IKT – Institute for Underground Infrastructure

What Goes Back Into the Sewer Trench? – Flowable Backfill Materials Put to the Test

Posted 14. July 2025

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Settlement damage, uneven bedding, and poor re-excavation capability – these are common issues on sewer construction sites. Often, the cause lies in the backfill. Temporarily Flowable Self-Compacting Backfill (TFSB) materials promise better performance – but which ones actually deliver? We tested five different TFSB products in full-scale sewer trench simulations. The aim: to evaluate how these materials perform under realistic construction conditions.

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After six years: IKT researchers dig up their test stand for tree roots

Posted 05. September 2024

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How to keep roots away from sewage pipes? IKT investigates protection systems in a long-term project. Researchers want to find out which protective measures are suitable. They have now dug up their worldwide unique in-situ test rig. The initial results are surprising.

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Withstanding the pressure: liners for pressure sewers put to the test

Posted 05. July 2023

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Aging pressure sewer pipes, just like gravity sewers, require renovation. But which methods are best suited for the job? What are the pros and cons of each? The latest IKT comparative product test on pressure sewer liners offers valuable insights. Pressure sewers are critical and sensitive elements of urban wastewater infrastructure. Many are ageing so sewer network owners are increasingly having to deal with their rehabilitation and there are different methods…

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Innovating the Urban Drainage System: a new collaborative approach

Posted 25. October 2021

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IKT has joined with six other urban drainage labs to form Co-UDlabs, a new international “Consortium of Urban Drainage laboratories”. Together we are enabling access to our research facilities, providing training and undertaking common research activities with funding by the EU, and will build long term collaboration in urban drainage research. IKT will host a free workshop on optimising urban drainage assets.

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Pressure Sewers: UK, Irish an Dutch Sewer Network Owners Undertaking Partner Projects Alongside Current IKT Project

Posted 10. December 2020

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construction pit for installation of liner for pressure sewer

Around the world sewer network owners are struggling to address the options for replacement or rehabilitation of ageing pressure sewers. Often the preferred solution is to dig them up and replace them. Rehabilitation solutions using trenchless technology tend to be used only when it is too difficult to excavate, but sewer network owners are interested in using such technology more often. First, they need to fully understand it.

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Liquid > Solid > Ready? Comparison of Five Flowable Backfills for Sewer Pipe Trenches

Posted 14. October 2020

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We have evaluated with sewer network owners the suitability of “Flowable Backfill” for use sewer trench backfilling in an IKT-Compare evaluation of this technology. Five products were compared and all were found to flow well into 1:1 scale excavation pits in our large-scale test facility – around pipes and manholes shafts and into every corner of the simulated trenches. However, during the subsequent performance tests it became increasingly clear that…

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