UHTCC单轴受压韧性的试验测定与评价指标

EXPERIMENTAL MEASUREMENT AND EVALUATION INDEXES OF TOUGHNESS PROPERTIES FOR UHTCC UNDER UNIAXIAL COMPRESSION

韧性指标是评价超高韧性水泥基复合材料(简称UHTCC)独特力学性能的重要指标。对比各国关于钢纤维混凝土弯曲韧性的测定与评价标准,该文以美国ASTMC1018标准、德国纤维混凝土标准和奥地利喷射混凝土标准为基础,分别采用等效抗压强度feq,n和开裂后的变形能Anp、韧性等级、评价纤维增韧作用的相对韧性指标RT1和评价UHTCC峰值后韧性的相对韧性指标RT2,从不同的角度详细定量地评价UHTCC的受压韧性性能。通过对棱柱体抗压强度在33MPa―52MPa之间的6组不同抗压强度的UHTCC进行单轴抗压试验表明,随着棱柱体抗压强度的增加,UHTCC开裂后所吸收的变形能和等效抗压强度增加;相对韧性指标计算结果表明添加体积分数为2%的PVA纤维使UHTCC的韧性性能达到相应基体韧性性能的2.6倍―3.8倍;使UHTCC峰值后的韧性性能达到峰值前的1.7倍―2.2倍,并证明纤维的作用主要体现在基体开裂后的韧性提高上;UHTCC的受压韧性等级主要在一级和二级之间。各组韧性指标均证明UHTCC具有较高的受压韧性性能和塑性变形能力,以及开裂后的高荷载承受能力。

Toughness index is one of the important mechanical indexes to evaluate the unique mechanical performance of Ultra High Toughness Cementitious Composites （UHTCC）. Comparing different testing and evaluating standards of flexural toughness for steel fiber reinforced concrete used in various countries,the fiber reinforced concrete standards of America （ASTM C1018）,Deutschland （DBV）,and Austria （ORSp） are referred. Five toughness indexes are used from different points of view to quantitatively evaluate the compressive toughness of UHTCC in detail. These indexes include the equivalent compressive strength feq,n ,the post-crack deformation energy An p,the toughness class,the relative toughness index RT1 for evaluating fiber effect,and the relative toughness index RT2 for evaluating the post-peak toughness of UHTCC. The test results,which are obtained from six groups of UHTCC at different compressive strength between 33MPa and 52MPa,indicate that the deformation energy after cracking and the equivalent compressive strength increase with the compressive strength. The relative toughness indexes of RT1 and RT2 show that the toughness of UHTCC is 2.6―3.8 times of the matrix,and the post-peak toughness of UHTCC is 1.7―2.2 times of pre-peak toughness. The fiber effect mainly improves the post-crack toughness. The toughness classes of UHTCC are mainly between class 1 and class 2. All of the indexes demonstrate that UHTCC possess high compressive toughness and plastic deformation capacity,and high post-crack load bearing capacity.