Search Results (11)

As a promising and sustainable construction material, alkali-activated slag lightweight high-strength concrete (AAS-LWHSC) may be influenced by lightweight aggregate (LWA) content. In this study, the effects of hollow glass microspheres (HGM) replacing granulated ground blast furnace slag (GGBFS) under varying LWA dosages on the workability, dry apparent density, mechanical properties, and microstructure of AAS-LWHSC were investigated. The results indicated that the dry density of concrete was significantly reduced by HGM, while the “ball-bearing” effect of HGM was observed to enhance workability at a dosage of 6%. The 7-day mechanical properties of AAS-LWHSC were found to decline progressively with increasing HGM content. However, at the shale ceramsite sand replacement rates of 35% and 65%, the incorporation of 6% HGM slightly improved the 28-day mechanical properties. Due to the absence of the water-releasing effect from shale ceramsite, the pozzolanic reactions of HGM were restricted, resulting in coarse hydration products and a reduction in the mechanical performance of AAS-LWHSC. Full article

High-strength lightweight concrete (HSLC) is increasingly in demand for reducing the self-weight of concrete structures, achieved in this study using shale ceramsite aggregate. Despite its potential, HSLC has been underutilized in field projects due to concerns about its strength and long-term stability. This study investigates the impact of shale ceramsite content on the mechanical properties of HSLC through uniaxial compression, flexural, and bending tests. The results reveal that ceramsite content significantly influences the concrete’s mechanical properties and failure mechanisms. An optimal design of HSLC was proposed in this study and further used in a real field highway project, demonstrating its applicability to bridge pavements. Newly developed fiber Bragg grating sensors were installed in the material to monitor the performance of the HSLC. Concrete performance monitoring was conducted using a new type of fiber Bragg grating sensor independently developed by the research team. The results showed that the higher the ceramsite content, the greater the shrinkage deformation. And similarly, the higher the strength, the greater the shrinkage deformation. The outcome of this study would provide an alternative approach for the application of HSLC in civil infrastructures. Full article

In investigating the mechanical properties and chloride corrosion resistance of all-light shale ceramsite concrete (ALSCC), samples of ALSCC20–ALSCC45 with a compressive strength of C20–C45 were individually prepared. The compressive strength, split tensile strength, and elastic modulus of ALSCC were analyzed. Additionally, the chloride salt corrosion resistance of ALSCC was assessed by examining chloride ion penetration depth, steel corrosion rate, and compressive strength after ALSCC30 corrosion. Furthermore, the microstructure of ALSCC hydration products was observed using scanning electron microscopy (SEM). Results indicate that as the strength grade increases, the water–cement ratio decreases, and the internal structure becomes denser, thereby improving the mechanical and corrosion resistance properties of ALSCC. Notably, the chloride corrosion resistance of ALSCC surpasses that of ordinary concrete. SEM images reveal that the hydration of ceramsite with Ca(OH)₂ in concrete generates Ca[Al(OH)₄]₂ precipitation and C–S–H gel, which enhances internal filling and improves chloride corrosion resistance. Furthermore, based on the results of the ALSCC30 corrosion test, a calculation model for predicting compressive strength in a chloride environment was proposed. This model effectively predicts the compressive strength of ALSCC under chloride exposure conditions. Full article

To develop lightweight high-strength concrete (LWHSC) for offshore structures in a harsh seawater environment, LWHSC with shale and clay ceramsites was designed. LWHSC was experimentally investigated in terms of density, compressive strength, and durability in a coastal environment. Then, its feasibility for offshore structures was also assessed. The results show that the compressive strength and oven dry density of LWHSC appropriately improve with increases in cement content, while they are reduced by the replacement of shale ceramsite with clay ceramsite. The compressive strength of LWHSC also increases first and then decreases with an increase in the pre-wetting of shale and clay ceramsites. Their optional pre-wetting time is about 0.5 h. LWHSC exhibits a higher brittleness compared with conventional concrete. LWHSC has increases in the resistances of freeze–thaw, carbonization, water penetration, and chloride penetration when the shale and clay ceramsite light aggregates decrease in the concrete. The LWHSC prepared in this paper is suitable for the harsh seawater environment of offshore oil platforms but is limited to the southern region where there is no requirement for the freeze–thaw resistance of concrete. The results of this study can provide some reference for the application of LWHSC in offshore structures and other similar aspects of engineering. Full article

