Preparation of fly ash and rice husk ash geopolymer

The geopolymer of fly ash (FA) and rice husk ash (RHA) was prepared. The burning temperature of rice husk, the RHA fineness and the ratio of FA to RHA were studied. The density and strength of the geopolymer mortars with RHA/FA mass ratios of 0/100, 20/80, 40/60, and 60/40 were tested. The geopolymers were activated with sodium hydroxide (NaOH), sodium silicate, and heat. It is revealed that the optimum burning temperature of RHA for making FA-RHA geopolymer is 690℃. The as-received FA and the ground RHA with 1%-5% retained on No.325 sieve are suitable source materials for making geopolymer, and the obtained compressive strengths are between 12.5-56.0 MPa and are dependent on the ratio of FA/RHA,the RHA fineness, and the ratio of so dium silicate to NaOH. Relatively high strength FA-RHA geopolymer mortars are obtained using a sodium silicate/NaOH mass ratio of 4.0, delay time before subjecting the samples to heat for 1 h, and heat curing at 60℃ for 48 h.     

热处理对石墨填充高岭土基矿物聚合物复合材料摩擦学性能的影响

对20%石墨填充高岭土基矿物聚合物复合材料在不同温度下进行热处理,利用扫描电镜、X射线衍射和红外光谱等表征手段及显微硬度实验、三点弯曲实验,研究了材料的微观结构、机械性能及摩擦学性能与热处理温度之间的关系。结果表明,随热处理温度的提高,材料的微观结构发生较大变化,材料的显微硬度和弯曲强度均呈现先下降后又缓慢上升的趋势;材料经300℃和600℃的高温处理后仍具有较好的摩擦学性能,处理温度较低时,材料的磨损形式以磨粒磨损和粘着磨损为主;处理温度较高时,磨损形式以磨粒磨损和疲劳磨损为主。     

地聚合物基活性粉末混凝土的制备及特性研究

利用粉煤灰取代部分偏高岭土，以强度为指标寻求最佳地聚合物基体配合比，在标准养护，蒸汽养护，压蒸养护三种养护制度中，选出最有利于发挥胶凝材料活性的养护工艺，然后在最佳基体中掺入三种钢纤维，选用最佳养护工艺，可得到一系列强度的纤维增强地聚合物基活性粉末混凝土（RPC），其抗压强度最高达55.2MPa，弯拉强度达22.44MPa，对其抗氯离子渗透和抗碳化性能进行的研究结果表明，地聚合物基RPC具有非常优异的耐久性。     

ESEM追踪K-PSDS型地聚合物水泥的水化

应用环境扫描电镜原位定量追踪K-PSDS型地聚合物水泥在相对湿度80％条件下水化产物生成-发展-演化的全过程.结果表明：在水化早期，偏高岭土颗粒松散地堆积在一起，存在许多大空隙；随着龄期的增长，生成的大量海绵状胶体积淀在颗粒表层，并向外扩充；到了后期，颗粒被胶体厚厚包裹，空隙被填满，基体变得非常致密．通过能量散射分析(EDXA)发现，随着水化的进行，K2O与Al2O3，SiO2与Al2O3的摩尔比逐渐减小，最终产物的这两个比值分别为1．28，6．54，接近理论值．另外，在任何龄期均未出现外形规则的结晶产物，而仅生成了一种均匀的海绵状胶体．     

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。     

Effects of fiber contents on the mechanical and microwave absorbent properties of carbon fiber felt reinforced geopolymer composites

In this paper, phosphate-based geopolymer composites are studied and the effects of different carbon fiber felt contents (from 20?vol% to 40?vol%) on the phase composition, microstructure, mechanical properties and microwave absorbent properties from 2?GHz to 18?GHz frequency band of the composites were systematically investigated. The results indicate that with the increase in carbon fiber felt contents, flexural strength and Young's modulus of the composites gradually increased. The fracture mode of the composite changed from brittle failure to ductile failure with the presence of carbon fiber felt. It was mainly due to the micropore deformation as well as fibers pulling-out and the crack deflection, which consumed most fracture energy. However, microwave absorbent performance tended to increase at first and then decreased as the carbon fiber felt content ramping up. When the content of carbon fiber felt in the composite was 26.7?vol%, the composite showed the best microwave absorbent performance and the reflection loss reached to ??59.3?dB. It is mainly attributed to the Debye polarization of the carbon fibers and the interface polarization between fibers and the matrix.     

