Research On Modification And Mechanical Properties Of Dolomite Stone Powder Concret

Due to the shortage of natural river sand resources,the use of manufactured sand as a replacement for river sand in concrete preparation has become the prevailing trend today.However,the production of manufactured sand from dolomite results in the generation of non-degradable solid waste known as dolomite stone powder.This waste material occupies significant land space and,when dried,can contribute to the formation of dust and haze when carried by the wind.Discharging it into rivers would lead to environmental pollution and ecosystem destruction,exacerbating the existing environmental issues.Furthermore,the rapid development of national infrastructure has significantly increased the demand for cement,which in turn has caused serious environmental pollution and resource wastage.To address these challenges,China has frequently employed fly ash as a mineral admixture to partially replace cement in order to mitigate the problems associated with cement production.However,due to the emphasis on reducing carbon dioxide emissions,the availability of fly ash has been greatly reduced.To tackle the aforementioned issues,this paper proposes two approaches: using only dolomite stone powder as a replacement for cement(single mixing),or simultaneously incorporating fly ash and dolomite stone powder as substitutes for cement(mixing)to produce dolomite stone powder concrete.These approaches aim to reduce the consumption of cement and fly ash.By doing so,not only can the waste of stone powder be effectively utilized,but also the problems of environmental pollution,resource wastage,and fly ash reduction in cement production can be addressed.Furthermore,this aligns with the national development strategy and promotes the green and efficient development of the concrete industry.The main contents of the paper are as follows:(1)Study on the Basic Properties of Dolomite Stone Powder: This section investigates the physical properties,chemical composition,microscopic images,and activity of stone powder.Test results indicate that the two types of stone powders exhibit similar characteristics in terms of density,water content,and methylene blue value.However,in terms of fluidity ratio and activity,the 0-80μm stone powder performs better than the 0-150μm stone powder.(2)Study on the Performance of Dolomite Stone Powder Concrete: This part examines the working performance of concrete containing dolomite stone powder.Parameters such as slump,expansion,cohesion,and water retention are analyzed.The findings demonstrate that as the content of dolomite stone powder increases,the slump and expansion of concrete gradually decrease.Only when the content reaches 30%,does the concrete exhibit slight slurry precipitation and aggregate exposure.(3)Evaluation of Mechanical Properties: This section investigates the compressive strength,flexural strength,splitting tensile strength,compressive elastic modulus,and total electric flux of concrete at different ages.The study compares single mixing and mixing techniques.The results indicate that the addition of stone powder improves the mechanical properties and resistance to chloride ion penetration of concrete.Combining the four indicators,the optimal mechanical properties are achieved when the fineness I stone powder content is 15% and the mixing ratio(fly ash: stone powder)is 3:1.The best chloride ion penetration resistance is achieved with a stone powder content of 10%.When the content exceeds 15%,the chloride ion penetration resistance of concrete is worse than that of the reference group.(4)Microstructure Analysis of Dolomite Stone Powder Concrete: This section discusses the interface microstructure of stone powder concrete,the morphology of hydration products,and the bonding between stone powder and concrete components.The analysis is conducted using scanning electron microscope(SEM)tests.The incorporation of stone powder provides more attachment positions for hydration products,allowing for better filling of internal pores and microcracks.Its micro-filling effect and ability to adsorb hydration products are superior to those of fly ash.Based on the above test results and considering the economic impact of stone powder,the optimal fineness of stone powder is determined to be fineness I(0-80μm).The recommended single admixture dosage is 15%,and the optimal mixing ratio for the mixed admixture is 3:1(fly ash: stone powder).The practical application of the research results can contribute to improving the working and mechanical properties of concrete to a certain extent.It holds significant theoretical and practical value in promoting the green and sustainable development of the construction industry.Additionally,it provides valuable insights for the engineering application and theoretical research of other rock powders in the field of civil engineering construction.