| In recent years, the development momentum of China's construction industry is not reduced, and the large amount of construction waste has been created in the process of new construction, renovation and demolition, and the trend is increasing year by year.The main treatment methods of construction waste in our country are stacking and landfill. The actual utilization of construction waste is less than 1%. At present, the main means of resource utilization of construction waste is grinding them into coarse aggregate or fine aggregate, and for making into recycled productions of recycled concrete and recycled aggregate mortar and so on. However, in the process of grinding construction waste, it is inevitable to produce a certain amount of ultra-fine construction waste powder , its size is not more than 75 micron. These ultra-fine powders have a certain activity and good physical properties. If not used them, this is not only a waste of resources, and is bound to cause the second pollution.We can collect them, or direct crushing and grinding construction waste into powder whose particle size not more than 75 micron. Use them to replace cement or fly ash and then to preparation of recycled mortar. This is not only achieve the purpose of recycled using of construction waste, but also conducive to the protection of the environment, and in line with the requirements of national sustainable development.The main components of ultra-fine construction waste powder are:Hydrated cement particle, unhydrated cement particle, fine sand powder particles, fine stone powder particles, clay powder particle and so on. It has the characteristics of high porosity, surface roughness, large specific surface area, low moisture, have certain activity, good adhesion with cement. Based on the above characteristics, this paper introduces the ultra-fine construction waste powder replace the cement or fly ash , and the ultra-fine brick powder replace the cement, to used to the preparition of mortar. We have 3 kinds of mortar of different strength, who commonly used in engineering: M5,M7.5,M10.We studied the effect of content of ultra-fine powder on the basic working performance, mechanical properties and frost resistance of mortar. When the consistency of the mortar is maintained at 70?90mm,the experimental results show that: (1) The water consumption of mortar increases with the increase of the substitution rate of ultra-fine brick powder, and increases slowly with the increase of the substitution rate of construction waste ultra-fine powder; (2) Adding the brick ultra-fine powder or construction waste ultra-fine powder to the mortar, its water retention is better than ordinary mortar; (3) Construction waste ultra-fine powder has a certain activity, can play a good filling effect and shape effect, when the dosage is less than 10%, the strength of mortar lose is little, can be used as mineral admixture; (4)The addition of construction waste ultra-fine powder has little effect on the freeze-thaw resistance of mortar. (5) The incorporation of construction waste ultra-fine powder has little influence on the frost resistance of mortar. |
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