ABSTRACT
Once the variables having the statistically significant influence on the responses were identified, a Doehlert experimental design [Doehlert, 1970] was used to optimize the levels of these variables. The number of experiments required (N) is given by N = n2 + n + n0, where n is the number of variables and n0 is the number of center points. In this study, three factors (i.e., variables) percentage of fly ash (X1), molarity of the hydroxide solution (X2) and the percentage of silicate solution (X3). Therefore, 13 experiments were conducted along with the reference mix in order to keep track on the change in the environmental conditions. The second degree polynomial (Equation. (1)) was fitted to the experimental data by using the statistical
1 INTRODUCTION
Concrete usage around the world is second only to water. Ordinary Portland cement (OPC) is conventionally used as the primary binder to produce concrete. The amount of carbon-di-oxide released is in the order of one ton for every ton of OPC produced. So, one of the ways to produce environmentally friendly concrete is to replace OPC with by-product material such as fly ash, slag, rice husk etc.
