Wang Dongyun, Shen Xuan, Wang Zhiyan, Zhang Xiucheng, Chen Xue-Fei
School of Architectural Engineering, Huanggang Normal University, Huanggang 438000, China.
Huanggang Ecological and Renewable Resources Research, Huanggang 438000, China.
Materials (Basel). 2025 Feb 6;18(3):707. doi: 10.3390/ma18030707.
Herein, we synthesized fly ash aggregates (FAAs) through a hydrothermal synthesis process utilizing fly ash, quicklime, and cement under saturated steam conditions at 180 °C. We systematically investigated the influence and mechanisms governing the physical and mechanical properties of autoclaved FAAs by incrementally replacing cement with quicklime in 5% equal mass intervals. Our results revealed that the substitution of cement with quicklime yielded lightweight aggregates (LWAs) exhibiting water absorption ranging from 1.33% to 22.88% after 1 h and 1.67% to 26.22% after 24 h, loose bulk densities between 847 kg/m and 1043 kg/m, apparent densities spanning from 1484 kg/m to 1880 kg/m, and cylinder compressive strengths varying from 11.9 MPa to 18.5 MPa. Notably, as the proportion of quicklime substitution for cement increased, there was a corresponding augmentation in water consumption during granulation, resulting in an elevated water-cement ratio ranging from 27.5% to 51.39%. This led to an enhancement in the water absorption of the FAAs, accompanied by a decrement in cylinder compressive strength and overall density. The hydration products, including tobermorite and calcium silicate hydrate, contributed to the creation of a dense microstructure within the FAAs. However, with higher quantities of quicklime replacing cement, the content of hydration products increased while the proportion of unreacted fly ash particles decreased significantly. The resultant weakening micro-aggregate effect emerged as a pivotal factor contributing to the observed decrement in the strength of these FAAs. The findings of this research are anticipated to provide significant theoretical insights and technical support for the selection of calcareous materials in the resource-recycling process of fly ash.
在此，我们通过水热合成工艺，在180°C饱和蒸汽条件下，利用粉煤灰、生石灰和水泥合成了粉煤灰集料（FAA）。我们以5%等质量间隔逐步用生石灰替代水泥，系统地研究了其对蒸压FAA物理和力学性能的影响及作用机制。我们的结果表明，用生石灰替代水泥后得到了轻质集料（LWA），其1小时后的吸水率为1.33%至22.88%，24小时后的吸水率为1.67%至26.22%，松散堆积密度在847kg/m至1043kg/m之间，表观密度在1484kg/m至1880kg/m之间，圆柱体抗压强度在11.9MPa至18.5MPa之间。值得注意的是，随着生石灰替代水泥比例的增加，造粒过程中的用水量相应增加，导致水灰比从27.5%提高到51.39%。这导致FAA的吸水率增加，同时圆柱体抗压强度和整体密度降低。包括雪硅钙石和硅酸钙水合物在内的水化产物有助于在FAA内部形成致密的微观结构。然而，随着生石灰替代水泥的量增加，水化产物的含量增加，而未反应的粉煤灰颗粒比例显著降低。由此产生的微集料效应减弱成为导致这些FAA强度下降的关键因素。预计本研究结果将为粉煤灰资源回收过程中钙质材料的选择提供重要的理论见解和技术支持。
