For many years, the most prevalent method for dealing with poor quality or contaminated soil was to remove it, treat it off-site, and replace it with better material. This is a massive logistical undertaking involving numerous truck movements, sometimes in densely populated areas. Environmentally, economically, logistically, and socially, this was not a sustainable solution to the soil problem.
Recently, there has been a discernible shift towards the more sustainable approach of treating the soils on-site and making them construction-ready, without the need for unnecessary logistics.
In the field of soil stabilisation, Ecocem has a long history of providing a variety of binder solutions, ranging from pure GGBS that can be blended on-site with the appropriate amount of CEM I or Quick Lime, to a CEM III/A binder composed of 50% GGBS and 50% CEM I, and even a high-GGBS binder (70%) for the most technically demanding situations. These solutions can provide both technical and environmental benefits over the CEM I heavy options that have been used more frequently to date.
This range of products enables Ecocem to cover a wide range of applications, including geotechnical improvements, brownfield remediation (stabilisation of heavy metals and hydrocarbons), sulphatic soils treatment (swelling suppression), and port dredged sediments valorisation. To illustrate these capabilities, we have outlined two such case study examples below:
Geotechnical improvement for residential home development in Porterstown, Co Dublin. Image: (2020) Newton Ground Engineering
On this worksite, the contractor opted for Ecocem’s CEM III/A solution to enhance the geotechnical properties of the existing on-site soils, aiming for higher shear strength (> 130 kPa) and CBR (> 15%) than were initially observed. Treatment was performed by mixing the soil with 3% of CEM III/A.
Within three days, the performance met and substantially exceeded the specified requirements. In this realisation, the environmental benefits are essentially: a drastic reduction in the carbon footprint of the chosen solution, up to 50% compared to traditional practices involving pure CEM I treatments, and the elimination of unnecessary transport of additional raw materials to provide geotechnical improvement (aggregates).
Howth port extension recycling dredged and polluted sediments. Image: (2021) John Sisk & Son
The objective of this project was to valorize the Howth port dredged sediments. In addition to presenting high-moisture content (w > 60%) and relatively fine grains (passing at 80 µm > 90%), these sediments were contaminated with multiple heavy metals (zinc, copper, nickel) and organotin’s (TBT).
With the assistance of the EPA, the contractor aimed to treat sediments to improve their geotechnical properties and to ensure that all identified pollutants were effectively captured by the solidified matrix.
This project's completion resulted in the construction of a port extension utilising only the treated sediments that were directly dredged in the port. Geotechnical performance was achieved within seven days, and pollutant leaching was reduced below the EA requirements and further monitored on-site for several months
The environmental benefits of this project of on-site stabilisation are essentially the following: circular economy through the direct valorisation of sediments on site, avoidance of their discharge in a specific landfill, and a significant reduction in the amount of road transport that would have been required for material extraction and replacement.
In addition, the use of a binder with a high GGBS content (70% GGBS) and a low carbon footprint contributed to additional significant carbon reductions when compared to a binder containing only cement.
Howth Middle Pier near completion by John Sisk & Son Ltd
Established by Donal O’Riain in 2000 with the initial goal of bringing a low carbon cement to the Irish market, Ecocem’s mission is to pioneer low carbon cement technologies. In Ireland Ecocem operates out of their facility in Dublin’s Ringsend in the south docks.
This article was written by Aidan Fogarty, Quality Manager of Ecocem Ireland.