地下室混凝土外墙开裂预估的探讨

Discussion on Cracks Forecast of Basement Concrete Exterior Wall

地下室混凝土外墙施工期间开裂情况较为普遍,是影响地下室耐久性的主要因素之一。裂缝预估是进行裂缝控制的前提,本文在工程调查的基础上,讨论了基于外约束的裂缝预估理论和基于补偿收缩混凝土的裂缝预估理论,两种理论预估结果的对比表明基于外约束的裂缝预估理论和工程实际情况较为吻合。考虑地下室外墙约束条件、水平钢筋配筋率、补偿收缩混凝土的特点等因素,将两种控制理论结合起来,提出了使用泵送补偿收缩混凝土的地下室外墙裂缝控制指标及其限值,并根据工程调查结果对裂缝控制指标限值进行修正。该指标可近似预测采用补偿收缩混凝土的钢筋混凝土地下室外墙裂缝,较好地满足了施工期间预估地下室外墙裂缝的需要。

Basement concrete exterior wall cracked widely during the stage of construction and cracks were one of the common quality faults which had harmful effects on basement durability. The crack forecast was the precondition of crack control According to the investigation of actual projects, the current crack forecast theories of basement concrete exterior wall have been discussed. The crack forecast theories based on the external restraint condition and the crack forecast theories based on shrinkage-compensating concrete were compared. The results showed that the former is approximately consistent with the engineering facts. The simple and practical crack forecast empirical formula was needed in construction site. Considering the restraint condition, horizontal bar percentage and characteristic of shrinkage-compensating concrete, the crack-controlling parameter and the restricted value of the parameter were brought forward by combining two above crack forecast theories. Furthermore the parameter restricted value was revised according to the investigation results of actual projects. The crack-controlling parameter can approximately predict the cracks on basement exterior concrete wall which adopts shrinkage-compensating concrete and meets the demand of cracks forecast during construction.