地聚合物材料在软土路基中的应用研究

地聚合物作为一种绿色聚合物材料已在许多工程建设项目中得到应用,本文针对软土路基进行地聚合物材料的加固处理进行研究。将地聚合物材料代替部分水泥应用于软土搅拌中,分别设计了6组不同掺量的组合方案进行室内研究,通过观测地聚合物土3d、7d、28d的抗压强度和抗剪强度进行综合分析,研究认为地聚合物能够代替水泥功效对软土起到较好的固化作用,软土的抗压强度和抗剪强度较纯水泥软土加固可分别提升4%左右。作为低碳可循环建筑材料,地聚合物具有较大的发展应用前景。     

水泥及其复合体系固化放射性核废物研究现状

水泥优良的物理化学性能使其在放射性废物固化领域应用广泛。介绍了水泥固化的机理和对水泥固化体的基本性能要求,并综述了硅酸盐水泥、碱激发胶凝材料、硫铝酸盐水泥和磷酸镁水泥在放射性废物固化领域的研究进展。对水泥基固化材料的发展具有一定的借鉴意义。     

浅析道路工程中软土地基处理技术的应用

随着我国道路工程建设不断发展,所涉及建设过程中的软土地基处理技术逐渐趋于复杂化。通过系统总结国内外学者针对软土地基的研究成果,从工程技术的应用角度,对道路工程软土地基处理技术进行分析。研究结果表明:软土具有天然含水率高、孔隙比大、压缩性高等基本特征,采用夯实与碾压、竖向排水体、真空预压、粒料桩、水泥搅拌桩、粉喷桩复合地基等技术手段,可实现对软土基本性能的改善,对工程建设中软土地基处理具有重要意义。     

骨料对地聚合物混凝土性能影响的研究进展

地聚合物是一种以硅铝质材料与激发剂常温下作用后固化形成的新型胶凝材料,其制备工艺简单、能耗低、CO_2排放量少,被认为是最具潜力的一种水泥替代品。含骨料的地聚合物混凝土在很多方面拥有比普通硅酸盐水泥混凝土更优异的性能。本文综述了近年来国内外研究者在骨料与地聚合物凝胶相的界面过渡区域、骨料对地聚合物混凝土的性能(包括力学性能、耐久性能和热稳定性能)的影响以及相关理论模型方面的主要研究进展,并对地聚合物混凝土的工程化应用进行了展望。     

探究软基加固技术在市政道路施工中的应用

在市政道路施工过程中,受到地质条件及施工环境等因素的限制,在施工过程中不可避免会遇到软土地基的问题,一定程度上增加了市政道路施工的难度。为了保证市政道路施工的质量和安全,有必要科学合理的进行软土地基的加固处理。为此,本文先是分析软土地基的特点,然后就软土地基加固处理的重要性,具体分析市政道路施工中应用的软土地基加固技术,以供参考。     

水化产物钙矾石在软土地基加固中的增强作用

通常加固软土地基是使用第一的水泥用为固化剂。研究与实践表明,由于软土中孔隙量很高,采用工业废石膏与水泥配合加固软土,其中产生的水化产物钙矾石可以高效率的填充孔隙,对固化工的强度增长有显著的增强作用,从而得固人疆土工与单纯用水泥加固相比有大幅度的提高,钙矾石形成过程中,液相ＣａＯ,ＯＨ浓度决定钙矾石的形貌和膨胀性能,不同土样对ＣａＯ,ＯＨ消耗量不同,导致固化上液相中ＣａＨ,ＯＨ,浓度不同,因而,对不     

地质聚合物力学性能影响分析及应用前景探讨

随着水泥的生产成本越来越高以及政府对节能减排政策的大力支持，新型绿色环保材料地质聚合物越来越受到人们的青睐，是潜在替代水泥的最佳建材之一。地质聚合物抗压强度高，其耐火、耐高温、耐腐蚀等性能优秀，以来源广泛的工业废渣为原材料，像矿渣、粉煤灰等，可以达到固废资源回收利用的目的。综述了地质聚合物的反应机理，分析了硅铝材料种类、激发剂、养护条件、液固比等制备因素对地质聚合物力学性能的影响机理，概述了当前地质聚合物在道路修复与固化、固化重金属和研制特殊材料领域的工程应用现状及前景，指出了当前地质聚合物在工程应用中存在的难题，提出可行的解决方案，并对其未来应用进行了展望。     

