【作者】 张云国；

【导师】 吴智敏；

【作者基本信息】 大连理工大学 ， 结构工程， 2009， 博士

【摘要】 有关普通自密实混凝土和轻骨料混凝土的研究很多,但是关于自密实轻骨料混凝土的研究却很少。自密实轻骨料混凝土兼有自密实混凝土和轻骨料混凝土的特性,它不需要振捣便可自动在模板里通过钢筋密实成型而不发生离析现象,有广阔的应用前景。目前关于自密实轻骨料混凝土的研究主要集中在它的工作性能和基本力学性能方面。作为重要的土木工程材料,自密实轻骨料混凝土除了这些基本性能之外还包括许多其它方面重要的性能,在实际工程应用推广之前还需要对它的性能进行更全面、深入的研究。因此本文在已有的关于自密实轻骨料混凝土性能研究的基础上,开展了进一步的研究工作,为自密实轻骨料混凝土的进一步研究和推广应用奠定基础。本文主要通过试验对自密实轻骨料混凝土的性能开展了以下几方面的研究工作:1.自密实轻骨料混凝土配合比设计和工作性能研究采用固定砂石体积和全计算相结合的方法,同时考虑轻骨料的吸水率,经过多次反复试验得到了工作性能良好的强度等级为C40和C50的两种自密实轻骨料混凝土SCLC1和SCLC2。针对所配制的自密实轻料混凝土开展了流动扩展度、V型漏斗、L槽、U型槽、湿筛、表面沉降试验,并采用了轻骨料分层试验和切片试验研究了轻骨料在混凝土中的分布状况。结果表明,所设计的自密实轻骨料混凝土具有良好的流动性、变形性、骨料均匀性和良好的抗离析性,采用这种设计方法可以配制出满足实际工程需要的自密实轻骨料混凝土。2.自密实轻骨料混凝土收缩徐变性能研究对SCLC1、SCLC2及与SCLC1强度等级相同的普通混凝土NC和与SCLC1配合比相似的自密实混凝土SCC四种混凝土开展早龄期收缩徐变试验,其中SCC是将SCLC1中轻骨料用普通骨料等体积代换得到的自密实混凝土。结果表明,由于轻骨料的吸水返水作用,自密实轻骨料混凝土的自生收缩小于普通混凝土和普通自密实混凝土,并且自密实轻骨料混凝土在前10天龄期出现了轻微的膨胀现象,而普通混凝土和普通自密实混凝土则一直表现为收缩现象。徐变试验结果表明,自密实轻骨料混凝土的弹性变形明显大于普通混凝土和普通自密实混凝土,徐变值则略大于普通混凝土和普通自密实混凝土,徐变系数明显小于普通混凝土和普通自密实混凝土。3.自密实轻骨料混凝土高温性能研究采用电阻式高温炉对SCLC1、SCLC2、SCC和NC四种混凝土进行200℃、400℃、450℃、500℃及600℃高温试验,并对高温后的混凝土试件开展质量损失、超声波检测、抗压及抗折试验。试验结果表明,自密实轻骨料混凝土的高温爆裂温度低于普通自密实混凝土和普通混凝土,质量损失无明显差异。但是通过超声波检测发现自密实轻骨料混凝土内部损伤小于普通混凝土和普通自密实混凝土,同时抗压强度和抗折强度损失也明显小于普通混凝土和普通自密实混凝土。4.自密实轻骨料混凝土断裂性能研究采用尺寸为100×100×500mm、缝高比为0.1、0.2、0.3、0.4、0.5和0.6的30个试件,对自密实轻骨料混凝土SCLC1小梁开展三点弯曲断裂试验。通过计算得到了自密实轻骨料混凝土的起裂断裂韧度、失稳断裂韧度及断裂能等断裂参数,并根据考虑了边界效应的断裂能确定了适合自密实轻骨料混凝土的软化曲线本构关系模型。5.自密实轻骨料混凝土剪力墙结构性能研究分别设计了4片自密实轻骨料混凝土剪力墙和2片普通混凝土剪力墙,自密实轻骨料混凝土采用SCLC1,普通混凝土采用NC,并开展了低周反复荷载试验。试验结果表明,自密实轻骨料混凝土剪力墙的延性略好于同强度等级的普通混凝土剪力墙,但二者的耗能能力无明显差异,破坏时均表现出一定的脆性特征。更多还原

【Abstract】 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.更多还原