Search Results (113)

The combined application of fibers and lightweight aggregates (LWAs) represents an effective approach to achieving high-strength, lightweight concrete. To enhance the predictability of the mechanical properties of fiber-reinforced lightweight aggregate concrete (LWAC), this study conducts an in-depth investigation into its hydration characteristics. In this study, high-strength LWAC was developed by incorporating low water absorption LWAs, various volume fractions of basalt fiber (BF) (0.1%, 0.2%, and 0.3%), and a ternary cementitious system consisting of 70% cement, 20% fly ash, and 10% silica fume. The hydration-related properties were evaluated through isothermal calorimetry test and high-temperature calcination test. The results indicate that incorporating 0.1–0.3% fibers into the cementitious system delays the early hydration process, with a reduced peak heat release rate and a delayed peak heat release time compared to the control group. However, fitting the cumulative heat release over a 72-h period using the Knudsen equation suggests that BF has a minor impact on the final degree of hydration, with the difference in maximum heat release not exceeding 3%. Additionally, the calculation model for the final degree of hydration in the ternary binding system was also revised based on the maximum heat release at different water-to-binder ratios. The results for chemically bound water content show that compared with the pre-wetted LWA group, under identical net water content conditions, the non-pre-wetted LWA group exhibits a significant reduction at three days, with a decrease of 28.8%; while under identical total water content conditions it shows maximum reduction at ninety days with a decrease of 5%. This indicates that pre-wetted LWAs help maintain an effective water-to-binder ratio and facilitate continuous advancement in long-term hydration reactions. Based on these results, influence coefficients related to LWAs for both final degree of hydration and hydration rate were integrated into calculation models for degrees of hydration. Ultimately, this study verified reliability of strength prediction models based on degrees of hydration. Full article

The use of short cylinders of recycled aggregate concrete (RAC) reinforced with basalt fiber-reinforced polymer (BFRP) circumferential strips and polyvinyl chloride (PVC) tubes has been proven effective in previous studies. However, BFRP circumferential strips are cumbersome to install and do not ensure the integrity of the BFRP strips. Therefore, this study investigates axial compression experiments on RAC short cylinders reinforced with BFRP spiral strips and PVC tubes. A combination of experimental studies, finite element simulations, and theoretical analyses revealed that the winding angle and spacing of BFRP strips significantly affect the load-bearing capacity and ductility of the restrained specimens. Additionally, an improved strength model was developed based on an existing model. When evaluated using both computational and experimental results, the equations generated in this study showed an average error of less than 10%. The findings indicate that the composite structure provides effective reinforcement and offers valuable reference information for practical applications. Full article

To elucidate the effects of iron ore tailings (IOTs) and basalt fiber (BF) on the durability of recycled aggregate concrete (RAC) with different recycled aggregate replacement rates, this study used IOTs to replace natural sand at mass replacement rates of 0%, 20%, 40%, 60%, 80%, and 100% and incorporated BF at volume fractions of 0%, 0.1%, 0.2%, and 0.3%. Carbonation and freeze–thaw cycle tests were conducted on C30 grade RAC. The carbonation depth and compressive strength of RAC at different carbonation ages and the mass loss rate, relative dynamic elastic modulus, and changes in compressive strength of RAC under different freeze–thaw cycle times were determined. Scanning electron microscopy (SEM) was utilized to meticulously observe the micro-morphological alterations of BF-IOT-RAC before and after carbonation. We then investigated the mechanisms by which BF and IOTs enhance the carbonation resistance of RAC. Utilizing the experimental data, we fitted relevant models to establish both a carbonation depth prediction model and a freeze–thaw damage prediction model specific to BF-IOT-RAC. Furthermore, we projected the service life of BF-IOT-RAC under conditions typical of northwest China. The results showed that as the dosages of the two materials increased, the carbonation resistance and frost resistance of RAC initially improved and then declined. Specifically, the optimal volume content of BF was ascertained to be 0.1%, while the optimal replacement rate of IOTs was determined to be 40%. Compared to using BF or IOTs individually, the composite incorporation of both materials significantly improves the durability of RAC while simultaneously enhancing the reuse of construction waste and mining solid waste, thereby contributing to environmental sustainability. Full article

