Physico-mechanical, structural, and mineralogical analysis of composite concrete incorporating hydraulic lime and pozzolan

Abstract

This study investigates alternatives to Portland cement (PC) through the utilization of pozzolanic materials like natural hydraulic lime and pozzolan in mortar and concrete production, offering both environmental and economic advantages. Natural hydraulic lime is particularly esteemed for its relevance in restoring architectural relics and preserving cultural heritage, while the incorporation of pozzolan and fine and coarse aggregates adds value to local resources. The study employs a range of comprehensive characterization techniques, including physico-chemical, mineralogical, and mechanical analyses such as X-ray fluorescence, particle size assessment, bulk density evaluation, shrinkage testing, water absorption analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and Proctor Normal and compressive strength tests, among others. Five different formulations, varying from 20 % to 40 % hydraulic lime content and a fixed 25.00 % pozzolan content, underwent testing across five curing periods (7, 14, 28, and 90 days). The results underscore the significant influence of curing time and hydraulic lime proportion on the physical, mineralogical, and mechanical characteristics of lime concrete. Scanning electron microscopy reveals a well-structured matrix in samples from various formulations, credited to effective void filling by lime and pozzolan. Furthermore, the identification of C-S-H phases through X-ray diffraction analysis enhances the concrete matrix, leading to a notable increase in compressive strength of up to 22.00 MPa. Water absorption rises with curing time due to the air curing process, fostering the formation of minor surface pores. This research assesses the environmental impact of hydraulic lime concrete across its lifecycle, underscoring the potential of pozzolans and natural hydraulic lime to produce locally-sourced, economical, and environmentally friendly construction materials, thereby contributing to global efforts in reducing carbon emissions.