Research Of High Performance Concrete Admixture

Concrete admixture has gotten rapid development in civil engineering field in reform and opening for thirty years. The development tend of concrete is high performance concrete (HPC) with high strength, high working performance and high durability. In order to meet the needs of HPC, some HPC admixtures are synthesized. It can insure concrete with high reducing water ratio, high adaptability, high durability and good workability. The HPC admixtures not only can reduce the mixing water content in concrete to keep fresh concrete good workability during transport and construct procedure, but also ensure hardened concrete good properties of strength, impermeability, frost resistance and corrosion resistance. Meanwhile, it can save resource and protect environment.This paper studies the synthesis and application performance of the high-performance concrete an-water-reducing agent and rust inhibitor. Polycarboxylate water reducing agents are synthesized through molecular structure design. This subject is to test further the anti-corrosion resistance molybdate. Put rust inhibitor and water-reducing to the standard concrete blocks, do research in the influence to the concrete steel and the work ability, strength and durability to determine the resistance against rust and influence to concrete.The copolymerization of water reducing agent experiment shows that way of feeding, various reaction concentration, the initiator dosage had great influence on the performance of water reducing agents.Too low or too high dosage does harm to the plastics of water-reducer. Through tests it is found that the ratio of bottom water to soluble initiator by water and (?)solving monomer water is 60%/10%/30%, so that cement and reducer reach maximum compatibility. When the dosage of initiator is 2%-3%, the performance reaches the best. As the increase of temperature, the color deepened ceaselessly. With reaction temperature in 80℃, holding time for 1.5h, water reducer performance achieves optimal. Synthetic polycarboxylate water-reducer has high water reducing rate with small dosage. In the dosage of 0.38% (solid content), water reducing rate is 30%. The slump loss of C60 concrete with synthetic polycarboxylate water reducer is low, and concrete has no segregation or bleeding but with good cohesiveness.It can be widely used in high strength and high performance concrete projects.The dry-wet-cold-hot circulation test and concrete simulation liquid test showed that the home-made anti-rust inhibitor had better anti-corrosion performance. The molybdate inhibitor increased the fluidity of mortar and concrete, but the strength was more than 90% of the benchmark concrete. The anti-rust inhibitor played the best rust resistance effect at the dosage of 3%.Compared with the basic concrete, the setting time of concretes with inhibitors significantly delayed. Initial set time delayed 35 minutes and final setting time delayed 45 minutes. Added inhibitors, water reducing ratio of concrete reached to 29%. Compared to concrete only using polycarboxylate water-reducer,56d chloride diffusion coefficient of concrete can be reduced significantly from 8.1×10-14m2/s to 3.3×10-14m2/s, and the anti-permeability ability can be improved significantly.Synthetic polycarboxylate water-reducer with the cost of 6,400 yuan/t has some certain price advantage compared with the market price of 8,000 yuan/t. This product has comprehensive stable performance and achieves the same products abroad level, which can be widely used in concrete industry with a broad market prospect. Homemade molybdate inhibitors admixture can save the cost of concrete with low price and dosage, and can produce considerable economic benefit. The molybdate inhibitor is a kind of pollution-free green inhibitors. It can be widely used in civil engineering construction for its huge promotion value.In this paper, the results could help to increase the level of compound polycarboxylate type superplasticizer with other chemical admixture and application in construction, and reduce the cost of composite admixture.