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

Abstract

Masonry units (i.e., bricks or earth blocks) made from agro and demoliti on waste have become popular day-by-day as a sustainable soluti on for environmental polluti on. At the same ti me, such developments are also proposed as “adsorpti ve units” to treat heavy metals and organic dyes in industrial effl uent 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 adsorpti ve unit with a compressive strength of 3.61 MPa and 51% water absorpti on, which is suitable for non-load-bearing applicati ons and can eff ecti vely adsorb common pollutants in wastewater (i.e. Pb(II), Hg(II), As(V)). However, the reported adsorpti on and mechanical properti es have not been linked with the brick’s microstructure and surface characteristi cs. Thus, an in-depth understanding of the brick’s performance is unclear. In this regard, the present study uti lizes Scanning Electron Microscopy (SEM) and Fourier Transformati on Infrared Spectroscopy (FTIR) techniques to investi gate the above. As per study outcomes, a pozzolanic reacti on is evident in the brick through SEM and FTIR analyses. The phases portlandite, ett ringite and calcium hydroxide phases are visible in the brick aft er 28 days of development, and the brick’s physical properti es (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 acti ve groups (O-H and C-S-H) exist on the brick’s surface to assist the adsorpti on of Hg (II), Pb(II) and As(V) adsorbates.