Terefil® - The Number 1 Void Filling Solution For Difficult Structural Fill Applications

Mainmark’s proprietary Terefil is an advanced engineered fill material providing an excellent solution when granular fills or aggregate material options are too heavy, site access is limited, or project schedules are extremely tight.

Terefil is highly flowable, easily placed, and does not require compaction. It will fill voids and can be pumped for distances up to 1000 metres. Terefil contains a uniformly distributed cell structure encapsulated by cementitious materials creating an engineered, low density solution used across a wide range of civil, infrastructure, construction and mining projects.

Terefil can be designed to meet the project specific density and strength requirements.

Mainmark’s comprehensive range of void filling solutions include:

  • Abandoned pipework, tunnel or culvert
  • Annulus fill
  • Underground tanks and voids
  • Compensation rafts

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Fast, Economical, and Structural Void Filling Solutions




Helping to reduce pressure on founding substrates, retaining walls, bridge approaches and slip planes.

Flowable and self-levelling

Terefil is able to completely fill annular spaces, and mass fill large voids (such as tanks, pipes, sink holes and abandoned mines) not leaving a void across the top of the space.

Rapid installation

Terefil can be placed at greater than 200m3 per day with up to 5 times fewer heavy vehicle movements required on site.


Reduced transportation of material, reduced energy and water costs all provide significant cost savings.

Quality controlled

Providing the customer with a reliable, consistent product. Terefil density is measured by sampling the product as it is placed and strength testing can be undertaken in the lab at 7, 14 or 28 days or as required.

Environmentally inert and low carbon footprint

Terefil requires less raw material to be transported to site, reducing traffic congestion and fuel use.

Who can we help?

Airports and Ports

We raise, re-support or rehabilitate civil infrastructure, enhancing the safety and stability of roads, rail, tunnels, culverts and other public assets. Our services also provide solutions to safely decommission and abandon below ground infrastructure and fill voids.

Sinking Floors - Mining

Mining and Resources

Mainmark is an expert in solving ground problems and extending the life of assets in the mining sector. Poor compaction, substandard ground material, flooding and repeated vibration can all impact the ground’s long-term behaviour under load. Underground voids and surface cracks can cause serious safety issues for roads which support heavy, off-highway vehicle traffic. Weak ground can also contribute to movement and damage of fixed equipment and may impact pipelines, leading to degradation and the potential for costly removal or replacement.

image inside a culvert

Pipe Abandonment

Replacing ageing or damaged assets, such as underground pipes and culverts, is an expensive process that often requires ground excavation works that could take weeks or even years to complete. It can also have a significant impact on the environment and cause major disruption to roads and facilities that the community relies on.

Holes and Voids - Civil

Holes and Voids

Holes and voids can be either concealed or open cavities that present naturally as a result of erosion and geological changes, or due to building, mining, and other commercial or industrial ground activity. Ranging from small to large, all holes and voids underneath structures will contain air, and possibly water, which can cause instability. Filling these spaces can prevent wider damage to the ground, on-ground structures, and the surrounding environment.


Remediating collapsed retaining walls on building sites

Landslip Repairs

andslips and subsidence put pressure on building site retaining walls, posing a significant risk of wall collapse if ground conditions become too unstable. Whatever the cause, emergency remediation will often be needed to ensure site safety and minimise damage to adjacent buildings. Solutions such as Terefil® lightweight cementitious fill, and Teretek® resin injection, can benefit engineers and builders when there is a need to backfill, remediate or support a retaining wall quickly without compromising its structural integrity or strength.

Remediating collapsed retaining walls on building sites

Wing Wall Backfill

Mainmark has a number of void fill solutions such as polyurethane and cementitious grouting. We assess each situation to determine the best course of action and the best material to use. Smaller voids in underground rock strata are generally filled with a void filling foam or concrete void filler; a material like urea silicate or polyurethane resin that not only fills the void but also ‘glues’ the surrounding rock together.

Terefil® Void Fill

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Terefil® from Mainmark is a lightweight, engineered void fill solution for pipes of every size.

