Influence of Chemical Admixtures on Fresh and Hardened Properties of Prolonged Mixed Concrete

摘要

Effects of different chemical admixtures on fresh and hardened properties of prolonged mixed concrete and their cost-effectiveness were investigated. Influence of sand to aggregate volume ratio, cement content, and use of chilled mixing water on the properties of prolonged mixed concrete was studied as well. Different concrete mixtures were prepared using five different types of chemical admixture (one water reducer based on lignosulfonate and four superplasticizers based on sulfonated naphthalene polymer, polycarboxylic ether, second-generation polycarboxylic ether polymer, and organic polymer), varying s/a ratio (0.40 and 0.45) and cement content (340 kg/m3 and 380 kg/m3) and using chilled mixing water. Slump tests were performed at 15-minute intervals to assess the fresh performance of each prolonged mixed concrete mixture. 100 mm by 200 mm cylindrical concrete specimens were prepared and tested for compressive strength, Young’s modulus, splitting tensile strength, and ultrasonic pulse velocity. Results indicate that concretes with sulfonated naphthalene polymer-based superplasticizer and second-generation polycarboxylic ether-based superplasticizer show best performances in both fresh and hardened states. Concrete with lignosulfonate-based water reducer exhibits poor performance in comparison with the concretes with superplasticizers. The cost per unit compressive strength of concrete with sulfonated naphthalene polymer-based superplasticizer is lower compared with the concretes with other types of chemical admixture.