矿物掺合料对聚羧酸减水剂与水泥相容性的影响

高性能减水剂与水泥适应性差会导致混凝土流动性和坍落度损失过快,矿物掺合料将影响高性能减水剂与水泥的相容性。对比研究矿物掺合料种类和掺量对水泥净浆、砂浆和混凝土流动性的影响;采用TOC法测试了矿物掺合料对聚羧酸减水剂吸附量的影响;分析了矿物掺合料影响聚羧酸减水剂与水泥相容性的机理。结果表明,粉煤灰和矿渣对提高水泥净浆流动性具有一定的叠加效应,可用胶砂减水率的加权平均值进行量化;硅灰对水泥浆体流动性的不利影响远大于粉煤灰和矿渣的辅助减水分散作用,不利于改善聚羧酸减水剂与水泥的相容性;粉煤灰和矿渣增加聚羧酸减水剂在水泥体系中的吸附量;粉煤灰和矿渣对聚羧酸减水剂在混凝土中的减水分散效果有改善作用但不显著。     

不同活性高岭土矿物聚合反应的研究

使用8M氢氧化钠溶液和模数为3.2的硅酸钠水玻璃的混合溶液为激发剂,选用两种不同活性的高岭土在室温、4MPa的压力条件下制备了矿物聚合物材料.通过XRD、IR和SEM等手段研究了矿物聚合反应的机理,考察了高岭土的活性对矿物聚合反应的影响,观察了基于高岭土的矿物聚合物材料的形貌.结果表明,较高活性的高岭土在激发剂作用下发生了较完全的矿物聚合反应,其产物可以用XRD得到明显的鉴别,而低活性高岭土与激发剂的作用产物XRD上没有明显的特征识别;两种活性高岭土基的矿物聚合反应产物均为层状结构,基于高活性高岭土的矿物聚合反应产物的层的连续性和致密性比基于低活性高岭土的好.     

不同温度煅烧凹凸棒土的水化活性

研究了煅烧温度(200～800℃)对凹凸棒土外观、矿物组成和活性SiO2含量的影响,煅烧前后凹凸棒土对水泥浆体化学结合水量、反应程度和水泥胶砂抗折、抗压及劈裂强度等力学性能的影响.结果表明:煅烧温度改变了凹凸棒土的矿物组成,从而影响了水泥基材料的水化活性,经500℃煅烧的凹凸棒土对水泥基材料水化活性的提高效果最佳.     

碳化导致水泥基材料微观结构演变的研究进展

水泥基材料的微观结构是表征其抗碳化性能的重要因素。首先总结了水泥基材料在加速碳化条件下碳化前后固相组成、孔相结构以及液相组成的演变,然后分析了温度、湿度、二氧化碳浓度等环境因素对水泥基材料碳化过程及微结构演变的影响,最后介绍了矿物掺合料在水泥基材料碳化方面的应用,并展望了碳化条件下微观结构演变的发展方向。     

液／固与气／固ZN催化烯烃聚合反应的研究

本文综述了研制多功能ZN催化剂用于乙烯、丙烯、1-丁烯、苯乙烯、1,4-丁二烯进行液相均聚反应和二元、三元共聚反应,以及对制得的产物的结构和性能进行表征。研究了采用ZN多功能催化剂进行气相乙烯均聚和乙烯、1-丁烯共聚反应,并对上述液相聚合反应和气相聚合反应规律、聚合反应动力学进行了详细的研究和比较。     

