Development of limestone calcined clay cement concrete in South China and its bond behavior with steel reinforcement

Abstract

Limestone calcined clay cement (LC3), consisting of ordinary Portland cement (OPC) clinker, calcined clay, limestone powder, and gypsum, has been considered a promising solution to current challenges in the cement and concrete industry, such as high carbon emissions, high energy consumption, and resource shortages. This study carries out a series of experimental investigations of LC3-based paste, mortar, and concrete, including microstructural analyses (e.g. hydration product characterization and pore structure analysis) and macro-scale testing (e.g. workability and mechanical properties), using raw materials from south China. The results show that, in LC3 paste, the replacement of clinker by calcined clay and limestone leads to an increased volume of small pores but decreased total volume of pores. The workability of LC3 mortar and concrete can be readily tailored using conventional superplasticizers. When designed for comparable 28-d compressive strength, the LC3 mortar and concrete tend to have lower early-age compressive strength, but comparable compressive strength and higher flexural strength than those of the OPC counterparts at late ages. This study also examines the bond-slip behavior between LC3 concrete and steel bars and finds that the bond strength is comparable to that of OPC concrete with the same 28-d compressive strength, but that the LC3 concrete-rebar interface exhibits higher bond-slip stiffness. These findings on LC3 concrete provide fundamental information and guidance for furthering the application of LC3 binder in structural concrete in the near future.