Mechanical and microstructural analysis of geopolymer composites based on metakaolin and recycled silica

This paper evaluated mechanical and thermal stability of alkali-activated materials obtained from metakaolin and alternative silica sources, such as rice husk ash (RHA) and silica fume (SF), and were reinforced with recycled ceramic particles (RP) obtained by grinding bricks. Specimens were produced, and after 7 days of curing, they were exposed to temperatures between 300 and 1200°C to determine the influence that different percentages of RP had on the mechanical behavior and microstructure of the produced composites. The results showed a reduction in the linear contraction by 10.22% with 20 wt% RP and that the reinforcing materials improved the mechanical performance of the geopolymers after exposure to high temperatures; the compressive strengths reached 137.7 (±11.4)  MPa after being exposed to 1200°C for the matrix based on RHA and 180.6 (±19.15) MPa after being reinforced with 20 wt% RP. The improvement was mainly due to densification and the formation of crystalline products such as leucite, kalsilite, and mullite.     

偏高岭土-矿渣-磷渣地聚合物配比性能的研究

通过正交实验的方法，以地聚合物稠度、凝结时间、胶砂强度为研究依据，以偏高岭土、矿渣、磷渣、碱激发剂用量为研究对象，每个因素取3个水平，分析4个因素在各自水平上对地聚合物性能的影响。试验结果表明，偏高岭土用量是地聚合物稠度的最主要影响因素；偏高岭土和碱激发剂用量是初凝时间的主要影响因素，磷渣和偏高岭土用量是终凝时间的主要影响因素；偏高岭土用量是3 d 抗压强度的主要影响因素，矿渣用量是28 d 抗压强度的主要影响因素。按30%偏高岭土-40%矿渣-30%磷渣-10%碱激发剂制备的地聚合物具有良好的抗碳化性能，但收缩率较普通硅酸盐水泥高。     

粉煤灰基地质聚合物凝结时间的影响因素研究

以粉煤灰为原料,系统研究了水玻璃模数及掺量、水胶比、温度、外掺剂等参数对粉煤灰基地质聚合物凝结时间的影响。研究结果表明,随着温度升高,地质聚合物凝结时间显著降低; 在10 ℃条件下,地质聚合物凝结时间随着水玻璃掺量增加而增加,随水玻璃模数增加先增加后减小,水胶比对地质聚合物凝结时间影响较小,掺入Ca(OH)₂会促进地质聚合物的凝结。在粉煤灰掺量100%、水玻璃模数1.2、水玻璃掺量8%、水胶比0.35、养护温度10 ℃条件下,地质聚合物的初凝及终凝时间分别为65 min和114 min,在养护3 d和28 d后,地质聚合物的强度分别为23 MPa和51.7 MPa。     

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.     

Development of mix design method based on statistical analysis of different factors for geopolymer concrete

The present study proposes the mix design method of Fly Ash (FA) based geopolymer concrete using Response Surface Methodology (RSM). In this method, different factors, including binder content, alkali/binder ratio, NS/NH ratio (sodium silicate/sodium hydroxide), NH molarity, and water/solids ratio were considered for the mix design of geopolymer concrete. The 2D contour plots were used to setup the mix design method to achieve the target compressive strength. The proposed mix design method of geopolymer concrete is divided into three categories based on curing regime, specifically one ambient curing (25 °C) and two heat curing (60 and 90 °C). The proposed mix design method of geopolymer concrete was validated through experimentation of M30, M50, and M70 concrete mixes at all curing regimes. The observed experimental compressive strength results validate the mix design method by more than 90% of their target strength. Furthermore, the current study concluded that the required compressive strength can be achieved by varying any factor in the mix design. In addition, the factor analysis revealed that the NS/NH ratio significantly affects the compressive strength of geopolymer concrete.     

新型节能无机矿物聚合建筑材料研究概况

无机矿物聚合材料是一种新型节能建筑材料,其化学组成与沸石相近,物理形态上呈三维网状结构.由于无机矿物聚合材料具有良好的力学性能,并且耐腐蚀性强,抗渗性好等优点,备受各国关注.介绍了无机矿物聚合材料的国内外发展现状,反应机理以及理化性能,并展望其应用前景.     

CFBC固硫灰地质聚合物强度性能研究

100%以CFBC(Circulating Fluidized Bed Combustion)固硫灰为胶凝材料,采用碱激发方法,选取水玻璃模数、激发剂含碱量、养护温度、养护时间和碱液陈化温度等为变量,系统研究了其对CFBC固硫灰地质聚合物砂浆试块强度性能的影响。结果表明当水玻璃模数为1,养护温度60℃,养护时间3 h,陈化温度为50℃时,砂浆块的抗压强度最高。     

含重金属固废地聚合物的化学药剂改性及其机理初探

以粉煤灰为主要原材料,分别单掺冶金污泥(MS)和城市垃圾焚烧飞灰(MSWIFA),制备了含重金属固废地聚合物,并引入化学药剂对其进行改性,同时进行了机理研究.结果表明:冶金污泥-粉煤灰(FS)地聚合物中冶金污泥的适宜处置量(质量分数,下同)为15%,最佳化学药剂为二硫代氨基甲酸盐(DTCR);城市垃圾焚烧飞灰-粉煤灰(FM)地聚合物中城市垃圾焚烧飞灰的适宜处置量为5%,最佳化学药剂为三巯基均三嗪三钠盐(TMT).化学药剂的掺入抑制了重金属的破坏作用,提高了地聚合反应程度,使产物结构更匀质、致密,提升了固化效果;采用DTCR改性、含15%MS的地聚合物试样FS-15-D和经TMT改性、含5%MSWIFA的地聚合物试样FM-5-T具有良好的抗酸碱侵蚀性能.     

粉煤灰基地聚合物的制备及性能研究

以电厂废渣Ⅱ级低钙粉煤灰为原料,利用碱激发搅拌法制备了粉煤灰基地质聚合物。当水玻璃模数为1.2,nSi/nAl为1.96,养护温度为60℃时,强度最高为41.13 MPa,体积密度为1.66 g/cm3;水玻璃的模数、nSi/nAl、养护温度对地质聚合物的强度、体积密度影响较大,随着参数的增加,抗压强度都表现为先增加后降低的趋势;粉煤灰地质聚合物XRD谱图与原灰相比,在29.508°处出现非晶的漫散射宽峰,且莫来石、石英衍射峰降低,说明地质聚合反应已发生,形成一种“半晶态”物质。