Compaction and Spall of UHPC Concrete Under Shock Conditions
Compaction and Spall of UHPC Concrete Under Shock Conditions
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DOI：
10.1007/s40870-018-0173-3
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发表时间：
2018-08
影响因子：
1.7
通讯作者：
C. Neel
中科院分区：
文献类型：
--
作者：
C. Neel
几十个冲击实验利用枪驱动，平行板冲击在几种互补配置中产生弱冲击波，被称为“cortuf”的超高性能混凝土（UHPC）。这种UPHC变体是在位于MS维克斯堡的美国陆军工程研究与发展中心（ERDC）开发和制造的，没有纤维增强或粗骨料。材料在0-21 GPa范围内的Hugoniot被报道，尽管在较低的冲击压力下，材料是高度分散的，不传递冲击，导致在传递冲击构建结果时出现一些模糊。与其他混凝土类型的类似研究结果相比，结果表明，未加纤维加固的波特兰水泥基混凝土的冲击性能低于3 GPa，这取决于配方和养护，但高于3 GPa，大多数可以用经验冲击关系US= 2.35 km/s + 1.66 up表示，至少是本研究的最大压力（21 GPa）。此外，在大多数混凝土中存在的三种类型的孔隙中，在所检查的混凝土中，只有被困的空气作为孔隙，在冲击期间被压实。该研究表明，尽管不同等级的混凝土在准静态抗压和抗拉强度方面差异很大，但在动态冲击荷载（单轴应变）下，大多数混凝土具有相似的屈服点，可以描述为~ 0.5 GPa的Hugoniot弹性极限或0.4 GPa的屈服强度。此外，动态确定的抗压屈服点与准静态确定的屈服点（单轴应变条件下）非常接近，这意味着在UHPC中应变率强化很小，但在低强度（常规）混凝土中，动态确定的屈服点远高于相应的准静态屈服点。因此，发现混凝土在高速率单轴应变下的屈服点与无侧限屈服强度无关，其上限为~ 0.4 GPa （HEL = 0.5 GPa）。屈服后压实是应变率依赖于科特以及其他公式的文献数据是可用的。在单轴应变拉伸下，棉花的剥落强度约为50 MPa，与其他地方有限的剥落数据大致一致，并且工作表明棉花的剥落和拉伸行为大致遵循最近其他人提出的趋势。
Several dozen impact experiments were conducted utilizing gun-driven, parallel-plate impacts in several complimentary configurations to produce weak shock waves in an ultra-high performance concrete (UHPC) known as “cortuf.” This UPHC variant was developed and fabricated at the U.S. Army Engineer Research and Development Center (ERDC) in Vicksburg, MS with no fiber reinforcement or coarse aggregate. The Hugoniot of the material in the range of 0–21 GPa is reported, although at lower shock pressures the material is highly dispersive and does not transmit a shock, leading to some ambiguity when conveying the results in the construct of a shock. The results, when compared with similar studies on other concrete variants, suggest that Portland cement based concretes without fiber reinforcement display shock behavior below 3 GPa which is dependent on the formulation and curing, but above 3 GPa,mostcan be represented by the empirical shock relation US= 2.35 km/s + 1.66uPup to at least the maximum pressure investigated in this work (21 GPa). Furthermore, it is shown that of the three types of porosity present in most concrete, in the concrete examined, only the entrapped air acts as porosity that is compacted during the shock. This investigation shows that although different grades of concrete vary widely in quasi-static compressive and tensile strength, under dynamic shock loading (uniaxial strain), most have similar yield points that can be described as a Hugoniot elastic limit of ~ 0.5 GPa or a yield strength of 0.4 GPa. In cortuf, the dynamically determined compressive yield point agrees closely with the quasi-statically determined yield (in conditions of uniaxial strain), implying very little strain-rate strengthening in UHPC, but in low strength (conventional) concrete, the dynamically determined yield is much higher than the corresponding quasi-static yield point. Therefore, the yield point of concrete in high-rate uniaxial strain is found to be independent of unconfined yield strength, and limited to an upper bound of ~ 0.4 GPa (HEL = 0.5 GPa). Post-yield compaction is strain-rate dependent in cortuf as well as other formulations for which literature data is available. In uniaxial-strain tension, cortuf has a spall strength of ~ 50 MPa, in rough agreement with the limited spall data available elsewhere, and the work shows that the spall and tensile behavior of cortuf loosely follows trends recently proposed by others.