Integrated evaluation of strength and moisture resistance in fly ash-bound rammed earth with incineration slag aggregate, Master´s Thesis Manish Jaiswal

This thesis investigates the use of recycled materials, such as incineration slag and fly ash, in rammed earth construction as a sustainable alternative. The study focused on evaluating the strength, durability, and moisture resistance of stabilized rammed earth mixes using incineration slag as the aggregate and fly ash as the binder.

Various binder-to-aggregate ratios, moisture content, and aggregate mixes were tested. Key tests included uniaxial compressive strength (UCS), freeze-thaw resistance, ultrasonic pulse velocity (UPV), and calorimetry. The best performance was observed in a mix with a 1:4 binder-to-aggregate ratio and 16 % water, using incineration slag, crushed concrete, and Nilsiä sand, achieving a UCS of 11.1 MPa after 28 days. In comparison, mixes with only incineration slag reached 5.21 MPa. After 15 freeze-thaw cycles, the UCS of the 1:4 incineration slag only mixes increased by 41 % to 7.33 MPa, while the 1:5 mix increased by 33 % to 5.96 MPa. Hydrophobization reduced capillary water uptake by about 96 %.

Calorimetry tests indicated that higher binder content and adequate water significantly improved hydration. The 1:4 mix with 20 % water released about 220 J/g binder after 72 hours, while the same mix with 17 % water released 190 J/g binder, indicating more complete hydration and better pozzolanic activation of the fly ash. Further research is needed to assess the long-term performance of hydrophobization treatments and moisture control, as well as their application at a larger scale.