淡化海砂中贝壳含量及粒径对胶砂性能的影响研究

建筑用砂量的不断增长和天然砂资源的日益短缺,使得淡化海砂进入工程领域并得到了极大的推广与应用,但淡化海砂中的氯离子和贝壳含量等阻碍了其广泛应用.通过对淡化海砂进行筛分和盐酸溶解等处理,得到不同贝壳含量和粒径的淡化砂,对其胶砂性能进行测试,研究贝壳含量和粒径对胶砂流动度及其强度的影响.试验表明,贝壳含量降低和粒径减小对胶砂性能都起到了促进作用,当筛除大于5.0 mm贝壳粒径时,其胶砂流动度和强度增长幅度最大.试验结论可为其他类似工程提供借鉴.     

砂的颗粒级配对自流平砂浆性能的影响

研究了采用不同颗粒级配的砂所配制的自流平砂浆的初始流动度、流动度经时损失,以及硬化砂浆的力学性能.试验结果表明:砂的表面积越小,新拌砂浆的初始流动度越大,而具有最佳粒径分布的砂所配制砂浆的保水性最好,流动度经时损失最小,成型后可获得较高的密实度,硬化后砂浆各龄期的抗压强度和抗折强度最高,性能最佳.     

粉煤灰粒度分布对其胶砂性能的影响

用Malvern MS2000激光粒度仪测定了几种不同细度粉煤灰的粒度分布,以灰色关联方法分析了粉煤灰粒度分布与相应粉煤灰-水泥胶砂力学性能之间的相关性,并分析了不同细度粉煤灰对其胶砂的强度、流动度等技术性能的影响。研究表明:粉煤灰粒度分布明显影响其胶砂力学性能;分布在0～20μm粒径范围内的颗粒对胶砂力学性能有积极贡献,其中,尤以10～20μm的颗粒贡献最大,而大于20μm的颗粒对胶砂力学性能起削弱作用;当比表面积不超过600m2/kg时,增加粉煤灰的细度可以提高胶凝材料体系的流动性;在胶凝材料体系中掺粉煤灰时应使用高效减水剂,且随水胶比的减小,减水剂用量也要增大以满足流动性的要求;掺粉煤灰的胶砂可在减少减水剂掺量的情况下,达到与基准胶砂相同的流动度;随水胶比的降低,胶砂强度呈增高趋势。     

高性能混凝土的影响因素研究

现代建筑工程对混凝土的要求日益提高,促进了高性能混凝土的发展。采用正交试验,探究了砂胶比、水胶比、硅灰掺量、钢纤维掺量以及砂粒径范围对高性能混凝土的影响。结果表明,随砂胶比的增大,高性能混凝土流动度减小,抗折、抗压强度均先增大后减小;随水胶比的增大,流动度增大,抗折、抗压强度都是先增加后降低;随硅灰掺量的增大,流动度及抗折、抗压强度都先增大后减小;随钢纤维掺量增大,流动度减小,抗折、抗压强度增加到一定程度后变化不大;砂粒径范围对流动度影响明显,对高性能混凝土后期强度影响不大。     

矿粉-水泥体系颗粒分布与其流动性的关系

将不同颗粒群分布的矿粉与水泥按一定比例混合，探讨了该体系颗粒群特征参数与其净浆标准稠度用水量和胶砂流动度的关系。发现：按R—R分布描述颗粒群特征时，均匀性系数与特征粒径的乘积值和其净浆标准稠度用水量、胶砂流动度有较好的相关性。当均匀性系数与特征粒径的乘积值在一定范围内时，净浆标准稠度用水量、胶砂流动度较为理想。     

机制砂颗粒形状评价方法的相关性

采用间隙率法、流动时间法以及数字图像处理等方法测试了不同机制砂的颗粒形状,研究颗粒级配及细度模数对测试结果的影响,并分析了3种方法测试结果与相应水泥胶砂流动度的相关性.结果表明,当采用流动时间法测试时,流动时间随机制砂颗粒粒径增大而延长,且流动时间与水泥胶砂流动度相关系数仅为0.064 4;当采用间隙率法机制砂测试时,未压实间隙率随机制砂粒径增大而减小,其与水泥胶砂相关系数为0.719 3,相关性良好.     

蒸压混凝土配合比优化

通过压碎值、级配和流动度测定等手段,研究了不同骨料在不同条件下的强度和不同粒径卵石的优化质量比,以及聚羧酸盐高效减水剂对水泥净浆和含砂粉水泥浆流动性的影响,并利用正交试验的方法基于抗压强度和抗折强度对蒸压混凝土强度进行了配合比优化.     

