Effect of Plasticizing and Retarding Admixtures on the Properties of High Strength Concrete

Abstract

From year to year the Earth’s temperature increases due to global warming resulting in new challenges in the concrete industry. It still remains very important branch of the modern economy. Concrete is the material which is used widely. Due to the temperature rising, the transportation of fresh concrete in hot weather becomes complicated, especially high strength concrete, which contains higher amount of cement in comparison with traditional concrete. In spite of this the fresh concrete should be delivered in plastic state to provide proper placing and compaction. That’s why it is compulsory to use retarders and plasticizers if high strength concrete is designed. In this article the influence of plasticizers and retarder on properties of cement paste, fresh and hardened concrete was studied, because it is important to enhance the workability and slump retention of such concrete under hot weather. The setting time and compressive strength of cement paste with different dosages of polycarboxylate and lignosulphonate based plasticizers with retarding effect and retarder on the basis of sodium gluconate (SG) were studied. Experimental researches were carried out to determine the optimum dosage of plasticizing and retarding admixtures and their effect on compressive strength of concretes. The influence of optimal amount of polycarboxylate based plasticizer and SG on slump loss and compressive strength of concrete was established as well. The obtained results show that correlation between setting time of cement paste and slump loss isn’t observed, but rational technical decisions allow to obtain designed properties both fresh and hardened concretes.