The purpose of this study is to assess the Embodied Energy (EE) and Carbon IV Oxide (CO 2 ) emissions saving potentials of Corn Cob Ash (CCA) as partial replacement of Ordinary Portland Cement (OPC) in concrete. Cement manufacture is energy intensive and contributes considerable amount of CO 2 emissions into the atmosphere. Globally, Concrete is the most consumed man-made material and about 95% of CO 2 emissions from a cubic meter of concrete are from cement manufacturing. In this study, the experimental plan was designed to carry out compressive strength, flexural strength, density and water absorption tests on the concrete using 0, 5, 10, 15 and 20% CCA contents to replace OPC. Inventory method of analysis was used to determine the EE and CO 2 emission for all the concrete mixes. The results indicated that the water absorption, density, 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. The EE and CO 2 emission decreased with increase in CCA contents. At 20% CCA content the EE was 2382 MJ/m 3 which is 12.04% less than that of control samples. Also, 16.37% embodied CO 2 emission saving was obtained for samples containing 20% CCA. The regression equations generated gave standard deviation, S, < 1.0, P-value < 0.05, T-statistics > T24, 0.05 and F-statistics > F1, 23, 0.05. All these indicated that there is good relationship between the predictors and the responses.

Mortars provide the continuity required for the stability and exclusion of weather elements in masonry assemblies. But because of the heterogeneity of the mortar, its mechanism of behaviour under different load effects is dependent on the properties of the constituents of the mortar. The aim of paper is to determine the effect sand grading for various cement-sand-lime mortar designations (BS) and strength classes (EC) on the compressive strength and stiffness of mortar. Two silica sands; HST 95 and HST60 were used to make mortars in three strength classes: M2, M4 and M6, corresponding to mortar designations iv, iii and ii respectively. The results show that mortar made with the HST60 sand (coarser grading) usually resulted in mortar with a higher compressive strength and stiffness. The One Way ANOVA analysis of both compressive strength and stiffness at a significance level of 5% on the effect of sand grading on the two parameters also shows that they are both significant. There is also strong evidence of a linear correlation between the stiffness and compressive strength. The results indicate that in order to replicate full scale behaviour of masonry at model scales, the grading of fine aggregate in the models should be similar so as to properly model full scale behavior.

This research predicts the strength properties of concrete containing Calcined Black Cotton Soil (CBCS) using response surface methodology. Cement production requires large amount of energy and emits greenhouse gases that have negative impact on the environment. Utilization of CBCS as cement replacement in concrete will reduce these negative impact. Experimental plan was designed using response surface method in Design Expert software to predict compressive strength, density and water absorption of concrete containing CBCS. The CBCS was varied from 5 to 20% while the curing period was varied and 7 to 28 days. Face-centered central composite design method of response surface was used. The design consists of two design factors at three levels (coded as -1, 0, +1) each. The factors are the curing period, and the CBCS contents. The results showed that CBCS is a pozzolana. CBCS increases durability of concrete by decreasing its water absorption. All the response surface models developed for the water absorption, density and compressive strength showed very good relationship between the predictors and the responses with coefficients of determination, R 2 ˃ 0.94 and p-values ˂ 0.05.

This paper investigates the effect of the size and shape of coarse aggregates on the compressive strength of concrete. Concrete strength is affected by the surface texture, grading and maximum aggregate size. Six different sizes of coarse aggregate have been selected for both angular and rounded coarse aggregate. The coarse aggregates were used in the production of concrete and tested for workability, density and compressive strength. The specimen was cured for 3, 7, 14, 21 and 28 days by full water immersion. The results indicated that under the same curing conditions and water-cement ratio, the compressive strength of concrete produced with both angular and rounded aggregates increased with increasing aggregate size, up to an aggregate size of 14 mm. The optimum compressive strength of 27.58 N/mm2 and 25.88 N/mm2 were achieved at 28 days curing and 14 mm aggregate size for concrete with angular and rounded aggregates respectively. Coarse aggregates with angular shape result in concretes with better compressive strength than coarse aggregates with a rounded shape. The model equation developed to predict the compressive strength of rounded aggregate has R2 value of 95.66%, and the higher the value of R2, the better the model fits the data.