Experimental Study On Properties Of Sulphoaluminate Cement Concrete Modified By Compound Admixture And Basalt Fiber

Sulphoaluminate cement concrete can meet the needs of fast hardening,early strength and high strength of pavement repair materials.However,there are some unavoidable shortcomings,including the high cost,the difficulty of setting time control,as well as the hidden dangers of late strength reduction and cracking.In this paper,fly ash and mineral powder are used to replace part of sulfoaluminate cement,and determine the suitable admixture range of single admixture and the best proportion of double admixture to realize complementary advantages and reduce material cost.At the same time,basalt fibers of different sizes(9mm,18mm)and content(0～0.4%)are added into sulphoaluminate cement based concrete in the form of single or compound mixing to improve the macroscopic properties of concrete.and conduct microcosmic test on concrete,analysis of its internal structure characteristics and strengthening mechanism,the following research conclusions:(1)Fly ash and slag prolong the setting time of SAC,but inhibit the development of its strength.The suitable dosage range of mineral powder is 0～20%,and that of fly ash is 0～10%.When 10%fly ash and 5%ore powder are added,the setting time of the cementing material is prolonged and the strength loss is relatively minimum.(2)The fluidity of concrete mixed with basalt fiber decreases.The compressive strength of concrete can not be improved by fiber,and the compressive strength can even be reduced by excessive fiber.The flexural and tensile strength of concrete can be improved with appropriate dosage,especially when multi-scale fiber is mixed.(3)Basalt fiber can improve the frost resistance of concrete,and the different sizes of basalt fiber show the inhibition effect on the drying shrinkage of concrete,especially when the mixed size of basalt fiber is added.Basalt fiber can also inhibit the early cracking resistance of concrete,and the early cracking resistance is the best when the basalt fiber with the ratio of 9mm and 18mm is 2:1 and the content of 0.3%.(4)The microscopic test shows that the basalt fiber has good adhesion to the concrete matrix,but excessive fiber will lead to the phenomenon of fiber aggregation in the matrix,forming a weak interface.In the process of loading,the fibers dispersed in the matrix restrict the development of cracks.After the multi-scale basalt fiber concrete is destroyed,more cracks occur in the interior,but the structural integrity around the fiber bundle is well,showing a positive hybrid effect.