Improvement of concrete performance through a ternary aggregate system: Microstructural insights into pore structure and ITZ characteristics
Haibo Hu, Xiaosong Ma, Junqing Zuo, Yongqi Wei, Anming She, Wu Yao, Min Wu
Abstract
Durability remains one of the key factors determining the long-term performance and service life of concrete structures. This study investigated a novel way to use waste dolomite powder (WDP) in concrete, aiming to develop a ternary aggregate system that simultaneously improves mechanical properties and durability. Experimental results showed that incorporating WDP in the concrete increased the 90-day compressive strength by up to 21.06% and the splitting tensile strength by 10.84%. Meanwhile, durability was significantly enhanced: compared to that of the control concrete, the reductions in drying shrinkage, water absorption and chloride migration coefficient of the concrete containing WDP were up to 17.27%, 35.59%, and 43.20%, respectively. The XRD, FTIR, and TGA results verified that WDP provided a stable crystalline phase dolomite (CaMg(CO 3 ) 2 ) which contributes to maintaining long-term dimensional stability. Acting as a micro-aggregate, WDP effectively filled into pores and refined the interfacial transition zone (ITZ). Pore structure analysis confirmed that the cumulative pore volume decreased by up to 21.83%, while the content of the harmless pore content (≤ 20 nm) increased by 35.49%. The SEM-EDS and Vickers hardness measurements further showed a narrower ITZ. Notably, the microhardness of the ITZ and the matrix were improved by 38.38% and 39.62%, respectively. In addition, the life-cycle assessment results show that incorporating WDP in concrete effectively reduced CO 2 emissions, energy consumption, and economic costs. These findings demonstrate that WDP can be effectively utilized to produce more sustainable concrete with superior durability and mechanical performance.