Hydraulic fracturing using micro-particles is an effective technology in the petroleum industry since the particles facilitate crack propagation of the shale layer, creating pathways for oil and gas. A new kind of polymer-coated ceramsite particles (PCP) was generated. The friction and wear properties of the particles under different loads and speeds were also studied. The tribological relationship between the newly fabricated polymer-coated ceramsite particles and the fracturing fluid was studied through tribological experiments under the condition of fracturing fluid lubrication. The results show that, in contrast, the wear of the new-generation particles is relatively stable, indicating that it has good adjustable friction properties. In addition, under the lubrication condition of fracturing fluid, the new-generation particles have better hydrophobicity, high-pressure resistance, and low reflux rate, which have an important value as a practical engineering application for improving shale gas production efficiency and production. Full article

The excellent performance of graphene oxide (GO) in terms of mechanical properties and durability has stimulated its application potential in high-strength lightweight concrete (HSLWC). However, more attention needs to be paid to the long-term drying shrinkage of HSLWC. This work aims to investigate the compressive strength and drying shrinkage behavior of HSLWC incorporating low GO content (0.00–0.05%), focusing on the prediction and mechanism of drying shrinkage. Results indicate the following: (1) GO can acceptably reduce slump and significantly increase specific strength by 18.6%. (2) Drying shrinkage increased by 8.6% with the addition of GO. A modified ACI209 model with a GO content factor was demonstrated to have high accuracy based on the comparison of typical prediction models. (3) GO not only refines the pores but also forms flower-like crystals, which results in the increased drying shrinkage of HSLWC. These findings provide support for the prevention of cracking in HSLWC. Full article

An effective pathway to achieve the sustainable development of resources and environmental protection is to utilize shale ceramsite (SC), which is processed from shale spoil to produce high-strength lightweight concrete (HSLWC). Furthermore, the urgent demand for better performance of HSLWC has stimulated active research on graphene oxide (GO) in strengthening mechanical properties and durability. This study was an effort to investigate the effect of different contents of GO on HSLWC manufactured from SC. For this purpose, six mixtures containing GO in the range of 0–0.08% (by weight of cement) were systematically designed to test the mechanical properties (compressive strength, flexural strength, and splitting tensile strength), durability (chloride penetration resistance, freezing–thawing resistance, and sulfate attack resistance), and microstructure. The experimental results showed that the optimum amount of 0.05% GO can maximize the compressive strength, flexural strength, and splitting tensile strength by 20.1%, 34.3%, and 24.2%, respectively, and exhibited excellent chloride penetration resistance, freezing–thawing resistance, and sulfate attack resistance. Note that when the addition of GO was relatively high, the performance improvement in HSLWC as attenuated instead. Therefore, based on the comprehensive analysis of microstructure, the optimal addition level of GO to achieve the best mechanical properties and durability of HSLWC is considered to be 0.05%. These findings can provide a new method for the use of SC in engineering. Full article

Despite the continuous improvement in the research and development of concrete precast composite slab technology, problems like easy cracks and excessive weight at the joints remain. In this study, high-titanium heavy slag was mixed with different kinds of ceramsite to prepare ceramsite lightweight high-titanium heavy slag concrete. The joint of the composite slab was optimized to develop a novel ceramsite lightweight high-titanium heavy slag concrete precast composite slab, hereinafter referred to as “CLHCPCS”. Two CLHCPCS and one ordinary concrete composite slab were prepared. This study analyzed the effects of new materials and improved joints on the flexural capacity and crack resistance of CLHCPCS. It concluded that the density of high-titanium heavy slag concrete with shale ceramsite decreased by 12.0%, and the density of high-titanium heavy slag concrete with fly ash ceramsite decreased by 10.6%. At a 30% dosage of fly ash ceramsite, the compressive strength and splitting tensile strength of concrete reached the maximum. At a 20% dosage of shale ceramsite, the mechanical properties were optimal. Finally, fly ash ceramsite was selected as part coarse aggregate of CLHCPCS. CLHCPCS 1 and 2 demonstrated superior ultimate bearing capacity and crack resistance than ordinary concrete composite slab DBS1, with its ultimate bending capacity test value higher than the average value of ordinary concrete composite slab. ANSYS established the joint model of CLHCPCS for a bending simulation test. The stress and strain distribution of the model and the ultimate bending capacity under the plastic line method were obtained, consistent with theory and experimental analysis results. Full article

