Off-spec fly ash-based lightweight aggregate properties and their influence on the fresh, mechanical, and hydration properties of lightweight concrete: A comparative study
Off-spec fly ash-based lightweight aggregate properties and their influence on the fresh, mechanical, and hydration properties of lightweight concrete: A comparative study
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DOI：
10.1016/j.conbuildmat.2022.128013
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发表时间：
2022-06-03
影响因子：
7.4
通讯作者：
Farnam, Yaghoob
中科院分区：
文献类型：
--
作者：
Balapour, Mohammad;Khaneghahi, Mohammad H.;Farnam, Yaghoob
通过实验室中试生产了一种不合格的粉煤灰基球形轻骨料（LWA），称为球形多孔反应骨料（SPoRA），并对其工程性能（包括比重、干棒单位重量、吸水率、机械性能和孔结构）进行了评估。使用 SPoRA 制备了轻质混凝土 (LWC) 样品，并评估了它们的新鲜性能、机械性能和水化性能，并与使用美国市场上两种商用 LWA 制备的 LWC 样品进行了比较。结果表明，细SPoRA和粗SPoRA的72小时吸水能力分别为16.4%和20.9%，高于两种商业LWA。与商业 LWA 相比，SPoRA 的饱和表面干比重较高，导致相应 LWC 的新鲜密度较高。使用 X 射线计算机断层扫描，在 SPoRA 中观察到大的球形孔隙，类似于商用板岩 LWA 中的孔隙。通过动态蒸汽吸附分析仪表征的 SPoRA 孔径分布表明，97% 以上的孔径大于 50 nm。 SPoRA 的平均散装抗碎强度为 6.8 MPa，小于商业 LWA，可能归因于制造工艺的差异。尽管如此，SPoRA LWC 的 28 天抗压强度为 29 MPa，通过了 ASTM C330 要求，并且具有与用商业 LWA 制备的 LWC 相当的强度，表明 LWA 强度的重要性较低。与使用流动性 >= 18% 的商业 LWA 制备的 LWC 相比，SPoRA LWC 的流动性为 5%。这一观察结果可能与 SPoRA 生产中使用的助熔剂有关。 SPoRA 在 12 天时具有 70% 的水合度，与用商业 LWA 制备的 LWC 相当。
An off-spec fly ash-based spherical lightweight aggregate (LWA), designated as Spherical Porous Reactive Aggregate (SPoRA), was manufactured through a lab pilot-scale production and its engineering properties, including specific gravity, dry rodded unit weight, water absorption, mechanical performance, and pore structure, were evaluated. Using SPoRA, lightweight concrete (LWC) samples were made and their fresh, mechanical, and hydration properties were assessed and compared with LWC samples made using two commercial LWA available in the US market. The results indicated that fine and coarse SPoRA had 72 h water absorption capacities of 16.4 % and 20.9 %, respectively, which were higher than that of the two commercial LWAs. Higher saturated surface dry specific gravity of SPoRA compared to commercial LWAs led to a higher fresh density for the corresponding LWC. Using X-ray computed tomography, large spherical type pores were observed in SPoRA similar to those in the commercial slate-based LWA. The pore size distribution of SPoRA, characterized by a dynamic vapor sorption analyzer, indicated that more than 97 % of the pores had diameters greater than 50 nm. SPoRA's average bulk crushing strength was 6.8 MPa which was smaller than commercial LWA and was potentially attributed to the differences in manufacturing processes. Nonetheless, SPoRA LWC with 28 days compressive strength of 29 MPa passed the ASTM C330 requirement and had a comparable strength with LWC prepared with the commercial LWAs indicating lesser importance for the LWA strength. SPoRA LWC had a flowability of 5 % compared to LWC prepared with commercial LWAs having flowability of >= 18 %. This observation was potentially related to the fluxing agent used in the SPoRA production. SPoRA had a 70 % degree of hydration at 12 days which was comparable with that of LWC prepared with commercial LWA.