古城墙黏合剂之一糯米粉糊化及剥离强度研究

以砌古城墙用的黏结剂之一糯米粉为原料,采用快速黏度分析仪（RVA）糊化淀粉,研究不同浓度、搅拌速率、搅拌时间和最高温度对糊化曲线的影响.结果表明：随着浓度的增加,最低黏度和峰值黏度与最终粘度相差越大,即衰减值和回生值分别增大,说明糨糊的稳定性差、冷却后凝胶性强.随着最高温度变高,峰值黏度升高,峰值时间减小;随着搅拌时间和速率的增加,最终黏度下降,说明剪切力影响其黏度.利用物性仪测试了不同陈化时间对成糊淀粉黏结力的影响.陈化时间越长,胶体不易凝集,形成清稀的胶状.糊化淀粉随陈化时间增加发生大分子链降解或重结晶等不同程度的老化,表现为剥离强度减小,粘附性下降.以上实验分析与研究给古城墙修复提供了理论依据.

A Study of the Gelatinization of Glutinous Rice as Adhesive and its Degree of Peeling off

With RVA, the study uses glutinous rice to analyze different factors that influence the curve of gela- tinization, including density, rate of stirring, length of stirring and highest temperature. The findings show that the adhesive＇ s stability is weak while the degree of adhesiveness is high after cooling down; with the increase of tem- perature the apex of adhesiveness also rises, although the length and rapid of stirring decreases adhesiveness. Also, the ageing decreases the adhesiveness of the material, which results in the downgrading of the degree of peeling off and adhesiveness. The findings provide theoretical foundation for ancient city wall＇ s repair.