To reveal the energy consumption characteristics of a steel bar and all-lightweight shale ceramsite concrete (ALWSCC), focusing on hot rolled crescent ribbed bars (CRB) and hot rolled plain steel bars (PSB), a series of pull-out tests were carried out. The bonding failure modes, the contribution of the ribs to bond-slip failure and the energy consumption characteristics were analyzed based on the curves of pull-out load F-slip displacement S and energy consumption W–slip displacement S. Results show that the splitting failure is the main failure of the CRB specimen, and the pulling out failure is the main failure of the PSB one. The ratio of the total energy dissipation of splitting failure to that of the pulling out failure is less than 30%. The mechanical bite force between CRB and concrete contributes more than 95% to the bond strength. The pull-out force is divided into four stages, such as the chemical adhesive force stage (elastic and micro-elastic strain stage), the common-effect stage of mechanical bearing force and static frictional force (plastic development stage), and the frictional force stage (crushed stage). The new design is proposed to guarantee the ductility of the reinforced concrete structure, which is based on the bond-slip energy consumption rather than the traditional strength design. The conclusions provide a reference to the reinforced concrete practice. Full article

In this study, a type of artificial lightweight shale ceramsite (ALSC) was used as the coarse lightweight aggregate for shotcrete (LAS), of which the mechanical properties, chloride penetration ion resistance, and rebound behavior were investigated. Based on the experimental results on compressive, tensile, and bond strength, LAS meet the strength requirements, and the replacement rate of fly ash (FA) and silica fume (SF) are suggested to be kept at ~15% and 10%, respectively, to result in the best mechanical properties of LAS. Adding FA and SF to the mixture significantly improved the chloride ion penetration resistance (CPR) of LAS because of morphology effects and secondary hydration of FA and SF that lead to a denser microstructure of the mixture. The electric flux and chloride ion migration coefficient (D_RCM) of LAS decreased by 56% and 67%, respectively, with FA increasing from 0 to 10%. The electric flux and D_RCM further decreased by 71% (153C) and 66% (3.24 m²/s), respectively, with FA increasing from 10 to 20%. As 5–10% SF was further added, the electric flux and D_RCM of LAS decreased to extremely low levels; for instance, with FA = 10% and SF = 10%, D_RCM = 1.61 m²/s, and the electric flux was too small and could be ignored. The contact stresses between aggregate and shotcrete mixtures were measured to investigate the rebound trend of ALSC in shotcrete. According to the analyses of the theoretical model of the rebound behavior of aggregate in shotcrete proposed by Armelin and Banthia, because of the reduced contact stresses between ALSC and mortar and the smaller density of LAS compared with normal-weight aggregate, the rebound rate of ALSC was about half of that of normal-weight aggregate in the shooting process of the shotcrete. Full article

This study analyses the deterioration of mechanical properties in lightweight concrete after exposure to room temperature (20 °C) and high temperature, i.e., up to 1000 °C, including changes in visual appearance, loss of mass, and compressive strength. All-lightweight shale ceramsite aggregate concrete (ALWAC) and semi-lightweight shale ceramsite aggregate concrete (SLWAC) are prepared using an absolute volume method to analyse the relationships between relative ultrasonic pulse velocity, loss rate of compressive strength, damage degree, and temperature levels. Our results show that, under high temperature, the lightweight aggregate ceramsite concrete performs better compared to normal concrete. After exposure to 1000 °C, the ALWAC shows a strength loss of no more than 80%, while the normal concrete loses its bearing capacity, with a similar strength loss as the SLWAC. Furthermore, the relative ultrasonic pulse velocity and damage degree are used to evaluate the effects of high temperature on the concretes, including the voids and cracks on the surface and inside of the specimens, which induces the deterioration of mechanical properties and contributes to the thermal decomposition of the cementing system and the loss of cohesion at the aggregate interface. Based on internal structure analyses, the results from this study confirm that the lightweight aggregate concrete shows a high residual compressive strength after exposure to the high temperature. Full article