Structural and base materials · Aggregates & Groundworks
Polymer Concrete
Explains the resin-bound mineral casting that linear drainage channels and similar thin, dense units are made from, and why its binder puts it outside the cement family it is named after.
Educational reference entry. Suitability depends on the complete assembly, substrate, exposure, installation method, manufacturer documentation, local requirements and qualified professional review.
Overview
What polymer concrete is
Polymer concrete contains no cement. It is graded mineral aggregate — typically quartz or basalt sands and fines — bound in a thermosetting resin, mixed and cast into a mould where the resin cures by chemical reaction rather than by hydration. The name comes from the appearance and the aggregate content, not from the binder, and that is the single most important thing to know about it in a library whose other concrete entries are all hydraulically bound.
Because the binder is a resin rather than a cement paste, there is very little water in the mix and very little porosity in the result. That is what makes the material worth using: units can be cast thin and dense with a smooth, closed surface, which is difficult to achieve in a cement mix of the same shape. It is why the linear channel bodies used in surface water drainage are commonly made from it, and why the same material appears as sink and laboratory basin castings, manhole and chamber components, and cable and utility troughs.
The cure also changes the product's life story. A cement unit gains strength for a long time after casting and is affected by moisture for longer still; a resin-bound casting comes out of the mould essentially finished. Nothing about it depends on curing conditions on site, and it arrives as a manufactured item to be bedded, jointed and loaded rather than a material that continues to develop in position.
The trade-offs belong to the resin as well. A polymer binder responds to heat and to sunlight differently from a cement one, its behaviour in fire is a resin question rather than a mineral one, and its response to particular chemicals depends entirely on which resin system the manufacturer used. Those are all matters for the manufacturer's documentation for the specific product, and none of them can be generalised from the words polymer concrete.
Terminology
Common names and aliases
These names describe the same thing. The library keeps one entry per material so that an acronym, a trade name or a regional spelling never becomes a second, thinner page.
- Resin concrete
- Resin-bound mineral composite
- Polymer modified mineral casting
- Synthetic concrete
Applications
Common applications
Where this material is typically encountered. A typical application is not a statement that it suits your project.
- Linear drainage channel bodies in drives, yards, forecourts and trafficked external areas.
- Slot drainage and threshold drainage units where a narrow, dense section is needed.
- Chamber, sump and access components in surface water drainage arrangements.
- Cable, duct and utility troughs and their covers.
- Cast basins, sinks and worktop-integrated bowls in laboratory and utility settings.
- Moulded units and features where a thin, dense, smooth section would be difficult to cast in a cement mix.
Consideration
Where it is commonly considered
- Where a drainage channel has to run in a narrow slot with little room around it.
- Where a unit needs a dense, closed surface rather than the porous face of a cement casting.
- Where the design calls for a thin section that would be fragile in a hydraulically bound material.
- Where units need to arrive finished and be installed without any on-site curing.
- Where the manufacturer's information indicates the resin system suits the chemical exposure in question.
- Where the profile is complex and repeatable, so a factory mould is doing the shaping.
Professional review
Where additional professional review is especially important
These are the situations where the answer depends on the specific building, and where a qualified professional should be involved before anything is decided.
- Where vehicle loading over the unit has not been established and discussed against the manufacturer's information.
- Where fire behaviour of the material matters in the location and has not been considered.
- Where sustained high temperatures or direct heat may reach the unit.
- Where specific chemicals are expected and the resin system has not been checked against them.
- Where the unit is being substituted for a cement-based one on site without reference to the designer.
- Where the installation depends on a concrete surround and the interaction between the two has not been detailed.
Properties
Key properties to discuss
Qualitative topics worth raising. Measured values, classes and grades come from the manufacturer's technical documentation for the specific product, not from a reference page.
- Moisture behaviour
- The low porosity of a resin-bound casting is the reason it is chosen for water-carrying units, but it also means the material interacts differently with a cement-based bedding and surround than a concrete unit would.
- Thermal behaviour
- A polymer binder expands and contracts with temperature differently from cement-bound material around it. How that is accommodated at joints and at the surround is a detailing matter set out by the manufacturer and the designer.
- Fire-related questions
- Behaviour in fire is governed by the resin rather than by the aggregate, and it is not comparable to a cement-bound unit. Nothing is stated here about performance; that belongs to the manufacturer's documentation.
- Surface wear
- The exposed faces of a channel or trough take grit, traffic and cleaning, and how the dense surface holds up depends on the product and the use rather than on the family name.
- Installation dependency
- The unit arrives finished, so the work is bedding, aligning, jointing and forming the surround. Nothing cures on site, and the concrete around it becomes the part that has to be got right.
- Documentation
- Almost everything worth knowing — load class, chemical resistance, temperature range, jointing method — is manufacturer information for the specific product, because resin systems differ from one another.
- Repairability
- A cracked or damaged unit is generally replaced rather than patched, and replacement means breaking out the concrete surround around it.
Exposure
Exposure and environmental conditions
- What traffic will pass over this unit, and has that been discussed against the manufacturer's information?
- Is the unit exposed to direct sunlight or to sustained heat in its position?
- What is likely to be discharged into it — surface water, wash-down, fuels, chemicals?
- Is the location subject to freezing conditions, and is standing water likely inside the unit?
