Improvement of the Mechanical Properties of an Encrusting Tuff Treated with Sewage Sludge Bottom Ash and Lime

The limitations of some mechanical properties of encrusting tuff, a local material abundant in the southern regions of Algeria, prevent its extensive use in different layers of roads. However, treatment or mixing of tuff with other materials or products can overcome this problem. In this context, this work aims to improve the mechanical strength of the encrusting tuff and reduce its water sensitivity through a mixed treatment with sewage sludge bottom ash (BA) and lime. Several formulations composed of encrusting tuff, BA, and lime were tested in both the short and long term. The results showed that the formulation TL4BA12 (84% tuff + 4% lime + 12% BA) has the best strength in simple compression (Rc) and indirect tension (Rtb) compared to tuff alone and the other tested formulations. This improvement in strength is observed for both short- and long-term periods. At 7 days, the Rc of TL4BA12 reached double that of tuff alone, and itwas triple at 180 days. Additionally, the Rtb of TL4BA12 was approximately four times that of tuff alone at 7 days and more than double at 180 days. The water sensitivity study revealed that the specimens prepared from the treated tuff remain intact after 24 hours of immersion in water. In contrast, those prepared from tuff alone dissolved within 8 to 10 minutes.