Search Results (64)

This study aims to enhance the performance of an innovative steel slag–ceramsite foam concrete (SSCFC) to advance sustainable green building materials. An eco-friendly composite construction material was developed by integrating industrial by-product steel slag (SS) with lightweight ceramsite. Employing a three-factor, three-level orthogonal experimental design at a fixed density of 800 kg/m³, 12 mix proportions (including a control group) were investigated with the variables of water-to-cement (W/C) ratio, steel slag replacement ratio, and ceramsite replacement ratio. The governing mechanisms of the W/C ratio, steel slag replacement level, and ceramsite replacement proportion on the SSCFC’s fluidity and compressive strength (CS) were elucidated. The synergistic application of range analysis and analysis of variance (ANOVA) quantified the significance of factors on target properties, and partial least squares regression (PLSR)-based prediction models were established. The test results indicated the following significance hierarchy: steel slag replacement > W/C ratio > ceramsite replacement for fluidity. In contrast, W/C ratio > ceramsite replacement > steel slag replacement governed the compressive strength. Verification showed R² values exceeding 65% for both fluidity and CS predictions versus experimental data, confirming model reliability. Multi-criteria optimization yielded optimal compressive performance and suitable fluidity at a W/C ratio of 0.4, 10% steel slag replacement, and 25% ceramsite replacement. Full article

In this study, a kind of sustainable ultra-high-performance concrete (UHPC) was designed by using coal gangue ceramsite (CGC) and a modified Andreasen–Andersen model. However, when CGC lightweight aggregate with high water absorption is used in UHPC with a low water–cement ratio, CGC has an adverse effect on the working performance of UHPC and may lead to the decrease of mechanical properties. This study found that a 5% silane coupling agent KH560 can make CGC hydrophobic, and cause its contact angle to increase from 0° to 111.32°. Adding 100% hydrophobic modified CGC into UHPC will significantly improve its working performance, with the highest increase of 38.51%. At the same time, the addition of 20% modified CGC can further improve the compressive strength of UHPC (28 days reached 150.1 MPa), reduce the internal porosity by 21.4%, and make the interface bond more compact. In addition, the hydration degree of UHPC has also been improved, a result caused by the cement obtaining more free water for a more complete hydration reaction. This study can provide a new scheme for solving the problem of the solid waste of coal gangue. Full article

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

The examination of crack propagation in concrete under fatigue conditions is crucial for comprehending the mechanisms of concrete fatigue failure. Variations in aggregate types result in notable differences in the fatigue crack propagation characteristics of lightweight concrete compared to ordinary concrete. Consequently, this research focused on analyzing the locations and angles of cracks in ceramsite lightweight concrete subjected to four-point bending fatigue conditions, while accounting for different levels of fatigue loading (i.e., stress levels). Furthermore, the study aimed to clarify the influence of ceramsite size and content on the fatigue crack propagation behavior in ceramsite lightweight concrete. The results indicated that an increase in the replacement rate of 5–10 mm and 10–20 mm ceramsite led to the highest probability of fatigue cracks occurring within the range of 15–45 mm from the specimen center, reaching 41.2% and 44.7%, respectively. The crack angle exhibited an increase corresponding to an increase in the content of 5–10 mm ceramsite, with the maximum average crack angle attaining a value of 86.5°. Conversely, a decrease in the content of 10–20 mm ceramsite resulted in a reduction in the crack angle. However, 20–30 mm ceramsite did not have a significant effect on the characteristics of fatigue cracks. The level of stress predominantly influenced the path of crack propagation. At stress levels of 0.55, 0.65, and 0.75, the highest proportions of crack angles fell within the range of 75° to 80°, with values of 47.1%, 43.8%, and 53.3%, respectively. Furthermore, an increase in stress levels did not affect the location of the cracks. Full article

