Experimental Study On The Preparation Of Non-autoclaved Aerated Concrete By Recycled Fine Aggregate Powder

Since the reform and opening up 40 years ago,the construction industry has been rapidly developed as one of the pillar industries of the national economy.However,there has also been a shortage of natural aggregate resources such as gravel and excessive discharge of construction waste such as waste concrete.In this context,this article uses recycled fine aggregate powder obtained from waste concrete through a series of treatments as part of the siliceous material to prepare aerated concrete,and use non-autoclaved curing for it.The main experimental research results of this article are as follows:1.Firstly,the reference mix ratio of non-autoclaved aerated concrete was determined by referring to relevant literature and trial-mixing test.Then based on the benchmark mix ratio,the single factor analysis method is used to test the water-to-material ratio and the key raw material content in order,and the mix ratio is optimized based on the dry density,compressive strength and thermal conductivity of the product.Finally,the optimal mixing ratio is obtained:the water-to-material ratio is 0.65,the cement content is 20%,the quicklime content is 14%,the recycled fine aggregate powder content is 18%,the fly ash content is 46%,and the gypsum content is 2%,the amount of aluminum powder is 0.06%,and the amount of foam stabilizer is 0.12%.2.Due to the recycled fine aggregate powder contains less SiO2 and the products are not cured by non-autoclaved,there is still a certain gap between the compressive strength and non-autoclaved aerated concrete.Therefore,based on the optimal mix ratio,the effects of physical grinding,chemical excitation and process parameters on the performance of non-autoclaved aerated concrete were studied respectively.The results show that the grinding time of recycled fine aggregate is 50 min,0.04%triethanolamine and 0.5%sodium silicate can improve the compressive strength of the product,and the optimization effect of triethanolamine is more significant,while the effect of sodium sulfate on the product still needs further experimental study;the optimum slurry pouring temperature is 35℃,and the optimum static and stationary gas environment is 40℃ constant temperature and humidity curing box.3.The morphology and types of hydrated products of non-autoclaved aerated concrete were tested by SEM and XRD.The main hydration products of non-autoclaved aerated concrete were C-S-H gels,ettringite(AFt),carbonic acid Calcium(CaCO3),calcium hydroxide(Ca(OH)2).In addition,proper time of physical grinding and appropriate amount of chemical activator can promote the progress of hydration reaction,improve the number,crystallinity and density of non-autoclaved aerated concrete hydration products,thereby improving the performance of products.4.The combination of experiment and software processing was used to study the porosity characteristics of non-autoclaved aerated concrete,including the effect of pore size distribution,porosity,and average pore size on its performance..The results show that the pore diameter of 65%to 80%of the pores in non-autoclaved aerated concrete is between 0 and 0.25 mm;the compressive strength of the product shows a decreasing trend as the porosity or average pore diameter increases,while the heat conduction The coefficient is reversed.