Experimental Study On The Mechanical And Frost Resistance Of Polypropylene Fiber Rubber Powder Lightweight Aggregate Concrete

This paper studies the use of pumice light aggregate widely distributed in Inner Mongolia as the raw material of concrete coarse aggregate,mixed with rubber powder and different content of polypropylene fiber to make polypropylene fiber rubber powder light aggregate concrete.Test the macro-mechanical properties of concrete through compression test and split tensile test.Set up two test conditions of water-freeze-thaw cycle and salt corrosion-freeze-thaw cycle to study the damage degradation process,damage mechanism and durability of concrete.Characterize the macroscopic frost resistance of concrete through the mass loss rate and relative dynamic elastic modulus of concrete.Combine SEM environmental scanning electron microscopy and nuclear magnetic resonance technology to study the hydration products,microscopic morphology,pore changes and the development of cracks in the concrete.Use the Weibull distribution function based on probability theory and mathematical statistics to study the reliability of concrete under salt erosion-freeze-thaw environment.The results show that:1.The cubic compressive strength of polypropylene fiber rubber powder lightweight aggregate concrete gradually increases with the increase of age,and the cubic compressive strength shows a trend of first increasing and then decreasing with the increase of polypropylene fiber content.The incorporation of propylene fiber will delay the strength development rate of concrete;the splitting tensile strength shows a trend of first strengthening and then weakening with the increase of polypropylene fiber content.Under the experimental conditions,when the volumetric blending rate of polypropylene fiber is 0.1%,the compressive strength and splitting tensile strength of concrete are both the highest,and the mechanical properties are the best.2.According to the gray correlation theory,among the characteristic parameters of pores,the free fluid saturation has the greatest influence on the compressive strength of concrete,followed by the bound fluid saturation;in the pore size classification,the most important influence on the compressive strength of concrete is 1 ～ 10 μ m pore size,followed by 0.1～1μm pore size.3.Appropriate amount of polypropylene fiber mixed into the rubber powder lightweight aggregate concrete can improve the frost resistance of the concrete.With the increase of the number of freeze-thaw cycles,the small pores in the concrete gradually transform into large pores,and the incorporation of fibers plays a role in cracking resistance,delaying the expansion of internal cracks and the increase of pores in the concrete.4.The damage degree of concrete under the coupling action of salt erosion-freeze-thaw is more serious than that under clear water conditions.In the early period of freeze-thaw,the ettringite and gypsum generated in the concrete can effectively fill the pores and cracks.In the later period,the internal structure of the concrete is caused by the expansion of the product.Accelerate the damage and promote the internal damage of the concrete,but the incorporation of polypropylene fiber delays the damage.5.The estimated values of Weibull distribution parameters calculated based on the least square method have high accuracy.The probability density function and reliability function based on this can effectively describe the failure process of concrete,and intuitively reflect the remaining life and damage of concrete Degradation process.