MULTI-FUNCTIONAL FEATURES OF POURABLE WOOD-CEMENT COMPOUNDS – MECHANICAL, BUILDING-PHYSICAL, ECONOMIC AND ECOLOGICAL PERFORMANCE Marco Maeder, Daia Zwicky 1 ABSTRACT: Cement-bonded wood products are used in construction since the beginning of the 20 th century. Until today, however, they are essentially applied as non-structural finishing layers, e.g. as support for stucco, as fire protection or acoustic insulation panels, providing good fire resistance, thermal and acoustic insulation properties with a relatively low and thus, structurally advantageous material density. If to be applied structurally, these materials should not be regarded as substitution material for regular structural concrete but rather be used in composite elements. They also exhibit rather low stiffness and strength properties. Structural wood-cement compounds (WCCs) may also provide further functional features e.g. contributing to thermal and acoustic insulation or fire protection, thereby compensating for their reduced mechanical properties. The contribution presents results from different tests performed with the objective to determine short- and long-term mechanical properties, thermal insulation, specific heat capacity, acoustic insulation, and combustibility features of WCC-based constructions. It further examines and assesses the economic and ecological potential of WCC-based structural elements and discusses potential challenges in the structural use of WCCs. KEYWORDS: wood-cement compound, structural properties, short-term, long-term, building-physical properties, combustibility, economic performance, ecological performance. 1 INTRODUCTION 123 The most widely used construction material is reinforced concrete which is heavy, has high embedded carbon, strongly draws upon non-renewable resources, is challenging to re-use, and exhibits rather poor building- physical properties (except for specific heat capacity). A high potential for a more sustainable construction development of building is located in timber-based composite elements. These should, however, not be produced with regular concrete, as this still results in the mentioned disadvantages. Mixes of cement with wood components, so-called wood-cement compounds (WCCs), may be an answer for an even more sustainable evolution of timber-based composite construction. Some of the non-renewable parts (gravel, sand) of concrete are substituted with renewable ones, with the objective to create a light-weight, pourable, self-compacting, cheap, easily recyclable, and thus, “greener” cement-based construction material that also provides further benefits with regard to building-physical properties to be exploited in multi-functional structural elements. This contribution summarizes and complements previous research [1]-[11], and analyzes the potential and 1 Institute of Construction and Environmental Technologies (iTEC), School of Engineering and Architecture of Fribourg (HEIA-FR), Univ. of Applied Sciences Western Switzerland (HES-SO), daia.zwicky@hefr.ch challenges of WCC application in timber construction in view of the expected WCTE audience. 2 CONCPETUAL REFLECTIONS Timber-WCC composite (TWCCC) elements may be an answer to the challenge of finding TCC elements which are more sustainable. Nowadays, WCC elements are usually used as non-structural finishing layer such as fire protection or acoustic insulation panels. As WCC shows rather low stiffness and strength properties [4], this material should be placed in the compressive layer of a TWCCC slab. This allows to increase the stiffness while maintaining a light-weight construction element. Furthermore, it is still possible to recycle the whole element. By combining WCC with timber for internal load-bearing systems, the advantages of both materials may be coupled. Such hybrid elements [8] not only fulfil a structural task but merge all advantages - e.g. fire resistance, thermal and acoustic insulation - of each material (timber and WCC). The low thermal conductivity of WCC allows to retain the stored thermal energy which has a positive effect on life- cycle assessments (LCA). The demand of thermal energy