电化学改性加固地基的研究进展

软弱地基压缩性高、承载能力差,在荷载作用下容易产生较大的沉降变形,影响建筑物的正常使用,因此必须对其进行加固处理。针对地基处理中的化学类方法,介绍了化学改性加固与电化学法加固的原理与研究进展,并对化学改性与电化学加固联合处理地基进行了展望,分析了其固化机理与应用前景。     

地质聚合物的土木工程耐久性能的研究进展

地质聚合物是由硅铝酸盐材料通过碱激发形成,具有网络结构和无定形性质的胶凝材料。由于地质聚合物具有优于普通硅酸盐水泥的力学性能,并且制备过程中CO2排放量较少等优点,被认为是硅酸盐水泥的良好替代品。尽管相当部分的研究者认为地聚物的耐久性也要好于普通硅酸盐水泥,但其他研究者对此持怀疑态度并认为很多方面还需进一步的研究。本文回顾了近几年有关地聚物耐久性研究的现状和进展,总结和讨论了地聚物的吸水性、碳化、硫酸盐侵蚀、酸腐蚀、碱-集料反应和氯离子渗透等耐久性能及其作用机理的研究成果,并提出了现有研究存在的主要问题。     

粉煤灰固化施工在地基加固处理中的应用

为探究粉煤灰固化施工在地基加固处理中的高效应用方法,分别将普通石灰、石膏、水玻璃溶液作为固化剂,制备不同灰水比的测试浆液。以某路面工程项目中的一小段废弃路段为试验路段,利用测试浆液实施地基加固处理施工,使用大型切割机将施工结果切割,作为试验试块,测试试块性能。结果表明：使用石膏作固化剂时固化粉煤灰浆液的初凝、终凝时间最短;以石膏为固化剂的固化粉煤灰浆液的地基加固方格试块的压实系数最大、无侧限抗压强度最高、低温强度最高,三者数值达到最高时的灰水体积比分别为15:10、15:10、13:10。以石膏为固化剂时,固化粉煤灰浆液的地基加固方格试块的性能表现最佳。     

铝土矿选尾矿制备硅铝聚合材料的反应产物及抗化学侵蚀性能(英文)

以煅烧铝土矿选尾矿为硅铝质原料,以矿渣微粉为促硬剂,以水玻璃为激发剂,制备得到了硅铝聚合材料。运用X射线衍射、扫描电镜、热分析研究了硬化浆体的反应产物及其微观形貌、热性质。通过观察3%硫酸钠溶液、3%硫酸镁溶液、5%硫酸溶液、5%盐酸溶液对砂浆试样外观、质量、强度的影响,研究了其抗化学侵蚀性能,并比较了其与铝酸盐水泥、快硬早强硫铝酸盐水泥、中抗硫酸盐硅酸盐水泥及矿渣硅酸盐水泥的区别。结果表明:反应并不生成晶体物质,而是无定形态的铝硅酸盐;硬化体中呈现片层状显微形貌的物质能够吸附水分,从而在灼烧过程中表现为脱水吸热及质量损失;该片层状物质随着龄期的延长而变得愈发细小和复杂,进而在宏观上表现为强度增长及脱水温度升高;硅铝聚合砂浆分别经3%硫酸钠溶液、3%硫酸镁溶液浸泡28d后,与各水泥砂浆试样比较,其不仅外观完整,而且强度并没有下降,反而具有几乎相同的强度增长,即说明其具有更优异的抗硫酸侵蚀性能;硅铝聚合砂浆与各水泥砂浆经稀酸溶液浸泡28d后,前者不仅能保持原始外观,而且表现为更低的质量及强度损失。     

矿渣-粉煤灰地聚物固化淤泥力学性能和路用性能研究

为实现河底淤泥的资源化处置,常采用水泥等胶凝材料固化淤泥提高承载力作为路基材料。传统固化材料能耗大、碳排放量高。为开发可持续性固化材料,本研究采用矿渣-粉煤灰二元地聚物固化淤泥,研究其力学性能及路用性能。通过研究Si/Al摩尔比、Na/Al摩尔比对地聚物凝结时间和抗压强度的影响规律,确定地聚物配合比设计。依据优化配合比固化淤泥,研究地聚物掺量、养护龄期对固化淤泥力学性能的影响,并对固化淤泥进行水稳性、加州承载比、干缩和温缩试验,以评估其路用性能;采用扫描电镜和X射线衍射等试验方法对固化淤泥进行微观分析,揭示其固化机制。试验结果表明,矿渣-粉煤灰基地聚物地质聚合产物为无定形地聚物凝胶、水化硅酸钙、水化铝酸钙等,增强了土颗粒之间的胶结并且填充了孔隙,提高了固化淤泥的力学性能和路用性能。研究结果为地聚物固化淤泥土工程应用提供了实验基础。     

