Production of Semi-lightweight Concrete Using Calcite Powder Pellets as Coarse Aggregates

Abstract

The present study discussed on utilizing the Calcite fines (wood ash) in the production of semi-lightweight concrete (sLWC). Wood ash is obtained from nearby industrial areas and made into pellets by pelletization process. Calcite powder pellets (CPP) were replaced entirely with coarse aggregates and employed in the preparation of sLWC. Before the production of sLWC, five types of pellets with different compositions were produced. The five combinations are calcite fines + NaOH, Calcite fines + cement, calcite fines + fly ash, calcite fines + fly ash pellets with cement coating and calcite fines + cement + fly ash. Experiments such as specific gravity, bulk density, water absorption, and crushing strength were conducted on pellets. As a result, the pellets with the combination of calcite fines + cement + fly ash has achieved the specific gravity, bulk density, water absorption and crushing strength as 2.0, 1140 kg/m3, 23% and 4.44 MPa, respectively, which is found to be better-performed pellets in comparison with other pellets. Those pellets were taken to further experimental studies by making into sLWC such as fresh property (i.e., slump cone test) and hardened properties (i.e., density, compressive test and Young’s modulus). ACI 211.1 method was followed for mix design. Cement was kept in the range of 300, 400 and 450 kg/m3 to examine the properties of sLWC from lower cement content to higher cement content. From the results, the sLWC mix with 450 kg/m3 cement shows a better performance than other sLWC. The maximum compressive strength was found to be 28.4 MPa with a density of 2200 kg/m3 which achieves nearly a conventional M25 grade concrete.