Modifying of expansive clay soils using alkali activated ESKOM dump ash

Cyril Attwell, ARC Innovation
Phenyo Mvuyana, Eskom Holdings SOC LTD
Kelley Reynolds-Clausen, Eskom Holdings SOC LTD

Description

Modifying of expansive clay soils using alkali activated ESKOM legacy ash Authors Mr. Cyril Attwell - South Africa - ARC Innovation Ms. Phenyo Mvuyana - South Africa - Eskom Holdings SOC LTD Dr. Kelley Reynolds-Clausen - South Africa - Eskom Holdings SOC LTD Abstract Expansive clays are the more commonly occurring problem soils in South Africa. Due to spatial constraints, substation construction is increasingly undertaken on these marginal soils, thus increasing earthworks construction costs by approximately 70%. To reduce these costs, the option of using Eskom legacy ash to modify expansive clayey soils should be explored. This study investigated the use of alkali-activated Class F legacy coal ash, to stabilize highly expansive soils as an alternative to importing engineering soils, for the construction of substation terraces. A low carbon, safe to use, waste saline mix alkali activator (activator HC™), with a low molar concentration was used to activate the ash. The modified soils were sampled and taken to an accredited soils lab. Foundation Indicator and California Bearing Ratio tests were undertaken on the soils. The results showed that alkali activated ash can be used to modify expansive soils, resulting in a material that can be used as a subgrade in the foundation layers of low stiffness pavements. Resistivity and durability values however tested as low, therefore indicating that the modified soils would not be competent for placing above a substation earth grid, as trace metals from the ash would leach and result in the corrosion of the earth grid. This paper will expand on the work completed to date and highlight the on-going research, particularly studies aimed at enhancing the durability of the modified soils.

 
May 14th, 3:00 PM May 14th, 3:30 PM

Modifying of expansive clay soils using alkali activated ESKOM dump ash

Grand Rapids, Michigan

Modifying of expansive clay soils using alkali activated ESKOM legacy ash Authors Mr. Cyril Attwell - South Africa - ARC Innovation Ms. Phenyo Mvuyana - South Africa - Eskom Holdings SOC LTD Dr. Kelley Reynolds-Clausen - South Africa - Eskom Holdings SOC LTD Abstract Expansive clays are the more commonly occurring problem soils in South Africa. Due to spatial constraints, substation construction is increasingly undertaken on these marginal soils, thus increasing earthworks construction costs by approximately 70%. To reduce these costs, the option of using Eskom legacy ash to modify expansive clayey soils should be explored. This study investigated the use of alkali-activated Class F legacy coal ash, to stabilize highly expansive soils as an alternative to importing engineering soils, for the construction of substation terraces. A low carbon, safe to use, waste saline mix alkali activator (activator HC™), with a low molar concentration was used to activate the ash. The modified soils were sampled and taken to an accredited soils lab. Foundation Indicator and California Bearing Ratio tests were undertaken on the soils. The results showed that alkali activated ash can be used to modify expansive soils, resulting in a material that can be used as a subgrade in the foundation layers of low stiffness pavements. Resistivity and durability values however tested as low, therefore indicating that the modified soils would not be competent for placing above a substation earth grid, as trace metals from the ash would leach and result in the corrosion of the earth grid. This paper will expand on the work completed to date and highlight the on-going research, particularly studies aimed at enhancing the durability of the modified soils.