Experimental Study On Preparation Of Autoclaved Lime Sand Bricks From Andalusite Tailings In Gansu Province

Zhangxian Andalusite Processing plant after years of construction already have production conditions,production will produce a large number of low-grade weathered ore and andalusite tailings,and bring environment hazards and hidden dangersto the mountains and forest besides.In order to solve this problem,the paper takes andalusite tailings as the research object,on the basis of the full understanding of the properties of the tailings,we explore the reutilization of the andalusite tailings,in order to achieve the zero discharge of andalusite tailings.It's not only possible to reduce the cost of production and management,to solve the safety problems such as ecological environment damage and dam breakage caused by tailings storage,but alsothe process is simple and the product market demand is broad and the economic benefit is considerable,,thus effectively solve the problem of wasting of Andalusite tailings resources,in line with the national industrial policy.In this paper,by using andalusite tailings to produce high-intensity autoclaved sand lime bricks as the main purpose,The process parameters such as formula design,stirring process,autoclave process and molding process were detailed studied.The influence of C/S on the strength of autoclaved lime sand brick was explored,and the technical and economic analysis of the project was carried out.The main results and conclusions are as follows:?1?Andalusite tailings containing quartz,can be used for the preparation of autoclaved lime sand brick as siliceous material,but the free quartz content is only 50%and the particle size of tailings is fine,didn't reach the relevant requirements of"sand for building silicate products"standard?JC/T622-2009?.In view of the unique properties of tailings,the suitable process parameters were explored,The research indicates that the quartz sand can effectively improve the strength of autoclaved lime sand brick,and well particle size distributed quartz sand can increase the strength of more obvious;adding gypsum and cementto the formula will reduce the strength of autoclaved lime sand brick;in a certain range,with the increase of molding pressure and moisture,vapor pressure,step-up,constant pressure and step-down time,the strength of autoclaved lime sand brick will increase,but there is an extreme point,beyond the extreme point,continue to increase the parameters will make the sand brick strength to reduce or increase the cost of production.?2?Determine the appropriate formula for Andalusite tailings'mixing amount is66.6%,lime's mixing amount is 18.4%,quartz sand mixing amount is 15%,among them,and particle size of quartz sand is-0.45mm+0.15mm?-0.90mm+0.45mm?-1.25mm+0.90mm particle accounted for 3%,6%,6%respectively.The autoclaved lime sand bricks with compressive strength of 28.52MPa were prepared under the conditions of forming pressure of 20MPa,forming water 12%,autoclave pressure1.1MPa,boosting pressure 2h,constant pressure 6h and natural buck.,Tobermorite is an important material basis and guarantee for the source of autoclaved lime bricks.?3?XRD and SEM show that when the C/S in the raw material is relatively low,the amount of hydrated calcium silicate formed by the autoclave reaction is insufficient,and the strength of the lime sand brick is reduced.When the C/S in the raw material are relatively high,therebe easier to generate C₂SH_n,C₂SH_nintensityis low,making the strength of lime sand brick is not high;Only when the calcium silicon ratio in the raw materials in a reasonable range,is conducive to tobermorite and CSH?I?generation,and generated more tobermorite,autoclaved lime sand brick strength greater.