Short- and Long-Term Performance of Compressed Earth Blocks and Sandwich Panels with Natural Skins

Abstract

A drastic increase in environmental awareness has increased demand for renewable materials, energy efficient design and low embodied energy. Two technologies that purport to address this demand are Compressed Earth Blocks (CEB) and Structural Insulated Panels (SIP). CEBs, a form of earthen masonry, can be a cost-effective, locally produced material that provides high thermal capacity with low environmental impact. There is increasing interest in using the blocks in cold climates. However, CEBs are limited by manufacturing controls and susceptibility to water damage. In this study, various combinations of cement and lime stabilizers were tested with metakaolin, a pozzolan, and Plasticure, a water repellent, to determine the compressive strength when CEBs are dry and fully saturated at unconditioned and freeze-thaw conditioned states. Results showed that the most beneficial additive for improving wet-state capacity was Plasticure. Blocks manufactured with 10% cement and Plasticure yielded the best performance, with a dry unconfined strength of 10.23±0.81 MPa and an 11.6% reduction in strength when wet. When exposed to freeze-thaw cycling, Plasticure reduced variability in strength reduction from 90.9% to 23.5%, and increased strength retention by up to 74.7%. SIPs are becoming increasingly popular because of their light weight, ease and speed of installation, and high thermal insulation capabilities; however, conventional systems are unsustainable due to their reliance on synthetic fibres and petroleum-based resins. This study focused on the short- and long-term performances of Flax Fibre Reinforced Polymer (Flax-FRP) and compared it to Glass-FRP. Then it assessed the replacement of conventional Glass-FRP skins with skins made of Flax-FRP and a resin blend containing epoxidized pine oil. Results showed that Flax-FRP had a tensile strength and modulus of one third the values of Glass-FRP. Using the Arrhenius relationship, it was estimated that Flax-FRP would retain 60% of its tensile strength after 100 years of saltwater exposure at an annual mean temperature of 10°C. Sandwich panels with three layers of flax fibres provided equivalent strength and stiffness, but better deformability, than panels with one layer of glass fibres. Epoxidized pine oil-based skins decreased strength by up to 23% compared to epoxy-based skins.