【摘要】 为研究混凝土早期塑性收缩发展机制，探究不同的减缩抑制剂对混凝土收缩及裂缝发展的控制效果，分析水泥净浆的裂缝发展状态及主应变变化规律，分别选用再生混凝土微粉、碳化再生混凝土微粉、氧化镁基膨胀剂、聚乙烯纤维作为掺入材料，按照相应配合比拌合水泥净浆；通过二维非接触数字图像方法(2D-DIC)研究了不同净浆的收缩裂缝发展历程，定量评价了不同工况下试件中线位置最大主应变的变化趋势；最后通过扫描电镜对不同掺料作用下的裂缝开展状态进行评估。结果表明：不同材料对混凝土早期塑性收缩的裂缝发展影响不同；掺入再生混凝土微粉与碳化再生混凝土微粉均能有效抑制水泥净浆的早期塑性收缩，碳化后的再生混凝土微粉较普通再生混凝土微粉能够进一步提升水泥净浆的收缩控制效果，裂缝出现时间延迟了10 min;加入聚乙烯纤维可有效提高塑性开裂的发展时间并减少裂缝的开展宽度；随着浇筑时间的增加，最大主应变逐渐增大，在4.5 h后达到0.033 80;不同掺加剂对主应变的发展趋势影响各不相同，掺入碳化再生混凝土微粉工况下最大主应变在4.5 h时为0.027 95,能够使塑性最大主应变降低17.30%;无掺加剂的水泥净浆中裂缝往往呈现主裂缝贯通、其余裂缝分散分布的特征；掺入碳化再生混凝土微粉的情况下，裂缝之间的连接性增强，表明碳化再生混凝土微粉的掺入有效降低了水泥基材料的早期塑性开裂程度。更多还原

【Abstract】 In order to study the early plastic shrinkage development mechanism of concrete, explore the control effect of different shrinkage reducer on concrete shrinkage and crack development, and analyse the crack development state and principal strain change law of cement paste, the recycled concrete powder, carbonated recycled concrete powder, magnesium oxide-based expanding agent, and polyethylene fiber were selected as admixtures, and cement paste was mixed according to the corresponding mix ratio. The shrinkage crack development process of different pastes was studied by two-dimensional digital image technology(2D-DIC), and the change trend of the maximum principal strain at the midline position of the specimen under different working conditions was quantitatively evaluated. Finally, the crack development state under the action of different admixtures was evaluated by scanning electron microscopy. The results show that different materials have different effects on the crack development of early plastic shrinkage of concrete. The addition of recycled concrete powder and carbonated recycled concrete powder can effectively inhibit the early plastic shrinkage of cement paste. The carbonated recycled concrete powder can further improve the shrinkage control effect of cement paste compared with ordinary recycled concrete powder, and the crack appearance time is delayed by 10 min. The addition of polyethylene fiber can effectively increase the development time of plastic cracking and reduce the width of crack development. With the increase of pouring time, the maximum principal strain gradually increases and reaches 0.033 80 after 4.5 h. The effects of different admixtures on the development trend of principal strain are different. Under the condition of adding carbonated recycled concrete powder, the maximum principal strain is 0.027 95 at 4.5 h, which can reduce the maximum plastic principal strain by 17.30%. The cracks in cement paste without admixtures often show the characteristics of main crack penetration and scattered distribution of other cracks. When adding carbonated recycled concrete powder, the connectivity between cracks is enhanced, indicating that the addition of carbonated recycled concrete powder effectively reduces the degree of early plastic cracking of cement-based materials.更多还原