Performance of hybrid steel fibre reinforced concrete :subjected to air blast loading

In Malaysia, most of the buildings are constructed using reinforced concrete. The main problem with the reinforced concrete is that it has a low tensile strength and it’s a brittle material. When subjected to blast loading or attack by the terrorist it will be damaged badly and also cause fragmentation. The fragmentation can lead to substantial injuries to personnel, causing loss of life and also damage to the surrounding area. Therefore, there is need to enhance the capability of the concrete to resist blast loading from any kind of attack and also explosion. Previous research on the behavior of single fibres reinforced concrete under blast loading found that steel fibre has the potential to be used in the blast resistance concrete material. However studies show that the use of a single fibre in the mix improved the mechanical properties of the concrete to a limited level. Many researchers have started using concrete mix by having a combination of two or more fibres which are also known as hybrid fibres that are proportionally mixed. Concrete mixtures of hybrid fibres have the better energy absorption capability than the single fibre. Until now there has been no study carried out by researchers to investigate the potential of using hybrid steel fibre in the concrete mix for the application in blast protective structure and also explosive storage buildings. Therefore this research examines the properties of the hybrid steel fibre concrete focusing on the blast resistance capability of the concrete materials. The methodology is divided into two parts. In the first part the experimental work was conducted to investigate the performance of hybrid steel fibre concrete subjected to air blast loading. A total of twenty one mixes, including one control mix without fibre, with different aspect ratios and steel fibre volume were prepared and tested to obtain the mechanical properties of hybrid steel fibre concrete. In addition to this, ten concrete panels with different aspect ratios were tested under one kilogram of plastic explosive to investigate the performance of the concrete materials under air blast loading. In the second part of the research, simulation work was carried out using AUTODYN simulation program to simulate the blast loading effect on hybrid concrete panel and validate the simulation using experimental data. The results of mechanical properties for hybrid steel fibre with the combination of 70 % long and 30 % short hooked end steel fibre at 1.5 % volume shows that the flexural strength of the concrete was increased up to 114 % and the split tensile strength test was increased up to 67 % . On the other hand the compressive strength of the hybrid concrete was increased up to 24 % as compared with all other mixes. The air blast test result shows that hybrid steel fibre with the combination of 70 % long and 30 % short steel fibre at volume fraction of 1.5 % have the optimum performance to blast loading as compared with the control mix. In the simulation works, hybrid concrete panel with the combination of 70 % long and 30 % short hooked end steel fibre at 1.5 % volume were simulated and the results were compared with experimental results. The simulation results using AUTODYN simulation program are found to be tally with experimental results. Based on the experimental and simulation results a blast resistance concrete material using hybrid fibres was developed. It is recommended that this material to be tested further under internal blast loading.