Using Pozzolanic Materials to Improve Mechanical Properties of Lime-Based Mortar

Abstract

The environmental impact associated with the production of Portland cement has intensifed interest in sustainable alternatives such as lime-based binders. However, their application is constrained by low early strength and slow hardening. This study evaluates rice husk ash (RHA) and sugarcane bagasse ash (SCBA) as pozzolanic additives to enhance the mechanical performance and durability of lime mortars. Hydrated lime was partially replaced (50%) with RHA or SCBA, and the mortars were air-cured for 28 days. Both ashes satisfed the standard pozzolanicity requirements. RHA exhibited a higher amorphous silica content and greater reactivity, whereas SCBA demonstrated slower but sustained pozzolanic activity. The incorporation of these pozzolans signifcantly improved performance. Compressive strength increased from 0.43 MPa for pure lime to 4.64 and 3.84 MPa for RHA and SCBA mortars, respectively. Flexural strength improved from 0.17 to 2.70 MPa and 0.97 MPa for RHA and SCBA mortars,

respectively. Water absorption was substantially reduced in the modifed mortars, indicating improved pore structure and du- rability. RHA provided superior strength development and lower permeability, while SCBA ofered moderate strength en- hancement with improved fexibility. These characteristics make both materials suitable for nonstructural applications, including

heritage conservation and restoration. The fndings demonstrate that agricultural waste ashes can serve as efective, low-carbon pozzolanic materials for durable lime-based construction.