共查询到18条相似文献,搜索用时 890 毫秒
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为解决水泥固化海相软土工程性差、耐久性低,钢渣堆放、水泥生产污染环境等问题,采用激发钢渣粉替换部分水泥形成新型固化剂,选取海水中对固化土侵蚀影响较大的3种离子,深入探究单一离子引起的固化土强度劣化性能。通过室内物理力学试验,得到固化土在不同离子浓度的海水和蒸馏水养护条件下,各组无侧限抗压强度(UCS)变化规律;通过X-射线衍射(XRD)和电镜扫描(SEM)试验,得到钢渣粉+水泥固化土的微观形貌和物相随侵蚀时间的变化规律。研究发现钢渣粉中C_4AF和C_2AF可有效降低离子的侵蚀作用,3种离子对固化土的劣化影响为Mg~(2+)Cl- SO_4~(2-)。Cl~-侵蚀固化土会生成CaCl_2和F’s盐,F’s盐的无胶凝性引起固化土劣化;SO_4~(2-)与胶凝材料反应会生成石膏、硅钙石和钙矾石,当这些物质产生的体积膨胀量大于孔隙体积时,会使固化土产生裂纹;Mg~(2+)侵蚀会生成Mg(OH)2沉淀、Mg—S—H和Mg—A—H,同时也会降低孔隙溶液pH值,引起水化物凝胶的分解,造成固化土强度劣化。从微观结构与物相变化分析宏观物理力学特性变化和侵蚀机理,为钢渣粉+水泥固化软土在工程上的使用提供一定的理论依据。 相似文献
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《工业建筑》2016,(2)
考虑碱液浓度、迁入时间两个因素,通过浸泡试验方法,研究碱液迁入条件下碱污染红土的剪切、压缩等工程特性,分析碱液迁入与红土间的相互作用。试验结果表明:碱液浓度较低时,碱污染红土的抗剪强度、黏聚力、内摩擦角、压缩模量减小,低于素红土;碱液浓度较高时,碱污染红土的抗剪强度、黏聚力、内摩擦角、压缩模量增大,高于素红土;随碱液浓度增大,碱污染红土的抗剪强度、黏聚力、内摩擦角、压缩模量逐渐增大。随迁入时间延长,低浓度下,碱污染红土的抗剪强度、黏聚力、内摩擦角、压缩模量缓慢减小,存在极小值;高浓度下,碱污染红土的抗剪强度、黏聚力、内摩擦角、压缩模量明显增大,存在极大值。碱液迁入引起红土工程特性变化的实质在于迁入过程中碱液与红土间的相互作用,可以分为初期、中期、后期三个阶段来解释。 相似文献
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高碱溶液对高庙子膨润土侵蚀作用的研究 总被引:1,自引:0,他引:1
采用NaOH溶液模拟高放射性核废物处置库中可能产生的高碱性孔隙水,对初始干密度为1.70 g/cm3的高庙子(GMZ)膨润土试样进行渗透侵蚀试验,借助扫描电镜(SEM)和透射电镜(TEM)对侵蚀后试样的表观特性进行观察分析,对碱溶液侵蚀对膨润土试样膨胀性、渗透性、孔隙比和化学成分的影响规律进行解释,以研究碱性孔隙水侵蚀对膨润土性能影响的微观机理。结果表明,GMZ膨润土主要成分蒙脱石呈层片状结构,蒙脱石水化会在其表面形成羽翼状的胶体,会堵塞试样的孔隙;高碱性溶液的侵蚀会造成膨润土水化产生的羽翼状胶体溶解和膨润土结构的不可逆性破坏,并且破坏程度与碱溶液的浓度成正相关关系;经高碱性溶液侵蚀的膨润土试样,其表面有明显的溶蚀痕迹,说明碱溶液的入渗侵蚀会造成膨润土有效成分蒙脱石的溶解,试验结果与X射线衍射(XRD)测试结果吻合。因此,碱性孔隙水的入渗侵蚀会逐渐溶解膨润土中的蒙脱石,破坏了膨润土的结构,增大了膨润土的孔隙率,进而降低了膨润土的膨胀性,提高了膨润土的长期渗透性,最终造成膨润土的封闭和缓冲性能降低。 相似文献
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在抗震性能化设计中,对结构构件进行性能水准评价是重要内容,现有国内外规范标准主要提供了基于构件变形的评价指标。损伤变量作为损伤力学中表征损伤程度的基本概念,代表材料或构件受损后的性能劣化程度,在基于材料本构的弹塑性分析中得到广泛应用,但目前尚未形成统一的计算方法和评价标准。基于损伤力学理论,结合现行规范及相关研究成果,从理论分析和工程应用的角度,提出了标定混凝土损坏等级与损伤变量对应关系的方法,并进一步建立了钢筋混凝土构件基于材料指标的评价标准。结果表明:基于材料损伤变量的性能化评价方法具有坚实的理论基础,并与现行规范相衔接,符合软件应用习惯,对规范抗震性能化设计分析与评价具有理论与实践意义。 相似文献
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利用碱渣、粉煤灰和硅酸钠溶液制成新型采空区充填注浆材料,采用9组正交试验试样探索该注浆材料抗压强度发展特性、耐酸性和碱性渗出特性。结果表明:该新型注浆材料抗压强度具有显著的龄期效应。该注浆材料的碱性渗出是快速的,对局部环境的影响较大,建议工程应用时与易受腐蚀构造保持一定安全距离。9组独立的正交试验试样受5%质量分数的盐酸溶液侵蚀后,质量损失在4.2%~6.2%,抗压强度损失在2~8 MPa。受盐酸侵蚀过程中有CO_2和硅胶的生成减小了质量和强度。粉煤灰受碱激发生成的硅铝酸盐聚合物凝胶(N-A-S-H)一定程度上阻止了盐酸对试样的深化侵蚀。 相似文献
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Ogunsanwo Olufemi 《Bulletin of Engineering Geology and the Environment》1988,37(1):131-135
Laterite soils derived from four basement complex rocks and a sedimentary formation from Southwestern Nigeria are analysed for their basic geotechnical properties, chemistry and mineralogy. Results obtained show that the granite gneiss derived and the sedimentary laterite soils are good engineering materials. The amphibolite derived laterite soil has a linear shrinkage of 10% and contains SO 4 2? ions. The quartz schist derived and the micaschist derived laterite soils contain rather high amounts of muscovite ?30% and 25% respectively. The usability of the laterite soils and the implications of the presence of SO 4 2? ions and mica and the high linear shrinkage are discussed. 相似文献
