Enhancement of insulating properties of brick clay by renewable agricultural wastes

The use of agricultural wastes (byproducts) in various segments of brick and tile industry is increasing con- tinuously. These additives, which are previously mixed into the raw or compound clay, start to ignite during the firing process, providing extra thermal energy inside the product and decreasing the required external energy need. Besides this effect, the combustion of additives increases the porosity of the final product resulting in enhanced thermal insulation properties. In this paper the effect of some common agricultural wastes (sawdust, rice-peel and seed-shell) on the thermal properties of brick clay products was investigated. The brick samples were prepared from the mixture of the yellow and gray clay in the ratio of 4:1, water content was between 15.57-16.67 wt.% and the pore-forming additives in concentrations 0, 4 and 7 wt.%. To measure the steady state thermal conductivity of the clay mixtures, samples with dimensions of 300×300×50 mm were prepared. Drying and firing were performed using the industrial partner's standard procedures. Precise thermal conduc - tivity data was measured, using a RAPID-K type static thermal conductivity instrument. The results showed that increasing the quantity of agricultural byproducts in the clay mixture significantly decreases the thermal conductivity of the final products, while only a minor reduction in the mechanical strength was observed. It was found that the most efficient byproduct additive was the sunflower seed-shell. With the addition of only 7 wt.% seed-shell to the basic clay the thermal conductivity decreased from 0,27 W/m·K to 0,17 W/m·K (i.e. ~36%).