F1离子固化剂加固试验黄土的物理力学特性变化机理

为研究离子型土壤固化剂加固黄土的作用效果,对不同F1固化剂掺量的试验黄土进行物理力学参数试验以及微观试验,分析了固化剂加固土体的微观结构变化,探讨了固化剂对试验黄土物理力学性质的影响规律和加固机理.研究结果表明:F1固化剂能提供强正电或强阳离子分子,通过离子交换作用与永久带负电荷的黏土矿物颗粒吸附,使得土颗粒在外荷载作用下重新排列成联结力更强的层状堆叠结构,改善了土体的物理力学特性;F1固化剂阻碍了黏土颗粒对极性水分子的吸附,降低了黏土颗粒的水敏性,使得土体的液、塑限和最优含水率降低,最大干密度和无侧限抗压强度增大;微观电镜扫描与核磁共振试验表明,F1固化剂可减小土颗粒间的孔隙体积、孔隙面积比和粒间孔径,降低孔隙连通性;F1固化剂使用便捷、成本低廉、养护周期短,与石灰、水泥等传统土体改良材料相比有众多独有优点.     

利用工业废渣制备软土固化剂的可行性探讨

就如何高附加值地利用工业废渣制备软土固化剂进行了技术效果、经济效益及生产方式等方面的可行性探讨。基于固化土结构形成过程的特点及其对固化剂组成的特殊需求,提出了利用工业废渣制备固化剂的设计思想,给出了固化剂配比实例,与水泥进行了性价比对比分析,并初步探讨了利用工业废渣产业化生产固化剂宜采取的生产经营方式。认为只要能根据形成固化土结构对固化剂组成材料的特殊需求针对性地选择适当的工业废渣,就能够制备出高性价比的软土固化剂;宜根据拟加固土的性质个性化设计制备固化剂,采用多组分组配式生产方式以及设计、生产、销售一体化的经营模式。     

蒙脱土对聚羧酸减水剂的吸附行为研究

为揭示聚羧酸减水剂对砂石含泥量敏感机理,本实验研究了聚羧酸减水剂在蒙脱土上的吸附行为.采用紫外分光光度法,系统研究了聚羧酸减水剂溶液浓度、吸附时间和温度对蒙脱土吸附聚羧酸减水剂的过程及其吸附量的影响;利用Fourier红外光谱,表征分析了聚羧酸减水剂嵌入蒙脱土内部微观结构变化.结果表明:聚羧酸减水剂溶液浓度对蒙脱土层间吸附量影响较小;一定浓度的聚羧酸减水剂在蒙脱土表面的吸附量随吸附时间变化具有饱和吸附性;吸附时间小于90 min时,随时间延长,层间吸附量增大变化明显;吸附温度升高,聚羧酸减水剂在蒙脱土上的表面吸附和层间吸附量均增大;吸附聚羧酸减水剂后的蒙脱土,具有明显的减水剂特征吸收峰,聚羧酸减水剂嵌入了蒙脱土内部.聚羧酸减水剂在蒙脱土上的吸附为表面吸附和嵌入吸附.降低聚羧酸减水剂溶液浓度、缩短吸附时间、降低吸附温度,有利于减少聚羧酸减水剂在蒙脱土表面上的吸附;缩短吸附时间和降低吸附温度,可有效减少聚羧酸减水剂嵌入蒙脱土的驱动力,降低嵌入吸附量;最终达到提高聚羧酸减水剂对砂石含泥量适应性的目的.     

异向旋转双螺杆挤出机内的自由基聚合反应热效应

在聚合反应挤出过程中,化学热效应显著影响材料体系温度,从而影响反应速率以及高分子材料结构与流变性能。采用有限体积方法,数值分析了甲基丙烯酸正丁酯在异向旋转双螺杆挤出机内的自由基聚合反应热效应,描述了反应热释放量及其强度在挤出机内的变化特点,分析了其影响因素,为反应加工条件的优化设计提供了理论依据。     

复合固化砂土力学及水稳性能试验研究

为探究经水泥、石灰和改性聚丙烯纤维复合固化砂土的力学及水稳性能,进行了系列室内试验,结果表明:随水泥掺量增加,固化砂土无侧限抗压强度和劈裂抗拉强度增大,但增长幅度减小,用一定量石灰取代水泥会降低水泥土强度,纤维可以提高水泥土强度,尤其是抗拉强度;水泥可大幅提高砂土抗剪强度和抗压回弹模量,随着纤维掺量的增加,固化土抗剪强度低于水泥土,黏聚力和回弹模量先增大后又减小,内摩擦角与黏聚力表现出负相关性;0.3%纤维加筋8%水泥固化土可以满足简易机场对基层材料的要求。     

