基于响应面法的碱激发地聚物固化淤泥质土试验研究

为实现滩涂淤泥质土和工业废料资源化利用,定量优化地聚物固化淤泥质土的关键因素,基于Box-Behnken响应面法对碱激发矿渣-粉煤灰基地聚物固化淤泥质土的配合比进行优化,选取矿渣掺量、碱激发剂模数和碱激发剂掺量为主要考察因素,并结合宏观性能和微观形貌进行固化机理分析。结果表明：固化土最优配合比为矿渣掺量86.5%(质量分数),碱激发剂模数0.84,碱激发剂掺量7.3%(质量分数),此时固化土7和28 d无侧限抗压强度分别为5 823和7 027 kPa,预测值与实际值误差较小,所建立的模型与实际数据拟合准确可靠;固化土的水化产物主要为无定形凝胶水化硅铝酸钙(C-(A)-S-H)和硅铝酸盐聚合物(N-A-S-H),可增强土体的密实程度和骨架结构,以此提高固化土的强度。本研究为碱激发地聚物固化淤泥质土提供了理论依据和实验基础。     

固废基道路地聚物注浆材料的组分优化及机理研究

地聚物注浆材料作为低能耗、低CO₂排放的清洁材料，在道路注浆领域应用前景广阔，在未来有望取代水泥注浆材料。为了探究材料组分及用量对地聚物注浆材料性能的影响，采用三种硅铝源灰料(粉煤灰、矿渣粉和煤矸石粉)与不同碱活化方式制备道路地聚物注浆材料，对其组成材料进行优选；然后，采用单因素试验对道路地聚物注浆材料的配合比范围进行优化；最后，利用X射线衍射(XRD)、场发射扫描电子显微镜(FE-SEM)、能量色散谱(EDS)和傅里叶变换红外光谱(FTIR)对道路地聚物注浆材料的物相组成、微观形貌、微区能谱和化学键组成进行分析。结果表明：以粉煤灰和矿渣粉为硅铝源灰料，KOH和水玻璃溶液为复合碱活化剂制备的道路地聚物注浆材料性能最佳；推荐道路地聚物注浆材料的配合比范围为：粉煤灰、矿渣粉质量比4∶6,水玻璃用量10%～15%(质量分数),KOH用量5%～11%(质量分数),水灰比0.50～0.65;粉煤灰和矿渣粉被碱活化后溶解并重聚生成C-(A)-S-H等无定形凝胶产物，最终形成SiO₄和AlO₄正四面体网状结构，且伴随类沸石相、碳酸盐、...     

铁水脱硫渣固化土基层材料力学性能研究

基于土壤固化技术，将铁水脱硫渣、高炉矿渣微粉、普通硅酸盐水泥与素土按一定比例拌和制备铁水脱硫渣固化土基层材料，通过击实、无侧限抗压强度、劈裂强度等试验对其性能进行测定，并分析物料掺量对铁水脱硫渣固化土力学性能的影响，结果表明：提高铁水脱硫渣掺量和降低矿渣微粉掺量均会使混合料最大干密度增大、最佳含水率下降；铁水脱硫渣固化土基层材料具有较好的力学性能，7 d无侧限抗压强度均大于6 MPa;当矿渣微粉掺量为40%时，铁水脱硫渣固化土基层材料达到力学峰值，道路基层强度最佳。     

新型废渣软土固化剂的试验研究

通过配合比正交试验和优化,将脱硫石膏、钢渣、矿渣复合形成固化剂(简称GSC);采用扫描电镜对其水化产物进行微观分析;并通过无侧限抗压试验对GSC固化土与水泥土作了强度对比分析.研究结果表明,钢渣作为胶凝材料对GSC固化剂强度影响最大;发现GSC固化剂安定性、凝结时间可以满足使用要求,其水化产物和水泥相似;GSC固化土无侧限抗压强度随龄期的增长规律与水泥土一致,但早期强度比水泥土低;调节GSC的用量和水灰比大小可以实现与水泥相同的固化效果.     

