Experimental Study On Mechanical Properties And Durability Of Mold Bag Concrete In Hetao Irrigation District

After the seasonal freeze-thaw and regular wet-dry cycle,the concrete-filled concrete lining canal in Hetao Irrigation District appears partial or large-area cracking.In order to further improve the performance of the bag-filled concrete in the irrigation area,based on the mix ratio of the original bag-in-progress concrete,the amount of cement mixed with fly ash and marble powder is replaced in different proportions.The mechanical properties,durability and pore structure of bagged concrete with different mix ratios were studied through experiments.The factors affecting the durability of bagged concrete were evaluated using the rough set theory method,and the optimized mixing ratio of concrete filled with bagged concrete in Hetao irrigation area was obtained.The plan provides a reliable theoretical basis for the large-scale promotion and use of bag-shaped concrete channel lining works in Hetao Irrigation District and even the northern regions.The main contents and results are as follows:(1)The macro-mechanical property test results show that the appropriate amount of fly ash and marble powder incorporation will help improve the mechanical properties of the bag-concrete.Incorporation of 5% and 10% marble powder can effectively improve the early compressive strength of the bag-concrete.When the amount of fly ash and marble powder is 20% instead of cement,the compressive strength of the bag-concrete is the best.The change law of tensile strength of split bag concrete with splitting ratio is consistent with that of 28 d compressive strength.(2)Under the immersion of Yellow river water and clear water solution,freeze-thaw cycle and dry-wet cycle test were carried out respectively.Through comparison,it was proposed that the durability of the bag-packed concrete could be optimized for the ratio group A3(the fly ash content was 10% and the marble powder content was 10%)and B2(fly ash content 15%,marble powder 5%).(3)The pore structure test shows that it has a close relationship with the mechanical properties and durability of the bag-bag concrete.The mix of fly ash,marble powder and other mineral admixtures has been optimized in the bag-concrete to optimize its pore structure.The optimization of the pore structure has improved the mechanical properties of the bag-shaped concrete and the durability of the bag concrete.(4)Based on rough set theory,the factors affecting the durability of mould bagconcrete were evaluated,and the significance of the six factors on the mass loss rate of the bag concrete and the loss rate of the dynamic elastic modulus was determined.The significance levels are as follows: Freeze-thaw cycle > Dry-wet cycle > Yellow river water > Marble powder content > Fly ash content > Clear water.