Sustainability enhancement of calcined clay and limestone powder hybrid ultra-high-performance concrete using belite-rich Portland cement

Abstract

In this study, limestone calcined clay cement (LC3) was used to prepare ultra-high-performance concrete (UHPC), and the effects of different cement types (ordinary Portland cement (OPC) and belite-rich Portland cement (BRC)) on the performance of LC3-UHPC were investigated. The main objective was to develop UHPC with low autogenous shrinkage, low heat of hydration, low CO2 emissions, and high compressive strength. The water–cement ratio of the specimens was 0.2, the weight ratio of cement: calcined clay: limestone was 7:2:1, and the replacement rates of BRC for OPC were 0, 33, 66, and 100%. A series of macroscopic and microscopic tests were conducted for all specimens to assess their properties and performance. The experimental results show that BRC can effectively control cement hydration, reduce the internal temperature increase, slow the decrease in internal relative humidity, and effectively reduce autogenous shrinkage. After 28 d of curing, the compressive strength and ultrasonic pulse velocity of the BRC-doped specimens significantly increased, and the Ca(OH)2 content and resistivity decreased compared to those of the OPC specimens. In addition, the CO2 emission calculations revealed that the incorporation of BRC reduced the total and normalized CO2 emissions. The specimens doped with 33% BRC exhibited the lowest normalized CO2 emissions. In general, LC3-UHPC showed a good comprehensive performance, particularly after replacing OPC with BRC. It exhibited low autogenous shrinkage, low heat of hydration, low CO2 emissions, and high compressive strength, which promote sustainability and engineering applications of UHPC.