This study investigates the shear behavior of steel truss ceramsite concrete composite interfaces through double-sided direct shear tests and finite element simulations. The results reveal three distinct shear response phases: elastic deformation, plastic softening, and full yielding. The interfacial shear capacity arises from synergistic contributions of bond strength, friction, and truss reinforcement action. Comparative analysis of design codes identifies Eurocode 2 as providing an optimal alignment with the experimental data. An ABAQUS-based finite element model incorporating a cohesive spring composite interface mechanism confirms the model’s reliability. The findings validate Eurocode 2 for ceramsite concrete interface design and propose single-row truss configurations as economically efficient solutions for lightweight high-strength composite structures. The research results are aimed at providing a theoretical basis for the design optimization and code revision of ceramsite concrete composite structures, and promoting the wide application of lightweight high-strength concrete in sustainable buildings. Full article

The experiments were divided into two groups to establish a drying shrinkage model suitable for modified ceramsite geopolymer concrete (MCGC). In the first experimental group, via comparison with dry ceramsite (untreated), a method for modifying the ceramsite surface with a 6% silicone resin was proposed which could reduce its water absorption, enhance the compressive strength and slump of the corresponding concrete, and decrease the drying shrinkage. The second group systematically explored the influences of control factors on MCGC prepared from modified ceramsite. Different water/binder (w/b) ratios, [Na₂O]/b ratios, and metakaolin content (MK/b) ratios were used in the experiment. Compressive strength and drying shrinkage tests were performed for 90 d. High w/b and Na₂O/b ratios could enhance drying shrinkage. Moreover, 8% Na₂O/b enhanced the compressive strength. Low compressive strength was obtained using 10% Na₂O/b. A high MK/b ratio reduced drying shrinkage. However, high w/b and MK/b ratios hindered strength development. Finally, a model predicting drying shrinkage for MCGC with a high prediction accuracy was proposed by considering three control factors. Due to the variety of ceramsite pretreatment methods and the considered factor limitations, the model had potential for additional enhancements. Full article

Ceramsite concrete is a kind of green building material with advantages such as low weight, heat insulation, and fire resistance. However, it has low strength, high brittleness, and the problem of aggregate floating. In this study, by adding polypropylene fibers and optimizing the preparation process, the mechanical properties of ceramsite concrete have been significantly improved, which is of great significance for promoting the application of this material in the engineering field. Through uniaxial compressive tests on 54 specimens in six groups (divided into three strength grades), the failure characteristics and stress–strain relationships of each group of specimens were analyzed, and the effects of strength grades and fiber contents on parameters such as peak stress, peak strain, ultimate strain, and elastic modulus were studied. The results show that the addition of polypropylene fibers can improve the strength of ceramsite concrete, effectively improve the deformation performance and ductility of specimens before failure, and reduce brittleness. Specifically, as the fiber content increases, the peak stress first increases and then decreases, reaching its peak at a content of 0.05%, with an increase of 8.98%. At the same time, as the fiber content increases, the peak strain and ultimate strain increase significantly, reaching their peaks at a content of 0.075%, with increases of 21.3% and 25.2%, respectively. In addition, this paper proposes a piecewise correction model for the uniaxial compressive stress–strain curve of fiber-reinforced ceramsite concrete. This model has a good fit with the full experimental curve, providing an accurate theoretical reference for the application and development of this material in engineering. Full article

Prestressed concrete box girders are commonly employed in the development of high-speed railway bridge constructions. The prestressed strands in the girder may corrode due to long-term chloride erosion, leading to the degradation of its flexural performance. To examine the flexural performance of corrosion-affected simply supported prestressed concrete box girders, eight T-shaped mock-up beams related to the girders used in the construction of high-speed railway bridges were manufactured utilizing similarity theory. Seven of the beams underwent electrochemical accelerated corrosion, and then each beam was subjected to failure under the four-point load test method. Measurements recorded and analyzed in detail during the loading process included the following: crack propagation, crack width at various loads, crack load, ultimate load, deflection, and concrete strain of the mid-span section. The results demonstrate that a corrosion rate of just 8.31% has a considerable impact on the structural integrity of the beams, as evidenced by a pronounced reduction in flexural cracks and a tendency towards reduced reinforcement failure. Furthermore, the corrosive process has a detrimental effect on mid-span deflection, ductility, and ultimate flexural bearing capacity, which could have significant implications for bridge safety. This study provides valuable insights for the assessment of flexural performance and the development of appropriate maintenance strategies for corroded simply supported box girders in high-speed railways. 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

