Physicochemical Properties of a Brick Made from Clay Brick Waste/Cement/Rice Husk Ash – Insights from the Microstructure and FTIR Analyses

Masonry units (i.e., bricks or earth blocks) made from agro and demolition waste have become popular day-by-day as a sustainable solution for environmental pollution. At the same time, such developments are also proposed as “adsorptive units” to treat heavy metals and organic dyes in industrial effluent streams. In this regard, a brick made from rice husk ash/cement/clay brick waste has been proposed to serve as both a masonry and adsorptive unit with a compressive strength of 3.61 MPa and 51% water absorption, which is suitable for non-load-bearing applications and can effectively adsorb common pollutants in wastewater (i.e. Pb(II), Hg(II), As(V)). However, the reported adsorption and mechanical properties have not been linked with the brick’s microstructure and surface characteristics. Thus, an in-depth understanding of the brick’s performance is unclear. In this regard, the present study utilizes Scanning Electron Microscopy (SEM) and Fourier Transformation Infrared Spectroscopy (FTIR) techniques to investigate the above. As per study outcomes, a pozzolanic reaction is evident in the brick through SEM and FTIR analyses. The phases portlandite, ettringite and calcium hydroxide phases are visible in the brick after 28 days of development, and the brick’s physical properties (water absorbency and compressive strength) can be correlated with C-S-H and C-A-H phases. Based on FTIR studies, it is evident that active groups (O-H and C-S-H) exist on the brick’s surface to assist the adsorption of Hg (II), Pb(II) and As(V) adsorbates. Keywords: Rice husk ash; Clay brick waste; Brick; Adsorption; FTIR