Mechanical, microstructure and rheological characteristics of high performance self-compacting cement pastes and concrete containing ground clay bricks

Abstract

The work aimed to utilize ground clay bricks (GCBs) in the production of self-compacting concrete. Physico-mechanical, rheological and microstructure of cement pastes and concrete were investigated. Total powder contents were 400kg/m3, the cement was replaced by GCB by 0.0, 50, 100 and 150kg/m3. The compressive strength of concrete decreased with GCB content in the absence of self-compacting concrete (SCC) admixture, whereas, increases in the presence of SCC admixture up to 28days. Increase of GCB content up to 250kg/m3, the compressive strength of concrete increases. GCB enhances the compressive strength due to the pozzolanic reaction to produce additional CSH, which precipitated in some open pores. The compressive strength of OPC pastes increase with SCC admixture up to 1.5mass%, whereas decreases with SCC admixture up to 2mass%. On the other hand, cement pastes made with 12.5% and 37.5% GCB in the expanse of OPC cement show higher compressive strength with SCC admixture at 28–1095days. The efficiency of SCC admixture decreases as GCB content increases up to 12.5%, whereas the efficiency increases with GCB content up to 37.5%. The presence of SCC superplasticizer, the microstructure displayed a more dense arrangement of microcrystalline C–S–H as the main hydration products with sheets of Ca(OH)2 as shown in the micrograph. Useful conclusions and recommendations concerning use of 30–40mass% of GCB in self-compacting concrete.