Keg impact damage to fibre-reinforced paving flags

Abstract

The incidence of cracked and unserviceable paving slabs (or flags) in pedestrian walkways is high, often due to the fact that plain concrete flags cannot withstand impact loading arising from unloading of materials during delivery. Subsequently, lack of maintenance eventually leads to sufficient damage such that a trip hazard develops, creating a public safety issue. For example, in the delivery of beer kegs to hotels, restaurants, bars and nightclubs, the use of a buffer bag to absorb the impact energy of a falling cask is often ineffective, resulting in clearly recognisable cracking patterns in the flags. This paper will describe the crack patterns that arise from cask impact loading on pavements. It will outline how the addition of macro polypropylene or steel fibres into the concrete mix used for paving flags affects the impact response. The extent to which the fibres provide residual post-cracking strength to resist the subsequent vehicle or other loading will also be discussed. Further, a yield-line analysis will reveal the reduced dependency on the contribution of the subgrade to the response when the ductile behaviour provided by the fibres is taken into account.