Compton backscattering is a versatile non-destructive technique for material characterization and structural evaluation in reinforced concrete. This methodology enables a single-sided inspection of large structures—which is particularly useful where only one side of the material is accessible for examination—is relatively inexpensive, and can be made portable for field applications. This study aims to assess the influence of basaltic coarse aggregates on the accurate localization and dimensioning of rebar in reinforced concrete using the gamma-ray Compton backscattering technique at two distinct incident photon energies—59.5 keV and 1170 keV. The analysis was performed through Monte Carlo simulations using the FLUKA code, providing insights into the feasibility and limitations of this non-destructive method for structural evaluation. Both photon energies successfully detected the rebar embedded at a 3 cm depth in mortar, achieving a good spatial resolution and contrast, despite the presence of a significant amount of iron oxide within the aggregate. Among the evaluated sources, ⁶⁰Co yielded the highest contrast and count values, demonstrating its potential for rebar detection at greater depths within concrete structures. The single-sided Compton scattering technique proved to be effective for the investigated application and presents a promising alternative for the non-destructive assessment of real-world reinforced concrete structures. Full article

This study analyzed the effects of curing and maturation on the formation of shrinkage strain and destructive processes in concrete. Experimental tests were performed on commonly used concrete, class C30/37, with basalt aggregate and blast furnace cement tested: at constant temperature after water curing, at constant temperature without water curing, and under cyclically changing temperature without prior curing. Shrinkage strain was measured for 46 days with an extensometer on 150 × 150 × 600 mm specimens, and the acoustic emission (AE) method was used to monitor microcracks and processes in concrete in real time. The results were compared with the model according to EN 1992-1-1:2023. It was found that this model correctly estimates shrinkage strain for wet-curing concrete, but there are discrepancies for air-dried concrete, regardless of temperature and moisture conditions (constant/variable). Correlation coefficients between shrinkage strain increments and process increments in early-age concrete are proposed. Correlations between shrinkage strain and destructive processes occurring in concrete were confirmed. It was found that by using correlation coefficients, it is possible to estimate internal damage in relation to shrinkage strain. The results indicate the need to develop guidelines for estimating shrinkage strain in non-model environmental conditions and demonstrate the usefulness of the nondestructive AE method in diagnosing early damage, especially in concrete structures exposed to adverse service conditions. Full article

The demand for super-tall buildings and long-span bridges has driven concrete development toward higher strength and durability. Therefore, this study investigated the impact of composition of materials (aggregates, admixtures, and steel fibers) on the mechanical performance and economic feasibility of coarse aggregate reactive powder concrete (CA-RPC). The goal is to identify optimal combinations for both performance and cost. Scanning electron microscopy (SEM) and pore structure analysis were used to assess microstructural characteristics. The results demonstrated that replacing quartz sand with yellow sand as the fine aggregate in CA-RPC effectively reduced construction costs without compromising compressive strength. The use of basalt as the coarse aggregate led to higher mechanical strength compared to limestone. Incorporating 20% fly ash reduced the 7-day compressive strength, while the 28-day strength remained unaffected. The addition of 10% silica fume showed no obvious effect on the early strength but significantly improved the 28-day strength and workability of the concrete. Moreover, the incorporation of steel fibers improved the flexural strength and structural integrity of CA-RPC, shifting the failure mode from brittle fracture to a more ductile cracking behavior. SEM observations and pore structure analyses revealed that the admixtures altered the hydration products and pore distribution, thereby affecting the mechanical performance. This study provides valuable insights into the strength development and underlying mechanisms of CA-RPC, offering a theoretical basis for its practical application in bridge deck pavement and tunnels. Full article