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《Construction and Building Materials》2007,21(1):73-82
This paper describes the first part of a project that aims to evaluate laterite for building purposes from 4 widely placed major quarries of the Malabar region in Kerala in western India. The work reported herein is a comprehensive investigation of the laterite quarries, in view of assessing the characteristics of laterite for building purposes on a regional basis. The in situ characteristics of laterite like colour, texture, structure and hardness were determined by field study. Freshly quarried laterite building blocks from different depths of the quarry as supplied commercially, were evaluated for their engineering characteristics. The physical and mechanical properties of laterite were found to be dependent on the in situ profile characteristics of the rock, viz., colour, texture and structure. The properties of laterite were found to vary widely, based on the location and depth of the quarry. The process of selection of laterite for construction purposes, based on field observations, is also outlined in this paper. 相似文献
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The compressive strength and the expansion of conrete made with both highly and slightly/moderately indurated concretionary laterite gravels were studied. The compressive strength (19–42 MPa) of most of the laterite concrete is comparable with the average strength (45 MPa) of concrete made with the usual granite crushed rock aggregates from the region. The strength of the laterite concrete is mainly dependent on the aggregate-cement bond whereas the physical properties of the aggregates are only of secondary importance. The laterite concrete showed a net contraction when immersed inhot 1N NaOH solution (i.e. rapid alkali reactivity test). This behaviour is attributed to the low/very low contents of silica, clay and lime in the aggregates. The results of the study reveal that concretionary laterite gravels are potential alternative cheap sources of aggregates for structural concrete. 相似文献
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In this study, membrane introduction mass spectrometry (MIMS) was applied to evaluate the kinetics of cyanogen chloride (ClCN) destruction by chemical reduction methods, using thiosulfate, sulfite, metabisulfite, ferrous ions and zero-valent iron at various concentrations and pH. The ClCN destruction followed second-order reaction kinetics in all cases of using sulfur compounds, though the second-order rate constants varied substantially from approximately 0.3-25.7 M(-1)s(-1) under different experimental conditions. The destruction of ClCN