THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF CEMENTITIOUS MATERIALS COMPRISED OF LIMESTONE, CALCINED CLAY AND CLINKER

Abstract

Limestone, calcined clay and cement (LC³) are one of the low carbon cement materials which are used as a partial substitution of clinker and Portland cement. In this study, the effects of limestone and calcined clay (LC²) on the mechanical properties and microstructure of mortars were studied under multi-scales. It could be concluded that the compressive strength decreased slightly with an increase in the LC² content, but the flexural strength increased significantly due to the greater formation of crystalline aluminates in the LC³. The x-ray diffraction and thermal analysis results prove the pozzolanic activity of the calcined clay in the LC³ system which is in agreement with the results of the decreasing calcium hydroxide and the increasing ettringite content, and the LC² could reduce the heat of the hydration of the LC³ significantly. Also, the formation of calcium hemicarboaluminate (3CaO.Al₂O₃.Ca[(OH)(CO₃)0.5].xH₂O) and calcium monocarboaluminate (3CaO.Al₂O₃.CaCO₃.xH₂O), as well as the pozzolanic activity of the calcined clay contributed to the development of the mechanical strength.

Keywords

• calcined clay
• limestone
• mechanical properties
• microstructure