Abstract
The reduction in fly ash production in coal-fired power plants has created an opportunity to explore alternative types of fly ashes previously deemed unfit for use in concrete. In plants using flue gas desulfurization (FGD) processes, fly ash could contain high amounts of sulfur oxides, making its use in concrete inadvisable. However, the type of sulfur compound present in a fly ash strongly impacts its performance in concrete. In this study, two types of fly ash were used to evaluate the effect of sulfur oxides on mortar mixtures incorporating fly ash as supplementary cementitious material (SCM); one from an FGD unit, with high sulfur oxide content (in the form of hannebachite), and the other generated in a system without FGD, with negligible sulfur oxide. Calorimetry results show that hannebachite can effectively control C3A hydration similar to gypsum; however, its presence in FGD fly ash does not induce deleterious expansion associated with internal sulfate attack in mortars. TGA and XRD analyses suggest that hannebachite has lower reactivity than sulfate. Hannebachite not only maintains the pozzolanic reactivity of the fly ash, but its fineness may promote OPC hydration, increasing compressive strength. The results of this study indicate that FGD fly ash can be used as an SCM, allowing more sustainable concrete production.
| Original language | English |
|---|---|
| Article number | 124646 |
| Journal | Journal of Cleaner Production |
| Volume | 283 |
| DOIs | |
| State | Published - 10 Feb 2021 |
Bibliographical note
Funding Information:This project was supported by project Corfo #12IDL2-15156 and by the National Agency of Research and Development (ANID) of Chile under Grant ANID/Fondecyt Iniciaci?n/11170432, and doctoral scholarships ANID/PCHA/Doctorado Nacional/2015?21150946 and ANID/PCHA/Doctorado Nacional/2017?21170247 as well as by CEDEUS, ANID/FONDAP/15110020. The SEM analysis was performed using ANID/FONDEQUIP/145?225. The testing performed in this study was mainly conducted at the Construction Materials and Resmat Laboratories at the Pontificia Universidad Catolica de Chile. The authors acknowledge the assistance provided by the personnel working at these facilities, especially Mauricio Guerra, Luis Gonzalez and undergrad student of Universidad de los Andes, Chile, Sebasti?n Salazar, who performed the TGA and prepared samples for the TGA and XRD. The fly ash was supplied by AES-Gener, which is also greatly acknowledged.
Funding Information:
This project was supported by project Corfo # 12IDL2-15156 and by the National Agency of Research and Development (ANID) of Chile under Grant ANID/Fondecyt Iniciación/11170432, and doctoral scholarships ANID/PCHA/Doctorado Nacional/ 2015–21150946 and ANID/PCHA/Doctorado Nacional/ 2017–21170247 as well as by CEDEUS , ANID/FONDAP/15110020 . The SEM analysis was performed using ANID/FONDEQUIP/145–225. The testing performed in this study was mainly conducted at the Construction Materials and Resmat Laboratories at the Pontificia Universidad Catolica de Chile. The authors acknowledge the assistance provided by the personnel working at these facilities, especially Mauricio Guerra, Luis Gonzalez and undergrad student of Universidad de los Andes, Chile, Sebastián Salazar, who performed the TGA and prepared samples for the TGA and XRD. The fly ash was supplied by AES-Gener, which is also greatly acknowledged.
Publisher Copyright:
© 2020 Elsevier Ltd
Keywords
- Concrete
- Durability
- Ettringite
- Gypsum
- Hannebachite
- Internal sulfate attack