Comparative characteristics assessment of calcined and uncalcined agro-based waste ash with GGBS and its application in an alkali-activated binder system

Abstract

A lot of energy is released during the cement manufacturing process, and a large amount of carbon dioxide (CO₂) is discharged into the environment. Presently, researchers are focusing on reducing CO₂ emissions by researching sustainable alternatives to traditional Portland cement-based materials. A comparative study on the material characterization of both calcined agro-based waste ash (calcined ash) and uncalcined agro-based waste ash (uncalcined ash) and its utilization as a binder along with granulated blast furnace slag (GGBS) in the alkali activation process is carried out in this paper. The study regarding calcined and uncalcined ash would help in better understanding the variation in the properties of the material and its behavior during the alkali activation process. The tests conducted on both calcined and uncalcined ash along with GGBS include specific gravity, X-ray fluorescence, X-ray diffraction, scanning electron microscopy, reaction degree, Brunauer-Emmett-Teller (BET) analysis, particle size distribution, and the Puntke test for understanding its microstructural characteristics. Later, alkali-activated mortars are prepared using 30% weight of agro-based waste ash (both calcined and uncalcined) and 70% weight of GGBS. A comparison of the compressive strength of alkali-activated mortars prepared using calcined and uncalcined ash was studied, which showed a promising increase in the strength by 11.02% of mortar prepared using calcined ash (23.46 MPa) for 28 days when compared to mortar prepared using uncalcined ash (21.13 MPa). The major finding from this study indicates that calcined agro-based ash with GGBS shows better results compared to uncalcined agro-based ash with GGBS.

Keywords:

• Agro-based waste ash
• material characterization
• calcined ash
• uncalcined ash
• GGBS
• alkali-activation

PUBLIC INTEREST STATEMENT

A lot of energy is released during the manufacture of cement, with a large amount of carbon dioxide being discharged into the environment. The current research focuses on reducing cement utilization as a binder by incorporating the use of waste ashes produced from agricultural and industrial sectors. These waste ashes, which are directly obtained from various industries, have binding properties that can be activated using alkaline solutions such as sodium hydroxides. Even the binding properties of these ashes vary depending on whether they are incinerated at a high temperature or not. A comparative study on the material properties of both calcined (incinerated at high heat) agro-based waste ash and uncalcined (burned at low heat) agro-based waste ash and its utilization as a binder along with granulated blast furnace slag (GGBS) in the alkali activation process is carried out in this paper.

Disclosure statement

The authors have no relevant financial or non-financial interests to disclose.

Data availability statement

The datasets generated during and/or analyzed during the current study are available from the corresponding author upon reasonable request. We obtained our dataset for XRD analysis from ICSD database: https://icsd.fiz-karlsruhe.de