In some numerical simulations of collisions on concrete, the densification of the pore structure has been assumed to be attributed to collisions. However, a previous experimental study conducted by the authors revealed that the pore structure can be coarsened by impact. The conditions of this coarsening have not yet been clarified. In this study, impact tests were conducted on cementitious materials with and without sand, admixture materials, and with different moisture contents, to understand the influences of these factors on the cracking, pore structure, and compositional changes caused by impacts. In the water-saturated cement paste specimens, mercury intrusion porosimetry showed that the pore structure of the region near the impact point was coarsened. Conversely, the pore structure of the cement paste specimens with low-water content was densified. In the mortar, the pore structure was coarsened in both the saturated and dried specimens. To explain the mechanism of incurred pore structure changes due to collision, mechanical and thermal effects were proposed. These include compaction due to mechanical action, the expansion force generated by liquid-water pressure upon impact, and vapor pressure changes due to heat, respectively. The study’s findings improve our understanding of the responses of cementitious materials subjected to impact loads and allow us to obtain more accurate damage estimations. The findings revealed the necessity of the investigation on the cause of the high-stiffness response at impact other than compaction. If the liquid or vapor pressure caused the pore coarsening at impact, it may be reduced by the effective release of these pressures.

在混凝土碰撞的一些数值模拟中，孔隙结构的致密化被认为是由碰撞引起的。但是，作者先前进行的一项实验研究表明，孔隙结构可能会因撞击而变粗。粗化的条件尚未阐明。在这项研究中，对有或没有沙子，掺合材料以及含水量不同的胶凝材料进行了冲击试验，以了解这些因素对冲击引起的开裂，孔结构和组成变化的影响。在水饱和水泥浆样品中，压汞法显示了冲击点附近区域的孔隙结构变粗了。反过来，低含水量水泥浆试样的孔结构被致密化。在砂浆中，饱和和干燥样品的孔结构都变粗了。为了解释由于碰撞引起的孔结构变化的机理，提出了机械和热效应。其中包括由于机械作用引起的压实，冲击时液水压力产生的膨胀力以及由于热引起的蒸气压变化。这项研究的发现增进了我们对水泥材料在冲击载荷作用下的响应的理解，并使我们可以获得更准确的损伤估计。研究结果表明，有必要调查压实以外冲击时产生高刚度的原因。如果液体或蒸气压力在撞击时导致毛孔粗大，