【作者】 邓宏卫；

【导师】 巴恒静；

【作者基本信息】 哈尔滨工业大学 ， 结构工程， 2009， 博士

【摘要】 轻骨料混凝土具有轻质、造价低、高抗震性、高抗裂性、高耐久性、高耐火性、保温隔热等特点。轻骨料混凝土应用于建筑工程中在满足强度及其它性能要求的同时可大幅度减轻结构物的自重,这一特性使轻骨料混凝土有非常重要的应用价值。随着保护环境、实现可持续发展的国策不断深入以及建筑节能需求愈来愈高,利用各种工业废弃物生产人造轻骨料以及利用轻骨料配制的高性能的轻集料混凝土理论与应用技术具有重要的研究价值和现实指导意义。本文首先采用粉煤灰为主要原材料,掺入不同比例的助胀剂和助熔剂,在实验室内利用可控式电热炉,进行了高强粉煤灰烧胀陶粒制备的试验研究,结果表明,在焙烧温度区间为1200～1280℃;,焙烧时间在5～10min时烧制粉煤灰陶粒过程中,随着助胀剂掺量的增加,粉煤灰烧胀陶粒的体积密度、表观密度和24h吸水率而逐渐减小;助熔剂掺入后可显著提高陶粒的颗粒强度,降低其吸水率,改善陶粒内部的孔形结构。粉煤灰陶粒配料的酸碱系数Pk与粉煤灰陶粒的孔隙率、颗粒强度有很好的线性关系。获得符合轻质高强粉煤灰陶粒的要求三个密度等级(600级, 700级, 800级)的粉煤灰陶粒最佳配合比。随后在三个工厂进行了工业化生产中试试验,获得了烧制出轻质高强粉煤灰陶粒生产工艺路线。利用流变仪研究矿物掺合料种类与掺量对水泥浆体流变学参数影响规律,提出了单掺矿渣、粉煤灰、沸石粉和硅灰以及以不同比例复掺后水泥浆体的屈服强度和塑性粘度变化规律,获得了使粉煤灰陶粒混凝土获得良好的工作性能且陶粒在混凝土中分布得很均匀单掺和复掺矿物掺合料的最佳比例。为配制出高性能轻集料混凝土奠定了理论基础。通过对不同矿物掺合料的粉煤灰陶粒混凝土和普通同强度混凝土试件的单轴受压试验,得到了粉煤灰陶粒混凝土棱柱体强度与立方体强度的关系,并与普通混凝土的峰值应变、弹性模量、泊松比与立方体强度进行了比较。试验结果表明粉煤灰陶粒混凝土应力应变全曲线与普通混凝土相似,可以采用现行的规范进行设计。针对我国三北地区桥面铺装中大量应用轻骨料混凝土这一现状,利用欧盟推荐标准混凝土抗盐冻试验(CDF)对比研究了粉煤灰陶粒混凝土与普通混凝土的抗冻性。掺加矿物掺合料的粉煤灰陶粒混凝土的单面抗冻性大大优于普通混凝土的单面抗冻融性。单掺矿物掺合料的56次的耐单面抗冻顺序是:硅灰>粉煤灰>矿渣。复掺矿物掺合料的56次的耐单面抗冻顺序是:硅灰+矿渣>硅灰+粉煤灰>矿渣+粉煤灰。复掺矿物掺合料混凝土的单面抗冻性均大大优于单掺矿物掺合料混凝土的单面抗冻性。通过SEM-EDXA的分析,轻集料与水泥石之间的界面过渡区的范围约为5~20um,远远小于普通混凝土界面过渡区范围。界面区过渡区越小,混凝土的力学性能与耐久性越优良。研制开发了荷载下混凝土渗透性测试装置,可实现对承受0~70%抗压或抗拉强度的压应力或拉应力持续作用的混凝土试件的渗透性进行自动测量,混凝土渗透性以ASTM C 1202方法中的电通量表征。无论承受荷载作用或非荷载作用下,同强度等级的轻集料混凝土的电通量小于普通集料混凝土;当所受应力大于某一阈值时,混凝土的渗透性明显增大。以电通量评价混凝土的氯离子渗透性时,混凝土电通量Q与所受压(或拉)应力f间关系可用二次函数关系表示:Q = Af2 + Bf + C(A、B、C为常数)。更多还原

