prepared by varying the ratio of water-cement ratio, early-strength agent and mineral admixture, and their optimal ratios were determined. The research findings indicate that, the grouting materials with the best mechanical properties can be obtained when the water-to-binder ratio is 0.5, and the dosages of lithium carbonate, silica fume, microspheres, and granulated blast furnace slag are 0.2 %, 1.6 %, 5.0 %, and 5.0 %, respectively. The optimal dosage for shrinkage-reducing agents to improve the shrinkage behavior of grouting materials is in the range of 0.10–0.15 %. The accelerated early hydration reaction and improved compactness of the material matrix are the main reasons for the rapid development of the mechanical properties of the grouting materials. Mineral admixtures can undergo a hydration reaction similar to that of cement to produce a rigid gel consisting of very small particles with a laminar structure, which has a positive effect on the development of grouting material properties. The improvement in shrinkage behavior is achieved through the filling effect of silica fume and the micro-expansion effect of plasticizing expanders, which generate small and uniform bubbles.

This study proposes using KH-550 as a multifunctional admixture for improving the performance of alkali-activated slag (AAS). The hydrolysis products of KH-550 were characterized, and the influence of KH-550 on the fresh properties, hydration kinetics, pore structure, capillary water absorption, hydration products, compressive strength and micro-mechanical properties of AAS were investigated. The results showed that the addition of KH-550 improved the fresh properties of AAS. By adding 2.5 % KH-550, the initial and final setting time of AAS were prolonged by 105.1 % and 60.3 %, respectively, and the fluidity was increased by 10.26 %. The analysis of hydration kinetics showed that although the added KH-550 retarded the AAS hydration at early ages, the nucleation effect of KH-550 nanoparticles accelerated the hydration of AAS at later ages. Moreover, the addition of KH-550 improved the pore structure of the mortars, resulting in a denser microstructure of AAS, which was beneficial for capillary water absorption and compressive strength of AAS. Consequently, the capillary water absorption was reduced by 1.7—11.5 %, and the 28 d compressive strength was increased by 4.8—34.3 %.

Styrene-butadiene rubber (SBR) latex is used widely to increase the low-temperature resistance of asphalt binders. However, the high content of butadiene copolymer in SBR-treated asphalt causes oxidation and aging. Furthermore, following the SBR modification, the compatibility and thermal storage stability of SBR-modified asphalt is not satisfactory. Therefore, the best approach to improve the quality of short-term aged SBR-modified asphalt is to lower the manufacturing temperatures of the SBR-modified asphalt mixture. In this study, to reduce the preparation temperatures of SBR-modified asphalt mixes and improve their performance after short-term aging, several additives i.e., waste engine oil (WEO), warm mix agent i.e., ZycoTherm, and WEO/ZycoTherm combination (WEO+ ZycoTherm) were selected. The rheological properties and aging performance of binder samples were evaluated through the rational viscosity, dynamic shear rheometer, bending beam rheometer and Fourier transform infrared spectroscopy tests. The results showed that adding WEO together with ZycoTherm into an SBR-modified binder contributed to reducing the compaction and mixing temperatures. The chemical analysis showed that the three additives i.e., WEO, ZycoTherm, and ZycoTherm/WEO declined the aromaticity and chemical aging indicators of aged SBR-modified binders. Furthermore, it was demonstrated that both the ZycoTherm and WEO/ZycoTherm improved the asphalt resistance to rutting at elevated temperatures in both conditions i.e., before and after short-term aging. In addition, the findings revealed ZycoTherm /WEO compound yielded the best performance to improve the minimal-temperature cracking resistance of the SBR-modified binder, resulting in lower short-term aging temperatures. In summary, this study highlights the necessity of lowering preparation temperatures in asphalt mixes containing SBR to enhance binder resistance to rutting and cracking and reduce susceptibility to oxidation during short-term aging.