Experimental Study On Preparation Of Controlled Low Strength Material From Cement Stabilized Macadam Milling Mixture

Controlled low strength material(CLSM)is a cement-based material with water,fine aggregate,cement,and admixtures as main components.It has characteristics of high fluidity,self-compacting.Utilization of cement stabilized macadam milling mixture to produce CLSM is of great significance to reduce environmental pollution and expand recycling ways of cement stabilized macadam milling mixture.In this paper,preparation of CLSM by cement stabilized macadam milling mixture was studied from three aspects:crushing method of cement stabilized macadam milling mixture,workability of CLSM,mechanical and physical properties of CLSM.Main work and conclusions of this paper are as follows:(1)Three kinds of crushing methods were used to granulate cement stabilized macadam milling mixture into fine aggregates,its physical properties were tested and compared.Based on physical properties of recycled fine aggregate,crushing method was selected and optimized.The results show that granulation of cement stabilized macadam milling mixture can improve its physical properties and reduce variability of physical performance indicators by up to 74.9%.Among them,recycled fine aggregate produced by crushing method of hammer crusher and ball mill has best physical properties.After optimization,variability of recycled fine aggregate gradation is further reduced,water absorption is decreased by 0.1%-0.7%,and required revolution in ball milling process is reduced by 1/3.(2)Effects of different recycled fine aggregate gradation,powder content,blending amount and concrete admixtures dosages on working performance of CLSM were studied.The results show that fluidity of CLSM is greater than 200 mm,which is produced by three gradation recycled fine aggregate with fineness modulus of 2.75-2.90.Powder content of recycled fine aggregate should be controlled at 5%-15%.CLSM made entirely from recycled fine aggregates can reach a flowability of 240 mm and bleeding is less than 5%.Compared with polycarboxylic acid water reducer,mixture of polycarboxylic acid water reducer with polyether defoaming agent and rosin air entraining agent can increase fluidity of CLSM by 5.9% to 19.3%,up to 280 mm.(3)Based on conclusion of CLSM's working performance,effect of different recycled fine aggregate gradation,powder content,soundness and concrete admixtures dosages on mechanical properties and physical properties of CLSM were studied.The results show that CLSM made from recycled fine aggregate with G2 gradation has better mechanical and physical properties.Powder content of recycled fine aggregate should be controlled to 5%,which is more conducive to mechanical and physical properties of CLSM.Unconfined compressive strength,compressive resilient modulus and BDR of CLSM decrease with increase of soundness loss.mixture of polycarboxylic acid water reducer with polyether defoaming agent and rosin air entraining agent can increase mechanical properties of CLSM,improve frost resistance and reduce dry shrinkage slightly.