Research On The Performance And Mechanism Of Dry-Mixed Mortar Based On The Activation Of The Recycled Concrete Micropowder In The Architectural Wastes

The regeneration and utilization of construction wastes are able to promote the sustainable development of the construction industry.A scientific research on preparation of dry-mixed mortar with architectural wastes has been made by activating their activity.The research contents involve the feasibility study on the thermodynamic theory,experiment study of the excitation of the activity of recycled concrete micropowder,the study on the effect that temperature and mix ratio of reactant takes on the activity of recycled concrete micropowder and the activation effect of it,the study on the effect that the thermodynamics of the activity excitation of recycled concrete micropowder and the hydration degree of the main substances in the mortar system of recycled concrete micropowder take on the performance of the mortar,the study on the formula of the excitant of the recycled concrete micropowder and the performance of mortar under the action of the formula,the study on the strength increment modal of the mortar and on the mechanism of the prepared mortar under the exciting of recycled concrete micropowder.The conclusions in the paper include:The recycled concrete micropowder is of activity,and the activity can be released under the condition of activation.The thermodynamic study of the recycled concrete micropowder discovered that the chemical methods are superior to pulverizing in activity exciting.The study also forecast the possible resultant in the mortar under the excitation of the activity of the recycled concrete micropowder.In basic research the conclusion is drawn that recycled concrete micropowder mortar gelled by cement is a process of the hydrated resultant of cement gelling the granule of recycled concrete micropowder and filling the pores among the granules.When cement,lime/gypsum are used as gellants or excitants,expansible substances are produced and fill the pores in the mortar and make it dense.NaOH is able to improve the excitant effect of activity of recycled concrete micropowder mortar.The excitant effect of recycled concrete micropowder can be improved by Na2SO4 because the sulfate radical in Na2SO4 is able to promote the hydration of cement.CaCl2 plays an active role in excitation of activity of recycled concrete micropowder in early stages.The reaction joined by CaCl2 can produce the substances beneficial to strength,so CaCl2 can improve the strength of the recycled concrete micropowder mortar.The kinetic study discovered that the chemical reaction during the hydration process of cement producing Ca(OH)2 and that active constitutent consuming Ca(OH)2 comply with first-order kinetics reaction features.The kinetic constant kc and kf at each temperature can be determined by experiment data,based on which the study on the relation between the reaction degree of the main reactant and performance of the mortar is made.Study on formula gelling excitant obtained a formula with 6 factors and 12 mixed levels(LQ1)and a formula with 5 factors and 12 mixed levels(LQ2);The dry-mixed mortar is prepared with recycled concrete micropowder whose activity is activated by formula activator,and the mortar has superior performance and the cost of raw material is very low.The experiment research has obtained a forecast formula on strength increment capable of forecasting the strength of recycled concrete micro-powder mortar.The formula can forecast the effect of the change of each factor on strength and it is of great significance to guide LQ1 and LQ2 gelling activate the activity of recycled concrete micropowder into application practice.Experiment study and theoretical analysis proved that when alkaline excitant LQ1 is used to activate recycled concrete micropowder,the mechanism that dry-mixed mortar is prepared by activating the activity of recycled concrete micropowder is that the expansible ettringite is produced and interlude between gelling substances,in which diffusively distributed tobermorite,water garnet,with small and evenly pores,and good indexes in performance.When alkaline excitant LQ2 is used to activate recycled concrete micropowder,a certain amount of calcium carbonate,Friedel expansible substances,diffusively distributed tobermorite,water garnet are produced and they are cemented together to reduce the pores in the system.So the performance of mortar is improved.The temperature and curing age have an impact on the category and quantity of the resultant in the recycled concrete micropowder mortar,and in the end on the performance of the mortar.The research result described in the paper provide necessary theoretical and experimental basis for large scale resource utilization of recycled concrete micropowder of architectural wastes being prepared as mortar.It is of great practical significance for the recycle of architectural wastes in the future.