【作者】 石建光；

【导师】 叶志明；

【作者基本信息】 上海大学 ， 结构工程， 2011， 博士

【摘要】 中国处于工业化、城市化、现代化的进程中,这一特殊的发展阶段和人口众多的国情决定了各种资源材料的大量需求和各种垃圾、废料大量产生的共存局面。资源和环境问题的不断恶化,促使可持续发展战略的实施。土木建筑工程作为最大的资源耗费产业之一应成为实施这一战略的重点行业。土建废料和垃圾的再利用和资源化是落实这项战略的有效途径。建筑垃圾用于混凝土生产的方式一种为分解出建筑垃圾中的混凝土块体加工成再生混凝土骨料,一种为直接用建筑垃圾生产再生混合骨料。再生混凝土骨料的表观密度和堆积密度分别在2.31kg/m3～2.62kg/m3和1.29kg/m3-1.47kg/m3之间,其吸水率处于4%-10%之间,压碎指标在14.2%-23.1%之间。再生骨料混凝土抗压强度随再生骨料替代率增加而降低,随水灰比增大而降低。再生骨料混凝土的抗拉强度受替代率影响比较小,随着再生骨料替代率的增大,再生骨料混凝土的坍落度急剧下降、弹性模量降低、收缩值显著增大、抗冻性基本不变、渗透性增大、碳化速度略有增加、抗硫酸盐侵蚀性略有降低。建筑垃圾中砖瓦、混凝土碎块、玻璃、木纤维、沥青、旧塑料和贝壳等不同再生骨料成分对混凝土抗压强度、抗拉强度、弹性模量和收缩量等性能有不同的影响。玻璃骨料会产生有害的碱骨料反应,但当磨细到一定程度后能提高混凝土抗压强度,并减小膨胀。再生混凝土碎块对混凝土各项性能均有不利影响。旧塑料骨料可提高混凝土的延展性和抗渗性,减小收缩值。沥青骨料会影响混凝土的抗拉压强度,但提高了混凝土的韧性。贝壳骨料使混凝土的工作性能、弹性模量下降。通过不同再生骨料成分对混凝土性能影响的试验研究发现,由厦门地区建筑垃圾破碎而得到的再生混合骨料的密度要小于传统的再生骨料和天然骨料,且由于碎红砖等其他成分的存在,再生混合骨料的吸水率要高于再生骨料和天然骨料,强度也会低于再生骨料和天然骨料。再生混合骨料混凝土,当用水量为300kg、水胶比为0.6、再生混合粗骨料替代率50%时平均强度最高。正交试验表明,水胶比对抗压强度的影响最大,再生混合骨料的替代率次之,用水量更次。再生细骨料比再生粗骨料对混凝土强度的影响大,混凝土抗压强度和抗拉强度相差17.7%和18.5%。再生混合粗骨料含量不超过50%对混凝土强度不会产生影响。再生粗骨料中红砖成分的增加会使得抗压强度和抗拉强度分别降低11.3%和7.4%。再生粗骨料中碎瓷砖成分会使得混凝土的抗压强度和抗拉强度下降大约8.1%。预先将再生细骨料和再生骨料全部浸湿会严重降低再生混凝土强度。再生混合细骨料的取代率提高,再生混凝土的抗拉强度下降。随着砂率的提高,再生混凝土抗拉强度提高,添加一定量的聚羧酸系高效减水剂时,再生混凝土的和易性和流动性均有所提高,且坍落度也会增加,可提高抗压强度10%-15%,抗拉强度可提高10%-14%。当粉煤灰掺量分别为25%和35%时,其强度大约下降了32.1%和36.8%。再生混合骨料用于制造混凝土多空砖一般能满足砌块强度要求,掺加粉煤灰时,其合理掺量为小于15%。通过再生混凝土骨料级配对混凝土强度和工作性能影响的试验研究发现,采用再生骨料的自然级配制备混凝土,混凝土工作性能差,受压强度低。按《混凝土泵送施工技术规程》要求的骨料级配制备再生混凝土,混凝土工作性能差,受压强度比较低。再生骨料的抗压强度与其粗骨料的级配具有密切关系,当再生粗骨料的级配较差时,再生骨料混凝土的强度很低,28天抗压强度不到15Mpa,当再生粗骨料的级配合理时,其抗压强度将得到很大的提高,28天抗压强度将可以达到40Mpa。增加粒径范围19-26.5mm和26.5-31.5mm的骨料含量,混凝土工作性好,受压强度高。而增加粒径范围4.75-9.5mm的骨料含量,混凝土工作性能差,受压强度低。粗细再生骨料含量不超过60%时再生混凝土工作性能可以满足施工要求和强度可以达到40Mpa左右。再生骨料替代率分别为50%、60%时,调整粒径范围9.5-26.5mm的骨料,使其级配接近,再生混凝土强度可以高于天然骨料的混凝土强度。骨料本身作为复杂的非规则体,用传统的几何学来描述骨料非常困难。利用分形学对骨料的特征分析表明：骨料级配需要一定的粒径宽度,才能满足骨料的粒径级配分形条件；骨料的空隙率与骨料的最大,最小粒径,骨料级配以及骨料堆积密度分维有关；级配骨料的总表面积取决于骨料的最大、最小粒径,骨料的级配分形、表面积分形和骨料质量,同时还取决于测量尺度；由于骨料表面主要是和水泥发生作用,因此测量尺度一般取水泥粒子的粒径量级比较合理。混凝土中骨料总表面积和结合层厚度的乘积就是包裹骨料需要的水泥浆体积,用包裹骨料需要的水泥浆体积除以混凝土中水泥浆总体积可得浆裹比,浆裹比直接反映了水泥浆和骨料之间结合层的相互关系。浆裹比可以反映不同骨料级配变化引起的骨料表面的变化。浆裹比值越大,骨料的表面积越大,包裹骨料需要的水泥浆越多。当水灰比为0.55时,浆裹比大于0.085时,混凝土工作性能好差,受压强度低。当浆裹比小于0.085时,混凝土工作性能较好,受压强度高。当浆裹比比较小时,中部粒径范围9.5-26.5mm骨料级配差异较小时,混凝土工作性能较好,受压强度高；而当中部粒径范围9.5-26.5mm骨料级配差异较大时,混凝土工作性能差,受压强度低。以骨料级配确定骨料粒径的分布,在空间随机分布骨料颗粒,通过颗粒-弹簧模型模拟骨料颗粒和水泥浆,形成混凝土细观力学的计算模型,计算结果表明,这一方法不仅可以对普通混凝土进行细观分析,通过弹簧的调节,也可以对再生混凝土进行分析。更多还原

【Abstract】 China is in the progress of industrialization, Urbanization and modernization. In this special development stage, and because of large population, the situation that great deals of various resources material are consumed and great quantities of various garbage or wastes are produced is coexistence. With the resources and the environment problem are continuously worsen, the sustainable development strategy is urged to implement. The civil engineering should be the major field to bring into effect because it is the biggest resources waste industry. Recycling and resource recovery of C&D waste are an effective way to the implementation of this strategy.The C&D waste are used to concrete production in two way:one way that the decompounded concrete pieces are produced into the recycled concrete aggregate and another way that C&D waste is directly produced into the recycled combined aggregate.The recycled aggregate behaviour was found that apparent density and stacking density are between 2.31-2.62 (kg/m3) and 1.29-1.47 (kg/m3), water absorption is 4%-10%, crush index is 14.2%-23.1%. The compressive strength of recycled concrete reduces with the increase of recycled aggregate substituting ratio and water/cement ratio. Its tensile strength was less affected by substituting ratio. With the increase of recycled aggregate