Incorporation of coffee grounds into clay brick production D. Eliche-Quesada*, L. Pe ´ rez-Villarejo, F. J. Iglesias-Godino, C. Martı ´nez-Garcı ´a and F. A. Corpas-Iglesias This present study has been conducted to assess the viability of mixing increasing amounts of coffee ground as a solid waste material (1–5 wt-%) with raw clay. Samples have been compressed, dried and fired at 950uC for 24 h to laboratory scale. Using coffee grounds as organic residue has been proven to be effective for pore formation in clay body, increasing its insulating properties yet maintaining acceptable mechanical properties. Small amounts of waste (1–2 wt-%) were found to be effective at forming open cell porosity in clay bricks, which results in worse mechanical and thermal insulating properties. However, bricks with higher amounts of coffee grounds (3–5 wt-%) showed lower density levels and, therefore, higher porosity, which is mainly closed cell porosity, which shows higher insulating capacity and suitable mechanical resistance. Optimal results have been found in bricks with 3 wt-% coffee grounds, showing good mechanical, physical and thermal properties. Keywords: Coffee waste, Pore forming, Clay bricks, Environment, Physical, mechanical and thermal properties Introduction At present, the need for a progressive reduction in human produced waste has been reasserted by both social pressure for preserving the environment and high cost for the final disposition of waste. This implies a newly generated interest in using products whose raw material is waste, which may lead to product diversifica- tion and final cost reduction, as well as to provide some industrial sectors with an alternative material. These factors explain why appreciation towards waste materi- als is an increasingly important current issue, which is necessary to clear up problems derived from current development. Once waste has been generated, a wide range of techniques must be applied for its reintegration. The European Union and, in general, developed countries tend to the so called ‘3Rs’ waste hierarchy: reducing the amount of waste one produces and recovering waste which can be reused, recycling by means of multiple available techniques and reusing, directly or indirectly, materials. 1 Building is an excellent industry for the absorption of considerable amounts of solid waste material, not only in the form that they are found but also after being adapted. 2 Building offers several advantages, among which are as follows: being able to absorb huge amounts of material and admitting an enormous range of qualities, which allows setting a wide range of materials, each showing its standardised quality and suitability for a specific use. Research has discovered that base materials, such as polymer, cement and ce- ramic materials, are those most suitable for inertising and neutralising residues by means of encapsulation in their matrix. 3–6 Ceramic products, mainly bricks and tiles, are really heterogeneous since they are formed by clay, with a wide range in their composition. 7 Owing to this, these ma- terials may tolerate considerable amounts of different types of residue, 8 which may help reduce the costs in the building industry. Owing to the environmental regulations, the demand for high insulation capacity bricks is increasing. The decrease in thermal conductivity is a decisive factor for limiting energy demand. One way to increase the in- sulation capacity of the brick is to generate porosity in the clay matrix. 9,10 One of the most conventional ways to reduce the thermal conductivity in the ceramic ma- terial is to modify its microstructure by incorporating lightening, pore forming, organic additives into the clay matrix. 11,12 Coffee grounds are a solid organic residue, widely generated by the service sector, which, at present, is not recycled or is used as a fertiliser in agriculture or for compost production. Therefore, it is necessary to research new applications on this kind of residue. Porous ceramic production may be a significant application for coffee waste. Besides, coffee waste may contribute to autothermal combustion due to its high heating power, which involves lower fuel consumption during firing. Uses of organic residues in brick production in order to obtain porous ceramic bodies with better Departamento de Ingenierı ´a Quı ´mica, Ambiental y de los Materiales, EPS de Linares, Universidad de Jae ´ n, Linares, Jae ´ n 23700, Spain *Corresponding author, email deliche@ujaen.es ß 2011 Institute of Materials, Minerals and Mining Published by Maney on behalf of the Institute Received 27 January 2011; accepted 29 January 2011 DOI 10.1179/1743676111Y.0000000006 Advances in Applied Ceramics 2011 VOL 110 NO 4 225