Effects of Na2CO3 on engineering properties of cement-limestone powder-slag ternary blends

Abstract

Cement-limestone powder-slag ternary blends are construction materials that can significantly reduce carbon emissions and have a high potential for broad applications. This study investigated the effects of Na2CO3 on the engineering properties, hydration, and hydration products of cement-limestone powder-slag ternary blends. The compressive strength, ultrasonic velocity, and surface resistivity of ternary cement blends were determined. The exothermic process of paste hydration was monitored for 7 d. Furthermore, the hydration products at different stages were characterized and analyzed by X-ray diffraction, thermal gravimetry analysis, and Fourier transform infrared spectroscopy. Results for the heat of hydration indicated that Na2CO3 accelerated the early hydration of the ternary blends. Adding Na2CO3 improved the 1 d compressive strength and surface resistivity of the cement paste. As the hydration progressed, Na2CO3 limited the compressive strength and ultrasonic velocity development of the ternary cement blends in the later stages. With an increase in the content, Na2CO3 reduced the calcium hydroxide inside the cement and increased the crystallinity of calcium carbonate. This study addresses the gap in existing literature regarding the use of Na2CO3 in cement-limestone powder-slag ternary blends. Furthermore, it presents new ideas for producing cement materials with a low carbon footprint and high durability.