Zhang Guang-Zhu, Lee Han-Seung, Wang Xiao-Yong, Han Yi
Songsim Global Campus, Catholic College, The Catholic University of Korea, Bucheon-si 14662, Korea.
Department of Architectural Engineering, Hanyang University, Ansan-si 15588, Korea.
Materials (Basel). 2021 Feb 3;14(4):718. doi: 10.3390/ma14040718.
This study clarifies the effects of pre-soaked zeolite sand as an internal curing material on the hydration, strength, autogenous shrinkage, and durability of alkali-activated slag (AAS) mortars. The liquid-to-binder ratio (L/b) of all of the AAS mortars was 0.55. Sodium hydroxide solution was used as an alkali activator and an internal curing liquid. Calcined zeolite and natural zeolite sand replaced the standard sand at 15% and 30%, respectively. The setting time, autogenous shrinkage, compressive strength, ultrasonic pulse velocity, and surface electrical resistivity were tested. The following conclusions were drawn: (1) The addition of zeolite significantly reduces the autogenous shrinkage of AAS mortar. Compared with the control group, 30% calcined zeolite reduced the autogenous shrinkage by 96.4%. Moreover, the autogenous shrinkage of the AAS mortars was noticed in two stages (a variable temperature stage and an ambient temperature stage), and the two stages split at one day of age. (2) The compressive strength of all of the specimens increased as the zeolite sand content increased, and the highest compressive strength was obtained for AAS combined with 30% natural zeolite sand. (3) Internal curing accelerated the formation of the second peak of heat flow and reduced the accumulated heat release. (4) Calcined zeolite sand delayed the setting time of the AAS mortars. (5) The addition of zeolite significantly reduced the surface electrical resistivity of the AAS mortars. In summary, zeolite sand is extremely useful as an internal curing agent to reduce autogenous shrinkage and to increase the compressive strength of AAS mortars.
本研究阐明了预浸泡沸石砂作为内部养护材料对碱激发矿渣（AAS）砂浆的水化、强度、自收缩和耐久性的影响。所有AAS砂浆的液固比（L/b）均为0.55。氢氧化钠溶液用作碱激发剂和内部养护液。煅烧沸石和天然沸石砂分别以15%和30%的比例替代标准砂。测试了凝结时间、自收缩、抗压强度、超声脉冲速度和表面电阻率。得出以下结论：（1）沸石的加入显著降低了AAS砂浆的自收缩。与对照组相比，30%煅烧沸石使自收缩降低了96.4%。此外，AAS砂浆的自收缩在两个阶段出现（变温阶段和常温阶段），且两个阶段在龄期1天时分开。（2）所有试件的抗压强度均随沸石砂含量的增加而提高，并在AAS与30%天然沸石砂组合时获得最高抗压强度。（3）内部养护加速了热流第二峰值的形成并减少了累积热释放。（4）煅烧沸石砂延迟了AAS砂浆的凝结时间。（5）沸石的加入显著降低了AAS砂浆的表面电阻率。总之，沸石砂作为内部养护剂对于降低AAS砂浆的自收缩和提高其抗压强度极为有用。