Metakaolin-based geopolymers: Efflorescence and its effect on microstructure and mechanical properties

Efflorescence in geopolymers results from mobility of excess alkali and consequent crystallization of alkali carbonates. Efflorescence potential of various geopolymers has been reported previously but the knowledge regarding the effect of efflorescence on the microstructure and mechanical properties of geopolymers remains limited. In this work, metakaolin-based geopolymers were exposed to air, partially immersed in water, and fully immersed, to simulate different processes involved in efflorescence formation. The mechanical properties were assessed by compressive, splitting tensile and flexural strengths, and linear deformation. The microstructural features were investigated by SEM, synchrotron XRD, multinuclear MAS NMR, MIP and synchrotron X-ray microtomography. Extensive efflorescence resulted in a reduction of mechanical strength and changes in the nanostructure and microstructure, which is different from observations for Portland cement-based materials, where efflorescence is usually regarded as a surface or aesthetic problem. The understanding of the relationship between efflorescence formation, the synthesis and exposure conditions provides important insight into the manufacturing and application conditions of geopolymer related materials.     

Encapsulation of Mg–Zr alloy in metakaolin-based geopolymer

Investigations were carried out to propose a suitable material for the encapsulation of Mg–Zr alloy wastes issued from fuel cladding of the first generation nuclear reactors. Stability over time, good mechanical properties and low gas production are the main requirements that embedding matrices must comply with in order to be suitable for long run storage. One of the main issues encapsulating Mg–Zr alloy in mineral binder is the hydrogen production related to Mg–Zr alloys corrosion and water radiolysis process. In this context, metakaolin geopolymers offer an interesting outlook: corrosion densities of Mg–Zr alloys are significantly lower than in Portland cement. This work firstly presents the hydrogen production of Mg–Zr alloy embedded in geopolymers prepared from different the activation solution (NaOH or KOH). The effect of addition of fluorine on the magnesium corrosion in geopolymer has been investigated too. The results point out that sodium geopolymer is a suitable binder for Mg–Zr alloy encapsulation with respect to magnesium corrosion resistance. Furthermore the presence of fluorine reduces significantly the hydrogen release. Then, the impact of fluorine on the geopolymer network formation was studied by rheological, calorimetric and ¹⁹F NMR measurements. No direct effect resulting from the addition of fluorine has been shown on the geopolymer binder. Secondly, the formulation of the encapsulation matrix has been adjusted to fulfil the expected physical and mechanical properties. Observations, dimensional evolutions and compressive strengths demonstrated that addition of sand to the geopolymer binder is efficient to meet the storage criteria. Consequently, a matrix formulation compatible with Mg–Zr alloy encapsulation has been proposed. Finally, irradiation tests have been carried out to assess the hydrogen radiolytic yield of the matrix under exposure to γ radiation.     

工业废料稳定路基土的无侧限抗压强度及环境影响评价

随着社会的发展,道路工程建设规模日益庞大,常用的石灰、水泥等固化剂价格较高,然而电石渣、粉煤灰这两种工业废料应用于道路建设中,将很好地提高资源的回收再利用率,同时降低建设成本。本文研究了电石渣和粉煤灰固化土的最优配合比,并探讨了电石渣代替石灰用于固化土的可行性,另外,在电石渣-粉煤灰固化土中掺入聚丙烯纤维,探究了聚丙烯纤维的最优掺量。无侧限抗压试验结果表明,电石渣与粉煤灰的最优配比为1:1,聚丙烯纤维的最优掺量为0.6%(质量分数)。在此基础上探究了电石渣-粉煤灰固化土在雨淋条件下对环境的影响程度。pH试验结果表明,电石渣-粉煤灰固化土的pH值最大为12.28,其环境影响程度满足国家标准规范要求,可以在实际工程中得以应用。此研究为工业废料应用于道路基层提供了一定的借鉴意义。     

Formulation of caesium based and caesium containing geopolymers

Abstract

Cement encapsulation is widely used as a low- and intermediate level radioactive waste immobilisation process. Among these wastes, caesium ions are poorly immobilised by Portland cement based materials. This work consists of an experimental investigation into the ability of geopolymers to effectively encapsulate this chemical species and to determine the impact of caesium incorporation on the geopolymer properties. Geopolymers were synthesised with several compositions based on the activation of metakaolin with an alkali hydroxide solution containing caesium. The setting time, mineralogy, porosity and mechanical properties of the samples were examined for one month. Leach tests were conducted during the same period to determine the immobilisation efficiency. The results depend to a large extent on the composition of the activation solution in terms of soluble silica content and alkali used. These parameters determine both the degree of condensation and the geopolymer composition.     

