矿物微胶囊对水泥砂浆自修复性能的影响

Effect of mineral microcapsules on self-healing properties of cement mortar

  • 摘要: 水泥基复合材料受多种物化因素的影响易开裂,从而影响其耐久性能。提升水泥基复合材料的裂缝自修复性能,是提高其耐久性和降低整个生命周期维护成本的关键。因此,基于结晶膨胀、储水释水、助剂补强三种功能特性,本文以复合膨胀剂、Na-膨润土和滑石粉三种矿物为芯材,碱激发材料(水玻璃激发偏高岭土)为壁材,研发了一种集修复补强一体的全无机微胶囊型水泥基裂缝自修复材料。基于本征力学性能研究,以强度恢复率、裂缝宽度愈合率、裂缝面积修复率为评价指标,探究了微胶囊对水泥砂浆试件裂缝自修复效果的影响规律,通过微观测试分析了修复机理。结果表明,随着微胶囊掺量的增加,砂浆强度呈现先增加后减小的趋势;当其掺量为10%时,砂浆28d抗折和抗压强度最高,较空白组分别提高了6.17%和4.39%。同掺量下,二次养护28d强度恢复率达到了115.5%,35d时30条裂缝的平均面积修复率和归一化裂缝面积修复率分别为100%和72.3%,远高于空白组的55.3%和37.7%。XRD和SEM分析表明,二次养护条件下裂缝处生成了大量的Ca(OH)2、AFt、CaCO3、Mg3Ca(CO3)4以及C-S-H凝胶等微膨胀、高强、胶凝性好的水化产物,从而实现快速填充、修复裂缝和补强。

     

    Abstract: Cement-based composites are prone to cracking under the influence of many physical and chemical factors, which affects their durability. Improving the crack self-healing performance of cement-based composites is the key to improve their durability and reduce the maintenance cost throughout their life cycle. Therefore, based on the three functional characteristics of crystal expansion, water storage and release, and auxiliary reinforcement, this paper developed an all-inorganic microcapsule cement-based crack self-healing material integrating repair and reinforcement, with three minerals, namely composite expansion agent, Na-bentonite and talc powder, as the core material, and alkali exciting material (water glass stimulated metakaolin) as the wall material. Based on the study of intrinsic mechanical properties, with strength recovery rate, crack width healing rate and crack area healing rate as evaluation indexes, the influence of microcapsule on the crack self-healing effect of cement mortar specimens was explored, and the self-healing mechanisms were analyzed through microscopic testing. The results show that the strength of mortar increases first and then decreases with the increase of microcapsule content. When the dosage is 10%, the 28d flexural and compressive strengths of mortar are the highest, which are 6.17% and 4.39% higher than that of blank group, respectively. With the same dosage, the strength recovery rate reaches 115.5% after secondary cured in water for 28 days, and both the average and normalized crack area healing rates are 100% and 72.3%, respectively, at 35d, which are much higher than 55.3% and 37.7% of the blank group. The XRD and SEM analysis show that under the condition of secondary curing, a large number of hydration products such as Ca(OH)2, AFt, CaCO3, Mg3Ca(CO3)4 and C-S-H gel with micro-expansion, high strength and good cementitious properties are generated at the crack, so as to realize rapid filling, repairing and reinforcing of cracks.

     

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