Application of rice husk in the development of new composite boards Julieta António a,⇑ , António Tadeu a,b , Beatriz Marques b , João A.S. Almeida b,c , Vasco Pinto d a ADAI – LAETA, Department of Civil Engineering, University of Coimbra, Pólo II, Rua Luís Reis Santos, 3030-788 Coimbra, Portugal b ITeCons – Institute for Research and Technological Development in Construction, Energy, Environment and Sustainability, Rua Pedro Hispano s/ n., 3030-289 Coimbra, Portugal c Chemistry Centre, Department of Chemistry, University of Coimbra, Portugal, Rua Larga, 3004-535 Coimbra, Portugal d LogAcústica, Consultores Associados, Lda, Largo da UTIC, 100 – F5, 4430-246 Vila Nova de Gaia, Portugal highlights  Rice husk waste is an abundantly accumulated agro-industrial waste product.  Composites made from rice husks, expanded cork and recycled rubber granules.  Weighted reduction in impact sound pressure level ranging from 20 dB to 27 dB.  Thermal conductivity varying from 0.060 to 0.074 W/(m.°C). article info Article history: Received 30 August 2017 Received in revised form 12 April 2018 Accepted 4 May 2018 Keywords: Recovery of rice husk Rice husk composite Thermal and acoustic properties abstract The main objective of the paper is to propose a new composite material incorporating rice husk. This paper reports an experimental study on the mechanical, thermal and acoustic performance of new com- posite boards made of rice husk waste intended for construction applications. In this study, rice husk was mixed with expanded cork granules or recycled rubber granules in 50/50 and 75/25 (weight percent) pro- portions. A TDI-based polyurethane pre-polymer was used as binder in 20% of the mass of the fillers. A sufficient number of small boards were produced to perform small-scale tests and assess properties such as compressive strength, thermal conductivity, dynamic stiffness, improvement in impact sound insula- tion, sound absorption and transmission loss. The results are very interesting, in particular: the thermal conductivity, at 10 °C, varies from k 10 = 60.0 mW/(m.K) to k 10 = 74.3 mW/(m.K); the weighted reduction of the impact sound pressure level, DL w , ranges from 20 dB to 27 dB; the noise reduction coefficient (NRC) ranges from 0.15 to 0.45, with maxi- mum sound absorption coefficient of 0.96 for composite B1. These results suggest that optimized con- struction solutions based on these composite materials could improve the thermal and acoustic performance of buildings. Ó 2018 Elsevier Ltd. All rights reserved. 1. Introduction In general, a large amount of resources is consumed over the life-cycle of a building, including the exploitation of raw materials and manufacture of construction products in the design, construc- tion, use, renovation and demolition stages. This is responsible for significant negative impacts on the environment and people. According to a Communication from the European Commission [1], about half of all extracted materials and energy consumption in the EU are accounted for by the construction and use of build- ings. The sector also generates about one third of all waste. This is why authorities and researchers have been advocating the design of more sustainable materials and buildings. Furthermore, several authors have suggested that one of the most effective approaches to reducing resource consumption in buildings would be to incorporate recycled materials, materials made from waste and renewable materials [2–4]. Safiuddin et al. [5] presented a comprehensive review of the major solid waste products (e.g. agro-industrial, industrial, min- ing/mineral) and the potential for their use as alternative construc- tion materials, which would help to improve environmental performance and to reduce construction costs. Agrawal et al. [6] presented a more specific review of using industrial waste in con- crete and mortars by partially replacing cement and fine aggre- gates, and the impact of this on the mechanical properties. Examples of analysed waste materials include rice husk ash, fly ash, sewage sludge ash, paper mill sludge ash, quarry powder, rub- https://doi.org/10.1016/j.conbuildmat.2018.05.028 0950-0618/Ó 2018 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: julieta@dec.uc.pt (J. António). Construction and Building Materials 176 (2018) 432–439 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat