| China has stepped into the acceleration phase of urbanization, many old buildings demolition and transformation will inevitably produce a lot of waste concrete. If the waste concrete is randomly piled up, it can cause serious environmental pollution, but also huge waste of resources.. In recent years, the recycling of recycled concrete is limited to the use of recycled aggregate, and the research on the utilization of waste mortar in waste concrete is seldom.. From the point of view of the cost of raw materials, waste mortar is abandoned concrete in high cost "essence, as recycled aggregate using did not fully reflect its value; and attachment of waste mortar mechanical properties of recycled aggregate concrete is poor, made from recycled aggregate in the process of a large number of micro particles are dropped. But waste mortar grinding performance is good, especially after calcination after heat treatment more easily grinding, grinding energy consumption is relatively low. According to the fineness of cement admixture, this feature of scrap mortar is a great possibility for cement mixing..In order to improve the recycling value of waste mortar and overcome the defects of recycled aggregate, this paper analyzes the mechanism of how to separate and mill the mortar components in the waste concrete by high efficiency separation and milling.., to achieve the basic physical properties of waste mortar powder on experimental basis, and chemical activator modification and high temperature calcination method two methods of waste mortar powder mixed cement mechanical properties improved, found fully stimulate waste mortar powder activity to obtain high activity waste mortar powder method. The main research contents and achievements of this paper are as follows:(1)Through analysis of waste concrete mortar is divided into separation and ball milling grinding mechanism, put forward the principle of interface transition zone, the study of mechanical grinding and calcination heat treatment of waste mortar group divided into physical and chemical structure change, and the change of waste mortar component recovery efficiency and grinding performance impact. That extended milling time t, improve grinding media mass m and height h, and above 500 DEG C calcination method are in favor of the waste mortar separating collection and ground; and in the 500 to 600 DEG C the temperature interval after calcination of coarse aggregate performance to maintain a good, conclusion of high-quality reuse of recycled aggregate.(2)The effect of the waste mortar powder on the cement content, such as the water consumption, the fluidity and the strength of the cement mixture, is studied.. The experimental results show that the water absorption rate of waste mortar is relatively large, the fineness and content of the waste mortar can affect the strength, and the activity index of the waste mortar with the ratio of 0.08mm sieve residue is 77%,2.7%. The mixed cement compression ratio increased and the ductility of the material was good..(3)The study of waste mortar powder was modified by chemical activator. The results showed that doped 0.5%FDN-A water reducing agent of mixed with 30% of waste mortar powder mixed cement mortar fluidity change effect better. FDN-A reducing agent, dihydrate gypsum, sodium silicate, sodium sulfate are conducive to improving the strength of the mixed cement waste mortar powder, modified effect is good, and draw the chemical activation agent of the optimum mix amount and optimum formulation.(4)The effect of different calcination temperatures on the abrasive, fluidity and the activity of waste mortar are studied.. Experimental results show that the 600 degrees Celsius heat treatment, mixed with 30% of waste mortar powder mixed cement 28 day strength increase of 3.01MPa, combined with separation of waste concrete mortar was the optimum temperature in the conclusion of 500 to 600 DEG C to determine the 600 DEG C is the separation and stimulate the optimal temperature for activity of waste mortar.(5)Based on a chemical activator optimization formulation, after 600 degrees Celsius heat treatment thermal activated waste mortar powder was modified by chemical activator. When the waste mortar powder content is 20%,30%, mixed cement 28 day compressive strength of up to 48.61MPa and 45.03MPa, basic meet 42.5 cement strength grade requirements, when the content is 40%,50%, also can prepared in line with mixed cement 32.5 strength grade requirements when the higher dosage can be used as a low strength grade cement. |
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