Engineering properties and pore structure of lightweight aggregates produced from off-spec fly ash
Engineering properties and pore structure of lightweight aggregates produced from off-spec fly ash
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DOI：
10.1016/j.conbuildmat.2022.128645
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发表时间：
2022-09
影响因子：
7.4
通讯作者：
Mohammad Balapour;Thiha Thway;Newell Moser;E. Garboczi;Y. Grace Hsuan;Y. Farnam
中科院分区：
文献类型：
--
作者：
Mohammad Balapour;Thiha Thway;Newell Moser;E. Garboczi;Y. Grace Hsuan;Y. Farnam
本研究以低钙(F-FA)和高钙(C-FA)废弃飞灰为原料，采用热力学方法设计了轻集料(LWA)的工程特性。表征的LWA性能包括比重、真空吸水率、随时间的吸水率、水解吸率、孔隙率、孔径分布和渗透率。所研究的LWA具有较低的烘干比重，范围在1.22到1.45之间。F-FA LWA的真空吸收率和总开孔率随着助熔剂(NaOH)浓度的增加而降低，而C-FA LWA值则随助熔剂用量的增加而变化。所有LWA都通过了ASTM C1761吸水/解吸要求，可应用于混凝土的内部养护。用X射线计算机层析(XCT)和动态蒸气吸附分析仪(DVSA)表征了LWA的孔结构。结果表明，F-FA LWA的归一化孔隙率为4.0%~11.5%，而C-FA LWA的归一化孔隙率为1.7%~2.8%，归一化孔隙率仅为小于50 nm(胶孔+中孔)。用XCT测量了F-FA LWA的孔径分布，结果表明，随着助熔剂浓度的增加，F-FA LWA的孔径变大，预测的渗透系数增加。对于C-FA LWA，预测的渗透率随着NaOH浓度的增加而增加。由于孔尺寸分布具有较大的变异性，并不遵循特定的增加趋势，C-FA渗透率的增加只能是由于孔连通性的增加。
This study characterizes the engineering properties of lightweight aggregate (LWA) manufactured from low calcium (F-FA) and high calcium (C-FA) waste fly ash that were designed using a previously-developed thermodynamics-guided process. LWA properties that were characterized include specific gravity, vacuum water absorption, water absorption over time, water desorption, porosity, pore size distribution, and permeability. The LWA studied had a low oven dry specific gravity ranging from 1.22 to 1.45. The vacuum absorption and total open porosity of F-FA LWA decreased as the fluxing agent (NaOH) concentration increased while the values for C-FA LWA varied with increasing amounts of fluxing agent. All LWA passed the ASTM C1761 water absorption/desorption requirements for application to the internal curing of concrete. X-ray computed tomography (XCT) and dynamic vapor sorption analyzer (DVSA) techniques were used to characterize the LWA pore structure. It was found that for F-FA LWA the normalized porosity, counting only pores smaller than 50 nm (gelpores + mesopores), ranged from 4 % to 11.5 %, while for C-FA LWA, this same pore size range had porosity ranging from 1.7 % to 2.8 %. Pore size distribution measurements of F-FA LWA using XCT showed that the pores became larger and the predicted permeability coefficient increased as the fluxing agent concentration increased. For C-FA LWA, the predicted permeability increased with increasing NaOH concentration. Since the pore size distribution had greater variability and did not follow a specific increasing trend, the increase in C-FA permeability could only be due to an increase in pore connectivity.