The Influences of Retarding Admixtures on Volume Changes of Concrete.

摘要

A study was made of the effect of 65different chemical compounds and of three different ASTM Type D admixtures on the characteristics of cement pastes in both fresh and hardened conditions. Setting times,molecular configuration related to the effectiveness of the retarders,oven dry shrinkage,non-evaporable water and the specific surface area were determined for these admixtures. Concrete specimens were prepared to evaluate the long-term drying shrinkage of the proprietary admixtures which had been evaluated as pastes. Long term shrinkage of concrete was not appreciably affected by the admixtures tested. Plastic drying shrinkage of paste was evaluated from the completion of mixing until approximately initial set. The proprietary varieties of admixtures were used in this investigation. The amount of plastic shrinkage varied with the variety of admixture and an interaction was found between admixture variety and drying condition (humidity).