Reduction Effect Of Porous Aggregate On Shrinkage Of Concrete

Currently,a large number of high-strength concretes used in construction projects are often formulated with larger single cement dosages and lower water-cement ratios.Some of them are also mixed with silica fume and ultra-fine ore fines to improve the strength and resistance by refining cement stone capillary pores.Permeability and other durability,but it also brought a series of negative effects,such as the early autogenous shrinkage,easy to crack and other volume stability problems are very prominent.Because the structure of high-strength concrete is relatively dense and has good impermeability,even if the curing conditions are good,it is difficult for outside moisture to enter the interior of the concrete,and the autogenous shrinkage caused by the decrease in relative humidity caused by the self-drying of the concrete cannot be fundamentally solved..In this study,the water return function of porous aggregates treated with pre-absorbed water is used to self-contain concrete,and the main research object is to use pottery sand as the main research object to study the influence of water absorption,mix amount and pre-water absorption on the autogenous shrinkage of concrete.The influence of waterabsorbing clay sand on the micro-hardness and other microscopic properties of the interface transition zone of the concrete,and then the improvement mechanism of porous aggregate on concrete performance was analyzed.Research indicates:Pre-absorbed pottery sand will increase the autogenous shrinkage of concrete;the higher the pre-absorbed pottery,the higher the amount of pottery,the stronger the self-protection effect on concrete,and the pre-absorbed 24 h clay sand content is 20%.The autogenous shrinkage rate of the concrete is about 10% of that of the benchmark group;the reduction effect of the clay sand on the concrete is much higher than that of the same batch of ceramsite produced under the same experimental conditions,and when the high water absorption rate of 10% pre-absorbed water is added for 1 hour The autogenous shrinkage rate of the 120 h age of the concrete is equal to 100% of the concrete using ceramics,about 60% of that of the reference group,and the strength of the concrete 28 d when the preabsorbent treatment 1h of the high water absorption rate of the clay sand does not exceed 30%.No adverse effect;When the clay sand content is 40%,the surface distance between two adjacent clay sands is 2.13 mm,and the migration distance of the ink in the clay sand measured by the ink dyeing method in the cement stone is about 1mm.The water content of pottery sand can act on most of the cement stone and can effectively reduce the shrinkage,which is in agreement with the test results of concrete autogenous shrinkage.