Study On The Mechanical Properties Of Polypropylene/Basalt Fiber Modified Soil Cement

Cement soil is a mixed system in which binding materials based on Portland cement are uniformly added to the soil in a certain proportion into greatly improve various mechanical properties and stability.Its advantages are economic,applicable,convenient construction,etc.,so it is widely used in foundation and slope reinforcement,deep foundation pit support,etc.However,there are still many problems in the practical application of cement soil,such as its relatively low tensile strength and flexural strength,which have a great adverse effect on the application of cement soil.In this paper,based on the optimized ratio of activated slag modified cement-soil,fibers with different elastic modulus are mixed into cement paste and cement-soil,respectivly.The effect of fiber content on the mechanical properties of cement paste and cement-soil is studied and discussed in detail,which must be helpful to understand the reinforcement mechanism of such fibers and to improve the mechanical properties of cement soil for the engineering practice of cement soil.Based on the application research of many scholars on fiber-modified concrete,this paper firstly analyzes the effect of polypropylene fiber and basalt fiber on cement paste;through the tests of unconfined compressive strength,splitting tensile strength and the tension-compression ratio,it is discussed including the influence of different types and content of reinforced fibers,curing age,and curing conditions on the cement paste,as well as the comparison of the effect of different elastic modulus on the cement paste.On this basis,polypropylene fibers and basalt fibers was added to the cement soil in the same proportion,respectively,and the impact of different fiber content and curing age on the mechanical properties of the cement soil was analyzed through the compressive strength study;and then by changing the mixing amount of cementitious material it is further analyzed for the change law of its mechanical properties;the solidification structure of cement soil is analyzed by scanning electron microscope,and the effects of cement hydration and microstructure improvement are discussed in the process of cement hydration and hardening,the mechanism of soil solidification.The study found that the introduction of fibers can significantly improve the mechanical properties of cement-soil,and different elastic modulus fibers have different effects on cement-based materials due to their different physical and mechanical properties.When the fiber content is gradually increased from 0 to 2%,the compressive strength and splitting tensile strength of polypropylene fiber modified cement paste show an upward trend,but the basalt modified cement paste first increases and then slightly decreases;When the fiber content is 1%,both show good mechanical properties,and the tension-compression ratio is increased by 38% and 56% respectively;in the cement-soil test,when the fiber content is0.5%,polypropylene fiber modified cement Both soil and basalt fiber-modified cement soil show good mechanical properties,and when it exceeds 0.5%,the compressive strength of the former shows a downward trend,while the latter continues to increase slowly.Analysis believes that it is caused by the different physical and mechanical properties of polypropylene fiber and basalt fiber.In addition,whether in polypropylene fiber-modified cement soil or basalt fiber-modified cement soil,the increase in the content of cementitious materials will greatly improve the mechanical properties of both,indicating that cementitious materials with cement as the basic functional component are still It is the basic guarantee for the mechanical properties of cement soil.