| At present, it’s become a new research that phase change materials (PCMs) were put in concrete to control temperature in order to avoid the concrete destruction of temperature changes. PCM has regenerative property, when environment temperature increased to phase transition point, heat can be absorbed by PCM and when the environment temperature decreased below phase transition temperature, heat can be released by the PCM, so the PCM can be used controlling temperature rise rate of hydration in mass concrete in order to avoid temperature damage in concrete.Base on the research of predecessors, a model of controlling the adiabatic temperature rise of concrete was established in this study, and the basic theory of phase change temperature self-control concrete was proposed. Temperature control effect of several phase change on cement hydration process was studied, and the temperature control performance was evaluated.P-C phase change aggregate and R-P phase change aggregate were developed and the influences of ceramiste aggregate, P-C phase change aggregate and R-P phase change aggregate on workability, mechanical performances and durability of concrete were researched. The temperature field and thermal stress were calculated by ANSYS.Through research, the following results were achieved:1. According to law of cement hydration, ordinary concrete internal temperature changes was analyzed, adiabatic temperature rise model of phase change concrete was established, new ideas to control the temperature with phase change materials was proposed in this paper. The temperature field and thermal stress were calculated by ANSYS.(1) Adiabatic temperature rise model of phase change concrete was established, temperature rising process was divided into three segments, and the simulation calculation formula of adiabatic temperature rise model was as follows: (2) According to adiabatic temperature rise model of phase change concrete, it’s calculated by ANSYS that the highest center temperature of the phase change concrete was lower 3.8℃than the highest center temperature of the ordinary concrete, and the peak of the center temperature of phase change concrete was delayed 3-4 hours than the basic concrete.(3) In the temperature boundary and constraints boundary condition of the model, the maximum thermal gradient and maximum thermal stress of ordinary concrete and phase change concrete appeared in the long side direction of the model. The maximum stress of the 100th node of the basic concrete was 2.2MPa larger (tensile stress) than the stress of the same node of the phase change concrete, the minimum stress of the 172nd node of the basic concrete was 1.1MPa less (pressure stress) than the stress of the same node of the phase change concrete.2. Concrete Hydration Temperature Tester was designed. Single-phase change system, dual-phase change system and mineral admixtures were used in temperature control technology of hydration temperature concrete. The feasibility of using PCMs as temperature control materials was demonstrated.(1) Concrete hydration temperature tester, which provides a better test method for traditional one, has better maneuverability compareing with adiabatic temperature rise of concrete.(2) Paraffin b-PCMs had the best cutting-peak and delaying-peak effect in Single-phase change system including G-C system, Y-C system, Z-C system, Pa-C system and Pb-C system, cutting-peak temperature range was 28.5%, tmax was 9.8h. Z-C had the worst cutting-peak and delaying-peak effect, cutting-peak temperature range was 1.8%. Paraffin-PCMs had a better cutting-peak and delaying-peak effect than organic acid-PCMs. (3) When Pb was used as high temperature PCM in dual-phase change system, Pa had better cutting-peak effect than organic acid as low temperature PCM, the lower transformation temperature of onganic acid-PCM was, the better the cutting-peak effect was. The cutting-peak temperature range of Pa2-Pb8, Y2-Pb8 and G2-Pb8 was 18.2%,10% and 14%.3. Phase change ceramisite and P-cement phase change aggregate were prepared as Concrete coarse aggregate. Tempareture control capaility of phase change coarse aggregate were studied, the influences of phase change ceramisite on mechanical propertities and durabilities of concrete were analysized under standard curing and thermal cycling conditions.(1) Three kinds of ceramisite were selected to prepare phase change ceramisite with content of 9.9%、17.9% and 31.3% using vacuum absorption, the size of ceramisite was in 5～20mm range. P-cement phase change aggregate with content of 30% was prepared by simulating the ball shell structure, the size of aggregate was in 5～10 mm range. There was certain of peak cutting and delaying effect of phase change coarse aggregate on hydration temperature rise of cement, and effect of P-cement phase change aggregate was better than phase change ceramisite.(2) When the ratio of P was 10% in phase change, the compressive strength of phase change ceramisite was lower than ordinary concrete, and the compressive strength of P-cement phase change aggregate was roughly the same. Under high temperature cycling condition, the carbonation resistance and the chloride penetration resistance of phase change concrete increased, volume stability of P-cement phase change aggregate was better than ordinary concrete.4. Utilizing industrial rice husk ash, via the Composites Preparation Technology and Surface Modification Technology prepared phase change fine aggregates of R-PA, the technology of P capsulation by hush ash was developed. The workability between R-PA and concrete was enhanced. The influences of phase change ceramisite on mechanical propertities and durabilities of concrete are analysized under standard curing and thermal cycling conditions.(1) R-PC was prepared by industrial rice husk ash and P, and the limestone powder wrapped up on it to prepare R-PA. The ratio of P in R-PA was about 35%. R-PC bonded tightly, the workability of cement paste and fresh concrete was well good.(2) R-PA could make the temperature rise curve of cement pastes larger openings, and had significant effect of cooling clipping, effectively controlled the temperature rise rate of hydration of cement pastes. (3) Considering compressive strength of concrete, it’s reasonable that ratio of P in gelled material was 10%. R-PA resulting in the loss of concrete strength to some extent, and the strength of phase concrete was lower when the relatively net content of paraffin was 20% of the binding materials mass than 10%. In standard curing conditions and high temperature curing conditions, the 28d strength of phase change concrete is good stability.(4) R-PA significantly reduced the changes of concrete volume generated due to temperature rise and drop, improved the impermeability of concrete remarkably, especially, he impermeability is perfectly good in high temperature curing condition. |
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