Joaquim Simão

Reusing coffee waste in manufacture of ceramics for construction

Abstract This paper aims at studying the influence of different clay/coffee waste mixtures in structural ceramics by incorporating different amounts of spent coffee grounds as an additive. Clay paste with 5, 10, 15 and 20 wt-% of coffee waste was used to mould clay bodies, which were then fired at the temperatures of 900, 1000 and 1100°C. Morphological aspects were evaluated through SEM images, while several laboratory tests provide the physical and mechanical properties. Incorporation of coffee waste increases the water absorption and apparent porosity, and increasing the firing temperature causes an overall decrease in pore size. Samples with up to 10% coffee waste are in the highest grade of mechanical strength standards. The addition of 20% decreases by 70% the thermal conductivity value. The coffee waste residues could be used as a secondary clay raw material to form proper bricks with excellent thermal insulation proprieties.

Rock Finishing and Response to Salt Fog Atmosphere

Seven silicate rocks used as ornamental stones and having different surface finishing were submitted to salt fog atmospheres in order to compare different susceptibilities to alteration. Polished, honed, hammered and flamed finishing types were tested. Rocks come from Portugal, Brazil and Angola and are widely commercialized. Samples covered quartz rich rocks, silica saturated and undersaturated rocks, mono and plurimineralic rocks, coarse and fine grained rocks. Mineral composition, texture and open porosity showed to be important parameters which determine mass loss among samples, but the finishing type was very effective within samples. Mass loss and porosity increase are higher on hammered samples, contrasted with the lowest loss values on polished samples. The effect of surface hydrophobicity and roughness on the samples having polished finishing was also analysed by atomic force microscopy (AFM) and water contact angle (WCA), indicating that texture and mineral diversity influence the hydrophobic character of the rock surfaces.

Marine Aerosol Weathering of Mediterranean Calcarenite Stone: Durability of Ethyl Silicate, Nano Ca(OH)2, Nano SiO2, and Nanostructured Consolidating Products

ABSTRACT Calcarenite stone samples from a historic building (Bizerte, Tunisia) were collected and treated under different environmental conditions with several consolidating products: alkoxysilane (ethyl silicate), a surfactant-templated novel sol–gel, Ca(OH)2, and SiO2 nanoparticles. These were subjected to marine aerosol accelerated aging cycles and studied by several non-destructive tests and techniques to assess the stability of the products. Results show that weathering caused by salt crystallization is not inhibited but it is slowed down due to the enhancement of superficial mechanical properties (surface cohesion and micro-hardness) achieved after one month of treatments application. A high or low relative humidity of the consolidation environment significantly affects the final mechanical and aesthetical physical properties and therefore conditions the durability of the treated substrates, even producing higher damage than observed in the blank specimens, depending on the product.