Low-energy impact behavior of ambient cured engineered geopolymer composites

Engineered geopolymer composite (EGC) is a new kind of fiber reinforced geopolymer composite with tensile strain-hardening behaviors. This paper was intended to investigate the low-energy impact behaviors of EGC. To further reduce the carbon footprint and material cost of EGC, the feasibility of developing ambient cured EGC with cheap local PVA fiber was discussed according to the micromechanics-based analytical models. The compressive, tensile and impact tests of EGC, engineered cementitious composites (ECC), pure geopolymeric matrix and cementitious matrix were conducted and compared. It was found that the EGC specimens have similar tensile behaviors with ECC and the ultimate tensile strain of EGC can be as high as 7.5%. Under impact load, it was found that the PVA fibers could effectively restrict the crushing and spalling of geopolymeric matrix. Also, the dissipated energy of pure geopolymeric matrix is 3.8 times higher than that of cementitious matrix, indicating that it is recommendable to develop impact-resistant material based on geopolymeric matrix. The influences of NaOH molarity on the impact behaviors of EGC and geopolymeric matrix were discussed. It was found that the impact-resistance of EGC improved with the increase of NaOH molarity, while the threshold of NaOH molarity for geopolymeric matrix was recommended as 12 mol/L. Even though the compressive strength of EGC is lower than ECC, it can be concluded that EGC could have comparable or even higher impact-resistance than ECC under different low-velocity impact conditions.     

Assessment of mechanical and micro-structural characterization of novel ambient cured cement-free composite concrete

To minimize the utilization of natural resources & consuming of huge energy and in order to control the global warming, industrial waste based geopolymer has attracted by the researchers. The manufacturing of GGBS-FA based Geopolymer Concrete (GFGPC) are essential due to its cost-effective reuse by recycling the industrial wastes. The impact of various quantities of Ground Granulated Blast-furnace Slag (GGBS), activator concentration, alkaline solution to solid ratios and liquid ratios of silicate to hydroxide of sodium on experimented mechanical strength and microstructural characterization are investigated. The novelty and research significance lie in adoption of ambient curing techniques, reduced time interval between Alkali Activator Solution (AAS) preparation and concrete casting from 24 h to 3–6. It was observed that with decrease of GGBS content from 70% to 30%, compressive strength at 28 days was reduced from 53 MPa to 36 MPa. A mix containing 40–50% GGBS, AAS to binder ratio of 0.45–0.55, 7 M(Molar) solution of Sodium Hydroxide (SH), ratio of sodium silicate (SS) to sodium hydroxide (SH) of 1.5–2.0 along with 3–6 h of time interval between AAS preparation and concrete casting were proposed as an optimum design mix with respect to compressive strength, workability and setting time. The empirical predictions of splitting-tensile strength and flexural strength of developed GFGPC were made based on the experimental laboratory results and made comparisons with respect to the equations of ACI 318, Eurocode 2, AS 3600 and IS 456 for OPC based conventional concrete (CC_OPC) and others existing literature for GPC. Additionally, XRF, XRD, FESEM and EDS were conducted to investigate the microstructural properties and the reaction mechanism of GFGPC.     

硅酸镁铝及静置时间对3D打印地聚合物砂浆流变性能的影响

以粉煤灰、矿粉、石英砂为主要原材料,无水硅酸钠为碱激发剂,硅酸镁铝为专用外加剂,制备了粉煤灰基3D打印地聚合物砂浆(以下简称地聚合物砂浆),研究了硅酸镁铝掺量及静置时间对其流变性能的影响,并在最佳硅酸镁铝掺量和最适合静置时间条件下进行了3D打印上机试验.结果表明:地聚合物砂浆的流变性能随着硅酸镁铝掺量的增加而增加,且随着静置时间的增加总体呈增长趋势;采用宾汉(Bingham)流体模型和赫切尔-巴尔克(Herschel-Bulkley)流体模型拟合地聚合物砂浆的流变曲线后发现,上述2种模型的拟合度R²均较高,综合考虑后认为,宾汉流体模型比赫切尔巴尔克流体模型更具优越性;掺加1.0%硅酸镁铝和10 min左右静置时间的地聚合物砂浆能够较好地适用于3D打印工艺,且打印效果良好.     

Geopolymerization and Its Potential Application in Mine Tailings Consolidation: A Review

A new class of construction materials has been in development in the past several decades through geopolymerization reactions of aluminosilicate minerals, which can potentially replace ordinary Portland cement (OPC). In this paper, the brief history of the development of the geopolymerization technology was reviewed with particular emphasis on the differences between “conventional” geopolymers, alkali-activated metallurgical slags, and zeolites. Studies on both the raw materials and the alkali activators in the geopolymerization processes were also reviewed. As oil sands tailings and many mine tailings contain aluminosilicate minerals as their main constituents, geopolymerization reactions have been explored as a potential technological route to treat these tailings for tailings consolidation and heavy metal fixation.