Feasibility Study on Concrete Sandwich Panels as Innovative Building Systems for Residential Construction

Abstract

The aim of this project was to research and devise a structural configuration of lightweight sandwich panels, which would offer a solution for rapid and economical residential construction in Pakistan. The first phase of the project aimed at optimizing a suitable material configuration for mortar-wythes by integration of Fly Ash (Class-C) and Waste Marble Powder (WMP), which are potential indigenous wastes, to promote sustainability. Three mix recipes consisting of fly ash and waste marble powder replaced at 15% by weight of cement and control mix-recipe were tested for compressive strength, flexural strength, carbonation, chloride-ion penetration, drying shrinkage and flow-ability. The results revealed that all the mix recipes yielded a compressive strength in excess of 25 MPa and flexural strength in excess of 10 MPa, in addition to satisfying the criteria for carbonation, chloride ion penetrability, drying shrinkage and flow-ability, making the optimized mixes suitable for structural layers in sandwich panels. The second phase of this project consisted of devising structural configuration for sandwich panels, fabricating the finalized panel configuration and testing the scaled samples of panels in compression and flexure. Sandwich panels comprising of 50 mm mortar wythes and 80 mm EPS insulation layer with steel connectors spaced at 150 mm were chosen to be the proposed configuration. Four scaled sandwich panels with dimensions 750mm x 300mm x 186mm were fabricated and tested in compression. Moreover, one scaled panel with dimensions 1500mm x 1200mm x 186mm was casted, cured and tested in flexure using three-point bending test. The compression test results revealed sandwich panels were able to withstand compressive forces in excess of 600 kN, whereas the load at first crack during flexure testing was found out to be 32.5 kN. In addition, the thermal transmittance value of the scaled panel was evaluated using Heat flow apparatus and the average thermal transmittance (U-value) was found out to be 0.385 W/m2.k. The results of thermal conductivity test were used to conduct thermal analysis of the proposed panels using ECOTECT software and results revealed over 47.5% reduction in cooling loads, electricity costs, and CO2 emissions during life-cycle of building and over 12 times reduction in CO2 emissions during manufacturing phase when compared to manufacturing of burnt bricks