Study On The Key Technology Of Non-Autoclaved Curing High Strength Concrete Pipe Piles

Prestressed High Strength Concrete Piles are widely used for they have distinct advantages over other techniques like high loading capacity, wide range of application, reliable quality and high yield, etc. In recent years, with the rapid development of Chinese economic construction, prestressed high strength concrete pipe industry has been developed rapidly. According to incomplete statistics, by the end of 2007, there were more than 500 manufacturing enterprises in china, and annual production was about 300 million meters.At present, PHC piles are traditionally manufactured through a technique with two sections of curing process which includes atmospheric steam curing and autoclaved curing. The use of autoclave generally results in high energy consumption and unsafe working environments. Therefore, non-autoclave-curing techniques need to be developed.This investigation focuses on the problem of insufficient strength, change of water to cement ratio, low quality and low resistance to impact of PHC pipe piles caused by the leaking of paste. Effects of water to cement ratio, cement dosage and admixtures on the workability and strength of PHC pipe piles were investigated. In order to improve the impact resistance of the piles, fiber reinforced concrete impact resistance was investigated. At last, the durability of the fiber reinforced concrete and the plain concrete was studied.(1)Effects of water to cement ratio, cement dosage and admixtures on the workability and strength of PHC pipe piles were investigated, to determine the optimal amount of cement and water reducer dosage. Finally, the cement dosage was 480kg/m3, and the water reducer Ⅰ and Ⅱ were selected for the field experiment.(2)Optimization of Raw Materials was studied in the company. Different kinds of cement and the dosage of cement in each square, different kinds of water reducer on the properties of concrete had been studied in the company. The results showed that:when the cement dosage was the same, with the increase of water-cement ratio, the compressive strength of the concrete was decreased; the fluctuations of cement quality was a important factor affecting the compressive strength of the concrete; the water reducer II showed a better effect in improving the compressive strength of the concrete than water reducer I; the dosage of water reducer Ⅱ increased from 0.4% to 0.45%,1d and 3d compressive strength of the concrete improved greatly, and it was more obvious at a lower water-cement ratio, but its contribution to the later strength was not so obvious. The test piles with water reducer II showed a higher compressive strength, and the workability of the fresh concrete was good,the appearance of the test piles were also excellent.(3)The impact resistance of different steam-cured fiber reinforced concrete at different water-cement ratio were studied, the results showed that:all of steel fiber, PP fiber and PVA fiber improved the compressive strength of the concrete, among which the most obvious was steel fiber; the impact resistance of concrete slab improved greatly after steel fiber and PP fiber added in, and with the increase of water-cement ratio, the impact resistance of steel fiber reinforced concrete slab remained at a high level.(4)The durability of different steam-cured fiber reinforced concrete were studied, the results showed that:PP fibers and steel fibers both improved freeze-thaw resistance and resistance to sulfate attack, and PP fibers improved the performance of against freezing more significantly, steel fibers improved the performance of against sulfate attack more significantly.