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Strengthening Behavior of Cemented Paste Backfill Using Alkali-Activated Slag Binders and Bottom Ash Based on the
Qi Sun1, Xueda Wei1, Tianlong Li1
1School of Civil Engineering, Liaoning Technical University, Fuxin 123000, China.
Materials (Basel, Switzerland)
|February 20, 2020
Summary
This study optimized a new cemented paste backfill (CPB) using bottom ash and alkali-activated slag. The developed CPB exhibits decreasing porosity and forms a dense structure with calcium aluminosilicate hydrate gel during curing.
Area of Science:
- Materials Science
- Geotechnical Engineering
- Waste Management
Background:
- Cemented paste backfill (CPB) is crucial for mine site remediation and stability.
- Utilizing industrial byproducts like bottom ash (BA) in CPB offers sustainable waste management solutions.
- Alkali-activated slag binders present an alternative to traditional cementitious materials, potentially reducing environmental impact.
Purpose of the Study:
- To develop and optimize a novel cemented paste backfill (CPB) utilizing bottom ash (BA) as aggregate and alkali-activated slag as a binder.
- To investigate the influence of mix proportions on the properties of the developed CPB.
- To characterize the microstructural development and hydration products of the optimized CPB.
Main Methods:
- Central Composite Design (CCD) response surface methodology was employed for optimizing the mix ratio.
- Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS) was used for microstructural analysis.
- ImageJ software was utilized to quantify the porosity of CPB samples at various curing ages.
Main Results:
- The optimal mix ratio was determined as: aggregate-binder ratio of 3.28, alkali dosage of 3%, solid content of 67.44%, and air-entraining agent dosage of 0.1%.
- Porosity of the CPB samples decreased with increasing curing age.
- The primary hydration product identified was calcium aluminosilicate hydrate (C-A-S-H) gel, which binds the bottom ash aggregates. Calcium hydroxide (CH) crystals appeared at 14 days, contributing to structural densification.
Conclusions:
- The optimized CPB formulation using bottom ash and alkali-activated slag demonstrates promising performance.
- The material exhibits a reduction in porosity and development of a dense microstructure over time due to C-A-S-H gel formation.
- This research provides a sustainable approach for utilizing thermal power plant bottom ash in civil engineering applications.
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