Optimisation of Production Parameters to Develop Innovative Eco-efficient Boards

Laboratory tests were carried out to define production parameters of innovative eco-efficient composites made up of hazelnut shells as aggregate and a sodium silicate solution as adhesive. The aim was to maximize the content of bio-aggregates and minimize the amount of adhesive, guaranteeing the feasibility of producing samples. Therefore, after preliminary testing, the percentages of hazelnut shells and the sodium silicate solution were kept constant: 70% and 30% of the total volume, respectively. However, the characteristics of the considered composites did not allow the production of uniform samples. The sodium silicate solution was not rapidly absorbed by the bio-aggregates; during the drying process, it was deposited on the bottom side of the samples. The uniformity of the samples is required to guarantee a correct evaluation of their performance and future homogeneous panels. Hence, different production parameters were investigated, such as drying at T = 60 ℃ or T = 80 ℃ during different periods of time, and the addition of different percentages of sodium bicarbonate was also considered. The visual analysis during drying, the final uniformity, thus the distribution of the sodium silicate solution, the resistance and the crumbliness of the samples allowed defining the best production process. The most uniform sample was selected, and its production parameters can thus be applied to produce innovative composites.