粉煤灰基地聚物固化盐渍土的工程特性与微观机制

为探索粉煤灰基地聚物对盐渍土的加固效果，对固化后的土体开展了力学性能和细微观结构的试验，从本质上揭示粉煤灰基地聚物对盐渍土的固化机理。结果表明:随着粉煤灰基地聚物掺量的增加，盐渍固化土的最优干密度下降，最优含水率上升;当掺量从0增至6%时，盐渍固化土的无侧限抗压强度增加了5.5倍，而当掺量为8%时的强度没有明显提升;盐渍土的孔径分布呈双峰分布，随着地聚物掺量的增加，孔隙体积逐渐降低;盐渍固化土的阳离子交换量随粉煤灰基地聚物掺量增加而提高，且与无侧限抗压强度呈现线性相关;在盐渍土中加入粉煤灰基地聚物使土颗粒间的孔隙收缩，黏结性和密实度增强，进而达到固化的效果。本研究成果为粉煤灰基地聚物在盐渍土地区地基加固工程中的设计与施工提供了参考。     

碱矿渣复合水泥--放射性废物固化基材力学性能的研究(一)

在碱矿渣水泥中,掺入参改性其水化产物,提高其吸附性能的粘土矿物材料,构成用于放射性废物固化的碱矿渣复合水泥体系。研究了该体系的力学性能,结果表明,粘土矿物的掺量和养护制度对碱矿渣复合水泥的强度有较大影响,当热活化高岭土,沸石,改性凹凸棒掺量分别为１０％、５％、１５％时,其２８ｄ净浆抗压强度达８９．８ＭＰａ。该复合水泥浆体宜湿气养护,且具有良好的耐辐照和抗硫酸盐性能。     

偏硅酸钠激发胶凝材料性能及微观结构

以粉煤灰、矿渣为原料,研究了偏硅酸纳激发胶凝材料的力学性能及工作性能,通过XRD和SEM对水化产物进行表征,并采用量热试验对水化历程进行分析.结果表明:对于粉煤灰-矿渣体系,采用偏硅酸钠作激发剂时,碱当量为8％时,砂浆抗压强度最高;随着激发剂掺量的增加,砂浆流动度增加,凝结时间缩短,砂浆收缩率降低;体系主要水化产物为C-S-H凝胶,且随着碱当量的提高,粉煤灰和矿渣的反应程度变大,水化产物中凝胶的量增加.     

地聚物多孔轻质高强材料的制备及孔结构特性

为了解决地聚物多孔材料质轻与高强难以取得一致性的问题,本文采用正交试验,对粉煤灰地聚物多孔材料表观密度和强度进行试验,在此基础上,利用超细矿渣粉的独特性,对双氧水发泡剂及辅助稳泡材料进行了优选,制备出抗压强度达到5.9 MPa、表观密度仅为557 kg/m3的地聚物多孔材料.结果表明:当粉煤灰/矿渣比例为1:1,双氧水掺量为2.0％,硬脂酸钙掺量为1.0％,MnO2掺量为0.3％,制备的矿渣-粉煤灰基地聚物多孔材料可以达到质轻高强的目的.采用XRD、SEM和低场核磁共振技术对多孔材料进行了微观测试,并对其抗压强度、表观密度与孔结构之间关系进行了分析.     

膨润土对固化淤泥土抗冻融性能的提升效应

为了研究膨润土对固化淤泥土抗冻融性能的提升效应,针对冻融循环过程中不同膨润土掺入量的固化淤泥土,开展了无侧限抗压强度试验、直接剪切试验等宏观试验,以及相应的电镜扫描分析等微细观分析和理论分析.膨润土能够有效的提高固化淤泥土的破坏应变、无侧限抗压强度、粘聚力和内摩擦角等指标,并且能够保证上述指标在冻融循环作用下不发生衰减.膨润土的掺入量,存在一个最优值:该值附近,膨润土对固化淤泥土抗冻融性能的提升效果最好.膨润土对固化淤泥土抗冻融性能的提升,通过内部结构稳定性的强化和冻融循环作用的弱化等双重作用而实现.膨润土的颗粒填充能够减小固化淤泥土的孔隙率,同时膨润土可以参与固化反应生成固化骨架,从而促进固化淤泥土内部结构稳定性的强化.膨润土的吸水作用可以减少参与冻融循环作用的自由水,同时膨润土的湿胀干缩作用可以部分抵消冻胀融缩效应,进而促冻融循环作用的弱化.     