Microanalysis of calcium silicate hydrate gel formed within a geopolymeric binder

It is possible to have geopolymeric gel and calcium silicate hydrate (CSH) gel forming simultaneously within a single system. Scanning electron microscopy was employed in studying the morphology and elemental composition of the two phases. The elemental composition within the different phases was consistent. However, CSH gel formed in such system had a significantly lower Ca/Si ratio than the CSH commonly formed from the hydration of ordinary Portland cement. In addition, there were some calcium precipitate along the interface between the CSH and geopolymeric gels. It is suggested that the properties (e.g., size, elemental composition) of the geopolymeric and CSH gels forming simultaneously, and the reactivity of the calcium precipitates along the interfacial region, will hold the key in reformulating a new generation of concrete that matches the durability of ancient concrete. A chemical mechanism on how the presence of slag in the alkali activation of metakaolin would lead to the formation of both geopolymeric and CSH gels has been proposed.     

Fracture toughness of geopolymeric concretes reinforced with basalt fibers

The purpose of this work was to investigate the influence of the volumetric fraction of the fibers on the fracture toughness of geopolymeric cement concretes reinforced with basalt fibers. The values of fracture toughness, critical stress intensity factor and critical crack mouth opening displacement were measured on 18 notched beams tested by three-point bending. The a₀/h (notch height/beam height) ratio was equal to 0.2 and the L₀/h (distance between the supports/beam height) ratio was equal to 3.According to the experimental results, geopolymeric concretes have better fracture properties than conventional Portland cement. They are also less sensitive to the presence of cracks.     

Geopolymer technology: the current state of the art

A brief history and review of geopolymer technology is presented with the aim of introducing the technology and the vast categories of materials that may be synthesized by alkali-activation of aluminosilicates. The fundamental chemical and structural characteristics of geopolymers derived from metakaolin, fly ash and slag are explored in terms of the effects of raw material selection on the properties of geopolymer composites. It is shown that the raw materials and processing conditions are critical in determining the setting behavior, workability and chemical and physical properties of geopolymeric products. The structural and chemical characteristics that are common to all geopolymeric materials are presented, as well as those that are determined by the specific interactions occurring in different systems, providing the ability for tailored design of geopolymers to specific applications in terms of both technical and commercial requirements.     

In situ observing the hydration process of K-PSS geopolymeric cement with environment scanning electron microscopy

The hydration process of K-PSS geopolymeric cement was in situ quantitatively investigated by environment scanning electron microscope (ESEM) under 80% relative humidity. An energy dispersion X-ray analysis (EDXA) was also employed to determine the chemical composition of the hydration product. The ESEM micrographs showed that metakaolin particles pack loosely at 10 min after an initial mixing, resulting in an existence of many large voids. As the hydration proceeded, some gels were produced and gradually precipitated on the surfaces of these particles. At a later stage, these particles were covered by thick gel layers, and their interspaces among the metakaolin particles were also completely filled up. The corresponding EDXA results illustrated that the molar ratios of K/Al and Si/Al decreased with the development of hydration. The molar ratios of K/Al and Si/Al of the hydration products at an age of 13 h amounted to 1.06 and 2.14 respectively, which were very close to the theoretical values (K/Al = 1.0, Si/Al = 2.0) for K-PSS geopolymeric cement hardened paste. In addition, well-developed crystals could not be found at any ages, instead sponge-like amorphous gels have always been observed during the whole hydration process.     

