Experimental Study On Non-autoclaved PHC Pile Concrete Applying Polycarboxylate Superplasticizer

PHC pile(Prestressed High-Strength Concrete Pipe Pile) is the most commonly used concrete component as the foundation of structure, it has the advantages of high strength, high compactness, high load capacity, etc., and it is widely used in various industrial and civil engineering construction, road and rail transportation, port and terminal operators.Present PHC pile production adopts atmospheric pressure steam curing and high-pressure steam curing, i.e. two-step curing system, with the disadvantages of high energy consumption and high carbon dioxide emission, thus cannot achievement the energy saving requirements. In addition, since it is used as structure foundation, the durability of PHC pile draws a lot of researchers’ attention. However, the concrete body of PHC pile would crack during construction. Therefore, even the durability of PHC pile concrete meets the requirements, the harmful ions can still intrude the concrete by crack and corrode steel. Therefore, the use of PHC pile in high corrosive areas worth further research.To solve these problems, a study on on non-autoclaved PHC pile applying polycarboxylate superplasticizer is carried out. The curing system and mix ratio of PHC pile concrete are designed and optimized, and the manufacturing process is adjusted, and PHC pile samples applying non-autoclaved technology is successfully produced. In addition, the self-healing property of pile concrete is systemically studied, a test method and evaluation system on self-healing property is designed.The main work and results of the paper are summarized as following:(1) The influence of time distribution of curing system on concrete strength and ratio of tensile and compressive strength is studied The results show that given the time duration is guaranteed, the compressive strength of concrete is grows in direct proportion to the time duration. If the time duration is not guaranteed and concrete goes directly to the curing temperature, the strength would drop sincerely. And curing system with the total time consumption of 12 h and 8h is optimized.(2) Systemically studied several different mineral admixtures and combinations and their influence on concrete workability, strength, ratio of tensile and compressive strength and durability. The mix-ratio which meets the requirements of both strength and durability, with the workability can fulfill the needs of PHC pile manufacturing is optimized, and several mix-ratio that excels in one or several properties are find.(3) Design a test method and evaluation system on self-healing property of pile concrete, and test the self-healing abilities and speed of autoclaved and non-autoclaved PHC pile concrete. The result show that traditional autoclaved PHC pile concrete is not able to self-heal:The the age the concrete cracked is an important factor of self-healing speed: the longer the age is, the lower the self-healing speed would be. After the concrete cracked, the self-healing speed declines with the time goes, and 0~7d after the concrete cracked is the main period for the crack to cure.(4) Respctively on autoclaved and non autoclaved pile concrete specimen durability and carried out a comparative study, proved the curing system and gel system effects of components on the durability of pile concrete:under high temperature and high pressure steam curing makes the hydration products of concrete completely, the hydration of cementitious products uneven distribution, structure and large void ratio, cause the vapor pressure pipe the poor durability of concrete.Avoid using autoclave curing system for preparing durable concrete.(5) Test a non-autoclaved PHC pile production trial run; adjust and optimize the mix-ratio and manufacturing process. The results show that the production that the appearance of the test piles are of good quality, up to the standard of C80.