We Want to Change the Way Historic Mine Workings are Treated to Reduce Environment Damage

Wardell Armstrong has been working with BRE, Banah UK and The Coal Authority to change the way we treat historic mine workings resulting in less impact to the environment. We have recently submitted our project application to Innovate UK, which is part of UK Research and Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.

Abandoned mine workings identified underneath proposed development sites are typically filled with a pump-able low strength bulk filler grout (typically Portland cement and pulverised fuel ash (PFA), a by-product of coal-burning power stations). However, PFA is becoming increasingly scarce in the UK and therefore more expensive in line with a reduction in the number of coal-burning power stations (to zero by 2026). Increasing scarcity of PFA (compounded by demands from higher value uses such as a “cement”) is presenting a significant difficulty in the development of former coalfield areas in the UK.

This project seeks to develop a novel grout based on an alternative material (to PFA) that is available in sufficient quantities from local quarries. The proposed alternative material will possess the necessary properties at lower cost and with better environmental performance. They will be durable (meeting physical requirements over long periods), chemically stable in the context of interaction with flowing groundwaters and must also not be susceptible to leaching of elevated levels of chemical pollutants (e.g. heavy metals) into groundwater in line with environmental regulations. Promising grout mixes already prepared by Banah UK at laboratory scale requires further optimisation of system, scaleup to site trial, in-situ testing, environmental impact analysis to demonstrate that it is suitable for use in mine workings / mine entry void filling on a large, commercial scale. The partnership brings together a specialist engineering consultant, a grout/binder manufacturer, a key regulator, a grouting contractor and a construction research and technology organisation.

The project will establish stakeholder needs, develop and optimise grout formulations and assess their durability and leaching behaviour in the partner’s laboratories. Shortlisted formulations will be scaled up and assessed at site scale for properties such as pumpability, void filling ability and durability. Business models will also be assessed.

The project is expected to lead to significant efficiencies, a reduction in the transport of a known contaminate across the UK (as such a reduction in CO2 production via haulage) and cost savings, enabling more cost-effective re-development of land in former mining areas in the UK and globally.

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