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

Mainmark’s proprietary Terefil is an advanced structural 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 includes:

  • Abandon most pipes, tunnels or culverts
  • Annulus fill i.e., space between pipe within a pipe.)
  • Fill underground tanks and voids ( any shape or size)
  • Compensation rafts
  • Backfill behind retaining walls, and bridge-wing walls.

Get In Touch

Submit your enquiry using our online form. Include a brief message about the services required, and one of our technical engineers will be in contact with you.

Fast, Economical, and Structural Void Filling Solutions




Helps to reduce pressure on soils, 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, sinkholes and abandoned mines).

Rapid installation and reduced traffic congestion

Terefil can be placed at greater than 200m3 per day, and with up to 5 times fewer heavy vehicle movements required. Compared to traditional fill materials.


Less access pits/points means significant cost savings.

Quality control

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

Terefil is a cement-based product that is environmentally inert when it sets.

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

Terefil is a specialist flowable fill material that can fill long pipelines, tunnels  and culverts quickly and cost-effectively. Due to its pumpability and self-compacting properties, Terefil can fill abandoned pipes, leaving no air pockets or gaps. Unlike other fills and grouts, Terefil doesn’t release any bleed water as it sets, resulting in minimal shrinkage along the crown of the pipe.

Terefil is highly flowable. The resullt is that it travels easily through long pipes, tunnels or culverts. Mainmark have regularly filled pipes with length excess 800m.

Terefil is available in a range of strengths, densities and design.

  • Abandonment of in-ground pipes, tanks, tunnels and mine shafts.
  • Bridge approaches and landslip repairs.
  • Backfill for swimming pools, retaining walls, and service trenchs.
  • Permeable sub-grade beneath roads, major highways, airport runways, bridges, mine shafts and sporting facilities

Terefil® Void Fill

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Our Clients

We are proud that we have been able to help many customers. We look forward to seeing your logo too.

NSW Transport
29 Metals
Pilbara Minerals
Roy Hills
Water Corporation
PORT Waratah Coal Services
cassowary coast regional council
Gladstone Regional Council
Children Hospital School
Blayney Shire Council
Confluence Water
Next Rail
Laing O'Rourke
CPB contractors
Fulton Hogan
DOVAL constructions
Platfor Construction
Delcon Civil
Comdain Infrastructure
Lovelife Projects
Delta Group
McMahon Services
Newcrest Mining Limited

Where 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.

Company Snapshot




Years Experience


Successful Projects


Technical staff

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


What is a compensation slab?

A lightweight Terefil raft slab that replaces a poor or heavy natural void; so that it compensates for the weighty structure constructed on the site.

What is an annulus fill?

When a pipe is inserted within a pipe, the space between the two pipes is the annulus – this void is often grouted.

How do you fix voids under concrete?

Terefil is a solution that can be used as void fill or structural fill material. The concrete grout mix is highly-flowable, so it can be pumped over long distances, overcoming many site access issues. The lower pumping pressures also reduce the risk of damage to nearby pipes or other in-ground structures, such as an abandoned pipe.

What is the best fill under concrete?

Terefil is a structural fill that contains a uniformly distributed matrix of air bubbles generated by mixing cement slurry with stable, pre-formed hydrocarbon foam. Cementitious products encapsulate the air bubbles, then dissipate, leaving a lightweight concrete mix that provides the perfect lightweight backfill or lightweight concrete fill.

This Controlled Low Strength Material (CLSM) is a void filling foam that is far more stable, has a greater lift thickness, and can be pumped greater distances through a grouting pipe than typical concrete void fillers.

How do you fill a void under concrete?

Terefil is pumped through an application hose and directly applied to the area to be treated. The highly-flowable Terefil can be placed quickly, often within an hour. Once in place and set, Terefil is environmentally inert and continues to gain strength over time without adding significant weight to potentially overstressed subgrade soil.

Site access challenges can be overcome simply by using longer hoses to apply the Terefil solution.

Why Terefil is the best option for time-sensitive projects?

Terefil is lightweight, self-levelling, and cost-effective. The density and strength match the specific job requirements to deliver the required engineered outcomes, making Terefil a versatile and reliable solution. Terefil’s lightweight attribute reduces the pressure on retaining walls, bridge approaches, and slip planes.

Terefil is fast and easy to place, offers negligible shrinkage* and no capillary separation. Water is consumed during hydration into the mix. It can completely stabilise soil without disturbing or redirecting natural water flow.

Terefil is ideal for time-sensitive projects, able to be placed quickly and accurately. Once in place, Terefil can withstand heavy loads including large machinery and vehicular traffic. It doesn’t require compaction, so it is ideal for when future settlement can’t be tolerated.

  • Typically shrinkage is between 0.1% – 0.3%, subject to strength.