阿利特-硫铝酸钡钙水泥砂浆的力学性能和干缩性能

通过与硅酸盐水泥(portland cement,PC)对比,研究了阿利特-硫铝酸钡钙水泥(alite-barium calcium sulphoaluminate cement,SABC)砂浆的力学性能和干缩性能.采用X射线衍射和扫描电镜对养护28 d SABC砂浆水化产物的物相组成、形貌以及硬化砂浆的微观结构进行了分析和观察,用压汞法对硬化砂浆的孔结构进行了分析.结果表明:SABC砂浆具有较高的早期强度,添加适量掺合料的可以提高砂浆的强度.且添加矿渣的效果更显著.由于SABC的微膨胀性能,使其砂浆的干缩性能优于pC砂浆.用≤20%(质量分数,下同)矿渣和粉煤灰取代SABC后,可以减小砂浆的干缩率,当取代量超过20%后干缩率随之增大;与掺加矿渣的SABC砂浆的干缩率相比,加入粉煤灰的SABC砂浆干缩率较小.     

煤气化粗渣-矿渣基地质聚合物的制备与性能

在煤气化粗渣基地质聚合物中复掺矿渣可改善其早期力学性能。本文以煤气化粗渣和矿渣为原料制备地质聚合物,系统研究了不同矿渣掺量对煤气化粗渣基地质聚合物早期力学性能及微观结构的影响。利用X射线衍射、压汞测试、扫描电镜、傅里叶红外光谱等方法对煤气化粗渣-矿渣基地质聚合物的微观结构进行分析表征。结果表明,当矿渣掺量增加时,地质聚合物抗压强度呈逐渐增大趋势。矿渣掺量为40%(质量分数)时,样品28 d抗压强度高达53.1 MPa。由微观分析可知,掺入矿渣后地质聚合物表面生成了大量水化硅铝酸钙/钠(C(N)-A-S-H)凝胶,使地质聚合物微观结构更为致密,力学性能得到改善。     

Utilisation of steel furnace slag coarse aggregate in a low calcium fly ash geopolymer concrete

This paper evaluates the performance of steel furnace slag (SFS) coarse aggregate in blended slag and low calcium fly ash geopolymer concrete (GPC). The geopolymer binder is composed of 90% of low calcium fly ash and 10% of ground granulated blast furnace slag (GGBFS). Mechanical and physical properties, shrinkage, and detailed microstructure analysis were carried out. The results showed that geopolymer concrete with SFS aggregate offered higher compressive strength, surface resistivity and pulse velocity than that of GPC with traditional aggregate. The shrinkage results showed no expansion or swelling due to delayed calcium oxide (CaO) hydration after 320 days. No traditional porous interfacial transition zone (ITZ) was detected using scanning electron microscopy, indicating a better bond between SFS aggregate and geopolymer matrix. Energy dispersive spectroscopy results further revealed calcium (Ca) diffusion at the vicinity of ITZ. Raman spectroscopy results showed no new crystalline phase formed due to Ca diffusion. X-ray fluorescence result showed Mg diffusion from SFS aggregate towards geopolymer matrix. The incorporation of Ca and Mg into the geopolymer structure and better bond between SFS aggregate and geopolymer matrix are the most likely reasons for the higher compressive strength observed in GPC with SFS aggregate.     

Effect of nano silica and fine silica sand on compressive strength of sodium and potassium activators synthesised fly ash geopolymer at elevated temperatures

Environment friendly geopolymer is a new binder which gained increased popularity due to its better mechanical properties, durability, chemical resistance, and fire resistance. This paper presents the effect of nano silica and fine silica sand on residual compressive strength of sodium and potassium based activators synthesised fly ash geopolymer at elevated temperatures. Six different series of both sodium and potassium activators synthesised geopolymer were cast using partial replacement of fly ash with 1%, 2%, and 4% nano silica and 5%, 10%, and 20% fine silica sand. The samples were heated at 200°C, 400°C, 600°C, and 800°C at a heating rate 5°C per minute, and the residual compressive strength, volumetric shrinkage, mass loss, and cracking behaviour of each series of samples are also measured in this paper. Results show that, among 3 different NS contents, the 2% nano silica by wt. exhibited the highest residual compressive strength at all temperatures in both sodium and potassium‐based activators synthetised geopolymer. The measured mass loss and volumetric shrinkage are also lowest in both geopolymers containing 2% nano silica among all nano silica contents. Results also show that although the unexposed compressive strength of potassium‐based geopolymer containing nano silica is lower than its sodium‐based counterpart, the rate of increase of residual compressive strength exposed to elevated temperatures up to 400°C of potassium‐based geopolymer containing nano silica is much higher. It is also observed that the measured residual compressive strengths of potassium based geopolymer containing nano silica exposed at all temperatures up to 800°C are higher than unexposed compressive strength, which was not the case in its sodium‐based counterpart. However, in the case of geopolymer containing fine silica sand, an opposite phenomenon is observed, and 10% fine silica sand is found to be the optimum content with some deviations. Quantitative X‐ray diffraction analysis also shows higher amorphous content in both geopolymers containing nano silica at elevated temperatures than those containing fine silica sand.     

