Experimental Study On The Mechanical Properties And Durability Of Alkali-Excited Aeolian Sand Concrete

Under the background of global carbon neutrality and carbon peaking,based on the special service environment of hydraulic concrete in the Hetao Irrigation District of Inner Mongolia and the abundant local resources of fly ash and aeolian sand,it is studied to realize the high replacement of cement by fly ash in a room temperature environment through alkali excitation technology Configuring aeolian sand concrete is not only the reuse of solid waste fly ash and aeolian sand,but also an effective measure to reduce global carbon emissions.The mechanical properties,durability,pore structure and chemical composition evolution of fly ash aeolian sand concrete with different alkali contents under room temperature curing were studied from the perspectives of macroscopic,microscopic and chemical composition,and the Weibull distribution function was used to establish the alkali-induced aeolian sand Concrete life prediction model,explore the influence mechanism of various factors of room temperature on durability,and provide theoretical support for the popularization and application of alkali-excited aeolian sand concrete in practical engineering.The main research results are as follows:1.Alkali excitation technology in room temperature curing environment can effectively improve the utilization rate of fly ash,and help to increase the compressive strength of aeolian sand concrete.The study found that the content of fly ash is between 20%and 40%,and the content of 5% Na OH is the optimal amount of alkali.The compressive strength of ordinary aeolian sand concrete is similar,and the alkali excitation technology(5%Na OH)increases the replacement rate of fly ash to cement in concrete from 20% to40%.2.The preparation of aeolian sand concrete by alkali-excited fly ash at room temperature is beneficial to improve its resistance to wind erosion,freeze-thaw,and winderosion-freeze-thaw durability.Aeolian sand erosion causes erosion pits on the surface of aeolian sand concrete.The greater the amount of fly ash,the lower the erosion resistance.However,the erosion resistance of alkali excited aeolian sand concrete is better than that of ordinary aeolian sand concrete.An appropriate amount of alkaline activator can help improve the frost resistance of aeolian sand concrete.The alkali-excited aeolian sand concrete mixed with 5% Na OH in 20%～40% fly ash concrete has the best frost resistance;-Freeze-thaw coupling will accelerate the damage process of alkali-excited aeolian sand concrete,and the anti-wind erosion-freeze-thaw performance of alkali-excited aeolian sand concrete is better than that of ordinary aeolian sand concrete.3.Ultraviolet absorption spectrum and infrared absorption spectrum tests show that N-A-S-H,a hydration product with a higher degree of polymerization,is produced in aeolian sand concrete under the action of alkali excitation;microscopic pore structure test shows that the pore structure of aeolian sand concrete can be improved by adding appropriate amount of alkali.The highly polymerized hydration products are beneficial to reduce the porosity of concrete and optimize the pore structure;concrete mainly suffers physical damage in freeze-thaw environment,and the pore change is mainly the evolution of harmless pores to harmful pores;concrete pores in wind erosion-freeze-thaw environment mainly From harmless pores and less harmful pores to more harmful pores.4.The relative dynamic elastic modulus of freeze-thaw cycle and wind erosionfreeze-thaw was selected to describe the damage degree,and Weibull distribution theory was introduced to establish the freeze-thaw life prediction model and wind erosion-freezethaw life prediction model of alkali-induced aeolian sand concrete.It reflects the damage law of alkali-induced aeolian sand concrete in unfavorable service environment.