Sludge ceramsite (SC) can be utilized as a lightweight aggregate in concrete, especially in external wall materials, due to the increasing volume of polluted sludge, which contributes to water system deterioration and poses greater threats to human health. The influence of the fresh mortar’s slump flow on the dispersion of ceramsite was studied. The ultrasonic sound velocity, capillary water absorption rate, compressive strength, and coefficient of variation (CV) were measured in this study. Thermogravimetric (TG) analysis, ultra depth-of-field microscope scanning, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were used to analyze the performance mechanism of the ceramsite concrete. The results indicated that adding SC could reduce the fluidity of the fresh concrete, with a reduction by rates of up to 2.04%. The addition of WRA could improve the fluidity by rates of up to 60.77%. The relationship between the ultrasonic sound speed and the increasing fluidity could be deduced as a negative correlation. The water absorption was negatively correlated with the compressive strength. The concrete with a slump flow of 12.35 and 12.5 cm reached the maximum compressive strength, which had the lowest water absorption, and demonstrated internal homogeneity. The optimum slump flow was 12.35 and 12.5 cm. With the slump flow of 12.5 cm, the corresponding CV was the lowest, showing the optimum SC’s dispersion. Through TG, XRD, and SEM analyses, it was verified that the addition of 0.6% WRA promoted the hydration of cement. In addition, SC increased the hydration products. Full article

The present work analyzes the effect of releasing physically bound water from hydrogel, cork, perlite, and ceramsite on materials exposed to microwave radiation and subsequently investigates possible changes in the physical properties of these materials (water absorption and thermal conductivity coefficient). The release of physically bound water from individual materials has potential practical applications in materials engineering, for example, in the internal curing of concrete, where individual aggregates could, under the influence of microwave radiation, release water into the structure of the concrete and thus further cure it. Experimental analysis was carried out with samples of the above-mentioned materials, which were first weighed and then immersed in water for 24 h. Then, they were weighed again and exposed to microwave radiation. After exposure, the samples were weighed again, left immersed in water for 24 h, and weighed again. The focus of the study was on the ability of the aggregates to release water due to microwave radiation and on the changes in the properties (water absorption, thermal conductivity coefficient) of these materials when exposed to microwave radiation. The samples were further monitored by digital microscopy for possible changes in the surface layer of the materials. The hydrogels show the highest water absorption (1000%) and the fastest water release (45 min to complete desiccation). After the release of water due to microwave radiation, their ability to absorb water is maintained. Of interest, however, is that in the case of almost complete removal of water from the soaked hydrogel, the original powdered state of the hydrogel is not obtained, but the outcome has rather a solid structure. In the case of cork, the water absorption depends on the fraction of the material. Full article

Ceramsite concrete is one of the most widely used lightweight concretes at present. Although mechanical properties of ceramsite concrete have been extensively discussed, its permeability characteristics are neglected in previous studies. Considering the importance of permeability resistance to concrete, the permeability grade and residual compressive strength after permeability of ceramsite concrete are analyzed in this study. The influence of ceramsite content and size on the permeability grade and residual strength of ceramsite concrete were investigated by the orthogonal experimental method. To further understand the above influence, an improved Bayesian framework for small sample data is also established to analyze the permeability grade and residual strength. Results show that the water–binder ratio and the content of 20–30 mm ceramsite aggregates are the most and least significant influencing factors affecting the permeability characteristics, respectively. The 5–10 mm and 10–20 mm ceramsite aggregates play secondary roles. Increasing 5–10 mm and 10–20 mm ceramsite aggregates is not helpful for improving the permeability resistance of ceramsite concrete. Compared with the orthogonal method, the proposed Bayesian framework is a useful tool for revealing the effects of various factors, which can cut the time cost and provide parameter visualization for the analysis process. Results show that the permeability resistance and residual strength of ceramsite concrete are improved significantly under optimal conditions. The permeability grade and residual strength are increased 200% and 80.3%, respectively. In addition, the residual strength may be more suitable for evaluating the permeability characteristics than the permeability grade. Full article

