Utilization of Jebel Marra Volcanic Ash as Low Cost Material in Concrete Hollow Blocks in Darfur, Sudan

Abstract

Concrete hollow blocks (CHB) have an important place in modern building industry, and although the CHB is considered a better alternative to fired bricks from the ecological and economical points of view, however, its prices are still high, since the main cost-factor is the ordinary Portland cement (OPC). This study is mainly focusing on the utilization of volcanic ash (VA) from Jebel Marra as a low cost material for CHB. In this study a VA sample from Jebel Marra (Al-malam area) was investigated for its physical and chemical properties, different substitution levels of 10, 20, 30, 40, and 50% of the OPC with pozzolanas were tested. Combined aggregates of locally available sand and stone aggregates were also tested for their economical value of fineness modulus. Then the potential use of these materials was implemented in (CHB) with different blends and mix ratios. The results of the chemical and physical analysis of the VA showed their compliance to the international specifications. The strength activity index of the mix containing 20%VA of the OPC weight at 28 days was 87%. If consider 3.5 MPa as the minimum compressive strength of load bearing CHB required by the Indian standard, it can be concluded that the VA can be used successfully as low cost material in the CHB with the substitution level up to 40%, 30%, and 20%, for binder aggregates ratio by volume 1:6, 1:7, and 1:8, respectively, with subsequent reduction in binder cost by 34, 26, and 17%, In addition, increasing the compressive strength of blocks can be achieved by using high pressure blocks making machine.