OPTIMIZATION OF CONCRETE CONTAINING LIMESTONE DUST AND LOCUST BEAN POD ASH BY CENTRAL COMPOSITE DESIGN.

The over-reliance on concrete produced from cement had kept the cost of construction high and also prevented people from building modern and cost-effective houses most especially by rural dwellers in the developing nations. Emission of carbon footprint during cement production depletes the ozone layer which is a major concern to researchers all over the world. This investigation focused on the partial replacement of cement with Locust Bean Pod Ash (LBPA) and Limestone Dust (LSD) with a characteristic strength of 20 N/mm2 . Tests were conducted on slump, compressive, and flexural strength. The results of the physical properties showed that cement had a specific gravity of 3.14, LSD and LBPA had 2.72 and 2.61 respectively. The result of the slump test for the admixed concrete containing LSD/LBPA showed that they were workable and the higher the replacement of cement with LBPA/LSD, the higher the slump value. Optimization of the admixed concrete properties was done by numerical method. Limestone dust was kept at 5% for all the runs, and LBPA ranged from 5% to 25% at curing ages of 28, 60, and 90 days. The analysis of variance showed that the model developed was significant. The optimal value obtained was 5% LSD and 5.4% LBPA at 90 days with compressive strength of 26.9 N/mm2 and flexural strength of 3.5 N/mm2 . Model equations were developed for both compressive and flexural strengths. This research recommends 5% LSD and 5.4% LBPA as cement replacements in the production of concrete.