This study investigates the carbonation degree of reclaimed water (RW) and its potential use as mixing water for cementitious materials under controlled laboratory conditions using a simplified CO₂ injection method. To reproduce the chemical environment of actual RW, a synthetic reclaimed water (SRW) system with a cement-to-sand ratio of 8:2 was prepared and used throughout the evaluation. Thermogravimetric analysis revealed that the cementitious solids suspended in SRW exhibit high reactivity with CO₂, achieving a net CO₂ uptake of 16.8%, equivalent to 8.31 g of CO₂ sequestered per kilogram of RW. The use of untreated RW as mixing water slightly reduced flowability and increased superplasticizer demand compared with distilled water, whereas carbonation treatment of RW improved workability and mitigated the rapid initial setting typically observed with untreated RW. Notably, replacing 3% of the cement with carbonated RW solids did not cause any reduction in compressive strength, indicating that the carbonated solids can be incorporated without compromising mechanical performance. These results confirm that the CaCO₃ formed during RW carbonation remains stably retained within mortar and concrete, demonstrating the feasibility of using carbonated RW as a dual-function material—serving both as mixing water and as a medium for CO₂ sequestration.

This study aims to produce Ultra-High-Performance Concrete utilizing locally available material. The experimental study includes silica fume with rice husk ash in combination with steel fibers. Various trials were made using different volumes of local materials and steel fibers to produce UHPC. Different properties were evaluated, such as compressive strength, tensile strength, and Scanning Electron Microscopy (SEM). Results show that UHPC can be produced using locally available materials as both the properties were examined with and without heating at higher temperatures and providing satisfactory strength. SEM tests were also performed to evaluate the microstructural study of the ultrahigh-performance concrete. SEM observations discovered that the transition zone between fine aggregates and the cement paste is improved by using silica.