A Case study of Effect of Clinker Phase Changes on Cement and Concrete Performance (Concrete without Additive and Concrete with a Sample of Super Plasticizer Additive)

Clinker phases have a significant effect on the technical characteristics of cement and its performance in concrete, but sufficient information is not available to determine the effect of each of these phases on the optimal performance of concrete. Therefore, in this practical essay, it was studied and a laboratory operation was designed. In the first stage, regular sampling of clinker from 2 kiln of Tehran cement factory was done in 3 months. Then 11 clinker samples (Portland type II) were selected which their phase values were different from each other. During the second stage, laboratory cementing was done in completely identical conditions using 11 clinker samples. A super plasticizer additive sample was also prepared. In the third stage, physical and chemical analysis was done on laboratory cement samples. During the fourth stage, 22 concrete mixes were prepared with 11 cement samples, and their slump were fixed (8cm in the first group and 12cm in the second group) so that 11 mixtures were labeled "without additives" and 11 mixtures were labeled "with additives". Slump loss tests within 1 hour, determination of density, determination of air content of fresh mixed concrete, compressive strength of 7, 28 and 90 days in hardened concrete were performed on concrete mixtures. Based on the results, the comparison of the effect of C3S amount of clinker on the compressive strength of standard mortar and concrete showed that the direct relationship between C3S amount and compressive strength (mortar and concrete) is not favorable; but it can be said that with each increase of C3S percentage of clinker, the 7 and 28 days strength of concrete increases by about 1.5 units (kg/cm2) and with the increase of C3S from about 57% onwards, a drop in concrete strength can be observed. These points out the negative effect of excessive increase of C3S phase. Based on the results of the tests which determine the percentage of air in fresh concrete mixes containing additives and its decrease after 30 minutes, it was determined that the optimal amount of C3A was about 5-6%.