Accelerated carbonation curing of building mortars incorporating volcanic ash and brine sludge

Traditional cement composites production is a major contributor to greenhouse emissions due to the extensive use of cement. From a sustainability perspective, minimizing the use of cement in the building and construction sector will reduce CO₂ emissions and save energy and natural resources. Since there is insufficient theoretical and experimental data on cement composites incorporating volcanic ash (VA) and brine sludge (BS), the present study developed sustainable blended cement mortars containing VA and BS, which were used to replace up to 40% of cement and subjected to accelerated carbonation curing (ACC). The changes in the microstructure morphology, mineralogy, and CO₂ uptake were examined using SEM, XRD, and TGA. Furthermore, the mechanical properties of volcanic ash-brine sludge (VABS) mortars including compressive strength, modulus of elasticity, split tensile strength, and flexural strength were evaluated. Results indicate that the dilution effect of VA and BS particles enhanced CO₂ diffusion in mortar specimens leading to further carbonation and formation of CaCO₃. This improvement is linked to the enhancement of all mechanical properties of VABS mortars exposed to ACC, compared to water-cured VABS mortars. The 28-day compressive strength of ACC specimens exhibited an increase of 14.5%, 4.8%, and 9.0% for 10VA20BS, 20VA10BS, and 20VA20BS mortars, respectively. However, TGA of ACC samples shows that the well-crystalline CaCO₃ was highest in the control sample with 60% while it was limited in the 10VA20BS, 20VA10BS, and 20VA20BS samples with only 14%, 19%, and 6%, respectively.