新拌混凝土振动密实评价指标表征性试验研究

针对混凝土振动密实性尚无统一明确的评价指标问题，通过正交试验研究了不同工况下振动能量、硬化混凝土孔结构、密度、抗压强度、劈拉强度的变化特性，采用方差分析方法比较了各硬化性能指标评价混凝土密实性的表征优劣性，并探讨了原因机理。结果表明，振动时间仅在振动刚开始阶段影响振动强度，此外振动能量在传播过程并非线性衰减，而在振源附近显著减弱；混凝土孔隙率随振源距增加而增大，但在振源处较高，此外相比孔径分布，振动能量对孔隙率竖向分布影响有限；密度仅在距振源8 cm以内变化明显，而抗压、劈拉强度的空间分布呈波动性；相比其他指标，孔隙率较适合作为密实性评价指标，并可基于新拌物物料特性和振动能量构建预测模型。

Experimental study on characterization of evaluation indexes for vibration compaction of fresh concrete

As there is no unified and definite evaluation index for vibration compactness of concrete, we use orthogonal tests to study the characteristics of vibration energy, hardened concrete pore structure, density, compressive strength, and splitting tensile strength under different working conditions. The effects of various hardening property indexes on concrete compaction evaluation are compared and discussed through variance analysis. The results show that vibrating time period influences vibrating intensity only at the beginning of vibration, and vibration energy in propagation does not linearly attenuate but decrease significantly near the vibration source. For hardened concrete, porosity increases with the increasing distance from the source where it takes the maximum. And compared with pore size distribution, vibration energy has less influence on vertical variations in porosity. Moreover, concrete density varies markedly only within a distance of eight centimeters from the source, and spatial distributions of compressive and splitting tensile strengths are featured with significant fluctuations. This study concludes that porosity is a more suitable index for evaluating concrete compactness relative to other indicators and a prediction model can be built based on the characteristics of fresh mixture and vibration energy.