Geopolymer Vs. Underpinning: The Differences

Finding out your property has a subsidence issue can be daunting and choosing a solution can be difficult. 

This short article discusses five differences between subsidence repair techniques, underpinning, and geopolymer injection. 

How do the methods solve the subsidence problem?

Mass concrete underpinning aims to strengthen the foundation of an existing building or other structure. It involves excavating a segment of the ground below the existing building foundation. This is completed in controlled stages, to a depth where suitable bearing strata exists. The excavation is then filled with concrete and allowed to cure before the next stage is excavated. 

Geopolymer injection tackles the same subsidence problem but instead of physically deepening the foundations, geopolymer material is injected below the foundation, to improve the strength of the ground.

Method of Installation

Mass concrete underpinning is completed in controlled stages, to a depth where suitable bearing strata exists. The excavation is then filled with concrete and allowed to cure before the next stage is excavated. 

Geopolymer is injected through manually hand-held drills, with usually 16mm holes. It is usually injected at 1-metre centres beneath load-bearing walls or floors.

How do we know it has worked? What is the verification method?

The success of underpinning schemes gets measured by testing the concrete strength of that underpin. 

Geopolymer injection results are verified by pre and post-work soil testing.

How long does it take to complete?

As an example, underpinning a 4 bed residential home can take up to 6 months to complete. 

Geopolymer injection for the same home can take up to 10 days.