骨料对磷酸盐基材料性能的影响

研究了常温环境下不同骨料性质对镁质磷酸盐胶凝材料的流动度和强度的影响。结果表明材料的骨／胶比，骨料颗粒的粒径分布，是影响材料流动性和强度的主要因素。     

砂在砂浆中的堆积密度的计算方法

本文将砂浆体中的砂颗粒及其表面包裹着的一层水泥浆膜看作为复合颗粒,从而通过理论计算推导了砂在砂浆体中的堆积密度的计算方法。通过试验确定了公式的参数,并验证了该方法的有效性。通过该方法可以找出在相同流动度下砂在砂浆体中的最佳粒径分布;当给定砂的粒径分布与砂灰比时,可以推算其流动度。     

用胶砂试验方法确定生产用砂质量对混凝土性能的影响

结合混凝土用砂品质指标要求和检验方法,引用水泥胶砂流动度和胶砂强度试验方法,对比生产用砂与标准砂的检测结果,检测生产用砂对混凝土拌合物状态的影响和对混凝土强度的影响,从而判断不同来源不同种类和不同品质指标的砂子质量的好坏程度。     

基于砂石紧密堆积理论的混凝土配合比研究

根据Dinger-Funk方程,计算混凝土砂石材料的最紧密堆积理论级配,调整颗粒分布系数。混合现有不同级配的砂石,计算混合后砂石级配在不同情况下与理论级配的相关性,选取相关性较大的几组级配进行试验,对比混凝土流动性、强度。结果表明:碎石的紧密堆积有利于混凝土流动性,对混凝土强度影响不大;砂紧密堆积时无法满足混凝土和易性要求,需改变砂级配或通过特细砂对浆体稠度进行调整。     

Role of particle shape on the shear strength of sand-GCL interfaces under dry and wet conditions

Interface shear strength of geosynthetic clay liners (GCL) with the sand particles is predominantly influenced by the surface characteristics of the GCL, size and shape of the sand particles and their interaction mechanisms. This study brings out the quantitative effects of particle shape on the interaction mechanisms and shear strength of GCL-sand interfaces. Interface direct shear tests are conducted on GCL in contact with a natural sand and a manufactured sand of identical gradation, eliminating the particle size effects. Results showed that manufactured sand provides effective particle-fiber interlocking compared to river sand, due to the favorable shape of its grains. Further, the role of particle shape on the hydration of GCL is investigated through interface shear tests on GCL-sand interfaces at different water contents. Bentonite hydration is found to be less in tests with manufactured sand, leading to better interface shear strength. Grain shape parameters of sands, surface changes related to hydration and particle entrapment in GCL are quantified through image analysis on sands and tested GCL surfaces. It is observed that the manufactured sand provides higher interface shear strength and causes lesser hydration related damages to GCL, owing to its angular particles and low permeability.     

矿渣颗粒对砂浆强度的影响

研究了矿渣颗粒（KZP）以不同比例替代河砂时,对砂浆流动度和强度的影响规律。结果表明,采用矿渣替代河砂,砂浆的3d．7d抗折强度和抗压强度降低;28d抗压强度降低,但有一个先降低、后平缓增加的变化;而28d抗折强度变化不大。用矿渣颗粒替代河砂能较大程度地提高7d和28d的强度增进率。     

废旧橡胶微粒对水泥砂浆性能的影响研究

本文探讨了不同工艺加工而成的橡胶微粒掺量、粒径对砂浆工作性和强度的影响规律。研究结果表明：砂浆流动性随橡胶微粒粒径的增加而增加,随掺量的增加先增加后回落;切削法生产的橡胶微粒配制的砂浆流动度总体上高于摩擦法。橡胶微粒砂浆抗折强度、抗压强度均随橡胶微粒掺量的增加而减小,摩擦法生产的橡胶微粒砂浆力学性能要好于切削法橡胶微粒砂浆。并对其机理进行了探索与分析。     

Micromechanical analyses of the effect of rubber size and content on sand-rubber mixtures at the critical state