- Is the unit inside a building, outside, or in a position where fire behaviour is a design consideration?
Assembly
Substrate and system dependencies
What this material sits on, is fixed to or depends on. This is usually where performance is won or lost.
- The concrete bed and surround are usually what actually carry the load, so their detailing governs the installation.
- Grating, edge rail and cover arrangements are part of the unit's system and are matched rather than mixed.
- Falls, levels and the connection to the pipework downstream are set out before units are bedded.
- Jointing between units follows the manufacturer's method, since the material is not jointed like concrete.
- Movement between the unit and the surrounding paving or slab is accommodated by detailing rather than by the unit.
- Where the unit sits within a surfacing layer, the surfacing material and its edge condition become part of the assembly.
Appearance
Appearance and finish considerations
- The cast face is smooth and dense, quite unlike the open surface of a precast concrete unit.
- Colour is a property of the casting and is typically dark and consistent within a production run.
- In most positions only the top edge or rail is visible, so the visible element is often a metal grating rather than the body.
- Chips and damage to a dense casting show as bright breaks rather than blending in the way a concrete chip does.
- Where units are visible in a finished surface, alignment and the line of the joints is what the eye reads.
Durability
Durability questions
Questions to raise rather than a service life to expect. No material has a universal lifespan — it depends on the assembly, the exposure and the upkeep.
- What load is expected over this unit, and what does the manufacturer's information say about it?
- Is the surround detailed as the manufacturer sets out, and who is checking that on site?
- How does the material respond to what will actually be discharged into it?
- Has temperature movement between the unit and the surrounding construction been considered?
- What would a damaged unit mean for the run as a whole?
Upkeep
Maintenance and repair considerations
- How is the channel or unit cleaned, and are there cleaning agents the manufacturer advises against?
- How would a damaged unit be replaced, and what happens to the surround?
- Is there a record of the product so a matching replacement unit can be identified?
- What maintenance access exists to the run once the surfacing is complete?
- Who is responsible for keeping the unit clear so it works as intended?
Installation
Installation dependencies
What the installation depends on — not how to do it. Method belongs to the manufacturer's instructions and the trades carrying out the work.
- Setting out of falls and levels happens before any unit is bedded.
- The concrete bed and haunch are formed to the manufacturer's arrangement rather than improvised.
- Units are supported and protected while the surround is placed and while it gains strength.
- Site traffic across a newly installed run before the surround has set is a common source of damage.
- The connection to the downstream drainage is made and checked before surfacing goes over it.
- Edge rails, gratings and locking arrangements are fitted as part of the same system.
Documentation
Documentation to request
Ask for these in writing, for the specific product being proposed, and keep them with the project record.
- The manufacturer's technical information for the specific unit, including load class and installation arrangement.
- The installation detail for the concrete bed and surround.
- Chemical resistance information where anything other than rainwater will enter the unit.
- The drainage layout showing falls, connections and outfall.
- Product references kept in the building file so a replacement unit can be matched later.
Conversations
Questions for qualified professionals
Bring these to the relevant qualified professional, manufacturer or authority. Requirements vary by project and location.
- What is this unit made of, and does the design depend on the resin binder rather than cement?
- What load class has been chosen, and against what expected traffic?
- How is the concrete surround detailed, and who checks it before surfacing?
- What is expected to be discharged into it, and has the resin been checked against that?
- How are the units jointed, and does anything need sealing between them?
- How does this unit move relative to the paving or slab around it?
- What access is there for cleaning and maintenance once the surface is finished?
- If a unit is damaged during construction, what is the process for replacing it?
Blind spots
Commonly overlooked points
- The word concrete in the name refers to the appearance, not to the binder; there is no cement in it.
- The concrete surround usually does the structural work, so a correct unit in a poor surround is still a problem.
- Resin systems differ from one another, so chemical and temperature behaviour cannot be read from the family name.
- Units are commonly damaged by site traffic before the surround has gained strength.
- Replacement means breaking out the surround, which is a very different job from lifting a paving unit.
- Gratings and edge rails belong to the same system as the body and are not interchangeable between ranges.
What this page does not do
- This page does not state any load class, chemical resistance, temperature limit or fire performance; all of those are manufacturer information for the specific product.
- Drainage design, falls, capacity and outfall arrangements are matters for qualified professionals and for local requirements.
- This entry sits in a category whose published scope describes cement-based materials; the material itself contains no cement, and the placement is a library-structure question rather than a statement about the product.
- Build Design Hub does not supply, test, approve or endorse resin-bound products or any supplier of them.
Related entries
Common comparisons
Entries met at the same decision but which behave differently, so the comparison is about the difference rather than a swap.
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Often used alongside
Entries commonly encountered together with this one. Co-occurrence only — never a claim that any combination is compatible or suitable.
Inspiration
Related Ideas Library pages
Design directions where this material commonly appears.
Preparation
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Owner-side preparation before the conversation where this material comes up.
Go deeper
Related Build Design Hub guides
Planning guidance and neutral comparisons behind the decisions on this page.
Aggregates & Groundworks Materials
Reference entries for the unbound and geosynthetic materials that make up the ground beneath a building — crushed rock, fills, bedding, drainage media, geotextiles and the cellular products laid with them.
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