The development of novel materials made from waste is one of the main measures to achieve sustainable materials development. In this study, ash of mushroom and corn straw (MCA) and furnace slag (FS) were used as raw materials to prepare alkali-activated biomass ash-slag material (AABS) and sustainable ecological non-sintered ceramsite (SENC). In this paper, the effects of quicklime powder (QL), NaOH, and sodium silicate solution (SS) on AABS were analyzed using single factor and orthogonal tests, and the preferred ratio of the composite alkali activator configuration was established. SENC was prepared based on the composite alkali activator, and the microstructure and phase composition of SENC were explored using XRD and SEM–EDS. The results showed that 3 wt% QL enhanced the early age compressive strength of AABS. The composite alkali activator was best configured when the additions of QL, NaOH, and SS were 3%, 2%, and 15%, respectively. At this configuration, the 28 d compressive strength of AABS was 47.4 MPa, and most of the internal pores were less than 0.4 μm; the 28 d numerical tube pressure of the SENC reached 12.2 MPa with a softening coefficient of 0.96. According to the results of XRD and SEM–EDS, SENC contained various hydration products such as C-A-S-H, calcium hemicarboaluminate, hydrotalcite, portlandite, and vaterite. The largest proportion of hydration products was C-A-S-H, which contributed to the pore refinement and structural densification. SENC has the potential to be used as coarse aggregate in sustainable lightweight concrete. Full article

The utilization of dredged sediment (DS) as a transformative material in building applications presents an ideal consumption strategy. This study endeavors to create a novel ceramsite lightweight aggregate (LWA) through the co-sintering of DS and rice husks (RHs), further integrating this LWA into the construction of pervious concrete. Results revealed that the optimum production procedure for the DS-based LWA incorporated a 21% RH addition, a sintering temperature of 1100 °C, and a sintering duration of 21 min. Notably, the optimal ceramsite LWA, denoted as SDC-H, exhibited a cylinder compressive strength of 28.02 MPa and an adsorption efficiency for Pb²⁺ of 94.33%. Comprehensive analysis (encompassing bulk density, cylinder compressive strength, water absorption, and the leaching concentrations of heavy metals) confirmed that SDC-H impacted the specification threshold of high-strength light aggregate derived from solid waste (T/CSTM 00548-2022). Substituting 50% of SDC-H led to a diminution in the mechanical properties but an improvement in the dynamic adsorption capacity of the innovative pervious concrete, registering a mechanical strength of 26.25 MPa and a cumulative adsorption capacity for Pb²⁺ of 285 mg/g. These performances of pervious concrete containing 50% SDC-H might correlate with the evolution of an interconnected and open-pore structure. Full article

In the present study, 104 sets of flexural tests on corroded prestressed concrete (CPC) beams were gathered from different publications. A flexural strength database for CPC beams was created by incorporating standardized concrete strength and the corrosion rate of prestressed steel. This database enables the analysis of the impact of different factors on the flexural capacity, such as the beam’s width and effective depth, concrete compressive strength, shear span ratio, the prestressed steel’s corrosion level, prestressing ratio (PPR), and the effective prestress. The findings show that the flexural strength of the CPC beams is notably influenced by variations in beam width, shear span ratio, and the prestressed steel’s corrosion level and prestressing ratio compared to other parameters. Furthermore, a comparison was conducted of the Chinese code, Eurocode and ACI standard for evaluating the flexural strength of CPC beams using the established database. It shows that the three design codes overestimate the flexural strength of CPC beams, and it is unsafe to predict flexural strength using these three codes without taking into account the impact of corrosion. Finally, a practical model based on the ACI standard is suggested to provide precise and reliable predictions across a diverse set of test data. Full article