Effect Steel Fibre Content on the Load-Carrying Capacity of Fibre-Reinforced Concrete Expansion Anchor

The article presents the pull-out strength tests carried out on M10 expansion anchors in non-cracked and cracked concrete with a crack width cw = 0.30 mm. The breaking loads and the average pull-out strength of anchors in fibre-reinforced concrete substrates were determined. Fibre content ratios of 15, 30 and 50 kg/m3 were used. In addition, two different classes of concrete (C20/25 and C50/60) were tested. The addition of steel fibres caused a decrease in the pull-out strength by 5% for non-cracked concrete of C20/25 class and fibre content up to 30 kg/m3 and a further 7% for the remaining specified dosage. While for concrete of the C50/60 class, it a decrease in the pull-out strength of up to 20% was observed. For cracked concrete class C20/25 with crack initiation cw = 0.30 mm, the reduction was from 9% to 16% in relation to non-cracked concrete and a maximum of 18% for the fibre content of 50 kg/m3. The difference between the tensile load capacity of C50/60 class cracked and non-cracked concrete was lower than 5% and fell within the measurement error.