Research On Properties Of Self-compacting Lightweight Concrete

Numerous investigations have been conducted on normal self-compacting concrete(SCC) and normal lightweight aggregate concrete(LWAC),but there are relatively very few studies on self-compacting lightweight concrete(SCLC).SCLC combines the favorable properties of LWAC and SCC,needs no external vibration,and can spread into place,fill the formwork and encapsulate reinforcement without any bleeding or segregation.So,there is a comprehensive application prospect for SCLC.Currently,the researches on SCLC mainly focus on the workability of fresh SCLC or its basic mechanical performances.As a kind of important construction materials,there are also many other performances for SCLC besides workability and basic mechanical performances.An all-round and deeply study is need to carry out to generalize the practical application of SCLC.Therefore,this paper has made a relatively systemic study on performances of SCLC based on the previous investigations by other scholars to lay a foundation for the research and application for SCLC.These performances of SCLC have studied mainly by experiments or theoretical methods as follows:1.Study on the design method and workability of SCLCBy considering the water absorption of lightweight aggregate(LWA),two mix proportions for SCLC are designed by the overall calculation method with fixed fine and coarse aggregate contents after many times revised tests.The strength grades of the two designed SCLCs are C40 and C50,and noted SCLC1 and SCLC2 respectively.The workability of the two types of fresh SCLCs is quantitatively evaluated by the slump flow, V-funnel,L-box,U-box,wet sieve segregation,and surface settlement tests.The uniformity of distribution of LWAs along the specimen is also evaluated by the column segregation test and the cross-section images.It is found that the two types of fresh SCLCs have good fluidity, deformability,filling ability,uniform aggregate distribution and minimum resistance to segregation.It can be concluded that the two mix proportions for SCLC presented in this paper satisfy various requirements for workability and can be used for the design of practical concrete structures.2.Investigations on shrinkage and creep behaviors of SCLCEarly age shrinkage and creep tests have been carried out for SCLC1,SCLC2,SCC and NC,in which SCC is normal self-compacting concrete having the similar mix proportion with SCLC1 replaced the LWA by normal aggregate,and NC is normal concrete having the same strength grade with SCLC1.It is showed by the test results,autogenous shrinkage of SCLC is smaller than those of SCC and NC,because of water absorption and desorption function in LWA.It is also found that a slight expansion phenomenon happening during the first 10 days for SCLC,however,shrinkage for SCC and NC all around the age time.From the creep test, elastic strain of SCLC is obviously larger than those of NC and SCC,and creep strain is a slight larger than those of NC and SCC.Consequently,creep coefficient is smaller than those of NC and SCC.3.Investiagation on behavior of SCLC after high temperatureBox type resistance furnace is used to heat the 4 type specimens of SCLC1,SCLC2,NC and SCC to the temperature of 200℃,400℃,450℃,500℃and 600℃respectively for about 4 hour,then cool to room temperature.Mass loss test,ultrasonic inspection,cube compressive test and flexural test have been done to compare the high temperature behavior of SCLC with those of NC and SCC.It can be known from the test results that there is no obviously difference in mass loss among SCLC,SCC and NC,and the spalling temperature of SCLC is lower than those of SCC and NC.But the internal damnification,compressive strength loss and flexural strength loss is significantly lighter than those of SCC and NC.4.Investigation on the fracture performance of SCLCWith total number of 30 specimens,100×100×500mm in size,six type notch to height ratio of 0.1 to 0.6,fracture tests of three-point bending beams using concrete of SCLC1 are carried out.Based on the test results,initial fracture toughness,unstable fracture toughness and facture energy considering boundary effect are calculated.Finally,a softening constitutive relationship model is chosen for SCLC1 and it is verified by the fracture energy calculated from test results.5.Experimental study on behavior of SCLC shear wall4 shear walls made of SCLC1 and 2 shear walls made of NC are designed for low reversed cyclic loading test.It is indicated by the test results that the ductility of SCLC shear wall is a little better than that of NC shear wall with the same concrete strength grade,and the energy consumption is similar with NC shear wall.Both of them exhibited some brittleness when they destroyed.