Extra Rapid Hardening Cement
Extra rapid hardening cement accelerates the setting and hardening process. It imparts strength of about 25 % higher than that of rapid hardening cement at one or two days about 10% to 20% higher at 7 days. The gain of strength disappears with the age and at 90 days, the strength of extra rapid Hardening cement is not merely same as that of Portland pozzolana cement. Extra rapid hardening cement is obtained by inter-grinding calcium chloride with rapid hardening Portland cement. The normal addition of calcium chloride should not exceed 2% by the weight of rapid hardening cement. Its specific varies between 5000 to 6000 cm sq. per gram and the size of the particles is less than 3 microns. This type of cement should be transported, placed, compacted and finished within 20 minutes after mixing.