Effect Of Waste Clay Brick On The Clinker Formation And Property Of Recycled Cement Clinker

The technique of recycled cement produced from all components of waste concrete is an effective way to realize primary resource utilization of the waste concrete, and the technique not only has a substantial increase in the resource utilization level of waste concrete, reduces environmental load significantly, but also can effectively reverse the current situation that requirement for increasing scarce natural resources in the cement industry. Waste clay brick (WCB) and its surface-coated waste mortar are inevitably introduced into the raw meals while waste concrete is used in cement production, and it is high difficult to separate waste concrete and WCB and increase separation cost. Moreover, SiO2and Al2O3in WCB most exist in the vitreous form and have pozzolanic activity. Inert SiO2in waste concrete is partial substituted by active SiO2in WCB, and it can improve the quality of clinker. So on the basis of the composition of the present stage of construction waste, from the point of optimizing the performance of recycled cement, reducing raw material separation costs, improving utilization of construction waste, it’s necessary to study the effect of WCB on the clinker formation and property of recycled cement clinker, in order to lay the foundation for the industrial production of recycled cement from all components of recycled concrete.Firstly, the basic feasibility research on the calcination of Portland cement clinker with WCB and its surface-coated waste mortar as siliceous raw material was made with combination of theoretical analysis in chemical composition and mineral composition of WCB and composition triangle of CaO-SiO2-Al2O3ternary system. On the basis of theoretical analysis, effect of WCB on the clinker formation and mineral properties of cement clinker was studied by experimental study:WCB and its surface-coated waste mortar as siliceous raw material calcined cement clinker and using the traditional clay material for comparison reference; at different cement modulus and different calcination temperature, the burnability of raw meals and mineral properties of cement clinker are studied by f-CaO analyzer, X-Ray diffraction and petrography analysis. The results show that it’s entirely feasible to calcine Portland cement clinker with WCB as siliceous material through theoretical analysis and experimental demonstration; at the same cement modulus, the burnability of raw meals with WCB is better than the clay’s; compared with the clinker produced by raw meals with clay, mineral morphological characteristics of C3S in clinker produced by raw meals with WCB is better; characteristic peaks of silicate minerals and fluxing minerals in XRD patterns are higher and more sharp than clay’s ingredients, and else WCB’s sample has the similar diffraction peak with industrial clinker like Onoda and even a little higher intensity than the Onoda’s:in the same preparation conditions.3d compressive strength of recycled cement produced by WCB ingredients is slightly lower than Onoda’s, but28d strength is higher than Onoda’s by38.66%. and it can illustrate that the recycled cement with WCB as siliceous raw material has good quality as the industrial cement.The paper has further studied effect of different proportion WCB and waste concrete on the clinker formation and property of recycled cement clinker. On the basis of first part results of the paper and preliminary research results, appropriate cemet modulus and temperature were selected and three properation of WCB and waste concrete were designed; the burnability. clinker mineral composition, mineral morphology and compressive strength of recycled cement was studied. The results show that f-CaO content of clinker increased with the increased proportion of WCB. but less than1.5%; crystallinity of Alite and appearance of clinker were improved with WCB proportion increased; the clinker minerals diffraction peaks became more sharp and higher as the percentage of WCB raised; and the strength of3d and28d curing period were both enhanced with WCB proportion increased.For studying the mechanism of effect of WCB on the clinker formation and property of recycled cement clinker produced from all components of waste concrete, kinetic parameters of samples with WCB. clay and different proportion WCB ingredients were calculated. The results show that apparent activation energy of C3S formation of WCB group were lower than clay’s, and it can illustrate that WCB has the potential to reduce energy consumption and energy-saving advantage, compared with the traditional clay raw materials; when K H is relatively high, SM has little effect on the dynamics of clinkers, it can illustrate that WCB as siliceous materials can select two high rate of value to jion in ingredients. Kinetic parameters of different proportion WCB ingredients were calculated and the results show that the apparent activation energy of C.?S formation was increased with WCB percentage increased, and this can indicate that impurity ions of waste concrete play a role of fluxing and mineralization, and unhydrated cement particles as seed to drop the systematic minimum eutectic temperature, increase the amount of liquid phase and reduce the viscosity of liquid, and hydration products play a dominant promoting role on mineral formation and then the apparent activation energy of C?S formation dropped. When the proportion WCB is under80%. the effect of apparent activation energy is slight with the change of SM at high K.H.