The Low Impact Materials and Innovative Engineering Solutions network (LimesNet) was one of two research networks funded recently by the UK Engineering and Physical Sciences Research Council (EPSRC (grant EP/J004219/1)). A 2009 EPSRC review of ground and structural engineering research in the UK identified the need for research networks to identify grand challenges and new innovative research proposals in construction materials and infrastructure engineering. LimesNet, developed and managed by researchers in the BRE Centre for Innovative Construction Materials at the University of Bath, was funded by EPSRC for 13 months from September 2011.
The vision for LimesNet was to create an international multi-disciplinary community of leading researchers, industrialists, policymakers and other stakeholders who shared a common vision for the development and adoption of innovative low impact materials and solutions to deliver a more sustainable built environment in the 21st century. The network aimed to develop material-based solutions capable of delivering a step change in performance and impact necessary for the delivery of carbon dioxide reduction targets. LimesNet also created a forum for knowledge sharing, fostering innovative research ideas through new partnerships and collaborations between academia and industry. The following construction material fields were the focus for the network: cement and concrete-based materials, and their potential substitutes; innovative nano-materials and fibre reinforced composites; low-impact geo-based materials in ground and structural engineering; and renewable (plant-based) construction materials.
Initially LimesNet aimed to recruit 100 members drawn from academia, industry and other stakeholders. Over 70 members participated in the project kick off meeting at the University of Bath in September 2011. Further members were recruited through peer-review networks, targeted emailing, trade events and academic conferences. On completion LimesNet had recruited over 220 individual members, with approximately 40% from non-academic backgrounds and a significant number from outside the UK.
The original EPSRC review identified a lack of international collaboration and awareness as a current weakness in UK research in ground and structural engineering. To address this LimesNet supported 13 international research missions to visit overseas research centres of excellence for information gathering, dissemination of UK work and building of sustainable partnerships. Mission teams reported their findings to network members, facilitated on-going research exchange and contributed to discussions surrounding fundable research projects at themed research workshops and network conferences. This themed issue of Construction Materials presents papers from eight of the international missions undertaken by LimesNet members. The papers cover the four materials themes of LimesNet outlined above.
In the briefing paper Muir Wood (2013) summarises fascinating applications of biological means to improvement of ground materials. Acknowledged approaches range from using bacteria to bind particles together, ground-burrowing meso-scale fauna (e.g. ragworms), and plant roots for reinforcing soil structure. Understanding and developing use of these natural processes in engineering applications is now increasing through research and applications.
In the first paper, Heath et al. (2013) explores the opportunities for using geopolymer concrete in the UK. Geopolymers, also known as alkali-activated cements, have attracted interest in recent years for their potential to deliver concretes with significantly lower embodied carbon dioxide content than conventional Portland and blended cements. Their paper follows a LimesNet supported mission to France and Belgium. Precast construction elements, such as masonry blocks, are identified as early adopter opportunities for geopolymer concretes. Changing patterns in current waste material supply streams are highlighted as risks, with potential alternative supply chains suggested. As the authors note, it seems that we will, however, continue to use Portland cement-based concretes for some time to come.
Understanding the impact of construction materials is key to delivering more sustainable infrastructure. Following a LimesNet mission to Chalmers University in Sweden, a recognised international centre of excellence in life-cycle assessment (LCA), Glass et al. (2013) presents a paper discussing future use of LCA in civil engineering. The lack of LCA knowledge within the construction industry, stemming from limited inclusion within current university curricula, is highlighted. Lessons from Swedish experience are highlighted as a framework for future development of LCA in civil engineering in the UK.
Working under the LimesNet theme of nano-materials Pesce et al. (2013) present a paper on the use of nanolime for the consolidation of weathered limestone surfaces. This research paper, presenting novel experimental results, builds on a LimesNet funded international mission to Italy. The breakdown of historic stone buildings from weathering, pollution and human contact remains a significant problem for authorities responsible for their upkeep. Nanolime is a suspension of colloidal nano-sized particles of calcium hydroxide. Although some improvement in surface hardness was measured after nanolime application, this was found to vary depending on properties and condition of the stone substrate.
Textiles have been used in built environment applications for centuries. Current applications are primarily geotechnical although considerable interest has been shown recently in fabric formwork for concrete structures (Orr et al., 2011). Benefits of this approach include more efficient and interesting elements and improved concrete properties. The paper by Brennan et al. (2013) is an excellent example of the multi-discipline work undertaken in LimesNet, with successful collaboration between a textiles expert, materials scientist and civil engineers exploring the potential for broadening the use of textile formwork in construction. These include possible use of anisotropic textiles for concrete applications and sophisticated 3D woven multi-layer geogrids.
Bamboo is well known for its high strength to weight ratio, exceeding many other natural and industrial materials. However its poor durability, construction challenges and variability remain barriers for its wider use beyond simple vernacular buildings. Following a LimesNet mission to Colombia, Trujillo et al. (2013) report on the development and potential use of lightly modified bamboo, such as laminated panel products, for structural uses. Modern structural bamboo products, akin to glue-laminated and cross-laminated timber products, could provide the basis for much wider uptake of this remarkable renewable resource.
The sixth paper in this themed issue of Construction Materials presents a review of multi-functional nano-materials for construction timber (Ansell, 2013). Nano-material coatings can improve durability and fire resistance of timber materials, with a number already available on the market. The paper highlights problems with existing solutions and proposes that there is scope for increased use of natural lime and clay-based nano-coatings.
Construction materials from renewable, plant-based, resources are naturally hygroscopic, absorbing and releasing water vapour in response to changing environmental conditions. This behaviour is beneficial for indoor conditions as internal relative humidity conditions are often buffered to levels most beneficial to human health. The use of bio-based insulation materials, including wood fibre, hemp quilt, straw and hemp-lime, has grown in recent years. Lawrence et al. (2013) presents an overview of the benefits of natural insulation materials and presents novel data on dynamic performance. As a low carbon dioxide renewable resource the use of bio-based insulation materials will continue to develop.
Following the international missions a series of four two-day research workshops, along the themes outlined above, were held in April–May 2012, with over 150 delegates participating, including international participants. The workshops aimed to generate creative groundbreaking proposals from inter-disciplinary interaction as well as explore in a more generic basis, barriers to inter-disciplinary working and identify research opportunities to maximise future collaboration. The workshops produced key interdisciplinary research topics as well as seeding ideas for future proposals. Following a competitive process, EPSRC subsequently funded two large research projects generated from the international mission and workshop activities of LimesNet. Materials for Life (Biomimetic multi-scale damage immunity for construction material (EP/K026631/1)), led by Cardiff University, aims to develop self-healing solutions for concrete. Duracomp (Providing Confidence in Durable Composites (EP/K026925/1)), led by University of Warwick, aims to enhance confidence in the durability of advanced composite materials.
Finally, we acknowledge the support of the EPSRC in supporting LimesNet, the significant contributions of the Management Board members, the hard work of various colleagues at the University of Bath, and finally all LimesNet members for their support and contributions. Further details on LimesNet can be found at http://www.limesnet.org.
