Lightweight and robust both because of the high strength and low specific weight obtained with geopolymers and the double-layer structure incorporating wood

More eco-friendly than concrete panels because of the lower CO2 impact of geopolymers and because of the high amount of inorganic (50%w) and wood waste (40%w) recycled from CDW

More eco-friendly than natural stone cladding panels because they do not rely on non-renewable resources (natural stones) and avoid quarry mining activities which have an high impact on the environment

Aesthetically appealing building optics the ability of geopolymers to replicate fine details from the moulds and their versatility to incorporate different minerals allows to produce high quality surface textures/finishes

One of the main disadvantages of ventilated façade claddings are their typically high weight and cost e.g. in the case of fibre-reinforced concrete panels or natural stone claddings. The high weight means high energy costs for transportation and installation. In addition natural stone claddings rely on exploitation of non-renewable resources and concrete panels have a high CO2 footprint.

In this project we developed ventilated façade cladding panels, 59.5 x 59.5 cm in size, based on the geopolymer technology. The panels are composed of an outer High Density Geopolymer (HDG) layer (8 mm thick) incorporating 50%w of selected CDW and a rear (7mm thick) Wood-Geopolymer Panel (WGP) incorporating 40%w of CDW wood. The panel weights ca 9 kg (25 kg/m2) and has an average density of 1.44 kg/dm3 compared to 2.2-2.5 kg/dm3 for concrete and 2.4-3 kg/dm3 for natural stone (basalt, marble, porphyry, granite).

The role of the HDG layers is to act both as a shield to protect from wind loads, rain, snow/ice and as an aesthetic finishing to define the optics of the building. The role of the WGP layer, bonded to the HDG layer, is to provide the additional mechanical strength to the panel. The WGP is fabricated using a geopolymer binder formulated with metakaolin, slag and sodium silicate and recycled wood chips obtained from CDW through a simple shredding process of wood waste. The WGP layer is produced with a compression technique similar to that used for Cement Bonded Particle Boards (CBPB), substituting the Portland cement binder with the geopolymer binder.

Additives in the nanotechnology field were used to enhanceme the surface properties such as water absorption, self cleaning, anti-bacterial – antimold, thermal behaviour, produced by AMS providing photocatalytic effects, IR reflective or absorption properties, resulting in bio-protection and thermal insulation improvement. The nanoparticles are added in the final stage of production as a coating.

Taking into account current European standardization the mechanical and durability characteristics of ventilated façade cladding panels were tested.

Laboratory testing of WGP layer covers important properties that affect the durability of a product such as bending strength before and after 50 cycles of freezing, dimensions changes after freezing, water absorption, cyclic test in humid conditions, resistance to freezing in the presence of salt. While, HDG layer were tested for water absorption (Capillarity test), water vapour permeability, impact resistance, determination of resistance to carbonation, alkali silica resistance – fast method, alkali silica resistance – slow method, length change of samples exposed to a Sulphate solution, freezing in the presence of de-icing salt resistance, freeze – thaw resistance, determination of bond strength and porosity by means of MIP (mercury intrusion porosimetry).