粉煤灰基地聚水泥的研究

地聚水泥是一种新型的化学激发胶凝材料，其制备工艺和原材料以及水化硬化机理等都完全不同于普通硅酸盐水泥．性能及应用领域也远比普通硅酸盐水泥优越，是一种在某些工程领域有望取代硅酸盐水泥的极有发展潜力的化学激发胶凝材料。通过正交试验，在不掺水泥或水泥熟料及石灰的情况下，以原状低钙粉煤灰为原料，在碱性激发剂的作用下，制备了地聚水泥。重点探讨了碱激发剂种类，粉煤灰种类以及养护制度等因素对制备地聚水泥的影响。     

粉煤灰基地聚物的性能影响因素及其凝胶产物研究进展

粉煤灰基地聚物材料因绿色、低碳等优点受到建材行业关注。本文基于地聚物的形成及优势,分析了粉煤灰作为硅铝基材的优点,着重阐述了激发剂离子、养护方式和钙组分对粉煤灰基地聚物材料性能的影响,综述了粉煤灰基地聚物材料的凝胶产物变化及其反应机理研究进展。目前含钙固废作为添加物逐渐应用于改性粉煤灰基地聚物中,因此明确凝胶产物组成和反应机理将为粉煤灰基地聚物材料性能优化提供理论指导。     

粉煤灰碱激发制备地质聚合物研究进展

由于传统硅酸盐水泥基建材生产过程排放大量CO₂,近几年以地质聚合物(地聚物)为代表的新型低碳胶凝材料成为研究热点。作为我国大宗工业固体废弃物，粉煤灰富含硅铝酸盐，通过碱激发制备地聚物可实现粉煤灰大宗消纳。综合论述了粉煤灰的碱激发反应活性评估方法，总结了粉煤灰碱激发反应机理，归纳了粉煤灰类型、激发剂、原料配比和养护制度等关键因素对地聚物形成和性能的影响规律，提出了目前研究存在的问题，并从粉煤灰活性组分评估和碱激发体系元素组成的角度，对未来研究方向进行展望。粉煤灰的反应活性评价方法主要有Rietveld全谱图拟合法、饱和石灰溶液吸收法和酸碱溶出法。粉煤灰碱激发反应过程可分为解构—重构—凝聚—聚合4个阶段，解构过程中溶出的硅铝比(Si/Al物质的量比)对凝胶结构和材料力学性能有重要影响，不同研究获得的最佳Si/Al物质的量比存在较大差异。目前关于原料配比、养护制度和凝胶结构等因素对地聚物性能影响研究获得的变化规律并不一致，为粉煤灰碱激发反应机理和地聚物合成研究带来困难，未来应针对不同类别粉煤灰理化特性，建立碱激发体系各元素配比统一的计算方法，为粉煤灰基地聚物合成时统一设...     

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。     

应用煅烧石膏生产早强粉煤灰水泥

本文通过材料性能测定、化学结合水、扫描电子显微镜、差热分析等实验方法，研究煅烧石膏对粉煤灰水泥早强性能与水化过程的影响。实验结果表明，采用煅烧石膏代替二水石膏制造粉煤灰水泥，可使粉煤灰水泥的早强性能明显改善，有效地提高粉煤灰水泥的抗折和抗压强度，使粉煤灰水泥的早期强度明显提高，后期强度稳定增长。其增强机理是由于煅烧石膏可加速硅酸盐水泥熟料和粉煤灰的水化速度。     

水泥粉煤灰路面基层材料在高速公路中的前期试验研究

在十漫高速公路二期工程前期试验中，引入水泥粉煤灰稳定粒料新型半刚性基层材料，研究了掺不同剂量粉煤灰的水泥粉煤灰稳定粒料基层的无侧限抗压强度、劈裂抗拉强度、回弹模量等路用性能，并同水泥稳定粒料基层进行了对比。室内试验结果表明：利用10％粉煤灰等量替代碎石的水泥粉煤灰稳定碎石基层具有良好的路用性能，具有广阔的工程应用前景。     

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、...     