Facing sand and gravel shortages, construction waste accumulation, and the “double carbon” goals, improving the performance of recycled aggregate concrete (RAC) and utilizing mineral waste slag are key to the development of green, low-carbon building materials. To enhance the mechanical performance of RAC and facilitate the sustainable utilization of mineral waste, this study innovatively incorporated copper slag (CS), ground granulated blast furnace slag (GGBS), and basalt fiber (BF) into RAC. The modified RAC’s compressive, split tensile, and flexural strengths were systematically investigated. Experimental results indicated that incorporating appropriate amounts of CS or GGBS as single admixtures could effectively enhance the mechanical properties of RAC, with 20% (w) GGBS showing the most pronounced improvement. Compared with RAC, its 28 d compressive strength, split tensile strength and flexural strength were improved by 21.3%, 9.7% and 8.1%, respectively. As opposed to single admixture, 10% CS + 10% GGBS admixture can further improve the mechanical properties of recycled concrete. Compared with RAC, its 28 d compressive strength, split tensile strength, and flexural strength were improved by 25.6%, 29.7%, and 16.6%. The study also showed that 0.2% BF admixed on top of 10% CS + 10% GGBS could still significantly improve the mechanical properties of recycled concrete, and its 28 d compressive strength, split tensile strength, and flexural strength were improved by 31.3%, 35.9%, and 31.2%, compared with RAC, respectively. By XRF, SEM, and EDS techniques, the underlying mechanisms governing the mechanical behavior of RAC were elucidated from the microscale perspective of basalt fiber and industrial waste residues. These findings provide a solid theoretical foundation and a viable technical pathway for the widespread application of recycled aggregate concrete in civil engineering projects. Full article

This study focuses on improving the recycled coarse aggregate (RCA) replacement ratio in recycled aggregate concrete products. First, the mix design and compressive performance of recycled aggregate concrete (RAC, RCA replacement percentages of 20%, 35%, and 50%) were evaluated using the monofactor analysis method and response surface methodology under three different conditions: single addition of nano-calcium carbonate (NC, dosages of 0.1%, 0.2%, and 0.3%), single addition of basalt fibre (BF, volume content of 0.1%, 0.2%, and 0.3%), and combined addition of both. The results show that the compressive strength of RAC at 7 and 28 days rises as the BF or NC content increases and then falls as the NC content increases. According to the sensitivity analysis, RAC’s compressive strength is significantly impacted by the replacement ratio of RCA, with NC having a more considerable effect on RAC’s 7-day compressive strength than BF, while BF affects the 28-day compressive strength more than NC does. Based on the desirability function, the ideal BF and NC content in RAC was optimised and confirmed by the compressive strength test. It demonstrates that the best compressive performance is achieved by RAC with 1% NC and 0.3% BF. Finally, concrete pavement brick models were created using the ideal mix proportion provided by the compressive strength test. The model compression test results show that RAC pavement bricks (RCA replacement ratio of 60%) with 1% NC and 0.3% BF had a 28d compressive strength of 5.7% and 15.8% higher than NAC and RAC pavement bricks, respectively. Full article

With the advancement of urbanization, recycled aggregate concrete derived from construction waste has received increasing research attention. This study primarily focuses on a novel method to enhance the mechanical properties of recycled aggregate concrete derived from brick–concrete waste by mixing short-cut BFRP fibers. A series of experimental tests, including an axial compression test, a splitting tensile test, and a bending test, were conducted on specimens of RBCAC (recycled brick–concrete aggregate concrete) with different brick–concrete ratios and BFRP fiber contents. The effects of the brick–concrete ratio and BFRP content on various mechanical properties were systematically investigated. The results indicate that the brick–concrete ratio significantly affects the mechanical properties of RBCAC. The compressive strength decreased by approximately 2.0–4.7% as the brick-to-aggregate ratio increased from 0.25 to 4, with the peak strength (34.3 MPa) occurring at a ratio of 0.67. In addition, a strong linear relationship was observed between the compressive strength and other mechanical properties of BFRP-RBCAC. Based on the experimental data, the existing constitutive model for recycled concrete was modified by introducing a brick–concrete ratio correction factor and a fiber reinforcement factor. The proposed compression constitutive model is suitable for recycled brick–concrete aggregate concrete incorporating hybrid BFRP fibers. Full article

