Abstract
Increasing importance is being attached to materials in the life-cycle of a building. In the Netherlands, material life-cycle assessments (LCA) are now mandatory for almost all new buildings, on which basis the building is then awarded a building environmental performance or MPG [Milieuprestatie Gebouwen] score. The objective of this study is to reduce the environmental–economic (shadow) costs of precast reinforced concrete (RC) beams in a conventional Dutch office building, thereby improving its MPG score. Two main optimizations are introduced: first, the amount of concrete is reduced, designing a cavity in the cross-section of the beam; second, part of the reinforcement is replaced with a fibre reinforced polymer (FRP) tube. The structural calculations draw from a combination of several codes and FRP recommendations. Hollow FRP-RC beams (with an elongated oval cavity), and flax, glass, and kenaf fibre tubes yielded the lowest shadow costs. In particular, the flax tube obtained shadow costs that were 39% lower than those of the hollow RC beam (with an elongated oval cavity); which also contributed to decreasing the shadow costs of other building components (e.g., facade), thereby reducing the MPG score of the building. However, this study also shows that it is important to select the right type of FRP as hemp fibre tubes resulted in a 98% increase in shadow costs.
Highlights
The building sector is recognized as having a higher potential than any other to deliver quick, in-depth and cost-effective greenhouse gas (GHG) mitigation
Two optimizations were introduced: first, the concrete volume was reduced by designing various cavities with different shapes in the cross-section of the beam; and secondly, by optimizing the reinforcement, partly replacing it with a fibre reinforced polymer tube (FRP) of different fibres
The precast beam with a circular cavity in the cross-section offered a structurally more resistant result than the precast beam with a rectangular cavity of the same area. This strength gain is explained by the fact that the reinforcement of the circular cavity was surrounded with more concrete compared to the rectangular cavity
Summary
The building sector is recognized as having a higher potential than any other to deliver quick, in-depth and cost-effective greenhouse gas (GHG) mitigation. The environmental footprint of the building sector by percentage consumption comprises 40% energy, 30% raw materials, 25% solid waste, 25% water resources, and 12% land [1]. This sector is responsible for the generation of 860 million tons of waste, which is 34% of all waste produced in the European Union [2]. Buildings are beginning to adhere to higher energy efficiency standards, and as a result, the energy consumption during the operational phase is significantly reduced. Their facades and technical installations require more materials, some of which are highly-energy intensive [5]. It is increasingly important to assess the embodied phase of the building, and especially to consider its construction, when the aim is to improve the life cycle of the building
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