Granular Powder Of Construction Waste In Cement Concrete,

According to incomplete statistics, the amount of urban solid wastes has reached to 1.42*103 ton annual and the quantity of building wastes has accounted for 30%-40% in China. Building wastes recycling has received considerable attention and become one of the research hotspots in world, but up to now this doesn' t happen in China . In this paper, the research results about properties and production of recycled aggregate and concrete has been reviewed in world, and the recycling of particle and powder waste of concrete and brick are studied respectively. The study results show that building wastes recycling has obvious social, environmental and economic benefits and can facilitate sustainable development of material industry. In this paper the following work has been done:(1) The viewpoint of using pulverized powder waste of concrete and brick as mineral admixture for cement and concrete is put forward firstly: Because the research about building wastes recycling is focused on recycled aggregate and recycled concrete in domestic and foreign countries, but the smaller powder which is generated in the process of recycled aggregate production is abandoned and pollutes environment, in order to recycle waste concrete and waste brick completely, in this paper, the utilizing smaller powder as mineral admixture for cement and concrete through pulverization and excitation is put forward. The research results show that the way is feasible and waste concrete and waste brick have better recycling value.(2) The research shows that pulverized building wastes has potential hydration activity: the CaCO3 hydrate gel and unhydrated cement particle which are contained in pulverized waste concrete can react or form calcium carboaluminate hydrates and calcium carbosilicate hydrates crystal blank effect and new hydrates respectively, especially in the early stage. The alumina-silica minerals which is contained in pulverized waste brick have pozzuolanic activity and can react with Ca(0H)2 to form C-S-H.(3) the content of pulverized building wastes excited by mineral agent can be increased in cement and concrete: NaOH and Na2CO have excitation effect to pulverized waste concrete and brick, else lime and gypsum have better excitation effect only to pulverized waste brick. Pulverized building wastes has not bad influence on the physical properties of cement such as water requirement for normal consistency of cement paste, time of final setting and cement soundness, but in a way large content of pulverized waste concrete in cement can cause decrease of initial setting time because of crystal blank effect and the hydration between CaCO3 and C3S.(4) The content of pulverized building wastes in cement and concrete can greatly influence the mechanical property of cement and concrete: Pulverized building wastes can not greatly decrease the strength of cement if the content is not over 10 percent under equal substitution, but the strength will decrease with the content in linear if the content is over 10 percent. The mechanical property of 42. 5 grade cement ran keep or enhance when the content of pulverized building wastes is not over 10 percent and can still satisfy 32. 5 grade even when the content has reached to 30 percent. When the alkaline excitation agent exists, the concrete can still keep stable strength even if using the pulverized building wastes to replace cement 20% and at the same time replace sand not over 15 percent, or excessive substitution.(5) Through activation and intensification (immersion method) it is possible to make concrete whose strength is higher than 30Mpa by completely or partly using recycled coarse aggregate to take place of natural crushed rock aggregate: The properties of immersed recycled coarse aggregate can be improved obviously, especially inorganic impregnant disposal recycled coarse aggregate. The 28d compressive strength of concrete which is made by using inorganic impregnant disposal recycled coarse aggregate to completely substituting natural crushed rock aggregate almost reaches to 31.0Mpa, at...