碱激发地质聚合物固化软土的研究进展

软土地基处理是工程界公认的有较高风险的工程领域,传统软土固化中大量使用硅酸盐水泥,不仅消耗自然资源,还会对环境产生不良影响,使用环境友好型碱激发地质聚合物替代传统硅酸盐水泥越来越受到国内外学者的重视。论文基于国内外已有研究成果,从碱激发地质聚合物固化土发展历史、碱激发地质聚合物种类、碱激发地质聚合物反应机理、碱激发地质聚合物固化土力学特性和各类性能等方面进行研究进展的综述分析,重点谈论地质聚合物处理软土的力学特性,并对不同碱激发地质聚合物在软土地基加固中抗渗性能、抗冻融性能、抗腐蚀性能等进行分析,对碱激发地质聚合物在软土地基加固中的应用进行系统梳理和展望,以期引导和提升碱激发地质聚合物在软土地基加固中的应用,实现我国地基加固可持续发展。     

地聚物稳定废旧沥青混合料的强度与微观结构研究

发展高早强和低能耗的新型绿色道路建筑材料对我国公路建设与养护具有重要意义。本文采用地聚物稳定100%的废旧沥青混合料,制备了地聚物稳定冷再生混合料(GCRM),研究了矿渣掺量、水玻璃模数、激发剂用量以及地聚物掺量对GCRM劈裂强度的影响及其时变规律,通过扫描电子显微镜和EDS能谱分析了混合料的微观形貌及结构组成。结果表明,GCRM的早期强度发展较快,相较于水泥乳化沥青稳定冷再生混合料提升明显。当矿渣掺量为30%(质量分数)、水玻璃模数为1.0、激发剂用量为50%(质量分数)、地聚物总掺量为8%(质量分数)时,GCRM具有最佳的早期强度,7 d劈裂强度可达1.7 MPa。微观结构分析表明,GCRM破坏界面处裂缝易出现在地聚物反应程度偏低的位置。此外,水化硅铝酸钙(C-A-S-H)层状凝胶结构的形成更有利于混合料力学性能的发展。     

Partial replacement of metakaolin with red ceramic waste in geopolymer

Metakaolin was incrementally replaced (33.3%, 50% and 66.6%) by red ceramic waste in geopolymer formulation to study the effect on geopolymerisation and its resultant properties. The geopolymer binders composed of two calcined aluminosilicates (viz. Metakaolin and Red ceramic waste), NaOH and sodium silicate. In the experimental compositions, metakaolin was replaced gradually up to 66.6% in the clay fraction, the Si/Al increased from 3.36 to 5.16 and Na/Al increased from 0.93 to 1.38. The FTIR spectroscopic studies of geopolymer pastes along with XRD analysis indicated that the red ceramic waste partly reacts with alkali and takes part in geopolymer formation. Replacement of 33.3% metakaolin by the red ceramic waste in geopolymer binder did not reduce the compressive strength with respect to the pure metakaolin geopolymer here. Additional replacement resulted in a drastic decrease in the compressive strength of the geopolymer binder. However, the compressive strength of geopolymer mortars revealed interesting synergy between the amount of binder and particle packing in the mortar. Despite having a lower amount of binder phase, mortars with 33% and 50% red ceramic waste exhibited maximum compressive strength values. This has been attributed to improved particle packing through incorporation of red ceramic waste particles.     