substituting ratio, the slump of recycled concrete rapidly reduce, its elastic model reduce, its shrinkage markedly increase, its frost resistance is less infected, its permeability increase, its carbonization speed slightly increase, its sulphate resistance slightly reduce.The effects of different materials in the recycled combined aggregate on the properties of concrete were summarized, including the effects of tile、crashed concrete、glass、wood sawdust、asphalt、oyster shell and recycled plastic on the properties of concrete which include compressive strength、tensile strength、elastic modulus、shrinkage quantity. The activity of tile and glass which were crashed into some degree of fineness increased, and it could minish the effect on the properties of concrete. The crashed concrete had bad effect on the properties of concrete. The recycled plastic could enhance the toughness of concrete. The oyster shell would reduce the elastic modulus of concrete, but had not affect on its early-strength.Through different components of the recycled aggregate concrete performance test it is found that, the density of recycled combined aggregate broken from C&D wastes in the Xiamen area is less than the traditional density of recycled aggregate and natural aggregate, and because of broken brick and other ingredients exist, the water absorption of recycled combined aggregate is high than the recycled concrete aggregate and natural aggregate, the strength is lower than the recycled concrete aggregate and natural aggregate. The average strength of recycled combined aggregate concrete is the maximum when the water quantity is 300kg, water-cement ratio is 0.6, and the recycled combined aggregate replacement rate is 50%. Orthogonal tests results showed that water-cement ratio on the compressive strength has of the greatest impact, the recycled combined aggregate replacement rate is next, and water quantity is the minimum. Recycled fine aggregate has of high-impact on concrete strength than the recycled coarse aggregate. Compressive strength and tensile strength has a difference of 17.7% and 18.5%. The content of the recycled combined coarse aggregate have no clear impact on the strength of the concrete when it is not more than 50%. The increase of the red-brick component in the recycled combined coarse aggregate would make the compressive strength and tensile strength decreased by 11.3% and 7.4%. the broken tile component will make the compressive strength and tensile strength fell by about 8.1%. Beforehand wetted the recycled fine aggregate and recycled aggregate would seriously reduce the strength of recycled concrete. The replacement rate of the recycled combined fine aggregate increases, the tensile strength of concrete will fall. With the increase in the rate of sand, recycled concrete tensile strength increase. Adding a certain amount of polycarboxylate superplasticizer, the recycled concrete workability and fluidity are improved, and the slump will increase, can increase 10% to 15% of compressive strength, tensile strength can be increased by 10%~14%. When the fly ash amount are 25% and 35%, its strength declined by about 32.1% and 36.8%. The recycled combined aggregate can be used in the manufacture of concrete blocks and meet the general requirements of the block strength. Admixture of fly ash, its reasonable dosage is less than 15%Through the experiment results of the recycled concrete aggregate gradation on concrete strength and working properties, it is found that if using recycled aggregate natural gradation, concrete work performance is poor, compressive strength is low. Preparing the recycled concrete aggregate gradation on requirements of "Technical Specification