Study on Quality Control Methods for High Performance of Extremely Dry Concrete

本文旨在探讨如何控制极干混凝土的质量。现场压实使用重型振动压路机进行，可将碾压混凝土的孔隙率降低到相对较低的值。低孔隙率混凝土具有高强度和长期耐久性的特点，因此，优化压实工艺以使压实材料充分密实是非常重要的，本文采用作者开发的压实度试验方法来评价压实效率和评价最佳配合比。对极干混凝土压实特性的评价表明，最大压实是通过振动混凝土超过2.5 G的最小加速度来实现的。同一混合料的极干混凝土，即使振捣条件不同，其压实力与填充体积比的关系也是恒定的，并提出了一种压实函数。最佳砂集料比为 ...更多信息 通过对压实功的评定，可选择出压实功达到98%的填充体积比，其值与锤击试验和VB试验的结果相吻合。探讨了细集料和粉煤灰作为混合料的掺合料对混合料压实性能的影响，以及混合料的单位掺量对混合料压实性能的影响，并通过室内模型试验探讨了表面振动器的压实机理。表面振动器传递到压实层的加速度减小，频率趋于恒定。但由于混凝土的稠度和振捣条件的不同，压实层的加速度响应有时会减小。当振捣器的激振力超过其自身重量时，振捣器对加速度的响应不足，因此采用较重的振捣器有利于有效压实。刚性支承使压实层中的加速度和密度分布较陡，但上层孔隙率较低。弹性支撑使上下层的加速度和密度差异较小。通过对比压实度试验结果，对实例变形法预制混凝土构件的配合比进行了评价。少

The aim of this study is to discuss how to control the quality of extremely dry concrete. Compaction in the field is carried out using heavy vibratory rollers which can reduce the porosity of roller compacted concrete to relatively low values. Low porosity concrete leads to high strength and long term durability and thus it is important to optimize compaction procedures so that the compacted material is adequately packed.In this research, a compactibility test method developed by the authors is used to assess the efficiency of compaction and to evaluate the optimum mix proportion. The evaluation of the compaction character of extremely dry concrete show that maximum compaction is achieved by vibrating the concrete over 2.5 G of minimum acceleration. The relationship between compaction effort and filled volume ratio of a same mixture of extremely dry concrete is constant even if vibrating condition is different, and a compaction function is proposed. The optimum sand aggregate ratio is … More able to be selected by assessing the compaction effort attain 98% of filled volume ratio and the value is coincided to that from hammer test and VB test. The effects of fine aggregate and fly-ash as admixture on the compactibility is discussed as well as unit content of mixture too.Compaction mechanism of surface vibrator is discussed on laboratory medel test. The acceleration transmitted to compacting layr from surface vibrator decreases, and the frequency seems to be constant. But depending on a consistency of concrete and vibrating conditions the response of acceleration in the compacting layr diminish occasionally. As this lack of response of acceleration occurs when the exciting force of vibrator is over its weight, a heavier vibrator is advantage to effective compaction. Rigid support makes steeper distribution of acceleration and density in compacting layr but the porosity of upper layr is low. On the other hand springy support makes small difference in acceleration and density between upper and bottom layr.Mix proportion of precast concrete units manufactured by instance deform method is evaluated by comparing the results of compactibility test. Less