Effect of calcined Czech claystone on the properties of high performance concrete: Microstructure, strength and durability

Most supplementary cementitious materials (SCM) have been only rarely used in high performance concrete (HPC) design to date, silica fume being one of the very few exceptions in that respect. The content of many SCMs in blended cements was also often low because at higher dosage they were not capable to replace Portland cement effectively. Their environmental and economical advantages could thus be utilized in a limited extent only. In this paper, the effect of calcined Czech claystone (CCC) on the properties of HPC based on a binary binder containing Portland cement and silica fume was analyzed over a 10-60% range of Portland cement replacement in the mix. The material characterization experiments carried out using mercury intrusion porosimetry and scanning electron microscopy showed that an up to 30% presence of CCC in the blend resulted in a formation of closer packed HPC microstructures than if only silica fume was used as SCM. The highest compressive and bending strengths were achieved for the 30% Portland cement replacement level over the whole one year testing period. The best durability properties expressed in terms of water and water vapor transport parameters were observed for the same mix with 30% of CCC used instead of Portland cement.