海工高性能混凝土用复合胶凝材料的试验研究

在调查分析海工混凝土工程实例的基础上，试验研究了硅酸盐水泥中掺入矿粉、粉煤灰、硅灰等混合材料对海工混凝土性能的影响。研究结果表明，在硅酸盐水泥中掺加矿粉、粉煤灰、硅灰等混合材料可以改善海工混凝土的综合性能。矿物混合材料的复合掺入比单独掺入能更好地改善混凝土抗Cl^-侵蚀性能。海工专用复合胶凝材料生产时宜尽可能地采用多种混合材料。     

钙对粉煤灰基土聚水泥性能的影响研究

采用正交试验优化设计制备了粉煤灰基土聚水泥,并进一步研究了钙对粉煤灰基土聚水泥性能的影响。研究表明：硅铝比是影响粉煤灰基土聚水泥强度发展的重要因素,碱铝比次之,水碱比最小;土聚水泥的最佳配比为硅铝比4.6,碱铝比0.8-1.1,水碱比6.0-7.2;不同种类以及掺量的钙质组分对土聚水泥的强度发展影响很大,体系中的钙应控制在适宜范围。     

粉煤灰基地聚水泥的研究

地聚水泥是一种新型的化学激发胶凝材料,在某些工程领域有望取代硅酸盐水泥,极有发展潜力.通过正交试验,在不掺水泥或水泥熟料及石灰的情况下,以原状低钙粉煤灰为原料,在碱性激发剂的作用下,制备了地聚水泥.探讨了碱激发剂种类、粉煤灰种类以及养护制度等因素对制备地聚水泥的影响.     

地质聚合物应用现状及前景展望

地质聚合物是一种无机聚合铝硅酸盐胶凝材料。由于其特殊的缩聚三维网络结构,使其在众多方面具有高分子材料、水泥和陶瓷,金属等材料的特征。分析了地质聚合物的聚合反应机理,性能特点,简要叙述了地质聚合物的发展历程和应用现状,并概述了其在工程建筑、有毒废料、涂料、固封材料和陶瓷材料等领域的应用发展前景。     

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。     

The effect of microencapsulated phase change materials on the rheology of geopolymer and Portland cement mortars

The effect of microencapsulated phase-change materials (MPCM) on the rheological properties of pre-set geopolymer and Portland cement mortars was examined. Microcapsules with hydrophilic and hydrophobic shells were compared. The shear rate dependency of the viscosities fitted well to a double Carreau model. The zero shear viscosities are higher for geopolymer mortar, illustrating poorer workability. The time evolution of the viscosities was explored at shear rates of 1 and 10 s⁻¹. New empirical equations were developed to quantify the time-dependent viscosity changes. The highest shear rate disrupted the buildup of the mortar structures much more than the lower shear rate. Microcapsules with a hydrophobic shell affect the rheological properties much less than the microcapsules with a hydrophilic shell, due to the higher water adsorption onto the hydrophilic microcapsules. Shear forces was found to break down the initial structures within geopolymer mortars more easily than for Portland cement mortars, while the geopolymer reaction products are able to withstand shear forces better than Portland cement hydration products. Initially, the viscosity of geopolymer mortars increases relatively slowly during due to formation of geopolymer precursors; at longer times, there is a steeper viscosity rise caused by the development of a 3D-geopolymer network. Disruption of agglomerates causes the viscosities of portland cement mortars to decrease during the first few minutes, after which the hydration process (increasing viscosities) competes with shear-induced disruption of the structures (decreasing viscosities), resulting in a complex viscosity behavior.     

Effect of partial replacement of geopolymer binder materials on the fresh and mechanical properties: A review

The growth of demand for concrete raises concerns about the consumption of natural resources and ordinary Portland cement. Geopolymer composites show promise as a sustainable alternative for conventional cement concrete. Considering the wide range of potential geopolymer composites applications (including suitability for transportation infrastructure, underwater applications, repair and rehabilitation of structures as well as recent developments in 3D printing), the desired fresh and mechanical properties of the geopolymer composite may vary between applications: for example, rapid setting can be a merit for certain applications and a demerit for others. Therefore, the desired fresh and mechanical properties (e.g., workability, setting time, compressive strength, etc.) can be controlled for a given geopolymer source material through its partial substitution by natural or by-product materials. Recognizing the critical role of various replacement materials in enhancing the potential applications of geopolymer composites, the present review was undertaken to quantify and understand the effect of partial replacement by fly ash, metakaolin, kaolin, red mud, slag, ordinary Portland cement, and silica fume on the setting time, workability, compressive strength and flexural strength of various source materials addressed in the literature. The review also provides insights into research gaps in the field to promote future research.     

