粗骨料粒径对混凝土弯拉强度尺寸效应影响的试验研究

为获取粗骨料粒径对混凝土材料弯拉强度及尺寸效应的影响,完成27组素混凝土梁四点弯曲试验,获得粗骨料最大粒径10、20、30 mm,尺寸为100 mm×100 mm×400 mm、150 mm×150 mm×550 mm、200 mm×200 mm×700 mm混凝土试件的弯拉强度,采用Ba?ant尺寸效应理论对试验数据进行分析,提出指数型弯拉强度尺寸效应经验公式。研究结果表明：相同骨料体积率、水灰比和构件尺寸下,混凝土材料弯拉强度随着骨料粒径的增大而降低；各骨料粒径下混凝土弯拉强度均存在尺寸效应现象,小尺寸时尺寸效应现象更显著,骨料粒径30 mm时,混凝土弯拉强度随几何尺寸增大而降低趋势最平缓；Ba?ant尺寸效应率与试验结果吻合较好,但不适用于全尺寸范围,提出的指数型尺寸效应经验公式,在全尺寸范围内能够较好地反映混凝土弯拉强度,可用于混凝土材料弯拉强度尺寸效应预测。

Experimental Study of the Influence of Coarse Aggregate Size on the Size Effect of Concrete Flexural Strength

In order to obtain the impact of coarse aggregate size on the size effect of concrete flexural strength, the four-point bending tests were performed for 27 group specimens. The flexural strengths of specimens with the dimensions including 100 mmí100 mmí400 mm, 150 mmí150 mmí550 mm, 200 mmí200 mmí700 mm and the maximum aggregate size including 10, 20 and 30 mm respectively were obtained. The test data were analyzed by Bazant size effect law, and the index-type size effect law was proposed. The results show that the strength of the specimens decreases with the coarse aggregate size increasing under the same aggregate content, water cement ratio and specimen size. The size effect of concrete strength is apparent for the specimens of three aggregate sizes, and the smaller the specimens size,the more obvious the size effect is. With the specimen size increasing, the strength of specimens with 30 mm aggregate size decreases more gently than others. The Bazant size effect law fits well the test data. However the law is not suitable for the whole specimen scale. Therefore the index-type size effect law was proposed, which could be used to predict the size effect of the flexural strength of concrete in the whole specimen scale.