Autogenous Shrinkage Of High Strength High Performance Concrete Containing Fly Ash Exposed To Different Curing Temperatures

High strength high performance concrete has the characteristics of high strength, high performance, high durability, because of it, it is widely used in all kinds of high-rise, long-span, underground and marine structures. But in practical engineering, because of the characteristics of high amount of cementitious materials, low water binder ratio, high strength high performance concrete lead to expose some problems in the early age, such as poor volume stability, easy to crack. AS early cracking of concrete will lead to reduce the durability of concrete, it is becoming more and more significant to further the studies on the shrinkage of high strength high performance concrete. Some studies showed that fly ash has the performance to decrease the shrinkage of the concrete. Effective utilization of fly ash not only can reduce the cost, improve the service life of the building structure, but also reduce the pollution to the environment. This article take high strength high performance concrete as the object of study, by setting different water-binder ratio, study on the mechanical property and autogenous shrinkage of high strength high performance concrete contain fly ash exposure at different curing temperatures.The author summarized the devices and methods which could test the autogenous shrinkage of concrete at home and abroad and explored the feasibility of the embedded type strain which is self-made to measure the autogenous shrinkage of concrete. In the end, the author used a non-contact testing method to measure the autogenous shrinkage of concrete before the age of3days, used TDS-303to measure the autogenous shrinkage of concrete after the age of3days.The conclusions derived from the study are as follows:1Fly ash can extend the setting time of high strength high performance concrete, but when the water binder ratio is0.2while the curing temperature is10℃, it will shorten the setting time of high strength high performance concrete.2Fly ash will reduce compression strength of high strength high performance concrete before3days; but after3days, the strength development rate of fly ash is faster than pure cement, and its compressive strength at7days is close to pure cement concrete, its compressive strength even will higher than that of pure cement at28 days.3The autogenous shrinkage of high strength high performance concrete which in the same water-cement ratio had a greater value by the higher curing temperature; while in the same curing temperature, the autogenous shrinkage strain had a greater value since the lower water-cement ratio.4Fly ash can effectively reduce autogenous shrinkage of high strength high performance concrete, and the shrinkage effect mainly occurred in the age of1day.5The development rates of autogenous shrinkage were different and fast for each group test before3days. The autogenous shrinkage rate reaches the maximum in the concrete setting time; the rate has slowed down significantly after3days, and the development rate of autogenous shrinkage is slow and steady after10days.6The autogenous shrinkage of high strength high performance concrete mainly occurred in the early days.3days autogenous shrinkage accounted for more than50%of28days total shrinkage,28to60days autogenous shrinkage accounted for less than20%of60days total shrinkage.7The prediction accuracy of the existing autogenous shrinkage calculation model can’t meet the needs of the project; The equivalent age formula which based on the principle of Arrhenius is not effective in evaluation of the temperature dependence of physical properties of the concrete.