This work focuses on gas (air) flow through a model crack meant to represent a natural crack in concrete as accurately as possible. The purpose of the present study, which builds on previous works of the authors, is twofold: first, to highlight the test accuracy and second, to examine the impact of different crack geometries, relative to the same concrete formulation, on various aspects such as crack pressure distributions, the mass flow versus square pressure gradient relationship, and inlet and outlet pressure drops. The study reveals that while there is some variability in the results for a given crack geometry, this variability is relatively controlled, given the technical nature of the experiment. Additionally, the study shows that different crack geometries mainly affect results on small crack openings (smaller than 50 µm), whereas they remain negligible for those relative to larger openings (larger than 100 µm).

This study analyzed the influences of the unit content (UC) and grading distribution (FM) of fine aggregates on the long-term skid resistance (SR) of concrete pavement. For this purpose, laboratory specimens using fine aggregates with varying UCs and FMs were made. This study used to measure the SR using a dynamic friction tester (DFT). Additionally, three-dimensional (3D) profile data of the specimen surfaces were collected using a 3D laser profilometer after specific intervals of surface polishing. This study examined the characteristics of SR by surface amplitude indices at specific wavelengths. Furthermore, this paper presents an SR prediction model through multiple linear regression analysis using surface amplitude indices. The results revealed that a combination of micro- and macrotexture amplitude indices at specific wavelengths is suitable for expressing SR. This study also showed that both the UC and FM of fine aggregates have a significant influence on long-term SR. Furthermore, the evaluation of SR using the predicted indices showed the sharpness, shape, and roughness interaction at specific wavelengths with SR. This study recommends that road engineers use this information for better understanding.

The structural performance of reinforced concrete (RC) members affected by alkali–silica reaction (ASR) is difficult to predict because of the multi-scale phenomena. Recent structural tests reveal that the performance of RC members also depends on ASR-induced crack patterns, including localized cracks and dispersed microcracks. Additionally, microscopic factors, such as crack-filling by gel and presence of microcracks, are relevant. To explore this in detail, a computational system for finite element analysis of ASR-damaged RC members was developed. This study numerically investigated the structural behavior of ASR-affected RC members based on localized/dispersed crack patterns and microscopic factors. The applicability of the developed computational system was verified by comparing the analysis results with experimental data. The analysis results showed that ASR-damaged RC members with dispersed microcracks exhibited highly ductile behavior, while those with localized cracks failed in shear. This is because the dispersed crack pattern prevents the shear crack propagation and enhances the mechanical contribution of gel filling cracks, while the localized ASR cracks facilitate critical crack propagation, leading to failure, and minimize the gel-filling effect. Through the analytical investigations, it was found that the localized ASR cracks can result in significant loss of structural performance; thus, this study recommends the assessment of structural capacity of RC members in the case where the localized cracks were observed.

The focus on sustainable construction materials has prompted research into alternatives to reduce the carbon dioxide emissions associated with the production of Portland cement. Several studies have attempted to minimise the use of Portland cement in structural concrete mixtures. However, traditional formulations and prediction models are not applicable to low-carbon concrete. Therefore, this study aimed to evaluate low carbon concrete mortar matrices, focusing on cement replacement by supplementary cementitious materials (SCMs), such as fly ash, natural pozzolans and electric arc furnace slag, increasing the compactness of the mixtures, and limiting the water-binder ratio. Different binder powder contents were studied (350 and 400 kg/m³) in two types of concrete for prefabrication: dry consistency and plastic consistency. The results showed that dry consistency mixtures with a higher fly ash content allow higher compactness. Higher compactness promotes an overall increase in Young's modulus, up to 16%, for all eco-mixtures. The analysis enabled the estimation of the Feret coefficients for each combination of cement with SCMs and their correlation with a power function, dependent on the water-cement ratio. This allows the future estimation of the strength for binder pastes of mixtures incorporating different percentages of these additions.

Concrete slurry waste is generated at concrete plants and generally re-used in new batches of concretes. Due to the presence of hydrated cement paste it has the potential to be carbonated prior to re-use in order not only to store CO₂, but also to enhance its reactivity in blends with cement. In this study, a concrete slurry waste obtained at a ready-mix concrete plant was investigated. For accelerated carbonation, a wet process was used at laboratory scale. The carbonated product was dried afterwards, characterized and used as supplementary cementitious material. When carbonated, the hydrate phases of the concrete slurry waste decomposed to calcite, gypsum and a silica-alumina gel. When blended with Portland cement (30% replacement by mass) early hydration kinetics was accelerated by the carbonated concrete slurry waste. The pozzolanic reaction of the silica-alumina gel consumed a significant part of the portlandite and showed a slightly positive contribution to compressive strength compared to inert quartz powder and to the uncarbonated concrete slurry. This offers the use of carbonated concrete slurry waste to store CO₂ in concrete with the additional benefit of reducing the cement content.

The passivation of steel bars in concrete is determined by the characteristics of the concrete pore solution. However, ion evolution in the pore solution of alkali-activated slag/limestone powder (AAS/L) systems is not yet well known. Therefore, in this study, ion evolution in real and simulated pore solutions of alkali-activated slag/limestone powder mortars is investigated using high-pressure and solid-liquid extraction methods. The study focuses on investigating the passivation behaviour of steel bars when exposed to the simulated pore solution. The results demonstrate that the contents of Ca, Na, Al, Si, and S₂O₃^2- first increase and then decrease with time, whereas the contents of K and SO₄^2- consistently increase. Among the simulated pore solutions, the one with a solid-liquid ratio of 1 : 1 and an age of 14 days closely resembles the actual pore solution. In addition, the presence of a high S content resulting from the dissolution of S in the slag inhibits the passivation process of the steel bars in the simulated pore solution of AAS. However, the passivation film of the steel bars formed in the simulated AASL pore solution is strengthened by the addition of the limestone powder.

This study aims to discuss the effects of calcium-magnesia compound expansive agent on the mechanical strength, shrinkage, and creep of concrete. On this basis, the expansive mechanism is investigated by using XRD, TG measurement, and MIP with percolation and backbone fractal dimension analysis. It is shown that replacing fly ash with calcium-magnesia compound expansive agent has little effect on the axial compression strength, but significantly reduces the elastic modulus. Moreover, increasing the amount of expansive agent from 0% to 12% leads to a reduction in autogenous shrinkage values by 9.1% to 14.8% at 180 days while causing an increase in creep by 24.5% to 37.8%. Concurrently, the porosity of the concrete increases with the addition of the calcium-magnesia compound expansive agent, and the proportion of gel and medium capillary pores in the total porosity also increases. However, fractal dimension analysis shows that it also decreases the complexity of overall connectivity of interconnected pores. Furthermore, the results obtained from TG also indicate that the calcium-magnesia compound expansive agent is beneficial for the formation of gel hydration products.