was primarily attributable to the chemical reduction pathway. Hydroxide-assisted ClCN hydrolysis was only significant at pH 9 and also when the observed reduction rate was relatively slow. The second-order rate constants achieved by sulfur(IV) compounds in the form of sulfite were found to be higher than those obtained with thiosulfate and S(IV) compounds in the form of bisulfite. Ferrous ions and zero-valent iron demonstrated slow or no ClCN reduction up to dosages of 1000 mgL(-1) and 100 gL(-1), respectively. These findings suggest that applying moderately high dosages of S(IV) compounds under neutral or alkali conditions with sufficient contact time is required for wastewater ClCN destruction. In addition, ClCN losses during long-term preservation with excess reducing sulfur compounds prior to analysis can be substantial and should be avoided. 相似文献
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通过考虑酸、碱、盐、冻融循环环境影响后的碳纤维增强材料CFRP锚杆粘结性能试验,拟合不同环境粘结-滑移(τ-s)关系表达式;并基于试验参数,采用ANSYS非线性弹簧单元Combin 39模拟CFRP锚杆粘结单元,引用拟合τ-s关系曲线确定弹簧单元荷载-位移(F-S)关系参数;模拟分析与试验结果对比表明:由本试验拟合的τ-s关系曲线能很好地反映CFRP筋与环氧砂浆受特殊环境影响后粘结性能的变化。为经常处于特殊环境下的CFRP锚杆性能分析、设计理论及工程应用提供理论依据,也可为相关规范的编制和完善提供参考。 相似文献
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S. Malomo M. O. Obademi P. O. Odedina O. A. Adebo 《Bulletin of Engineering Geology and the Environment》1983,28(1):197-206
Problem laterite soils are those that do not yield reproducible results using standard laboratory testing procedures. The soils are difficult to evaluate as engineering construction materials. The peculiar problems of these soils have been identified as thermal and mechanical instabilities i.e. the susceptibility to significant changes on the addition of small levels of thermal or mechanical energy. A laboratory investigation of the instability characteristics of laterite soils from the forest and savannah-woodland zones of Southern Nigeria has been carried out. Mechanical instability was determined by multiple compaction test and thermal instability by oven-drying under varying conditions. The results indicate that the soils studied can be unstable on the application of thermal and mechanical energies. Parameters obtainable from the grain-size distribution of soils subjected to the different conditions were found suitable for assessing thermal and mechanical instabilities. The maximum dry density and optimum moisture content obtained from the compaction curve are independent of the number of compaction. 相似文献
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非饱和膨胀土总强度指标随饱和度变化规律 总被引:13,自引:0,他引:13
建立在有效应力基础上的非饱和土强度理论公式参数测试复杂、不便于工程应用,而包含吸附强度的总强度指标也能反映非饱和土的强度特性且易于获取。为此,以土水特征曲线为理论依据,采用抽气饱和、风干脱水法控制试样的饱和状态,用常规直剪仪对不同状态下的宁明膨胀土进行固结快剪试验,得到其总强度指标随含水量、饱和度的增大而衰减的变化规律。其中,黏聚力、内摩擦角的对数和含水量之间以及内摩擦角与饱和度之间成线性关系;黏聚力随饱和度的变化可用二次抛物线描述。对该规律的普遍性还用廖世文、卢肇钧同类试验结果的分析来加以检验。此外,针对膨胀土路堑边坡滑坍的特点,对如何将非饱和膨胀土总强度指标用于边坡稳定性分析进行探讨,研究结果可为工程应用提供参考。 相似文献