Study Of Shrinkage Compensation And Influence Factors Of High Strength Concrete

The phenomenons of cracking occurred frequently in the practical applications of shrinkage-compensating high strength concrete. And the influence factors of deformation of shrinkage-compensating high strength concrete were studied. Firstly, the influence of HCSA on the deformation of high strength concrete was studied. Furthermore, the impacts of curng conditions, types of mineral admixture and dosage of expansive agent on the restrained expansion deformation of high strength concrete were discussed.The results showed that:The critical period and end value of the relative humidity of concrete were shortened by the mixed HCSA. As a result, the rate and value of shrinkage of concrete were increased. But at the same time, the concrete was expansive own to the hydration of calcium hydroxide and Aft. Accordingly, the tatal deformation of concrete was the superposition between self shrinkage and compensation function of expansive agent.Compared to waterproof curing groups, the restrained expansion rate of water curing groups were higher and the rate of growth was faster. The effect of dosage of expansive agent on the restrained expansion rate was larger than the condition of external water supplying or not as the temperature rised. The higher the temperature, the larger influence of the dosage. And the difference between the water curing groups and waterproof curing groups was lowest when the temperature was 40 ?. And the difference of deformation between the core area and the surface was the lowest.The compressive strength of shrinkage-compensating high strength concrete was affected by dosage of expansive agent, restrained condition and curing conditions. The compressive strength in free condition was decreased by expansive agent. And the waterproof cured condition decreased obviously. Restrained compressive strength was enhanced by expansive agent. However, an optimum dosage was exsited for this influence. While temperature was increased, the increasing of dosage of expansive agent was helpful to the improvement of early stage compressive strength. But it is seemed that the strength in the later stage was decreased. The restrained strength was affected heavily by the curing condition, that is, water or waterproof. Yet the difference between the compressive strength of water cured groups and waterproof cured groups was deceased by expansive agent.Time-dependent development of restrained expansion rate of shrinkagecompensating high strength concrete was affected by the dosage of expansive agent and curing condition. And the influence was different for different types of mineral admixtures. As the dosage of expansive agent was increased, the restrained expansive rate end value of waterproof groups was increased by mineral admixtures. The restrained expansive rate end value of water curing groups was bigger than waterproof groups. However, the difference would be decreased by mineral admixtures, and it was affected by the dosage of expansive agent at the same time. And when silica fume and slags was added, the end value was the lowest. The more dosage of expansive agent, the bigger influence of mineral admixtures.In actual application, the adjustment of the types and dosage of mineral admixtures, dosage of expansive agent according to different application fileds and parts, then a kind of the restrained expansion rate of shrinkage-compensating high strength concrete which woludn't be affected by curing conditions could be got.