Geomaterials for eco-efficient construction applications: exploring Terra Rossa to design earth-based geopolymer mortar mixtures

This study explores the application of Terra Rossa (reddish clay soil) from the Apulia region (Southern Italy) as a partial replacement for sand to produce one-part geopolymer mortars. Firstly, the work involved characterizing Terra Rossa (TR) using density measurements, granulometry, thermogravimetry analysis (TGA), scanning electron microscopy (SEM), and X-ray diffractometry (XRD) to assess the soil’s properties. Then, for designing geopolymer mortar mixtures, TR was used in two forms, “as received” and sieved to < 1.7 mm, and replaced 50% of the sand component in the mixture. The samples were cured under two conditions: room temperature for 28 days, and another process involving heat treatment at 70 °C for 24 h followed by room temperature curing for 27 days. Mechanical strength, workability (slump), water absorption, and microstructure of the produced geopolymer mortars were examined. The present research highlights the potential of TR as a sustainable and locally sourced feedstock for geopolymer materials synthesis, providing a basis for further exploration of its use in non-structural building and architectural applications and contributing to the advancement of greener construction practices.