【Abstract】 Lightweight aggregate concrete is characterized with a lightweight, low-cost, high-seismic resistance, high crack resistance, high durability and high fire resistance, heat insulation and so on. Lightweight aggregate concrete used in construction projects not only meet the strength and other performance requirements but also substantially relieve the weight of the structure, which are of some very important value. With the national policy of environment protection and sustainable development of economic and society, as well as the rising demand for energy-saving construction, the theory and application Technology using a variety of industrial waste to produce man-made lightweight aggregate and high-performance lightweight aggregate concrete plays an important research value and of practical significance.This paper firstly discussed the preparation of high-strength lightweight aggregate using fly ash in laboratory and in factory. Fly ash used as the main raw materials, incorporated with sintering additive and Ca(OH)2 in different ratio, was sintered a high-strength lightweight aggregate of fly ash(Lytag)in the laboratory-controlled electric furnace. The results show that in the sintering temperature range of 1200 to 1280℃, retaining time of 5 min ~ 10min, the bulk density and the apparent density and 24 h water absorption of Lytag decreased with the increase of sintering additive and the decrease of the amount of fly ash. The addition of Ca(OH)2 can significantly enhance the compressive strength of Lytag pellets, reduces its water absorption at 24h and improve internal pore-shape of inner structure. The coefficient of burnability Pk kept a good linear relationship with porosity and particle strength of Lytag. The optimal mix proportion to meet requirements of high-strength Lytag density of the three grades (600, 700, 800) Lytag was obtained. Three test pilots in QiQihar, Hulan and Daqing were performed and the optimal production process and technology was promoted.Rheometer used to examine the effect of the type and amount of mineral admixture on the rheological parameters of cement slurry. The development rule of Yield strength and plastic viscosity of the cement slurry with single-doped slag, fly ash, silica fume and zeolite powder, as well as the different multiple-doping proportion were obtained. Then the optimal single-doped or multiple-doped ratio of various mineral admixture were attained in order that the fresh Lytag concrete can arrive better workability and Lytag gain in a very uniform distribution in concrete. These have laid a theoretical foundation for preparation of a high-performance lightweight aggregate concrete.The uniaxial compression tests have been used to examine Lytag concrete with the different mineral admixture and normal concrete. The relationship between the compressive strength of prism specimens and cube specimens was set up. Peak strain, elastic modulus, Poisson’s ratio and the cube compressive strength of these two concrete were compared. The results showed that the whole stress-strain curves of Lytag concrete and ordinary concrete were similar and the existing norms can meet the design requirement of Lytag concrete.In view of the bridge deck applied a large number of lightweight aggregate concrete in cold region, the European Union recommended standard (CDF) about frost resistance of concrete test was adopted in this paper to do a comparative study on frost resistance of Lytag concrete and ordinary concrete. The frost resistance of Lytag concrete adding mineral admixture is better than that of ordinary concrete. The order of frost resistance for single-doped mineral admixture after 56 cycles is: silica fume> fly ash> slag. The order of frost resistance for multiple-doped mineral admixture after 56 cycles is: silica fume +slag > silica fume+ fly ash > slag+ fly ash. The frost resistance of concrete for multiple-doped mineral admixture was much better than that of concrete with single-doped mineral admixture. The SEM-EDXA analysis indicated that the interface transition zone of lightweight aggregate and cement is about 5 ~ 20um, far less than the interface transition zone of ordinary concrete. The smaller the interface transition zone, the better mechanical properties and durability of concrete.A new testing device on concrete permeability under load was developed, which can make the concrete specimens bear the tensile stress or compressive stress of 0 to 70% and continue to examine the permeability of concrete specimens. The test method for permeability of concrete was conformed to ASTM C 1202 method of Cumulative electrical value. Regardless of loaded or unloaded, the permeability for the same level of intensity of the lightweight aggregate concrete was better than that of ordinary concrete aggregate. When the stress is greater than a certain threshold, the permeability of concrete increased significantly. In this test for permeability of concrete, the quadratic function relationship between concrete electric flux Q and the pressure (or pull) f stress can be demonstrated: Q = Af2 + Bf + C (A, B, C is a constant).更多还原