for Construction of Concrete Pumping, " the recycled concrete work performance is poor, compressive strength is relatively low. The compressive strength of recycled aggregate concrete has a close relationship with coarse aggregate gradation. When the recycled coarse aggregate gradation is weaker the strength of recycled aggregate concrete is very low,28 days compressive strength is less than 15Mpa. When the recycled coarse aggregate gradation is in the reason state, its compressive strength will be greatly improved; 28-day compressive strength will be able to reach 40Mpa. Increasing the size range 19-26.5mm and 26.5-31.5mm in aggregate content concrete workability is good, compressive strength is high. Increasing the size range 4.75-9.5mm aggregate content, performance of concrete is poor, compressive strength is low. When coarse and fine recycled aggregate content is not more than 60% the workability of recycled concrete can meet the construction requirements and the strength can reach 40Mpa around. Recycled aggregate replacement rates were 50%, 60%, adjusting the content of 9.5-26.5mm size of the aggregate to make gradation close; recycled concrete strength can be higher than the natural aggregate concrete strength.Aggregate itself as a complex non-rule body, using traditional geometry to describe the aggregate is very difficult. The use of fractal analysis to the characteristics of the aggregate shows that:aggregate gradation of particle size requires a certain width in order to meet the particle size aggregate gradation fractal conditions; aggregate porosity with the aggregate maximum size, minimum size, aggregate gradation and fractal dimension of packing density of aggregate has relationship; the total surface area of aggregate gradation depends on the largest and the smallest particle size, of aggregate, the fractal of aggregate gradation, surface area fractal and aggregate quality; also depends on the measurement scales; the aggregate surface mainly react with cement, so the measurement scales can take the particle size of cement.The product of aggregate total surface area with the thickness of aggregates combination layer is the volume of mortar required for wrapping aggregate. The mortar volume required for wrapping aggregate divided by the total volume of available mortar is called wrapped ratio. Wrapped ratio is a direct reflection of the inter-relationship between the aggregate combination layer and mortar. Wrapped ratio reflects the change of the aggregate surface changes due to the different aggregate gradation. The greater wrapped ratio the larger the aggregate surface area, more needed mortar to wrap aggregate. When the water-cement ratio was 0.55, the wrapped ratio was greater than 0.085, the concrete workability is poor, with low compressive strength. When wrapped ratio is less than 0.085, the concrete workability is better, compression strength is high. When the wrapped ratio is smaller, the difference of aggregate gradation in central particle size range 9.5-26.5mm is small, concrete workability is better, compressive strength is high; the difference of aggregate gradation in the middle size range 9.5-26.5mm is large, concrete workablity is poor, with low compressive strength.Determining the aggregate particles size distribution by aggregate gradation and randomly distributing aggregate particles in concrete space, through the particles-spring model to simulate aggregate particles and mortar the meso-mechanics calculation model can be established. The calculation results show that this method not only can be used to analysis of ordinary concrete, and can also be used to recycled concrete analysis through the spring adjustment.更多还原