Influence of different compacting methods on concrete compressive strength

ABSTRACT Adequate compacting is an important stage contributing for the durability and final quality of concrete structures. The two main ways of compacting concrete are: manual and mechanical (immersion vibrator). This paper has the goal of verifying the influence of those two compacting methods on the compressive strength of concrete from long term data. In order to do that, cylindrical test specimens of a same concrete were molded with different compacting methods and the compressive strength was investigated at 1, 3 , 7, 14, 21, 28, 63, 91, 180, 365 and 730 days. Concrete used was casted in plant. Manual compacting was performed using a metallic and cylindrical rod. Mechanical compacting was performed using a rigid immersion vibrator driven by an electric motor. This study confirmed greater compressive strength in test specimens compacted with immersion vibrator, when compared with results in manually compacted test specimens. However, the novelty of this article is that variance analysis test demonstrated that only from 63 days the difference between compressive strengths is significant. Long term data also made it possible to generate a trend equation with good coefficient of determination for estimating the difference between compressive strengths for the two compacting methods investigated over time.

摘要：充分振捣是保障混凝土结构耐久性与最终成型质量的关键工序。混凝土振捣主要分为两种方式：人工振捣与机械振捣（插入式振捣器，immersion vibrator）。本文旨在通过长期试验数据，探究这两种振捣方式对混凝土抗压强度的影响。为此，研究人员采用同一配比混凝土制备圆柱试块，分别通过不同振捣方式成型，并于1、3、7、14、21、28、63、91、180、365及730天龄期下测试其抗压强度。试验所用混凝土均于预制厂浇筑。人工振捣采用金属圆柱振捣杆完成；机械振捣则采用电动机驱动的刚性插入式振捣器完成。本研究证实，相较于人工振捣成型的试块，采用插入式振捣的试块抗压强度更高。不过本文的创新之处在于：方差分析检验结果显示，仅在63天龄期之后，两种振捣方式下的混凝土抗压强度差异才具有统计学显著性。此外，本研究的长期试验数据还可构建拟合优度优异的趋势方程，用于估算随龄期变化的两种振捣方式对应的抗压强度差值。