建筑修复用改性NHL砂浆的抗裂控制与粘结特性

Crack Resistance Control of Modified NHL Mortar for Building Restoration Adhesive Properties

摘要: 本文针对历史建筑修复中天然水硬性石灰(NHL)砂浆易塑性收缩开裂、粘结性能不足等问题，通过掺入生石灰、低碱水泥及稻壳、纸巾纤维等改性材料，系统研究了改性NHL砂浆的抗裂性能与粘结特性。实验设计了8组配合比(C0~C7)，在实验室模拟(大风环境)和现场施工条件下，对比分析了裂缝数量、长度、最大宽度及28 d粘结强度。结果表明：混掺10%生石灰与10%低碱水泥(C3)可显著减少裂缝，而进一步添加5%稻壳纤维和5%纸巾纤维(C5)可实现零开裂；低碱水泥掺量为30% (C6)时粘结强度最优，粘结强度达0.25 MPa。但掺量增至50% (C7组)时因体积失稳引发开裂。现场施工验证了实验室结论，室外环境下纤维的桥连与保水作用有效抑制了恶劣气候引起的开裂。本研究为历史建筑修复提供了一种抗裂性强、兼容性高且可规模化的改性NHL砂浆解决方案，兼具文化遗产保护与工程实践价值。

Abstract: In this paper, to address the problems of natural hydraulic lime (NHL) mortar’s susceptibility to plastic shrinkage and cracking and insufficient bonding performance in the restoration of historical buildings, the anti-cracking performance and bonding characteristics of the modified NHL mortar were systematically studied by mixing quicklime, low alkali cement and modified materials such as rice husk and tissue paper fiber. Eight groups of mixing ratios (C0~C7) were designed, and the number of cracks, length, maximum width and 28 d bond strength were comparatively analyzed under laboratory simulation (windy environment) and on-site construction conditions. The results show that: mixing 10% quicklime and 10% low alkali cement (C3) can significantly reduce the cracks, and further adding 5% rice husk fiber and 5% paper towel fiber (C5) can achieve zero cracking; the bond strength of low alkali cement is optimal when the dosage of low alkali cement is 30% (C6), with a bond strength of 0.25 MPa; however, the dosage is increased to 50% (C7), which triggers the cracking due to the volumetric instability. The field construction verified the laboratory conclusion that the bridging and water retention effects of fibers in the outdoor environment effectively inhibited the cracking caused by severe weather. This study provides a crack-resistant, highly compatible and scalable modified NHL mortar solution for the restoration of historic buildings, which is valuable for both cultural heritage preservation and engineering practice.