氯氧镁水泥胶凝材料的研究进展

氯氧镁水泥是由轻烧菱镁石粉和氯化镁水溶液按一定比例混合而成的一种新型镁质气硬性胶凝材料。它有很多优于普通硅酸盐水泥的性能,但其耐水性差等缺点也很突出。为了使氯氧镁水泥得到更好的应用,总结和分析了氯氧镁水泥的研究进展,包括水化行为、水化产物组成和结构、耐水性以及生产应用方面。指出了氯氧镁水泥在当前的发展过程中存在的不足和问题,以期为后续氯氧镁水泥的进一步研究提供参考。     

Geopolymeric Agent for Immobilization of Radioactive Ashes after Biomass Burning

Solidification of low-level radioactive wastes obtained after biomass burning was studied. Two solidification modes using Portland cement and geopolymeric binder were tested experimentally. The strength at various hardening times, compacting efficiency, and leaching rate of the resulting monolithic concretes were analyzed. The compacting efficiency in concretes prepared by two different modes is similar. At the same time, geopolymeric binder is solidified in significantly shorter period and its compression strength is several times higher, but its main advantage is chemical immobilization of strontium cations. The leaching rate under the static conditions after 28-day hardening is nearly 10^{- 6} g cm^{- 2} day^{- 1}. Thus, substitution of geopolymerization of the clay component (in general case, aluminosilicate material) for common solidification of low-level wastes using Portland cement is economically promising due to significant energy and resource saving. The geosynthesis can be easily realized as an environmentally safe process, yielding no liquid waste and involving no high-temperature stages with radioactive materials.     

硫铝酸钙改性硅酸盐水泥应用研究进展

硫铝酸钙改性硅酸盐水泥熟料兼具硅酸盐水泥熟料和硫铝酸盐水泥熟料的优良性能,同时该种水泥熟料对粉煤灰等火山灰类材料具有超强的活性激发效果,这使得硫铝酸钙改性硅酸盐水泥具有广阔的应用前景。主要概括了硫铝酸盐改性硅酸盐水泥的性能及水化特性,综述了该种水泥与不同矿物掺合料的复合性能以及与化学外加剂的适应性,提出了硫铝酸钙改性硅酸盐水泥存在的问题及改善措施。     

新型地质聚合物胶凝材料

介绍了新型地质聚合物胶凝材料的研究起源、材料结构、材料合成机理和材料性能,综述了当前国际上地质聚合物材料研究的现状、推广应用的情况及亟需解决的问题.对比国外的发展,我国应大力加强在这一领域的研究和开发.     

Use of a high-calcium fly ash in blended type cement production

Eighty percent of fly ash produced by Greek Public Power Corporation (PPC) is of a high-calcium variety. It has a low insoluble residue and a high content in CaO as well as in SO₃. It also shows self-cementing properties. About 20% of it is used by cement companies in blended type cement production.

In this paper mechanical strengths and some other characteristics concerning blended cement and concrete made with it are presented. Special difficulties anticipated in using such a marginal fly ash in cement are also mentioned.     

Potential utilization of class C fly ash-based geopolymer in oil well cementing operations

The early age compressive strength development of class C fly ash-based geopolymers under high pressure and high temperatures of curing is considered as an alternative to well cements. Uniaxial compressive strength (UCS) results show how the curing temperature affects the early compressive strength development. As the temperature rises from 87 to 125 °C, a consecutive reaction seems to take place at the higher concentrations of NaOH, which decrease the compressive strength at the higher temperature. The taken scanning electron microscope (SEM) images show a change in the morphology of the samples at 125 °C with the higher concentrations of NaOH. Ultrasonic cement analyzers (UCA) were employed to investigate the instantaneous strength development of the geopolymeric slurries. As the common cement models were not able to assess the compressive strength development, the custom algorithm option in the UCA software was applied. The developed empirical correlations were not able to accurately estimate the sonic strength of the slurries remarkably at 125 °C. The rheological measurements of the prepared geopolymeric slurries showed a Newtonian like behavior.