Investigating the Commercial Viability of Stratified Concrete Panels

• Main Author: Grange, Peter James Christopher
• Language: en
• Published: University of Canterbury. Department of Civil and Natural Resources Engineering 2013
• Subjects: Concrete; thermal properties; thermal mass; insulation
• Online Access: http://hdl.handle.net/10092/7430

Buildings consume more than 30 percent of the primary energy worldwide with 65 percent of this attributed to heating ventilation and cooling. To help address this, stratified concrete panels (SCP) have been developed to provide insulation without compromising the thermal mass of concrete. SCP is created by vibrating a single concrete mix containing heavy and lightweight aggregates. Vibration causes the heavy aggregates drop to the bottom so that two distinct strata are formed; an internal structural/heavyweight layer providing thermal mass and an external lightweight layer for insulation. SCP incorporates waste products, for both financial and environmental gains, from which technical benefits also result. Stratified concrete panels have been made and tested during past research projects with results suggesting that SCP could be a competitive product in the residential construction industry, an area in which precast concrete systems have not been favoured in New Zealand. Consideration has been given to the specific rheological requirements of the concrete mix design and the hardened properties of the finished panels. This research considers the commercial viability of SCP using an industrial setting. For practicality of the setting, some materials were altered from past laboratory work to materials that are more easily sourced and better understood but with similar properties as those used previously. Several panels were cast at Stahlton precast yard in an effort to optimise the production process. Consistent results were not achieved and a range of stratification levels were produced. This showed that some capital investment is required to commercialise SCP to provide more energy for vibration such that sufficient stratification can be reliably attained. Two panels were then stood up in an exposed area with the exterior facing north to test for warping effects in a practical setting. No measurable warping occurred over this time which concurred with past work and long term readings that were taken of four year old panels. Structural, thermal and durability tests were carried out on panels with a range of stratification levels to assess the sensitivity of these properties to the level of stratification. From this it was found that the panels with better stratification had significantly better thermal properties than those with moderate to poor stratification. Generally the thermal targets for this project were not met with the total thermal resistance (R-values) not meeting current code requirements. In some cases structural properties were improved with better stratification as the structural layer was stronger through better consolidation. Delamination potential increased with stratification and with age. This requires further research to minimise this effect using fibres across the layer boundary. Porosity was increased in the structural layer in the poorly to moderately stratified panels as the structural layer was not consolidated enough due to lightweight aggregate contamination. As with any new innovation, market acceptance is largely governed by public perception. With appropriate marketing as a sustainable energy saving product, SCP has the potential to be competitive in the residential construction market with some capital investment.