Improvement in the aging resistance of uncoated AR-glass textile reinforcement

Textile-reinforced concrete comprises fine-grained concrete and textile reinforcements, which are usually made of glass or carbon fibers that are coated with resins to activate all the filaments of the roving sections. Uncoated textiles are still used owing to their better recyclability and formability. A known challenge is that the tensile strength of uncoated alkali-resistant (AR)-glass fibers decreases over time because of corrosion in cementitious matrices. This paper shows the potential for optimizing the aging resistance of uncoated textile reinforcements made of AR-glass by using suitable concrete mixtures. In addition to the influence of different cement types and contents, the use of silica fume and calcined clay as metakaolin is also analyzed. Tensile tests were performed after 28 days of water storage as a reference and after 3–28 days of accelerated aging in water at a temperature of 75 °C. The investigations revealed that the known high strength losses on the order of 50 % and the failure strain reductions observed when CEM I Portland cements were used in accelerated aging tests can be considerably optimized by adding microsilica and metakaolin. Furthermore, an additional replacement of CEM I Portland cement with CEM III blast furnace cement does not lead to a decrease in strength or failure strain due to the very low alkali equivalent, even when uncoated AR-glass reinforcement is used. This study highlights the importance of selecting appropriate cement types and additives to improve the aging resistance of uncoated AR-glass textile reinforcements, contributing to the development of more sustainable construction materials. • Uncoated AR-glass in CEM I mixture shows high strength and strain loss. • Optimized mixtures maintain AR-glass strength and strain in accelerated aging. • Microsilica and calcined clay reduce alkalinity, improving AR-glass durability. • Mixtures with low-alkali cements enhance durability of uncoated AR-glass fibers. • Reduced cement content enhances durability and reduces carbon footprint.