Concrete Manufacturing

Cement manufacture is energy intensive and contributes a considerable amount of CO2 emissions into the atmosphere. In this study, Corn cob ash (CCA) was used as the blending agent with cement in concrete. The experimental plan was designed to carry out compressive strength, flexural strength, density and water absorption tests on grade 30 concrete using 0, 5, 10, 15 and 20% CCA contents. The results indicated that compressive and flexural strength decreased with increase in CCA content and increased with curing period. The optimum blend was obtained at 10% CCA and 90% OPC contents with compressive and flexural strength values of 30.17 N/mm2 and 5.64N/mm2 at 90 days respectively. Concrete containing 20% CCA has water absorption of 1.80% at 90

Every 1 ton of concrete leads to CO2 emissions which vary between 0.05 to 0.13 tons. About 95% of all CO2 emissions from a cubic yard of concrete are from cement manufacturing. The annual global production of concrete is about 5 billion tons. If the consumption of this building material remains at this frightening level, it is expected that about 3.5 billion metric tons of cement would be produced by the end of 2050 which amounts to doubling the CO2 emissions [1].

The need for sustainable and energy efficient construction materials has necessitated extensive research on alternative materials that can reduce the environmental impact of cement. It is important to reduce this impact through the replacement cement with artificial pozzolanas, clay, agricultural waste and others geo-based materials. Supplementary cementitious materials (SCM) are generally byproducts from other processes or natural materials. They may or may not be further processed for use in concrete. Some of these materials are called pozzolans, which by themselves do not have any cementitious properties, but when used with Portland cement, react to form cementitious compounds. SCM are primarily used for improved workability, durability and strength. They modify the microstructure of concrete and reduce its permeability thereby reducing the penetration of water and waterborne salts into concrete

Three (3) cubes were tested for each curing period and level of cement replacement. A total number of Seventy Five (75) cubes were tested in accordance with BS EN 12390 [16] and BS EN 12390 [17] specifications. Flexural strength test was carried out on the hardened concrete beams containing 0, 5, 10, 15 and 20% CCA to replace cement by weight, and cured for 7, 14, 28, 60 and 90 days respectively, in accordance with BS EN 12390 [18]. Three (3) beams were tested for each curing period and level of cement replacement. A total number of Seventy Five (75) beams were tested. The saturated density of the hardened concrete cubes prepared for compressive strength test was calculated as per BS EN 12390 [19]. The water absorption was determined on concrete cubes prepared for compressive strength test. The test was carried out in accordance with BS 1881 [20]. RESULTS AND DISCUSSIONS

3.1 Water