Effects of Si/Al ratio on the structure and properties of metakaolin based geopolymer

Geopolymer with Si/Al ratios from 2 to 4 were prepared by adding different contents of fused silica into geopolymer matrix. Effects of Si/Al ratios on the structure, mechanical properties and chemical stability in air of the obtained geopolymer were systematically investigated. The results showed that all the geopolymer samples were XRD amorphous. Geopolymer with Si/Al ratios of 2 and 2.5 showed similar structure and property and they were classed as KGP-I; and geopolymer with Si/Al ratios of 3, 3.5 and 4 were similar and they were class as KGP-II. In alkaline solution, reactivity of fused silica were higher than that of metakaolin, resulting in higher content of both residual metakaolin and free alkaline cation in KGP-II than in KGP-I. Fused silica partially reacted with the alkaline solution in KGP-II indicating chemical interfacial bonding between silica and binder phase. With the increase in Si/Al ratios, KGP-II especially for geopolymer with Si/Al of 4 showed much higher mechanical properties than KGP-I due to the increased Si-O-Si bonds and residual silica as reinforcement. However, KGP-II showed worse chemical stability in air than KGP-I, with the presence of efflorescence on the surface, which was attributed to their higher residual free K⁺.     

The benefits of incorporating glycerol carbonate into an innovative pozzolanic matrix

A green admixture, glycerol carbonate (GC), has been incorporated into an alternative binder composed of hydraulic lime and metakaolin. The new properties achieved are rapid hardening, an improvement of compressive strength and a reduction in shrinkage. A study of the rheological behaviour and monitoring of conductivity, pH and organic compounds concentrations in diluted solutions led to the conclusion of an early precipitation of calcium carbonate due to GC decomposition. This phenomenon is believed to be responsible for the early stiffening of the paste. XRD and TG analyses showed changes in the mineralogical hydrated phases formed in the presence of GC: calcium aluminium oxide hemi-carbonate hydroxide hydrate is the only aluminate phase existing in this mineralogical system and more C-S-H are formed. These differences could explain the enhancement in the paste mechanical performance. The study concludes that this innovative pozzolanic matrix has considerable potential as a binder in building ecocomposites.     

Influence of calcium content on the atomic structure and phase formation of alkali-activated cement binder

The effects of calcium on the atomic structure of alkali-activated binder materials were investigated. The alkali-activated binder samples with varied Ca/Si ratios were first statically examined with both the X-ray diffraction (XRD) and total scattering function analysis. The added calcium can reorder the atomic structure of the alkali-activated materials and enhance its crystallization based on the X-ray pair distribution function (PDF) and XRD analysis. In situ PDF experiments were undertaken to examine the evolution of the atomic structure of calcium-contained geopolymer. The increase in calcium content accelerated the dissolution of precursor and the formation of the binder. It was shown that the additional Ca(OH)₂ could serve as nucleation sites for the precipitation of sodium aluminosilicate hydrate gel to accelerate the reaction. PDF analysis and XRD characterization enable the examination of the phase development of alkali-activated materials at the atomic scale.     

Sodium silicate activated slag‐fly ash binders: Part I – Processing,microstructure, and mechanical properties

Alkali silicate activated slag and class F fly ash‐based binders are ambient curing, structural materials that are feasible replacements for ordinary Portland cement (OPC). They exhibit advantageous mechanical properties and less environmental impact than OPC. In this work, five sodium silicate activated slag‐fly ash binder mixtures were developed and their compressive and flexural strengths were studied as a function of curing temperature and time. It was found that the strongest mixture sets at ambient temperature and had a Weibull average flexural strength of 5.7 ± 1.5 MPa and Weibull average compressive strength of 60 ± 8 MPa at 28 days. While increasing the slag/fly ash ratio accelerated the strength development, the cure time was decreased due to the formation of calcium silicate hydrate (C–S–H), calcium aluminum silicate hydrate (C–A–S–H), and (Ca,Na) based geopolymer. The density, microstructure, and phase evolution of ambient‐cured, heat‐cured, and heat‐treated binders were studied using pycnometry, scanning electron microscopy, energy dispersive X‐ray spectroscopy (SEM‐EDS), and X‐ray diffraction (XRD). Heat‐cured binders were more dense than ambient‐cured binder. No new crystalline phases evolved through 28 days in ambient‐ or heat‐cured binders.