Analysis of sustainable building materials, their possibilities and challenges

Abstract

Sweden has as the first welfare state signed the petition of having net zero GHG emissions 2045. The construction industry is a large contributor to Sweden’s current GHG emissions and an action plan signed by several construction companies, including Veidekke, has stated several partial goals and one end goal of a construction industry with net zero emissions 2045. At the same time the demand of new residential houses is high. The choice of material affects the GHG emissions during the entire lifetime, making it a key parameter when planning a construction. 80 % of the emissions during a construction origin from the production of the materials used. The R&D intensity in the construction industry is low and the sector is ruled by a high level of competition and low margins. This thesis aimed to investigate more sustainable building materials for bearing parts of multifamily houses, how they compare with conventional materials and challenges facing them. The materials investigated was compared to a reference wall with KPI:s from one construction made by Veidekke. The GHG emission from the reference wall was calculated to be 107 kg CO2-eq/m2wall. The materials were evaluated with the method of Industrial Dynamics to investigate salient and reverse salient properties, lock-ins and important stakeholders. The materials investigated were Cross-laminated timber (CLT) and different types of sustainable concretes. Creating timber concrete hybrids were also explored. CLT currently has a small market share but is a promising material with several beneficial properties. The current development of more sustainable concrete resulted in the investigation of Recycled Aggregates Concrete, Alkali Activated Concrete and the Eco-concrete with reduced amount of cement in favor for limestone powder. A second step was to explore the social and economic challenges for integrating new building materials into the construction industry. As the industry is heavily project based, the timeframe and lack of budget to explore new options acts as barrier. The processes also tend to be repetitive. As of now the industry has made itself path dependent to concrete in a large extent. However, the social acceptance towards CLT is rising and making sustainability a strategic business goal is becoming more important to appeal to the customers. Interviews at Veidekke showed the rising interest of mixing timber and concrete, but also the difficulties of pushing development forward in the industry. The materials and their KPI:s resulted in the further investigation of CLT and Eco-concrete. By stating the salient and reverse salient properties of the materials further analysis could be done. CLT showed the greatest reduction of GHG emissions due to the embodied carbon resulting in a negative GHG emission of -66.2 kg CO2-eq/m2wall. In addition to this the construction time and several other beneficial properties were found. The reduction of GHG emissions of the Eco-concrete is great too, about 50 % comparing with the concrete used in the reference wall. As a concrete the Eco-concrete should also face less barriers as the industry is familiar with the product. Further analysis with tools from industrial dynamics showed the importance of creating incitements for developing the knowledge of a sustainable construction industry. Results also showed that new networks between the manufactures and the building sector is of essence to find and use new materials. Timber and concrete industries have the main responsibility of developing new and more sustainable products. The building sector also have a responsibility of choosing sustainable options. Advocating a diversity of solutions will create a more robust and resilient industry with fewer lock-ins and path dependencies occurring today. The key stakeholders identified from stakeholder mapping was the business developers, the department of purchase, the timber and concrete industry and lastly the customers. Business developers need to pursue projects with clear and tough goals of sustainability. This will increase the chance of succeeding. The department of purchase need to have incitements for mapping sustainable materials and the ability to explore new subcontractors. The results of the analysis show that not a single innovation will solve the goal of having a construction industry with net zero emissions 2045. The key innovation opportunities for CLT is to develop a standardization and modularization comparable with the concrete industry. Improving the fire safety of CLT is also of essence and the development of fire proofing plasterboards and insulation could be a solution. Further research on modified design mixing and the usage of pozzolanic materials like limestone in concrete is also an important way forward. Constructing timber concrete hybrids have also raised great potential both in the literature, analysis and from the interviews to simplify the integration of timber into the market.