Impact and blast resistance of ultra high performance fibre reinforced concrete (UHPFRC)

在中央情报局-军情五处峰会呼吁建立特别保护区以防范基地组织在英国发动的壮观恐怖袭击后，伦敦许多最受欢迎的旅游地标都被混凝土包围。2004年夏天，在议会大厦周围设置了混凝土屏障，以防止汽车或卡车炸弹袭击者的自杀式袭击。然而，军情五处正在建议对这些措施进行激进的安全改革，以保护威斯敏斯特宫免受恐怖袭击。人们担心，目前的混凝土障碍物如果被炸毁，即解体并产生弹片，将伤害障碍物后面的任何人，可能会有危险。还有人担心，如果钢屏障不够厚和吸收能量，也可能解体并产生弹片。目前的研究建议将着眼于一种新型的超高性能纤维增强混凝土（UHPFRC），这种混凝土可用于预制重量相对较轻的面板，可抵抗高速冲击（弹丸或车辆）和/或恐怖袭击的爆炸。UHPFRC可由不含粗骨料（即石头）的混凝土混合物生产。高水泥含量和特殊的活性硅砂，以及极低的水含量和减水及其他外加剂，用于生产具有极高抗压强度的混凝土，其强度可达普通混凝土的5-7倍。加入大量（2-4%）短而细的钢纤维可生产出易于生产和使用的混凝土，该混凝土具有很高的抗拉强度和韧性。这种混凝土的抗拉强度是普通混凝土的30-60倍，并且具有很高的延展性。如果爆炸发生在非常靠近传统钢筋混凝土面板的地方，冲击波会穿过面板的局部区域，并可能导致剥落的碎片从背面飞出，伤害附近的任何人。发生在较远的地方的爆炸将导致面板上更广泛的负载，这可能导致更大的弯曲或剪切破坏。利物浦大学的拟议项目将研究UHPFRC的不同配合比设计，以实现拉伸和压缩的最大实际强度，与高韧性和延性一致。由UHPFRC制成的面板将在实验室中在高速局部加载和整体压力加载下进行测试，以模拟附近和远处爆炸的影响。这些测试的结果将被用作输入，以创建一个计算机模型，可用于预测UHPFRC面板在真实的爆炸载荷下的行为。将在巴克斯顿的谢菲尔德大学爆炸实验室对小规模面板进行高爆炸测试，以验证计算机建模的准确性。在项目结束时，将在坎布里亚郡斯帕代达姆的军事爆炸实验室对数量有限的全尺寸面板进行测试，作为预测模型的最后验证。澳大利亚墨尔本的两所相邻大学已经在进行平行研究，但这两个项目仍处于早期开发阶段。两所大学将与英国两所大学建立合作联系，交流成果，并计划进行一次考察访问，讨论所有三个项目的进展情况，并比较成果。

Many of London's most popular tourist landmarks are being surrounded by concrete after a CIA-MI5 summit called for special protection zones to guard against a spectacular al-Qaeda terrorist attack in Britain. Concrete barriers were put up in summer 2004 around the Houses of Parliament to prevent a suicide attack by car or lorry bombers. However, radical security changes to these measures to protect the Palace of Westminster from terror attacks are being recommended by MI5. It is feared that the current concrete barriers could be dangerous if blown up, i.e. disintegrate and create shrapnel that will injure anyone behind the barrier. There are also concerns that a steel barrier could also disintegrate and provide shrapnel if not sufficiently thick and energy absorbing. The current research proposal will look at a novel ultra-high performance fibre reinforced concrete (UHPFRC), which could be used to prefabricate relatively light-weight panels, resistant both to high-speed impact (projectile or vehicle)and/or explosion from a terrorist attack.UHPFRC can be produced from a concrete mix containing no coarse aggregate (i.e. stones). A high cement content and a special reactive silica sand, together with a very low water content and water-reducing and other admixtures, are used to produce concrete with a very high compressive strength, up to 5-7 times as strong as normal concrete. The addition of a large volume (2-4%) of short, fine steel fibres produces a concrete which is easy to produce and use and which has a very high tensile strength and toughness. This concrete can be made between 30-60 times as strong in tension as normal concrete and has a very high ductility.An explosion which occurs very close to a conventional reinforced concrete panel will send shock waves through a localised region of the panel and can cause spalling fragments to come flying from the back face, injuring anyone in the vicinity. An explosion which occurs further away will cause a more widespread loading on the panel, which could cause a much larger failure in bending or shear.The proposed project at Liverpool University will investigate different mix designs for UHPFRC to achieve the maximum practical strength in tension and compression, consistent with a high toughness and ductility. Panels made from UHPFRC will be tested in the laboratory under both high-speed localised loading and overall pressure loading to simulate the effect of both a nearby and far away explosion. Results from these tests will be used as input to create a computer model that can be used to predict the behaviour of UHPFRC panels under real explosion loadings.High explosion tests will be carried out on small-scale panels at the Sheffield University explosion laboratory in Buxton to validate the accuracy of the computer modelling. At the end of the project a limited number of full-scale panels will be tested at the military explosion laboratory in Spadeadam, Cumbria as a final validation of the predictive modelling.Parallel research is already in progress at two adjacent universities in Melbourne, Australia, but both projects are still at an early stage of development. Collaborative links will be set up to exchange results between these two universities and the two UK universities and a study visit is planned to discuss the progress of all three projects and to compare results.