Abstract:
The aim of this thesis was to research and develop a structural lightweight concrete by incorporation of rigid polyurethane foam waste as coarse aggregates (5-10 mm), which would offer a solution for eco-friendly and economical construction in Pakistan. In this regard, the first phase of the project aimed at optimizing a suitable concrete mix design and promote sustainability by integration of Polyurethane Foam Waste and Silica Fume, which are potential indigenous wastes. Silica Fume was incorporated as a cement replacement at 0,5,10,15 and 20% by weight of cement. Three mix formulations consisting of polyurethane foam, cement coated polyurethane foam and pumice as coarse aggregates were tested for workability, compressive strength, flexural strength, elastic modulus, absorption, permeable voids, chloride-ion penetration, and drying shrinkage. Pumice based Lightweight concrete was manufactured as control mix for comparison. The results revealed that uncoated polyurethane based lightweight aggregate concrete yielded an air-dry density of 1829 kg/m3 with the corresponding compressive strength of 19.5 MPa and flexural strength of 2.78 MPa at 28 days, in addition to satisfying the criteria for elastic modulus, chloride ion penetrability and drying shrinkage, making the lightweight concrete suitable for structural use. Maximum mechanical strengths were achieved at 10% cement replacement by silica fume. The second phase of this project consisted of analyzing the durability and thermal properties of lightweight aggregate concrete, by testing the samples in freeze and thaw action. Polyurethane-based lightweight concrete demonstrated less internal structure damage against freeze and thaw action. In addition, the thermal conductivity value of the samples was evaluated using thermal conductivity meter and the average thermal conductivity value (K-value) was found out to be 0.371 W/m.k. Scanning Electron Microscope (SEM) analysis was conducted to study the interfacial transition zone and analyze the elemental percentages. Elemental data was comparable in both polyurethane-based concrete and pumice-based concrete. It is believed that utilizing these ‘‘low cost’’ lightweight aggregate helps to lower the cost per unit volume of lightweight aggregate concrete.
