The shrinkage-induced cracking resistance of C30 concretes with different mix proportions was studied using the ring with notch designed to replace the traditional ring in the concrete ring test. The results show that fly ash and expansive agent have little influence on the shrinkage-induced cracking resistance of concrete under the condition of 20℃ and relative humidity of 55%-65% The addition of 15% fly ash has negative effect on the shrinkage-induced cracking resistance of concrete, but the addition of 30% fly ash or 5%-l0% expansive agent is beneficial to the shrinkage-induced cracking resistance of concrete under the condition of 30 ℃ and relative humidity of 34%-40%. Under the condition of 40 ℃ and relative humidity of 20%-25%, the shrinkage-induced cracking resistance of concrete decreases with the increase of adding amount of fly ash; adding proper amount of expansive agent improves the shrinkage-induced cracking resistance of concrete. However, adding excessive amount of expansive agent is harmful to it.%采用带缺口混凝土环开裂试验研究不同C30混凝土的抗干缩开裂性能.试验结果表明:在温度20℃、相对湿度55％～65％条件下,粉煤灰和膨胀剂对混凝土的抗裂性能影响不大;在温度30℃、相对湿度34％～40％的条件下,掺15％的粉煤灰对混凝土的抗裂性不利,掺30％粉煤灰或掺5％～10％的膨胀剂有利于提高混凝土的抗裂性能;在温度40℃、相对湿度20％～25％的条件下,随着粉煤灰掺量的增加,混凝土的抗干缩开裂能力变差;适量掺加膨胀剂有利于提高混凝土抗干缩开裂能力,但当膨胀剂掺量过大时,混凝土的抗于缩开裂能力将变差.
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