Influence of thermally activated alum sludge ash on the engineering properties of multiple-blended binders concretes

• Heat activated alum sludge ash (AASA) can be classified as a Class N pozzolan.
• The water demand of the ternary mix of OPC, AASA and GGBS is reduced.
• The binary mix of OPC with 15% AASA resulted in maximum compressive strength.
• The compressive strength of AASA ternary mix concrete is higher than the binary.
• The strength gain pattern of the splitting tensile and compressive are similar.

This paper investigates the influence of thermally activated alum sludge ash (AASA) as partial cement replacement on the engineering properties of binary and ternary blended binders concretes that incorporate silica fume (SF), ground granulated blast furnace slag (GGBS) and palm oil fuel ash (POFA). The water/binder ratio for all the types of mixes is fixed at 0.30. The results show that AASA exhibits pozzolanic behaviour and can be classified as a Class N (natural) pozzolan. The binary blended binders with 15% AASA cement replacement increased the compressive and the tensile strength of concrete up to 85.3 MPa and 5.38 MPa at 28 days, respectively, and further increases in the AASA content gradually reduced these strengths. All the ternary combinations performed better than the binary mixes with AASA for the same replacement levels.