Unbonded Capping for Concrete Masonry Units

Mechanical characterisation of masonry in existing structures by means of laboratory and in-situ experimental techniques

“…Another reason is that specimens capped with sulphur-filled exhibited similar compressive strength than those capped with cement mortar in previous research on concrete specimens [156,157]. The use of unbonded Neoprene pads [8] was also not considered in this research because its use has been highly questioned [59,105,136,141,142,158]. Instead, two other novel testing procedures were proposed in this research to reduce the friction effect, i.e., covering with gypsum powder, and inserting two oiled leaves of PTFE.…”

“…Drysdale et al [140] evidenced that specimens tested with hard capped materials (gypsum plaster) produced higher experimental strengths, without establishing a relationship with those capped with soft materials like fibreboard. Crouch et al [141] studied the use of the Neoprene pads in concrete masonry units in 1999, reporting a 20% reduction in strength for the specimens tested with Neoprene pads compared to those tested with gypsum cement caps, due to the excessive expansion of the Neoprene pads. In 2010, Lourenço et al [55] recommended the use of oiled PTFE leaves to reduce the confinement while testing solid fired clay bricks.…”

“…Richardson in concrete specimens [127] and Crouch et al in concrete units [141]. The capping Neoprene can produce higher confinement in the centre of the specimen than in the borders, as analysed by Braga et al [143].…”