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This paper presents a hybrid-fibre-reinforced concrete containing different amounts of steel fibres, nanosilica and multi-wall carbon nanotubes. A combination of fibres in different sizes was considered for bridging and closure of cracks in different stages of the crack growth and improving post-fracture behaviour. Moreover, pozzolanic materials such as nanosilica with high surface energy were employed for increasing the strength of the transition zone. First, investigations were carried out to achieve an optimum mix design and evaluate strength properties and energy absorption capability. Second, impact tests with two types of projectiles were conducted on slab specimens of different sizes and types. In conclusion, the addition of nanoparticles and combination of fibres led to a significant increase in toughness and impact strength.

Recent advances in the development of high-performance insulating composite materials have created a new trend in the construction industry for the production of optimized lightweight structural sections. Although such sections are often found to have enhanced strength-to-weight ratio, their lower fracture resistance and toughness are commonly known to prone lightweight concrete sections to brittle failure with a low capacity to withstand crack propagation.To address this, in this study, six mixes containing lightweight expanded clay aggregates with a small quantity of hooked steel fibers ranging from 0 to 1.15 vol% are produced. As a result, it is found that the inclusion of steel fibers at 1.15 vol% can increase fracture energy and characteristic length by about 20 and 11 times, respectively. The result of this study is found to be significant and point to the development of highly ductile, structural-grade lightweight fiber reinforced concrete through the use of hooked steel fibers.

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