Thermal behaviour and characterization of cement composites with burnt kaolin sand

The kaolin sand containing 36 wt% of kaolinite was thermally transformed at 650 °C/L h to the burnt kaolin sand (BKS) with relevant content of metakaolinite. Thermal behaviour of composites with substitution of Portland cement (PC) by the BKS containing 0, 5, 10 and 15 wt% of metakaolinite and water-to-solid ratio of 0.5 kept for 90 days in 20 ± 1 °C water was studied by thermal analysis. TG/DTA/DTG studies concerned calciumsilicate hydrate and calciumaluminate hydrate formation, portlandite dehydroxylation and calcite decarbonation. The influence of curing time and metakaolinite content were estimated. The reduction in portlandite content was observed in PC–BKS composites opposite to that found in the reference PC system. Compressive strength uptakes were observed in PC–BKS composites relative to that of reference PC system. BKS is characterized as effective pozzolanic material giving cement composites of high performance. The above findings were confirmed by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM) results.