Abstract

The effect of fly ash type F and hemihydrate gypsum on the mechanical and thermal properties of unfired compressed clay bricks (UCSB) using a semi-dry mixture was determined. UCSB were molded from two different semi-dry mixtures, the bricks made with dark-brown soil + sand + chemical additives were labeled as DBS-LG while the other bricks made with the mixture dark-brown soil + sand + fly ash + chemical additives were labeled as DBS-FALG. SEM and XRD were used to investigate microstructure and mineralogical composition, respectively. Results showed that the addition of fly ash and hemihydrate gypsum improves the mechanical properties of UCSB compared to those of a clay-polymers system; thermal conductivity was similar to other clay based bricks. These results reinforce the suitability of these mixtures in low cost building bricks with energy conservation.

Key words: Carbon footprint, Earth construction, unfired clay bricks, fly ash.