Research On Behavior Of Shrinkage Swell And Durability Of Concrete With MgO

The long-term performance and durability of concrete material influence the use function of concrete engineering and service life. On long-term performance of concrete, shrinkage, expansion and creep has always been the hotspot and focus of engineering research subject, but also a difficult point for realizing high-performance concrete. With the rapid development of infrastructure construction and environment of green health needs, long-term performance of concrete, shrinkage, expansion and durability problem has become the key technical problems which restrict the development of the concrete application, therefore, to strengthen the research has important theoretical significance and practical value.Based on hydraulic concrete contraction, expansion and creep defects affect the service life of concrete and the durability problem. Put forward by adding fly ash, magnesia expansive agent and the method of compound ecological fiber to improve the performance of concrete, so as to improve the durability of concrete. Through contrast test, the magnesium oxide and compound ecological fiber on the mechanical properties of concrete, shrinkage resistance, resistance to blunt the impact of wear resistance, permeability resistance and its influence mechanism is discussed in this paper.The main research conclusions are as follows:(1) through the orthogonal experiment to determine the optimal mixture ratio of magnesium oxide compound ecological fiber for A1B2C2D1E3. The water/cement ratio0.30,15%dosage of fly ash, magnesia content is5%, sand ratio35%, compound ecological fiber volume content of0.9kg/m3, according to the mixing proportion of concrete strength to meet the design requirements.(2) orthogonal experiment results show that under the standard curing condition, various factors the influence of28d compressive strength of concrete significantly order:water-binder ratio> magnesium oxide content> sand ratio>> compound ecological fiber dosage of fly ash to replace rate; Various factors influence on concrete splitting tensile strength of28d significant order:sand ratio> water-binder ratio>> fly ash> magnesium oxide compound ecological fiber content.(3) optimization group of mechanics performance test showed that7d of MgO style concrete compressive strength is lower than21.2%of coagulation, down20.4%compared with plain concrete28d compressive strength, splitting tensile strength of28d a plain concrete reduced by10.2%. Early concrete mechanical properties not as good as the optimal set of plain concrete, but the7d increased by11.1%than those of MgO style concrete compressive strength,28d compressive strength and splitting tensile strength increased by0.5%and8.7%respectively than those of MgO style concrete.(4) contraction test showed that the addition of magnesia and compound ecological fiber to reduce the drying shrinkage of concrete value is extremely useful, especially compound ecological fiber after incorporation, the drying shrinkage of concrete value to reduce the effect is remarkable, magnesium oxide doped and effective control of the shrinkage of concrete in the late. (5) the impact abrasion test indicated that single compound ecological fiber ZX set and the optimal set of ZY group than the benchmark concrete what ZJ had dropped by16.9%and40.6%respectively, and the wear rate impact abrasion strength increased by20.8%and56.1%, respectively, of visible magnesium oxide and compound ecological fiber mixed significantly increase the impact of the concrete strength, and magnesium oxide’s contribution to the impact abrasion resistance of concrete is bigger.(6) test showed that the permeability of the single compound ecological fiber ZX and the optimal set of ZY group what ZJ had set a benchmark concrete relative permeability coefficient respectively increased by21.16%and52.38%respectively, fully illustrates the compound ecological fiber and magnesium oxide can improve the resistance to water penetration performance of concrete, and the effect of the mixed more prominent.