This study presents a series of monotonic drained triaxial tests consisting of mixtures of sand (stiff) and rubber (soft) particles simulated by the discrete element method (DEM). Sets of mixtures were prepared with different rubber size ratio of 1, 2.5 and 5 and contents ranging from 0% to 30% by weight. The numerical samples were sheared up to large axial strains to reach a critical state. The slope of the critical state lines is strongly affected when the rubber size is the same as sand. When rubber size increases, the critical state lines shift downward with little effect on the slope. While it is generally accepted that, for the given range of rubber contents used in the study, the sand-rubber mixture strength increases when adding rubber particles, the results from this study suggest that said strength diminishes as rubber size is incremented. Micro-scale information, including coordination number, geometrical and mechanical anisotropy, was obtained for all the tests. Regardless of the rubber particle size, rubber-sand contacts represent an important contribution to the overall strength of the material; however, the rubber particle size dictates how said contribution takes place. These findings highlight the importance of understanding new geomaterials to practicing engineers that different size ratios and rubber contents have positive or negative effect of strength and deformability and the choice of a sand-rubber mixture has to be based on the project nature.     

粉煤灰颗粒群特征及其与水泥胶砂性能的关系

提供了一个能够有效测量不同颗粒形貌特征的系统,即数字图像处理系统,将运用该系统得到的粉煤灰颗粒群特征数据,如粒径分布、圆度和填充度等作了灰色关联分析,研究了粉煤灰颗粒群特征与水泥基材料宏观性能的关系,为粉煤灰的有效利用提供了理论依据．     

Investigation of the ultimate particle size distribution of a carbonate sand

A series of ring shear tests were conducted to investigate the ultimate particle size distribution of a carbonate sand. The tests were carried out under different stress levels, on three types of specimens: 1) uniformly graded specimens made of dry natural sand 2) remoulded specimens of the crushed sand after first shearing to large strains 3) specimens made of natural sand grains but with the same grading as in (2). The first series of tests on type (1), carried out to very large strains, led to apparently stable gradings, distinct for each stress level. Only limited additional particle breakage could be induced by remoulding the specimens after shearing (type (2)) and subjecting them to more shearing. Tests on specimens created at the apparently stable gradings (type (3)) but from the intact sand particles however led to significantly greater breakage. For the three types a stable, fractal grading was achieved. Analyses of the soil particles’ shape showed that the aspect ratio, sphericity and circularity reach a steady value at large strains, in parallel to reaching a stable grading. The mobilized angle of shearing resistance however was not significantly different in the different types of samples, suggesting the final grading dominates the behaviour.     

橡胶自密实混凝土和易性及力学性能研究

利用3种不同粒径的橡胶颗粒替换混凝土中的骨料,分析了橡胶自密实混凝土(SCRC)的新拌及硬化性能。对新拌混凝土进行坍落度、T500和J环试验,对硬化混凝土的7 d、28 d抗压强度、抗拉强度、密度和28 d应力-应变进行研究。得出橡胶自密实混凝土中的最佳橡胶颗粒取代率和最佳粒径,以优化SCRC的新拌和硬化后性能。结果表明,随着橡胶取代率的增加,混凝土的坍落度和J环流动度减小,T500延长;橡胶颗粒为5 mm的混凝土抗压强度和劈裂抗拉强度最高;由应力-应变曲线可以看出,橡胶粒径的增加会导致更大的峰值应变。     

Microstructural investigation on mechanical behavior of soil-geosynthetic interface in direct shear test

Interface shear strength between soil and geosynthetics mainly depends on the mechanical and physical properties of soil, geosynthetics and the normal stress acting at the interface. This paper presents results of an extensive experimental investigation carried out on sand-geosynthetic interface using modified large direct shear box. The study focusses on the shearing mechanism at the sand-geosynthetic interface and the effect of different parameters on the shearing mechanism. Smooth HDPE geomembrane, nonwoven needle punched geotextile and two types of sand having different mean particle size, have been used in the present study. Microstructural investigation of deformed specimen through Field Emission Scanning Electron Microscope (FESEM) reveals the shearing mechanism which includes interlocking and fiber stretching for sand-geotextile while sliding, indentation and plowing for sand-geomembrane interface. The shearing mechanism for sand-geomembrane interface highly depends on the normal stress and degree of saturation of sand. The critical normal stress that demarcates the sliding and plowing mechanism for sand-geomembrane interface is different for dry and wet sand. The amount of scouring (or plowing) of the geomembrane surface reduces with increase in the mean particle size of sand. FESEM images revealed that the sand particles get adhered to the geotextile fibers for tests involving wet sands. The present microstructural study aided in understanding the shearing mechanism at sand-geosynthetic interface to a large extent.