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• Silane emulsion modification was used to improve the compressive strength of RA permeable concrete. • Silane emulsion modification was used to improve freeze–thaw durability of RA permeable concrete. • Mechanism of silane modification and freeze–thaw failure were verified. • Microstructure of cement matrix and ITZ were investigated based on BSE-IA technology. Currently, there are few effective methods for improving the freeze–thaw durability of recycled aggregate (RA) permeable concrete without reducing the strength or permeability. Thus, this study aims to improve the freeze–thaw durability of recycled aggregate permeable concrete without the degradation of strength and permeability. Accordingly, two silane emulsion modification methods, namely the surface modification of recycled aggregate and integral modification of cement matrix, were used to raise the freeze–thaw durability. The compressive strength, permeability coefficient, freeze–thaw durability of recycled aggregate permeable concrete were measured. The characteristics of interfacial transition zone (ITZ) and cement matrix were investigated to analyse the modification mechanism. The results indicate that surface modification of recycled aggregate can increase both the compressive strength and freeze–thaw durability of recycled aggregate permeable concrete more effectively than the integral modification of cement matrix. This study provides an effective method to improve the comprehensive performance of recycled aggregate permeable concrete. [ABSTRACT FROM AUTHOR]

Assessing the long-term durability of concrete structures subjected to external sulfate attack (ESA) poses a significant challenge, primarily due to the lack of a well-defined quantitative metric for durability limit states. Traditional performance indicators such as compressive strength, mass loss, and expansion strain are insufficient for providing a comprehensive understanding of the extent of damage and are often difficult to measure accurately in practice. The primary objective of this study is to introduce a novel durability failure indicator, namely the failure thickness of concrete under ESA exposure, designed to quantitatively assess the ultimate limit state of concrete durability. Experiments were conducted and the results confirmed that the failure thickness can reliably reflect changes in both the elastic modulus and compressive strength of concrete exposed to ESA. A prediction model for estimating the failure thickness was subsequently developed, integrating key influencing factors like sulfate concentration, initial aluminate content, and sulfate ion diffusion coefficient. The established model exhibited a high degree of correlation between the predicted and experimental failure thickness values, with a low margin of error. The findings of this research contribute to serve as a foundation for both lifespan prediction and durability design of concrete structures exposed to sulfate-rich environments. • We propose a durability failure indicator based on critical sulfate concentration. • Concrete performance deterioration can be well characterized by failure thickness. • The validity of the prediction model of failure thickness was confirmed. [ABSTRACT FROM AUTHOR]

Cathode ray tube (CRT) funnel glass has been used to partially or totally replace natural sand as fine aggregate in concrete. It is an effective and environmentally friendly method of recycling the increasing number of discarded CRT in the electronic industry. However, little research has been performed on its durability performance under environmental attacks, in particular in the areas of chloride ion penetration and sulfate attack, the two major environmental attacks on reinforced concrete structures. This study presents an experimental investigation on the durability performances of concrete using CRT funnel glass as fine aggregate in 8% sodium chloride solution, 5% sodium sulfate solution and 10% sodium sulfate solution. Four volume replacement ratios (the ratio of CRT glass to natural sand), i.e. 0%, 30%, 60%, 100%, are considered. The chloride ion content along concrete depth direction, compressive strength and elastic modulus of concrete was measured with attack time. The test results show that although the compressive strength and elastic modulus decrease with increasing content of CRT funnel glass in concrete, the long-term resistance to chloride ion penetration is enhanced by using CRT funnel glass as fine aggregate. Furthermore, the compressive strength, rather than dynamic elastic modulus of concrete containing CRT glass, is more sensitive to sulfate attack. The relative increase in strength of CRT glass concrete is obviously larger than that of control concrete under sulfate attack. This study also provides a reference for the durability design of concrete structures using CRT funnel glass as fine aggregate. [ABSTRACT FROM AUTHOR]

• Effect of titanium dioxide and graphene on the durability and mechanical properties of polyether sealant is studied. • Tensile strength after ultraviolet exposure of modified sealant improved by 102%. • Water absorption of graphene-modified sealant reduced by 85.7%. • The working mechanism of sealant with titanium dioxide and graphene has been revealed. The silane-modified polyether sealant is widely applied to fill the gaps between external walls in prefabricated buildings and to bear the deformation of joints. However, the weak tensile strength and poor ultraviolet and moisture resistance of sealant lead to severe degradation, posing threat to the building waterproofing and safety. To address the problems, titanium dioxide and graphene were adopted to improve the mechanical properties and durability of sealant. The tack-free time, tensile properties, ultraviolet resistance, and hydrophobic performance of pristine and modified sealant were investigated and the enhancement and erosive resistance mechanisms of modified sealant were revealed by microscale characterization. Results indicated that modified sealant with low content of titanium dioxide had greater tensile strength and ultraviolet resistance. The crystalline form of titanium dioxide and produced Si-O bond enhanced the ultraviolet resistance. Moreover, the 0.8% graphene-modified sealant possessed superior moisture resistance with 23% increased contact angle. Graphene increased the surface roughness and generated π-conjugated structure, improving sealant hydrophobicity. It is revealed that the enhanced properties were ascribed to the spatial structure of fillers and chemical bond energy. This work provides a novel sealant with high ultraviolet resistance and hydrophobicity, facilitating the development of durable and low-maintenance prefabricated buildings. [ABSTRACT FROM AUTHOR]