Mechanical and microstructural evolutions of fly ash/slag-based geopolymer at high temperatures: Effect of curing conditions

Designing a building material with excellent heat resistance is crucial for protection against catastrophic fires. Geopolymer materials have been investigated as they offer better heat resistance than traditional cement owing to their ceramic-like properties. Curing temperature and conditions are crucial factors that determine the properties of geopolymers, but their impacts on the heat resistance of geopolymers remain unclear. This study produced geopolymers from fly ash and ground granulated blast furnace slag by using sodium silicate and sodium hydroxide solutions as alkaline solutions. To examine the effect of curing conditions on the high-temperature performance of geopolymer, four different curing conditions, namely, heat curing (70 °C for 24 h), ambient curing (20 °C), water curing, and the combination of heat and water curing (70 °C for 24 h followed by water curing), were applied. At 28 d, the specimens were subjected to high temperatures (500 °C, 750 °C, and 950 °C), and their mechanical and microstructural evolutions were studied. The results revealed that the curing condition significantly affects the properties of the unexposed geopolymer; the effect on its high-temperature performance is insignificant. Furthermore, all the specimens could maintain adequate compressive strength after exposure to the maximum temperature of 950 °C, promising the use of geopolymer for structural applications.     

Assessment of recycling use of GFRP powder as replacement of fly ash in geopolymer paste and concrete at ambient and high temperatures

Environmental issues caused by glass fiber reinforced polymer (GFRP) waste have attracted much attention. The development of cost-effective recycling and reuse methods for GFRP composite wastes is therefore essential. In this study, the formulation of the GFRP waste powder replacement was set at 20–40 wt%. The geopolymer was formed by mixing GFRP powder, fly ash (FA), steel slag (SS) and ordinary Portland cement (OPC) with a sodium-based alkali activator. The effects of GFRP powder content, activator concentration, liquid to solid (L/S) ratio, and activator solution modulus on the physico-mechanical properties of geopolymer mixtures were identified. Based on the 28-day compressive strength, the optimal combination of the geopolymer mixture was determined to be 30 wt% GFRP powder content, an activator concentration of 85%, L/S of 0.65, and an activator solution modulus of 1.3. The ratios of compressive strength to flexural strength of the GFRP powder/FA-based geopolymers were considerably lower than those of the FA/steel slag-based geopolymers, which indicates that the incorporation of GFRP powder improved the geopolymer brittleness. The incorporation of 30% GFRP powder in geopolymer concrete to replace FA can enhance the compressive and flexural strengths of geopolymer concrete by 28%. After exposure to 600 °C, the flexural strength loss for geopolymer concretes containing 30 wt% GFRP powder was less than that of specimens without GFRP powder. After exposure to 900 °C, the compressive strength and flexural strength losses of geopolymer concretes containing 30 wt% GFRP powder were similar to those of specimens without GFRP powder. The developed GFRP powder/FA-based geopolymers exhibited comparable or superior physico-mechanical properties to those of the FA-based geopolymers, and thus offer a high application potential as building construction material.     

碱-矿渣水泥的水化、力学及干缩性能研究进展

碱-矿渣水泥是一种优良的绿色胶凝材料,由矿渣部分或全部取代水泥而制成。在碱激发剂的作用下矿渣水化产生活性,并且由于其独特的玻璃体分相结构导致碱-矿渣水泥的水化硬化产物表现出不同于普通硅酸盐水泥基材料的性能。本文介绍了矿渣的组成与结构,从理论层面解释碱-矿渣水泥具有潜在活性的原因,探讨了不同激发剂作用下碱-矿渣水泥的水化机理,并在此基础上综述其基本力学性能和干缩特性,为其在工程实践中的应用和推广提供依据。结合相关文献,总结了现有研究的不足并对今后的发展提出了建议。