ABSTRACT

The research aims to compare the performance of natural gypsum and Citrogypsum

as a set retarder in Portland cement. Commercial Portland cement which contains natural

gypsum was obtained from Northern Cement Corporation while Citrogypsum was

produced from the synthesis of citric acid, which was obtained from Blaine Corporation.

The Citrogypsum synthesized contains 90.73% calcium sulfate dihydrate. Half of it

was further converted into hemihydrate to compare the performance of Citrogypsum with

different hydrations. The Citrogypsum was added to the clinker at varying percentages of

3%, 4%, and 5%. Compressive strength and setting time were tested for each percentage to

determine the best concentration that would give the best value.

Using Analysis of Variance (ANOVA), it was determined that there is a significant

interaction between Citrogypsum concentration and hydration on compressive strength.

The differences among the compressive strength of Portland cement using varied

Citrogypsum concentrations were also significant. Statistical analysis further shows

significant difference between the Compressive strength of Portland cement with

Citrogypsum as Calcium sulfate dihydrate and Calcium sulfate hemihydrate.

The concentration and hydration which gives the best compressive strengths and

satisfies the required setting time for commercial cement is 3% calcium sulfate dihydrate.

Compressive strength of this cement was also compared with that of commercial cement

which uses natural gypsum. Results show that the performance of cement with

Citrogypsum exceeds commercial Portland cement. These results demonstrate the potential

of Citrogypsum as an alternative to natural gypsum as retarder for Portland cement.