| As a big steel country,China's steel output has been far ahead in the world for many years.The discharge of steel slag is about 15%-20%of steel output,but the utilization rate of steel slag in China is only 22%.This not only wastes land resources,but also affects the development of the steel economy.The efficient use of steel slag micro powder as a mineral admixture in construction can promote the development of circular economy and is a good way to save green energy.This subject mainly uses fine steel slag powder as the research object,with the help of macroscopic mechanical property test,microscopic XRD detection and SEM scanning electron microscopy.The properties and mechanism of steel slag micronized mortar in single-mixed steel slag micro powder system and binary compounding system were studied by comparison with blank group system.The main findings are as follows:(1)The steel slag micro powder contains some minerals with lower activity in the early stage,so the early strength of the cement mortar decreases with the increase of the amount of steel slag micro powder.When the age was 7 days,the compressive strength of the WSP2 test group was 27.55MPa,which was only about 87.49%of the blank group.With the increase of age,the rate of flexural strength growth of the steel-filled slag micro-powder gel system is greater than that of the blank group.The hot stew slag has stronger early activity than hot splashing slag.With the increase of test age,the gelation activity of the two steel slag micro powders at 28d age is not much different,when the amount is 10%,the flexural strength values differ only by 0.29MPa.(2)When the steel slag micro powder and fly ash are dual-doped,the early strength value of the composite admixture system is larger than that of the single admixture system,and the maximum increase is about 58.54%.When steel slag fine powder and fly ash are substituted for 20%and 30%by mass of cement at a ratio of 1:1?1:2?1:3,the strength decreases with the increase of the amount of cement substituted.At the 20%substitution,the strength of mortar 7d and 28d increased slightly with the increase of fly ash substitution.However,at 90 days,the strength of the WSP2F1 group is comparable to that of the WSP2F3 group,with a difference of only 0.61 MPa.In the steel slag micro powder and silica fume compounding system,the early strength value of the test piece is lower than that of the blank group.However,with the increase of age,the strength value of the specimen gradually increased and exceeded the blank group.When the dosage of the two was 20%,their late strength growth trend was the best.(3)WSP2?WSP2F1 and WSP2S2 were selected to study the effect of steel slag micro powder on the early crack resistance and durability of mortar.The results show that the early crack resistance of the binary compounding system is higher than that of the single-mix system and the pure cement mortar system,the impermeability and sulfate-resistant performance of the binary compounding system are also the strongest in the three systems.(4)It can be clearly seen from the SEM image that the finely pulverized steel slag particles are small,the gradation distribution is also uniform,and a good micro-aggregate filling effect is exhibited,and the microscopic morphology observation patterns of the three systems at the 90-day age are all observed.The presence of fibrous and flocculent C-S-H gels and other morphological hydration products can be seen.However,the internal structure of the single-doping system and the binary-doping system is denser than that of the blank group,and the large pores are also significantly reduced.The secondary hydration reaction in the complex doping system increases the gelation of the system,so the late strength and strength growth rate is higher than that of the pure mortar system. |
PDF Full Text Request