Study On Strength And Volume Stability Of Fly Ash Geopolymer Concrete

Fly ash geopolymer concrete is a new kind of cement material concrete,which has more advantages than traditional Portland cement concrete—high strength in the later stage,fire resistance,sulfate resistance,etc.One of the basic raw materials used is fly ash,which is the main pollutant in the atmosphere,and its full use can achieve the effect of turning waste into treasure.The research focus of this article mainly focuses on the tensile mechanical properties under the standard curing conditions,the compression,splitting tensile mechanical properties under summer maintenance,and the volume stability properties under.different curing conditions about fly ash geopolymer concrete,and compared with fly ash concrete under the same conditions.The conclusion is summarized as follows:(1)Under standard curing conditions,the uniaxial tensile strength of fly ash geopolymer concrete grows more slowly within 7 days,but the late strength growth rate is higher than that of fly ash concrete,and the uniaxial tensile strength is greater than fly ash concrete after 28 days.The ratio of tensile Young's modulus and compression Young's modulus of fly ash concrete is slightly larger than that of fly ash geopolymer concrete.The splitting-uniaxial tensile strength formulas of the two concretes are fitted by quadratic regression method.(2)It was subjected to regression analysis that the relationship between the uniaxial tensile strength and the compressive strength of the two concretes under standard maintenance by using the power function and the logarithmic equation,the results showed that the correlation of the logarithmic equations is better;in addition,compared with the expressions concluded by domestic scholars,the results are quite different.The reasons are mainly the different specimens and the raw materials used in the test.(3)Under the summer curing temperature of 33 ?,the compressive strength of the two kinds of concrete can reach above 43Mpa at 28 days,The compressive strength before 56 days increases with the age,but the compressive strength of 91 days decreases slightly.The splitting tensile strength increases with age within 91 days.The early compressive strength and splitting tensile strength of the fly ash concrete increase at a high rate,but the final strength is lower than that of the fly ash geopolymer concrete.it is inferred that the strength advantages of medium and long-term fly ash geopolymer concrete are more obvious.(4)The shrinkage of fly ash concrete during early age 1 day under drying curing is larger,then with the increase of age,the rate of shrinkage increases firstly and decreases then,the shrinkage of 180 days still is greater than fly ash concrete.the every shrinkage of 180 days under packaging curing are less than drying curing,mainly because the plastic film stops the water within specimen losing.it also presents that two kinds of concretes before 14 days under water curing both have an expansion hazard and then they present different degrees of shrinkage,this contributes to the data that fly ash geopolymer concrete is slightly lower when compared to the shrinkage of 180-days fly ash concrete.In addition,the time-dependent shrinkage relationship of fly ash geopolymer concrete under drying and packaging curing is further fitted to provide a theoretical basis for early crack prevention of engineering components.