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。     

Structure and mechanical properties of aluminosilicate geopolymer composites with Portland cement and its constituent minerals

The compressive strengths and structures of composites of aluminosilicate geopolymer with the synthetic cement minerals C₃S, β-C₂S, C₃A and commercial OPC were investigated. All the composites showed lower strengths than the geopolymer and OPC paste alone. X-ray diffraction, ²⁹Si and ²⁷Al MAS NMR and SEM/EDS observations indicate that hydration of the cement minerals and OPC is hindered in the presence of geopolymer, even though sufficient water was present in the mix for hydration to occur. In the absence of SEM evidence for the formation of an impervious layer around the cement mineral grains, the poor strength development is suggested to be due to the retarded development of C-S-H because of the preferential removal from the system of available Si because geopolymer formation is more rapid than the hydration of the cement minerals. This possibility is supported by experiments in which the rate of geopolymer formation is retarded by the substitution of potassium for sodium, by the reduction of the alkali content of the geopolymer paste or by the addition of borate. In all these cases the strength of the OPC-geopolymer composite was increased, particularly by the combination of the borate additive with the potassium geopolymer, producing an OPC-geopolymer composite stronger than hydrated OPC paste alone.     

Alkali-activated waste ceramics: Importance of precursor particle size distribution

The waste ceramics belongs to wide range of aluminosilicate materials which can be alkaline-activated to geopolymer cement – possible “green” alternative to conventional Portland cement. The studied ceramic material is generated during the size adjustment of ceramic building blocks by means of grinding. It means that most of the material is very fine, but it contains also some larger shards. This ceramic powder was used as geopolymer precursor “as received” and after removal of particles retained on 1, 0.5 and 0.125 mm sieves. These four types of precursor were activated by sodium silicate (SiO₂/Na₂O = 1) solution. The prepared mortars were tested for strength, basic physical properties, transport parameters and characterized by help of XRD and thermal analysis. It was found that the best mechanical performance provided the precursor after removal of particles retained on 0.5 mm sieve thanks to the highest geopolymerization rate. The presence of coarser particles in precursor gave rise to porosity, what consequently influenced transport parameter of geopolymers towards the lower thermal conductivity and faster moisture transport.     

Resistance of geopolymer materials to acid attack

This article presents an investigation into durability of geopolymer materials manufactured using a class F fly ash (FA) and alkaline activators when exposed to 5% solutions of acetic and sulfuric acids. The main parameters studied were the evolution of weight, compressive strength, products of degradation and microstructural changes. The degradation was studied using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The performance of geopolymer materials when exposed to acid solutions was superior to ordinary Portland cement (OPC) paste. However, significant degradation of strength was observed in some geopolymer materials prepared with sodium silicate and with a mixture of sodium hydroxide and potassium hydroxide as activators. The deterioration observed was connected to depolymerisation of the aluminosilicate polymers in acidic media and formation of zeolites, which in some cases lead to a significant loss of strength. The best performance was observed in the geopolymer material prepared with sodium hydroxide and cured at elevated temperature, which was attributed to a more stable cross-linked aluminosilicate polymer structure formed in this material.     

Synthesis and thermal properties of inorganic polymers (geopolymers) for structural and refractory applications from volcanic ash

The volcanic ash occurring as an abundant and readily accessible natural resource in the Central African country of Cameroon was used to synthesize aluminosilicate geopolymers using sodium hydroxide as the sole alkaline activator. Both the curing conditions and the Na₂O/SiO₂ molar ratio were found to influence the development of compressive strength of the geopolymer cement paste, which achieved a maximum strength of 55 MPa at Na₂O/SiO₂ = 0.3. The formation of a mortar by the addition of 40 wt% sand to the optimized geopolymer cement composition reduced the compressive strength to 30 MPa, still within the useful range for construction applications. The geopolymers consist largely of X-ray amorphous material with a small content of crystalline phases. Scanning electron microscopy showed a homogenously distributed mixture of lath-shaped and agglomerated morphologies, with a homogeneous distribution of Si, Al and O in the geopolymer matrix. The geopolymers are relatively stable to heat, shrinking only slowly and retaining about 60% of their as synthesized compressive strength on heating to 900 °C. The FTIR spectra of both the as synthesized and heated geopolymers show two broad absorbance bands, between 820-1250 cm⁻¹ and 450-730 cm⁻¹ assigned to the internal vibrations of Si-O-Si, and Si-O-Al respectively. The compressive strengths and the thermal stability of these materials suggest their suitability for building applications and low-grade refractories.