共查询到20条相似文献,搜索用时 500 毫秒
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混凝土因具有优异的力学和物理性能广泛应用于建筑行业,但其缺点也很明显,包括负面环境影响和低耐久性.提升混凝土性能以弥补这些缺点一直是该研究领域的热点,在混凝土中掺加天然沸石粉可以有效改善这些问题.讨论了沸石的结构和基本性质,以及作为辅助胶凝材料和内部养护剂在混凝土生产中的应用,分析了沸石对混凝土工作性能、力学性能、耐久... 相似文献
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采用超声强化NaCl对天然沸石进行改性,考察了改性沸石对氨氮的吸附去除特性。结果表明,在超声功率为560 W、改性时间为40 min、NaCl浓度为0.8 mol/L的条件下制备的改性沸石对氨氮的去除效果最佳;在氨氮初始浓度为10 mg/L、改性沸石投加量为5 g/L的条件下,吸附40 min后改性沸石对氨氮的去除率可达到86.9%,120 min后达到吸附平衡,此时对氨氮的去除率为91.11%,相比天然沸石提高了86.3%;准二级反应动力学模型可以较好地描述改性沸石的吸附行为,R2=0.991;改性沸石对氨氮的吸附符合Langmuir模型(R2=0.961 2),其最大吸附量可达到12.56 mg/g。 相似文献
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由于长期遭受卸荷和化学风化作用 ,特别是亚热带风化淋滤作用 ,下第三系泥岩或砂质泥岩的残积层不仅发生粘土矿物转化 ,而且造成密度的强烈降低。百色盆地膨胀土具有残积型膨胀土所特有的低容重 (约 19.0 2kN/m3)、高孔隙比 (0 .75~ 1.78)、高含水率 (2 5 %~ 41% )、高分散性 (<2 μm含量 >5 0 % )、强收缩 (体缩 >15 % )等一系列不良工程性质。这种膨胀土无侧限单轴抗压强度仅 0 .0 3~ 0 .42MPa左右 ,不属于膨胀岩范畴。扫描电子显微镜 (SEM )和X -射线衍射 (XRD)鉴定结果表明 ,其主要粘土矿物成分为I/S混层矿物 ,而不是伊利石 (有别于前人的认识 )。现行规范中膨胀势判别方法的缺陷造成设计安全系数偏低 ,是路基严重变形、破坏的重要原因之一。本文提出了进一步治理病害的工程措施 相似文献
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为了探索不同黏土矿物成分对黏土一维压缩特性的影响,采用高岭土、伊利土、蒙脱石及绿泥石,按不同质量比例混合来制备重塑土样,进行室内标准一维压缩试验。大量试验结果对比表明:①高岭土与伊利土混合土样的压缩指数(C c)和回弹指数(C s)都随伊利土含量的增加而增加;②高岭土、伊利土与蒙脱石混合土样的C c和C s随蒙脱石含量的增加而增大,且蒙脱石的作用占主导地位;③高岭土、伊利土、蒙脱石及绿泥石混合土样的C c和C s随蒙脱石与绿泥石二者含量之和的增加而增大,且蒙脱石的作用占主导地位。基于试验结果,总结出各黏土矿物成分影响的压缩指数与回弹指数的非线性表达式。此外,试验表明所有混合土样的压缩指数与回弹指数的比值(C c/C s)介于6.1和9.1之间变化。 相似文献
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在岩土工程中,可采用双尺度渐进展开法反演计算土体渗透率,其表征单元体(REV)的选取直接影响计算的准确度。以海洋黏土渗透率为例,对REV颗粒形状、排列方式、建模维度以及对土体实际性状代表性等因素进行对比分析。通过4种正多边形模型对比、圆形颗粒正对排布与交错排布对比、3D与2D模型对比,计算结果均与实测值存在较大偏差,而各对比模型彼此间差别不大,说明颗粒形状、排列方式与模型维度对计算准确度影响甚微。而在考虑黏土颗粒多呈扁平状,以及颗粒表面存在强结合水膜的情况下,采用椭圆颗粒结合水膜单元模型(E-W模型),其计算准确度大大提高,并且能够在孔隙比较小时减小结合水膜带来的计算误差,说明REV能否充分表示土体实际几何和物理特性是计算准确度的主要影响因素。E-W模型对高岭土与伊利土渗透率的计算同样有较高的准确度,因此可将其用作双尺度渐进展开法对黏土渗透率的计算REV模型。 相似文献
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This paper examines the relationship between the microstructure and chemical properties of soft Bangladesh clays due to cementation. The microstructure was investigated using X-ray diffraction, scanning electron microscopy, pH measurement, specific surface area and soil chemical tests. The results indicate that a multitude of changes occurred in the properties and behavior of cement-treated clays that can be explained by the interaction between four underlying microstructural mechanisms. That is, it is suggested that the hydrated lime is formed by hydration, which causes the flocculation of the little clay particles, by the preferential attack of the calcium ions on kaolinite rather than on illite and monmorillinite in the pozzolanic reaction, by surface deposition and shallow infilling by cementitious products such as calcium silicate hydrate and calcium alumino silicate hydrate (CSH and CASH) on clay clusters, and finally, by the presence of water trapped within the clay clusters. The chemical properties of the cement-treated clays were found to depend on the plasticity of soil. 相似文献
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《Construction and Building Materials》2007,21(1):52-56
In this study, use of wastes produced in phosphoric acid plants and boron concentrators in producing structural brick has been investigated. There are several parameters involved in using these wastes in brick production namely the rate of added waste, firing speed and firing temperature. The performance of these parameters can be measured by several criteria such as natural drying shortening, water absorption and weight loss. Therefore, so many experiments are needed to investigate the effects of these parameters on the bricks produced with these wastes. To this end, around 220 experiments for three different material combinations namely original waste plus normal brick clay, washed waste plus normal brick clay and normal brick clay with no additive were carried out. The results have shown that the industrial wastes produced by phosphoric acid plants can improve the performance of the bricks in terms of drying shortening, weight loss and water absorption. 相似文献
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A series of undrained, cyclic simple shear tests were performed on reconstituted specimens with various clay contents to study the effects of clay content on liquefaction characteristics of clayey sands based on a framework of an idealized binary packing model and intergrain state parameters. From observed liquefaction characteristics, clayey sands with different clay contents can be grouped as sand-like or clay-like soils depending on the clay content and the transitional fines content of the sand-clay mixture. A simple equation is derived and verified to correlate the transitional fines content with the void ratios of the clean sand and the pure clay consisting of the mixture. In addition, a new relationship for clay content correction is proposed based on the linear relationship between the cyclic resistance ratio and the clay content at the same intergranular void ratio. The cyclic resistance ratio of sand-like clayey sands can be divided into two components: (1) the resistance of the sand skeleton at the specific intergranular void ratio, and (2) the increment of cyclic resistance from clayey fines. The rate of increment for cyclic resistance varies with the properties of contained clay particles. Data from three independent studies have shown the proposed procedure is promising. 相似文献