Durability of concrete for blocks with incorporation of cementitious residue

Abstract

Abstract The incorporation of construction and demolition waste (CDW) into construction materials has stood out due to the search for sustainable practices, facing the environmental challenge of waste generation and reducing CO2 emissions in cement production, in addition to the consumption of raw materials. Therefore, this study aims to evaluate the durability of concrete for masonry blocks incorporating cementitious residue, used as a recycled aggregate, employing the particle packing concept to optimize dosage and reduce the consumption of natural materials. The research complements a previous study carried out that analyzed the mechanical and physical properties of the blocks. Different concrete mixes were analyzed, including a control trace determined by the traditional methodology, another by the unit mass test (reaching a content of 5%), and an optimized mix, based on Alfred's particle packing method. Durability was assessed through drying and wetting cycles, followed by analysis of compressive strength and carbonation depth under accelerated and natural conditions. Regarding carbonation, the carbonated depth advanced more quickly under accelerated conditions. After 4 days of exposure, the greatest depths of carbonation were 4.05 mm (natural) and 11.90 mm (accelerated), both in the mix with 5% replacement. Regarding mass loss, the results showed non-significant variations, with the greatest loss observed in the control trace (0.20%) between cycle 1 and cycle 4, and the smallest loss in the optimized trace (0.11%) between cycle 1 and cycle 3. In the analysis of compressive strength, all mixes showed reductions after completing the cycles, remaining below the minimum requirement of NBR 6136 at 28 days (3 MPa). These results indicate that there is degradation of concrete blocks after exposure to wetting and drying cycles.