Performance Research Of Recycled Aerated Concrete

The Recycling level of waste concrete is not high In the domestic at present,most of the application and research were focused on coarse aggregate.In addition,autoclaved aerated concrete block is promoting energy-saving wall materials of construction industry,which has the advantages of lightweight,Heat insulation and Sound insulation.but in the south area of China,production of aerated block need to consume a large amount of mountain sand or river sand.In this paper,a certain amount of powder,ground from waste concretes and called"recycled powder",was made into a kind of new aerated concrete which is called "recycled aerated concrete",and performance study was performed in order to explore the possibility of using waste concrete as raw material of aerated concrete.First,the recycled powder was sieved into five particle groups aceording to 0～0.075 mm,0.075～0.15 mm,0.15 mm to 0.3 mm,0.3～0.6 mm and 0.6～1.18 mm.Each group of powder was made into aerated concrete coupons according to the replacement proportion of sand in 25%,50%,75%and 100%respectively.experiments was performed to explore the impact on compressive strength,dry density and drying shrinkage rate by the size and replacement ratio of the recycled powder.Next,some of recycled aerated concrete blocks were created with recycled powder centered on 0.132mm diameter,replacing 25%and 50%of sand material,The experimental showed that:(1)There is no essential and complete difference between recycled aerated concrete and normal aerated concrete.Normal powder,mixed with recycled powder,just causes the lower silica content,and reduces the strength of the aerated concrete.(2)The powder affects aerated concrete strength with a extreme point within a certain range of particle size,excluding that of too big or too small.The best rang of particle size was from 0.126mm to 0.146mm.(3)For issues of replacement raito of recycled powder,is essentially the view of silica content:The higher silica content,the strength of the aerated concrete is also highe,so silica content is essential to recycled aerated concrete.In addition,the silica content in specific scope helps to reduce the dry density of recycled aerated concrete.(4)The bibulous rate of recycled aerated concrete is closely related to the dry density in the opposite direction,and the dry density is not relevant to the particle size but Porosity that mainly depends on gas agent in the mixture ratio.(5)The drying shrinkage rate of the recycled aerated concrete decreased as the moisture content increased.It has small changes In moisture content of 10%～20%,and bigger change if the moisture content exceeding 20%.In time,shrinkage follow the rule that "slow after the first fast".(6)Recycled aerated concrete blocks,made from recycled powder centered on 0.132mm diameter,with two replacement ratio of sand material,are up to the B06 A3.5 and B06 A5.0 technical standard of block,respectively,and dry shrinkage rate is within the limits prescribed in the specification.Finally,economic efficiency of the recycled aerated concrete was also analysed in the paper.Spreading recycled powder,not only decreases the cost of production of aerated concrete by 7.8～29.2 yuan,per cubic meter,but also reduces the excavation of natural resources,which has a good economic benefit and long-term significance of environmental protection.