Precast concrete

Résumé

Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels for tilt up construction. In contrast, cast-in-place concrete is poured into site-specific forms and cured on site. Recently lightweight expanded polystyrene foam is being used as the cores of precast wall panels, saving weight and increasing thermal insulation. Precast stone is distinguished from precast concrete by the finer aggregate used in the mixture, so the result approaches the natural product. Overview Precast concrete is employed in both interior and exterior applications, from highway, bridge, and hi-rise projects to tilt-up building construction. By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to pr

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https://en.wikipedia.org/wiki/Precast_concrete

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Thermal high performance walls for precast concrete panels

Thierry Voellinger

2013

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The scope of this research includes the development of composite concrete façade elements that are thin, loadbearing and of high thermal performance. The research applies to manufactured precast concrete elements and focuses on improving their structure in terms of their construction but also their cost and environmental impact. During the last four decades, society’s energy efficiency awareness has been steadily growing in everyday life and in scientific circles. The Swiss Federal Institutes of Technology are promoting a plan known as the 2000 Watt Society (Société à 2000 Watts) which would reduce the energy consumption of the country’s inhabitants. In the context of Swiss construction, Minergie type labels are a requirement ensuring improved living conditions at lower energy consumption levels. These new ambitions increase the thermal requirements which in turn lead to the inevitable thickening of the building envelope. In a Swiss urban context, such as the Geneva region in particular, land is increasingly rare and the price of leasable surface continues to rise. As a result, the materials commonly used for insulation are economical but bulky ; they increase the thickness of the façades and significantly reduce the usable surface available for buildings. In an urban context such as this, what is the suitable dimension and fair price of a wall ? The method used was to analyze the strategies that would result in the correct dimensions of high thermal performance walls. Diminishing their width increases the area of livable surface while maintaining the wall’s thermal, static and sustainable standards. The objective was to establish a process for determining the composition of products that carry the Minergie-P and Minergie-Eco label. To this end, several tests and a pilot project for an individual house were carried out using optimum high thermal performance precast concrete walls as a model. The test demonstrated the feasibility of this type of wall. The innovation was to place between the two layers of concrete, a high thermal performance Vacuum Insulated Panel (VIP) type material and a traditional one. This combination allowed optimizing the thickness of the wall while responding to construction constraints. The proportion of the combination of insulation materials was selected according to their thermal performance, environmental impact and price. The goal was to maintain a constant thickness from the stages of project design to its completion. The argument of this dissertation is based on the conviction and the importance to commit to the use of high thermal performance construction materials overall in the future. At present, in the midst of a fossil fuel crisis, this is no longer just an individual concern. Indeed, the scarcity of fossil fuels and global warming are vital and critical problems that can be solved by using appropriate architecture solutions such as heat traps.

EPFL2012

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Facilitating the incorporation of VIP into precast concrete sandwich panels

Andrea Bassi, Matthew Leslie Heitel, Thierry Voellinger

This research focuses on the development of thin, load bearing, composite concrete facade elements containing high performance thermal insulation. A pilot project involving the construction of a detached house has been completed resolving issues related to the construction, production and economic requirements of utilizing vacuum insulated panels (VIPs) within prefabricated concrete facade elements. During the project planning process it was discovered that particular VIP dimensions were necessary for avoiding wasted material and thermal bridging. VIPs produced for facade elements with widths corresponding to architectural modules of 15, 30, and 60 cm and lengths corresponding to 1/3rd of the project height would alleviate these issues. Within the building industry, VIPs are viewed as a viable solution for optimizing the space saving attributes of high performance walls. By correctly sizing mass-produced VIP elements for facade measurement modules, rather than expecting insulation along the border of each sandwich panel to be cut-to-fit, architects can more easily take advantage of the efficiency that VIPs offer when designing prefabricated fa ade panels. Currently, there is a demand for a new market catering to VIP inclusion within fa ade strategies that would facilitate the use of VIPs by architects and planners in building large-scale urban planning strategies. (C) 2014 Elsevier B.V. All rights reserved.

Elsevier Science Sa2014

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EPFL2012