Study On Activation And Properties Of Waste Clay Brick Powder

Construction waste refers to the residual mud,residue,mud and other wastes generated in the process of construction,demolition,repair and decoration of buildings and structures by construction and construction units or individuals.In recent years,with the rapid development of urban construction and the rapid development of construction industry,a lot of construction waste is produced in the process of demolition and new construction.There is a huge amount of construction waste in our country.From its composition,the main body is waste concrete and waste clay brick,especially the comprehensive utilization rate of waste clay brick is low.It not only occupies the land,changes the soil composition,but also causes a huge waste of resources.In view of the low activity of clay brick powder produced in the process of recycling and crushing waste clay brick,which can not be used efficiently,this paper proposes to use waste clay brick powder and cement as the main raw materials and calcium hydroxide and calcium sulfate dihydrate as the activator to prepare a new green cementitious material.In this paper,the effect of waste clay brick powder as admixture on the strength of mortar specimen is studied.Different activation methods are used to activate waste clay brick powder,including physical activation(grinding)and chemical activation(alkali excitation,salt excitation,composite excitation).According to the compressive strength and flexural strength of the rubber sand specimen,the activation index was used as the evaluation index to compare the activation effect of different activation methods.At the same time,the activation mechanism was analyzed by means of microanalysis.The main conclusions are as follows:1)The activity of waste clay brick powder is relatively low,which can be activated by different activation methods.When the physical activation method is used,the specific surface area and activity index of waste clay brick powder increase with the prolongation of grinding time.When the grinding time is more than 90 minutes,When the grinding time is 90 minutes,the activity index is 67%,and the specific surface area of the corresponding clay brick powder is 467 m2 / kg.Among the chemical excitation methods,the composite excitation of calcium hydroxide and calcium sulfate dihydrate has the most significant activation effect.The activity index of the waste brick powder increases first and thendecreases with the increase of the content of calcium hydroxide;the activity index of the waste brick powder increases first and then decreases with the increase of the content of calcium sulfate dihydrate;the activity index of the waste brick powder is better than that of calcium hydroxide and calcium sulfate dihydrate when calcium hydroxide and calcium sulfate dihydrate are mixed.(2)In the study of hydration heat test,the reaction time of activated waste clay brick powder is longer in the hydration acceleration period,which shows that activated waste clay brick powder can promote the hydration of cement;after about 35 h of hydration,the total heat release curve of each group of samples gradually tends to be flat,and the heat release of activated composite cementitious materials exceeds that of unexcited composite cementitious materials The amount of heat released by the condensing material.(3)Water cement ratio,water reducing agent content and curing conditions all have an impact on the experiment.Through the experiment,it is concluded that the optimal scheme of this experiment is to carry out standard curing at 20 ?,using water cement ratio of 0.32 and water reducing agent content of 0.2%.(4)When the industrial grade calcium hydroxide is used as the activator,the composite cementitious material,which is separately excited by 10% calcium hydroxide and mixed with10% calcium hydroxide and 3% calcium sulfate dihydrate and excited brick powder cement(2:8),its initial setting time,final setting time,compressive strength and flexural strength are not lower than the strength requirements of all ages of the used cement,indicating that the waste brick powder can be taken as the admixture Replace part of cement.