| As the foundation of the development of the times and the continuous progress of society,engineering construction is undoubtedly one of the industries that are most valued and should be developed in contemporary times.Concrete,as the most important engineering material in engineering construction,has universality and irreplaceability.However,it also exposes related problems such as environmental pollution,waste of resources and energy.Therefore,how to make good use of concrete as a "double-edged sword" has become a particularly important issue.Compared with river sand and machine made sand,windblown sand is a natural solid waste with the advantages of low price and sufficient reserves.The preparation of aeolian sand concrete by replacing river sand with equal proportions of aeolian sand is of great significance in reducing engineering costs,maintaining the ecological and natural environment,and reasonably developing and utilizing natural resources.However,due to its fine particles,it is easy to cause poor particle quality,so this characteristic is currently the main problem that needs to be solved urgently.As a new type of building material,recycled micro powder has advantages such as high volcanic ash activity and good filling effect.Moderate addition can improve the compressive strength and salt freeze-thaw resistance of concrete;But it can also cause a significant decrease in the workability of concrete;The appropriate mixture of recycled micro powder and windblown sand,as well as their mutual filling,fully improves the particle grading of the concrete mixture,forming a tightly packed state of particles inside the concrete,reducing internal pores,effectively improving the compactness of the concrete,improving the mechanical and durability performance of the concrete,in line with the current green concept of waste reuse,and achieving dual benefits of performance and economy.This article mainly studies recycled micro powder aeolian sand concrete from two aspects of mechanics and durability.Through experiments,the optimal dosage of both and the damage and deterioration mechanism of concrete under high salt concentration are obtained.Weibull theory is used to predict the service life of concrete and fill the research gap.The main conclusions are as follows:(1)The compressive strength of recycled micro powder aeolian sand concrete shows a trend of first increasing and then decreasing with the increase of recycled micro powder and aeolian sand content.Among them,the compressive strength of the group with recycled micro powder content of 10% and aeolian sand content of 40%(RP10AS40)is the highest.(2)The porosity of recycled micro powder aeolian sand concrete is always dominated by the bound fluid saturation throughout the entire age,supplemented by the free fluid saturation.Among them,the concrete porosity and T2 spectral area in the group with 10% recycled micro powder content and 40% aeolian sand content(RP10AS40)are the lowest;Combining the results of field emission scanning electron microscopy(SEM)and differential thermal gravimetry(TG-DTA),it can be concluded that the relative content of Ca(OH)2 in RP10AS40 group is the lowest,and the relative content of C-S-H gel is the highest.(3)By using grey correlation entropy and GM(1,4)concrete compressive strength prediction model analysis,it can be concluded that the main factors affecting concrete compressive strength are 0-0.01 μ Ratio of m aperture,0.01-0.1 μ The proportion of m pore size and bound fluid saturation;And the average relative error of the model is 2.20%,indicating high accuracy.(4)The frost resistance of recycled micro powder aeolian sand concrete is relatively good under high salt(Na Cl)concentration.The Weibull life prediction model was used to predict the actual service life of recycled micro powder aeolian sand concrete.The test results of the entire group of concrete exceeded 20 years,among which the service life of RP10AS40 group reached 33.1 years. |
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