Factorial Optimization of Gypsum Addition to Foundry Slag during Production of Maximum-Compressive-Strength Compliant Cement
- Corresponding Author:
- CI Nwoye
Department of Metallurgical and Materials Engineering
Nnamdi Azikiwe University
Received: 16/04/2014 Revised: 12/05/2014 Accepted: 26/05/2014
This paper presents the predictability and optimization of gypsum addition to foundry slag during production of maximum-compressive-strength compliant cement using a empirically derived model. The model expressed as; β = 0.04 α – 0.0024 α2 – 0.0288 is quadratic in nature, indicating that the slag cement maximum-compressive-strength is dependent on the optimum concentration of gypsum added. The slag cement compressive strengths per unit gypsum addition are 0.0160 and 0.0208 N mm-2/% as obtained from experiment and derived model respectively. The correlations between compressive strength and concentration of gypsum addition are 0.8839 and 0.9977 as obtained from experiment and derived model respectively. The maximum deviation of the model-predicted slag cement compressive strength from the corresponding experimental value is less than 12%. The validity of the model was rooted on the expression 17.3611 β + 0.0417 α2 = 0.6944 α – 0.5 where both sides of the expression are correspondingly approximately equal. The optimum concentration of gypsum addition which inputs maximum-compressive-strength: 0.1378 N/mm2 to the slag cement is 8.3333 %. At 15% gypsum addition, the slag cement compressive strength is minimum. Beyond 15% gypsum addition, the slag cement compressive strength becomes only imaginary in compression; a situation that typifies a build-up in its tensile strength.