Concrete and mortar production consumes significant natural resources, leading to environmental concerns and sustainability challenges. Sustainable alternatives, such as industrial byproducts, have been explored to replace clinkers and aggregates. Basalt rock powder (BRP) is a promising option due to its physical and chemical properties, including its better particle size distribution and compatibility with cementitious composites, and studies have highlighted its pozzolanic activity and its potential to improve mechanical properties (compressive strength, flexural strength, and durability). Reusing rock dust as a raw material could transform it into a mineral byproduct, benefiting the new material and reducing waste volumes. This article presents a systematic literature review on the use of BRP in construction materials, conducted using the Scopus, ScienceDirect, PubMed, and Web of Science databases and following the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) procedures. The search resulted in 787 articles (up to December 2024) and, after the screening process, 17 met the inclusion criteria. From the selected articles, information regarding the utilization of this waste product; its influence on mechanical properties, pozzolanic activity, and durability; and the sustainability associated with its use was compiled. The risk of bias was low as the search was comprehensive, all the papers were peer-reviewed, and all authors reviewed the papers independently. In conclusion, the studies demonstrate the potential of using BRP as a component of cementitious materials, indicating it as a possible innovative solution to the current challenges in the construction industry. Full article

Recycled aggregate concrete (RAC) holds significant promise for reducing the environmental impact of the construction industry. However, the poor mechanical properties of RAC compared to conventional concrete are mainly due to the porous and soft nature of recycled aggregates. While fiber reinforcement has been proposed as a promising method to address this issue, existing studies primarily focus on steel and polypropylene fibers, with limited systematic comparison of alternative fiber types and dosages. In particular, the mechanical enhancement mechanisms of basalt and glass fibers in RAC remain underexplored, and there is a lack of predictive models for strength behavior. This study evaluates the effects of basalt and glass fibers on RAC through uniaxial compression, splitting tensile, and three-point bending tests. Nine mixtures with varying fiber types and volume fractions (1.0–2.5%) were tested, and results were compared to plain RAC. Key properties such as strength, energy absorption, toughness, and flexibility were analyzed using load–displacement curves and advanced toughness indices. Both fiber types improved tensile and flexural properties, with glass fibers showing superior performance, particularly at 1.5% content, where the splitting tensile strength increased by up to 40% and the flexural strength improved by 42.19%. Basalt fibers dispersed more uniformly but were less effective in enhancing toughness and crack resistance. Excessive fiber content reduced matrix homogeneity and mechanical performance. Optimal fiber dosages were identified as 1–1.5% for glass fibers and 1–2% for basalt fibers, depending on the targeted property. Predictive formulas for the flexural strength of fiber-reinforced RAC are also proposed, offering guidance for the design of structural RAC elements. Full article

Concrete porosity is one of the fundamental properties for the structural characterization of cementitious materials. This study compares porosity data obtained with dynamic water vapor sorption (DWVS) with the more commonly used mercury intrusion porosimetry (MIP) method for a wide range of concrete samples made with basaltic aggregates, typical of the Canary Islands, which are porous. The objective was to propose an alternative method for routine concrete monitoring that avoids the use of a hazardous substance such as mercury. The results reveal fundamental differences between the MIP and water-accessible porosimetry (WAP) data, although a correlation between the methods was revealed where MIP = 1.18 × WAP. The study was completed by an analysis of the relationships between the porosity and the characteristics and properties of concrete (water/cement ratio and strength), as well as the calculation of the tortuosity factor and a frost durability factor. Full article

