Thermo-acoustic characterization and porosity evaluation of concrete composite materials based on cement and excavated earth

Using waste materials, especially those of natural origins is crucial for reducing resource depletion. Excavated earth, in particular, appears one of the most widely produced waste products in construction around Europe. The following study aims to reuse this type of earth in buildings, as a component of lightweight concrete, to create an innovative and environmentally friendly material, recovering natural wastes and reducing the quantities of raw materials in the cement mix. This work analyses the thermo-acoustic and porosity performances of two concrete composite materials based on cement and excavated earth, i.e. one (shot-earth) produced by spraying the earth at high pressure on the mix of aggregates, cement, and water, the other one (smart-earth) obtained by directly mixing the earth with the dry elements. Three smart-earth samples, produced by using increasing percentages of nanotubes (0.025%, 0.05%, and 0.1%), were later compared to a reference mix design. Sprayed soil samples have a higher thermal conductivity (around 1.2W / mK), compared to the smart-earth samples, with values between 0.5 and 0.6 W / mK. About transmission loss, it is better on the smart-earth samples, which reaches values around 60 dB. Shot-earth samples have a surface porosity of 20%, while for the smart-earth samples this value oscillates between 40 and 50%. In conclusion, the use of excavated soil in cement mixtures allows for reusing natural waste material. The overall characteristics of this innovative composite allows obtaining building elements characterized by good thermo-acoustic performances, enhancing living comfort.