Surpassing even the capabilities of cellular concrete or foam concrete, Terefil is a unique, specialist flowable fill material that can fill massive pipelines and concrete culverts quickly and cost-effectively. Due to its pumpability and self-compacting properties, Terefil can fill entire abandoned pipes, leaving no unfilled spaces, air pockets or gaps. Unlike other fills and grouts, Terefil doesn’t release any water as it sets, ensuring zero bleed and minimal shrinkage along the crown of the pipe. The solution provides firm contact between the material and the pipe as it sets, preventing the formation of underground cavities or voids as the pipe degrades over time.

Terefil is a lightweight concrete or flowable grout that travels easily through a grouting pipe to fill voids of any size, including large abandoned pipes and culverts. This innovative flowable fill makes it easy to apply regardless of the size or length of the pipe or culvert. Importantly, it means pipes can be filled and decommissioned even when access is extremely limited. Pipes can be filled from a single entry point with the highly-flowable grout applied very quickly. Terefil is the lightweight polymer-modified cementitious fill of choice for mission-critical projects, ideal for when granular fills or aggregate material options are too heavy, site access is limited, or project schedules are tight.Mainmark works fast to minimise downtime on site, with time spent on testing solutions and identifying the best formulation for the project before work begins.

Terefil is available as a pervious or impervious mix and can solve a large variety of civil and geotechnical challenges.

  • Mass fill or large geological voids.
  • Sinkholes or washouts.
  • Abandonment of in-ground pipes, tanks, tunnels and mine shafts.
  • Bridge approaches and landslip repairs.
  • Backfill for swimming pool, retaining wall, service trench and manhole excavation.
  • Permeable sub-grade beneath roads, major highways, airport runways, bridges, mine shafts and sporting facilities

Company Snapshot


Years Experience


Successful Projects


Offices Worldwide


Technical Engineers

Mainmark Fills Damaged Culvert at Brisbane Airport

Compared to traditional foam fills, the proprietary technology used in Terefil™ has increased stability, a greater lift height and can be pumped greater distances. Extensive compressibility testing has validated the ability of Terefil™ to resist cell collapse from pressure.

Mainmark used Terefil™, an air-entrained lightweight cementitious mass void fill material, to fill the culvert. The proprietary grout design mix was explicitly developed for the project. It was trial batched, cured and independently tested prior to the works to ensure pumpability and compliance with the project’s specifications. During the project, the grout was batched locally, augmented, and pumped on-site using a purpose-built pump and truck-mounted injection equipment.

Lightweight Terefil® Fills Redundant Culverts and Pipes in Newcastle

Senior project engineer for Diona, Gavin Bowen, had this to say: “Mainmark did a great job on the Terefil filling of the redundant stormwater culvert and pipes system in Mayfield. The crew were very efficient and very helpful to work with.”

Mainmark’s proprietary product, Terefil, is a technologically advanced, engineered, lightweight cementitious-based filler that is well suited to projects where alternative granular fills or aggregate material are considered too heavy.

Terefil is significantly lighter than standard grout fill, minimising pressure to surrounding structures and substrate soils, while at the same time, able to withstand significant pressure and maintain structural integrity under heavy loads, such as road traffic.

Terefil® Used to Abandon Pipeline at Iron Mine

Terefil® was the ideal material for this project due, in part, to its extremely low shrinkage rate and the lack of bleed water during curing time.

Mainmark was required to fill the pipes without exceeding 300kPa pressure on the pipes during a 12- hour continuous placement, and then cap the pipes on completion.

As the pipes could only be accessed through a single point, the project required a highly flowable fill material that would travel the length of the pipes to fill them completely. Work was required to be completed in a tight project timeframe of three

Underground Gas Main at Busy Melbourne Intersection Decommissioned with Terefil®

The Mainmark team was required to work within a tight work zone, approximately 3m by 10m, with additional access for two concrete agitator trucks that delivered material to the site.

Mainmark’s advanced engineered Terefil cementitious fill was used to fill a 300mm ‘T’ section of the gas main pipe. The ‘T’ shaped pipe had 2 major lengths; a 25m length section and a 100m length section.

A total of 10.2m³ of Terefil was required to completely fill the gas main pipe without any air pockets or gaps, with the cementitious fill placed at a density of 700kg/m³.

Terefil® Void Fill