Traditional concrete has low tensile strength, is prone to cracking, and has poor durability, which limits its scope of application. Basalt Fiber Textile–Reinforced Concrete (BTRC), a new type of fiber-reinforced cement material, offers advantages such as light weight, increased strength, improved crack resistance, and high durability. It effectively addresses the limitations of traditional concrete. However, the tensile properties of BTRC have not been fully studied, especially with fine aggregate concrete as the matrix, and there are few reports on this topic. Therefore, this study conducted uniaxial tensile tests of Basalt Textile–Reinforced Fine Aggregate Concrete (BTRFAC) and systematically investigated the effects of two mesh sizes (5 mm × 5 mm and 10 mm × 10 mm) and two to four layers of fiber mesh on the tensile strength, strain hardening behavior, crack propagation, and ductile tensile mechanical properties of BTRFAC thin slabs. The tests revealed that an increase in the number of fiber mesh layers significantly reinforced the material’s tensile strength and ductility. The tensile strength of the 5 mm mesh specimen (four-layer mesh) reached 2.96 MPa, which is 193% higher than plain concrete, and the ultimate tensile strain increased by 413%. The tensile strength of the 10 mm mesh specimen (four-layer mesh) was 2.12 MPa, which is 109% higher than plain concrete, and the ultimate tensile strain increased by 298%. The strength utilization rate of the 5 mm and 10 mm mesh fibers was 41% and 54% respectively, mainly due to the weakening effect caused by interface slippage between the fiber mesh and the matrix. An excessively small mesh size may lead to premature debonding from the matrix, but its denser fiber distribution and larger bonding area exhibit better strain hardening characteristics. More than three layers of fiber mesh can significantly improve the uniformity of crack distribution and delay propagation of the main crack. A calculation formula for the tensile bearing capacity of BTRFAC thin slabs is proposed, and the error between the theoretical value and the experimental value was very small. This research provides a theoretical basis and reference data for the design and application of basalt fiber mesh–reinforced concrete thin slabs. Full article

The elastic modulus is one of the fundamental parameters controlling the mechanical behaviour of concrete. In this study, the Movable Cellular Automata (MCA) method is applied to predict the Young’s modulus of concrete based on the properties of its components. Each automaton represents one component: cement paste, fine aggregate, or coarse aggregate. A parametric sensitivity analysis was performed using Grey System Theory (GST) on hypothetical concrete modeled with the MCA method. The analysis showed that the coarse aggregate type, coarse aggregate-to-total aggregate ratio, and water-to-cement ratio have the greatest impact on the Young’s modulus. To test the effectiveness of the MCA method in modelling concrete, results of numerical simulations were compared with experimental data available in the literature. The first numerical simulations were conducted for mortars containing cement paste and sand as well as for concretes produced by adding granite to them. Two approaches were used to perform the simulations; in the first approach, a sample contained automata representing cement paste, sand, and granite, while in the second the automata represented mortar and granite. High consistency was achieved, with results from both approaches differing by only 0.6%. Subsequent simulations focused on concretes with different water-to-cement ratios (0.45, 0.55, and 0.65), the origin of the basaltic aggregate, and various aggregate contents (60%, 54%, 48%, and 42%). Results showed high agreement between simulations and experimental data, confirmed by a high coefficient of determination R² of 0.84 and mean squared error of 2.43 GPa². Finally, simulations were performed for lightweight expanded clay aggregate concrete, resulting in an R² of 0.86 and mean squared error of 0.81 GPa², which demonstrates the effectiveness of the MCA method in predicting the static elastic modulus of concrete. Full article

Recent investigations have shown that the mechanical and durability properties of recycled aggregate concrete can be enhanced using fly ash (FA) and structural fibres. However, the financial viability of combining these products in concrete has not yet been evaluated. Therefore, this study assessed the long-term cost-effectiveness of using recycled concrete aggregates (RCA), FA, and basalt fibres (BF) simultaneously in high-rise reinforced concrete buildings exposed to corrosive environments. A life cycle cost analysis was conducted using five variables, two design alternatives, and twelve design scenarios. The analysis followed ISO 15686–5:2017 using a discount rate of 0.5% and a construction-to-material cost ratio of 150%. The components considered in the life cycle cost model included materials, construction, maintenance, and disposal. The results demonstrated that employing RCA, FA, and BF in combination in concrete buildings located near the ocean achieved approximately 21% cost savings compared to buildings made with conventional materials over a lifespan of 50 years. The maintenance component exhibited the most significant cost savings, with an average reduction of about 76% in the maintenance costs for all buildings utilising RCA, FA, and BF. The sensitivity analysis revealed that the proposed building with RCA, FA, and BF remained more cost-effective than the conventional concrete building, even with an increasing RCA-to-natural-aggregate price ratio, construction-to-material cost ratio, and increasing the discount rate to 200%, 250%, and 10%, respectively. Full article