EVALUATION OF ADDING WASTE PLASTIC FIBERS ON SOME PROPERTIES OF MODIFIED FOAMED CONCRETE

Abstract

Lightweight concrete has superior characteristics, especially in terms of thermal insulation and unit weight, in comparison with normal concrete.The reuse of plastic waste is very important for a sustainable management of solid wastes.This study was undertaken to find ways to enhance some of the properties of foamed concrete through the addition of waste plastic fibers (WPF).The fresh and hardened properties of 1500 kg/m3 foamed concrete mix was tested to determine the optimum mix for constant water-to-binder ratio of 0.35 and cement content of 350 kg/m3. 10%, 20% and 2% of cement replacement with silica fume and Class F fly ash and superplasticizer were made to enhance the strength of conventional foamed concrete. WPF in volume fractions (vf) of 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5% and 1.75% respectively and aspect ratios, L/D, of 40, 60, 80 were added. The results of fibers distribution as well as compressive strength and splitting tensile strength for the 1500 kg/m3 mixes show that the best mix has an aspect ratio ( L/D=60) and volume fraction (vf =1%). Hence, these ratios were used to fabricate mixes with varying densities of 1300, 1500, and 1700 kg/m3. Consistency test was carried out on all mixes under investigation with nominal densities of 1300, 1500 and 1700 kg/m3 to determine their spread diameter. The porosity, absorption, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity and toughness of the mixes were measured at age of 7, 14 and 28 days. In term of all selected densities (1300, 1500 and 1700 kg/m3). The reduction of total porosity for modified mixes were (5.2, 3.7) %, (4.5, 5.2) %, (8.1, 5) % for mixes (Fc3a, Fc3aw), (Fc5a,Fc5aw), (Fc7a, Fc7aw) respectively comparing with conventional mixes Fc3, Fc5 and fc7. The increment of compressive strength for modified were (108, 81) %, (99, 81) %, (64.6, 50) % for mixes (Fc3a, Fc3aw), xi (Fc5a, Fc5aw), (Fc7a, Fc7aw) respectively comparing with conventional mixes Fc3, Fc5 and Fc7. The increment of splitting tensil strength for modified mixes were (55.1, 132.8) %, (74, 99.8) %, (85.8, 125.8) % mixes (Fc3a, Fc3aw), (Fc5a, Fc5aw), (Fc7a, Fc7aw) respectively comparing with conventional mixes fc3, fc5 and fc7. The increment of flexural strength for modified were (88.2, 119) %, (60.8, 88.4) %, (59.3, 125) % for mixes (Fc3a, Fc3aw), (Fc5a, Fc5aw), (Fc7a, Fc7aw) respectively comparing conventional mixes Fc3, Fc5 and Fc7. The increment of modulus of elastisity for modified mixes were (410, 56) %, (334, 230) %, (160, 120) % for mixes (Fc3a, Fc3aw), (Fc5a, Fc5aw), (Fc7a, Fc7aw) respectively comparing conventional Mixes Fc3, Fc5 and Fc7. It if found that Fc7aw has the maximum toughness (14.34) Joule followed by Fc5aw(8.24) Joule and Fc3aw(7.8) Joule has the minimum. Test results showed that the addition of WPF with additives has an advantage effect on the hardened properties of foamed concrete. Significant improvements were observed in the compressive strength, splitting tensile strength, flexural strength, and toughness of the modified mixes.