IMPROVING BRICK-TO-MORTAR BOND STRENGTH BY THE ADDITION OF CARBON-FIBERS TO THE MORTAR

The addition of short carbon fibers in the optimum amount of 0.5% of t he cement weight to mortar increased the brick-to-mortar bond strength by 150% under tension and 110% under shear when the gap between the a djoining bricks was fixed, and by 50% under tension and 44% under shea r when this gap was allowed to freely decrease due to the weight of th e brick above the joint. This effect is attributed to a decrease of th e drying shrinkage by the fiber addition. The drying shrinkage decreas e was particularly large at 2 to 24 h of curing. At 24 h, the shrinkag e was decreased by 50% by the addition of fibers in the amount of 0.5% of the cement weight. Fibers in excess of the optimum amount gave les s bond strengthening due to increased porosity in the mortar. (C) 1997 Elsevier Science Ltd.