In this study, the multi-spray lay-up process using normal spray
lay-up method was used to control a volume fraction of fibers and
consistent thickness of layer. Spray lay-up operation was carried
out in accordance with layer-by-layer technique by the multispray
lay-up process up to a specific thickness to control a consistent
thickness (cf. [16]). Details of spraying operation by the multilay-
up process can be found in Ha [16]. The eight concrete specimens
were retrofitted and rehabilitated with the sprayed FRP composite
containing 25% volume fractions of fibers with fiber length
of 30 mm. Finally, proper roll-out work using a rigid aluminum
roller was carefully taken into consideration in the multi-lay-up
process to reduce any entrapped air voids and to make sure the