This study is aimed at the optimization of calcined termite mound material incorporated in mortar and concrete using Response Surfaces Methodology (RSM). The calcined termite mound material substituting cement in mortar and concrete varied from 5 to 15% at interval of 5% in mortar and concrete. Sikament NN was added from 1.0 to 3.0 at interval of 1.0. Test conducted on mortar were: consistency and setting times. For concrete, specimens were cast and tested to failure for all the mixes for curing periods of 3, 7, 28, 60 and 90 days. Modelling and optimization were carried out using Design-Expert software version 11.0 with CTM (5%, 10% and 15%) and Sikament NN (1.0%, 2.0% and 3.0%) levels taking as the input variables. The output responses for mortar were consistency, setting times, on concrete compressive strength test after 3, 7, 28, 60 and 90days curing. Comparison was made to the performance of CTM blended mortar and concrete with controls mortar and concrete in terms of consistency, setting times and in concrete compressive strengths. Results from analysis of variance (ANOVA) indicate that both CTM and Sikament are influential variable in the developed models and all the RSM models are statistically significant in all the factor levels. The optimum mix for mortar was obtained by addition of 2.09 % Sikament NN and 5% CTM replacement with 0.871 desirability. In concrete, 2.05 % Sikament NN and 5% CTM replacement with desirability 0.871 was the optimum.

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.