The effect of polyamide fibers on the strength and toughness properties of structural lightweight aggregate concrete

This study investigated the effects of single and hybrid use of micro and macro polyamide (PA) synthetic fibers on the workability, compressive, splitting tensile and flexural strength, as well as compressive and flexural toughness of structural lightweight aggregate concrete (SLWAC). The fibers were added into the concrete mixes as 0.25%, 0.5%, and 0.75% by the volume of concrete. Flexural toughness was evaluated in accordance with the JSCESF-4 and ASTM C1018-97 standards. The test results clearly show that while the increase in the splitting tensile and flexural strength of SLWAC was significant, the increase in compressive strength was not notable. Although the compressive and flexural toughness capacity of SLWAC with a low PA fiber content did not increase significantly, the increase in the toughness capacity of SLWAC with a high PA fiber content was remarkable. The JSCESF-4 and ASTM C1018 standards can only be applied to measure the toughness capacity of SLWAC that shows highly ductile behavior after the peak load. Furthermore, the use of PA synthetic fibers in the hybrid form was more effective in enhancing the strength and toughness properties of SLWAC compared to the single form. (C) 2018 Elsevier Ltd. All rights reserved.