| The Flash River Reservoir is located in Zhangjiakou City,Hebei Province.The reservoir is located in the northern cold area.The temperature difference is large,especially in winter,and the temperature difference between day and night is large.The concrete structure of the hydraulic structure of the Flash River Reservoir causes different degrees of freeze-thaw damage,threatening the service life and durability of the concrete structure.The later repair and maintenance of the damaged concrete cost is high.Therefore,it is urgent to find a low cost and meet the bearing capacity and frost resistance of hydraulic concrete to replace the original hydraulic concrete.Heavy industry is the main industry in Hebei area.There are too many industrial wastes such as limestone powder,fly ash and slag powder,which lead to more and more serious environmental pollution.However,three kinds of mineral wastes can be mixed into hydraulic concrete as mineral admixtures,which can not only improve the performance of concrete,but also realize the treatment of industrial waste residue resources and reduce the cost of use.Therefore,it is of great practical significance to systematically study the performance of mineral admixtures hydraulic concrete.In this paper,three industrial wastes including limestone powder,fly ash and slag powder are selected as mineral admixtures,which are mixed into hydraulic concrete in the way of double mixing and three mixing.The influence of mineral admixtures with different dosages on the mechanical properties of hydraulic concrete is studied by compressive strength test and concrete cube splitting test,combined with non-contact full-field strain system(VIC-3D),and then the influence of mineral admixtures on the frost resistance of hydraulic concrete is explored by rapid freezing and thawing test.The main research results are as follows:(1)According to the orthogonal test method,the mineral admixture hydraulic concrete mixed with limestone powder,fly ash and slag powder is divided into 9 groups according to different dosage,and the compressive strength of the specimens is analyzed for 3 days,7 days and 28 days.The mineral admixture hydraulic concrete(LSFl)mixed with 15%limestone powder,5%fly ash and 5%slag powder has the best comprehensive situation.After the superposition of the three admixtures,the strength is 105.4%of the strength of ordinary concrete(C1),and the tensile-compression ratio is 98%of ordinary concrete,indicating that the strength of LSF1 group is good and the brittleness is low.According to the orthogonal results analysis method,the significance of compressive strength and splitting strength of three kinds of admixtures in 3 days,7 days and 28 days is fly ash>slag powder>limestone powder.(2)Through the analysis of VIC-3D full-field strain and the actual failure of concrete,the failure modes of hydraulic concrete with nine groups of mineral admixtures are basically the same,and the axial strain is greater than the transverse strain.When the total amount of admixture is less than 20%,fly ash and slag powder will improve the internal structure of concrete,so that the strength and crack resistance of concrete are higher than those of ordinary concrete.Through the comparison of axial strain and transverse strain of nine groups of mineral admixture hydraulic concrete,the strength of mineral admixture hydraulic concrete with 15%limestone powder,5%fly ash and 5%slag powder is higher than that of ordinary concrete,and the strain is smaller than that of ordinary concrete.The axial strain is 88%of the axial strain of ordinary concrete,and the transverse strain is 65%of the transverse strain of ordinary concrete.(3)Through the analysis of mass loss rate and relative dynamic elastic modulus,limestone powder will reduce the frost resistance of concrete.After adding fly ash or slag powder,it can make up for the deficiency of limestone powder,and the frost resistance has been significantly improved.When the total amount of admixture reaches 30%,the frost resistance will decrease.By fitting the relative compressive strength and the number of freeze-thaw cycles,it can be seen that the decrease rate of compressive strength increases with the increase of freeze-thaw cycles when the compressive strength is 0～75 times.When the freeze-thaw cycle is 100 times,the decrease rate is slightly slower.The worse the frost resistance is,the closer the fitting curve is to a straight line.(4)Through the overall analysis,it is found that the superposition effect of the three admixtures can effectively improve the mechanical properties and frost resistance of mineral admixtures concrete when the total content is less than 25%.The strength of LSF1 group with 15%limestone powder,5%fly ash and 5%slag powder is higher than that of ordinary concrete(group C1),the strain and tension-compression ratio are smaller than those of ordinary concrete,and the frost resistance is better than that of ordinary concrete,which is the best group to meet the requirements of concrete bearing capacity and frost resistance. |
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