Abstract
One of the operational parameters in ball mill grinding process of composite cement is clinker hardness (litre weight of clinker). The quantity of fly ash to be blended in the composite cement is highly dependent on the clinker hardness. In this paper, the Response Surface Methodology (RSM) is used to formulate the experimental design and to analyze the effect of the operational parameters (input factors) such as clinker feed rate in tonnes per hour, fly ash feed rate in tonnes per hour and litre weight of clinker (clinker hardness) in grams/litre. The responses reported were mill output in tonnes per hour, cement residue in percentage, three days compressive strength in kg cm^-2, 28 days compressive strength in kg cm^-2, initial setting time and final setting time in minutes. The analysis using the RSM revealed that in general the clinker hardness significantly affected the mill output. Mathematical models were developed to predict the responses.

Key words
ball mill, fly ash, cement clinker, composite cement, response surface methodology

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