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Application

Geofoam Lightweight Civil Fill

Soft, compressible or low-bearing ground cannot carry the surcharge of a conventional soil or aggregate embankment without excessive settlement, lateral squeeze or bearing failure — and buried structures (basement roofs, culverts, services, retaining walls) cannot carry the earth pressure a full-weight fill imposes on them. Geofoam replaces that fill mass with engineered EPS block at roughly one to two percent of the weight of compacted soil, so the load applied to the subgrade or the structure is designed down rather than the ground being improved. It sits below the pavement or slab and above the subgrade or structure, entirely inside the civil works envelope — it is a load-management material first, and any thermal benefit is incidental.

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What it must achieve

Performance targets

RequirementTargetStandardNote
Sustained design stress in the blockAt or below the grade's compressive resistance @1% strain (the elastic / creep-control limit)ASTM D7180 (geotechnical design) / ASTM D6817 (grades)Never design to the @5% or @10% values — those are in the failure region and creep under permanent load. The per-grade @1% ladder is given in Key figures and is PROVISIONAL (datasheet, not an in-validity Technopol test).
Total and differential settlementProject-specific — set by the geotechnical engineer / roads authority, not by the materialProject specification, checked to ASTM D7180The design action is choosing how much soil mass is replaced by EPS. Technopol publishes no settlement figure and none should be quoted.
Flotation / upliftBuoyant uplift at the design groundwater or flood level must be exceeded by the permanent overburden (slab, pavement, cover soil) with the engineer's factor of safetyASTM D7180At 12–30 kg/m3 the blocks float. Uplift, not strength, usually governs where the water table can rise into the fill.
Hydrocarbon / solvent protectionContinuous impermeable geomembrane wherever a fuel, oil or solvent spill is credible (roads, fuel yards, workshops, oil-filled service trenches)Detailing requirement to ASTM D7180 practicePetrol, diesel and organic solvents dissolve EPS. This is a requirement, not an optional extra.
Fire performance in the permanent worksNo fire-resistance (E/I/R, minutes) rating exists for geofoam — blocks must be permanently covered by slab, pavement or soil and kept clear of flues and hot worksSANS 53501-1 gives reaction-to-fire only; it is NOT a fire-resistance ratingAll EPS is combustible (fire-retardant grades are treated, not non-combustible). Exact tested scope of the only current reaction-to-fire report is in Key figures.
Thermal contributionIncidental only — no R-value or U-value per thickness is published for geofoamn/aWhere thermal performance is the objective (under-slab insulation, SANS 10400-XA compliance), specify a board product with a declared lambda and thickness, not geofoam.
Where it goes

The assembly

  1. Pavement, surfacing or floor slab — The trafficked or loaded surface. Hot-applied bitumen must never be placed directly against the EPS — it goes on the base course above the load-distribution slab.
  2. Base / sub-base course — Conventional granular layerworks, thickness per the pavement design.
  3. Load-distribution slab (typically reinforced concrete) or geogrid-reinforced layer — Spreads wheel and point loads so the sustained stress reaching the block stays at or below its compressive resistance @1% strain.
  4. Separation and protection layer — geomembrane and/or geotextile — Impermeable geomembrane where a hydrocarbon or solvent spill is credible; geotextile to keep fines and bedding sand out of the block joints.
  5. Technopol geofoam EPS blocks — laid dry, no compaction — Staggered courses with cross-joints broken between layers, field-cut to line and level, mechanically inter-connected (barbed connector plates). Grade chosen from the EPS12–EPS30 ladder against the sustained design stress.
  6. Levelling / bedding layer on the prepared subgrade — Thin screeded sand or fine-graded layer. Geofoam is a rigid block — it will not conform to a rutted platform, and unsupported blocks crack.
  7. Prepared subgrade and drainage — Blocks kept above the design groundwater level with positive drainage so water cannot pond in or under the fill and generate uplift.

Layers listed outside → inside.

Which products, and why

The products that do this job

Product

Geofoam Lightweight Fill

The engineered lightweight fill itself — moulded closed-cell EPS block across the EPS12–EPS30 grade ladder, field-cut and placed dry without compaction.

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Product

Technoblock Slab Blocks & Void Formers

Raw large-format EPS block supply from the same moulding line — the stock from which geofoam blocks and bespoke cut shapes are produced. Cut EPS void formers used alongside the fill to form permanent voids, tapers and stepped transitions in the concrete works (slab soffits, abutment ledges) where full-block geofoam is the wrong shape.

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Product

2D Shapes & Sheets

Hot-wire cutting of blocks to bespoke profiles — tapered transition wedges, battered abutment faces, service cut-outs — to a factory cutting schedule.

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Every number, its source

Performance data & provenance

PropertyValueStandardSource reportStatus
Density (grade span, EPS12–EPS30)12–30 kg/m3ASTM D6817Technopol per-grade datasheet (register.json, geofoam)Provisional
Compressive resistance @1% strain — the design load limit15–100 kPaASTM D7180Technopol per-grade datasheet (register.json, geofoam)Provisional
Compressive resistance @1% strain, per grade (EPS12 / 15 / 20 / 24 / 30)15 / 17 / 45 / 70 / 100 kPaASTM D7180spec-tables.json geofoam footnote (per-grade safe-working ladder)Provisional
Compressive strength @10% strain — failure-region strength, NOT a design load60–200 kPaASTM D6817Technopol per-grade datasheet (register.json, geofoam)Provisional
Self-weight relative to compacted soil fill~1–2% (12–30 kg/m3 against ~1 800–2 000 kg/m3 typical compacted fill) ration/a — derivedDerived from the 12–30 kg/m3 density span aboveCalculated
Thermal conductivity (lambda) @10 degC — incidental; no R/U per thickness published0.033–0.045 W/m.KDatasheet value; no declared-value test on file for the geofoam gradesTechnopol per-grade datasheet (register.json, geofoam). The brochure summary's 0.030–0.038 conflicts with this and is not used.Provisional
Water absorption (long-term immersion)< 4 %Datasheet figure; no in-validity test on filespec-tables.json geofoam rowProvisional
Typical block size (other sizes cut to order)2500 x 1250 x 950 mmn/aspec-tables.json geofoam rowProvisional
Reaction to fire — FR (flame-retardant) EPS; tested scope is a 60 mm EPS FRCel 20DV sheet, NOT the buried geofoam block gradesB-s1,d0 classSANS 53501-1 (Euroclass) — reaction to fire, not fire resistanceIT 23-08-00009 (FIRELAB), valid to ~2028Verified
Fire-resistance rating (E/I/R minutes) for geofoamNone — no fire-resistance test exists for this product; all EPS is combustible and must be permanently covered in the works n/aSANS 10177-2 (no report on file for geofoam)register.json — no geofoam fire-resistance recordProvisional
Governing standards — no SANS geofoam standard and no Agrement SA certificate for geofoam existsASTM D6817 (physical properties) / ASTM D7180 (geotechnical design) / ASTM D7557 (sampling) n/aASTM D6817 / D7180 / D7557spec-tables.json geofoam rowProvisional
Manufacturing quality system (company credential, not a product approval)ISO 9001:2015 — scope includes EPS Blocks and EPS Sheets n/aISO 9001:2015 (EQCSA, SANAS C22)Reg no. Q 2016024, valid to 2028-06-02Verified

What these labels mean is defined on our data promise; every source report is on the register.

Size it

EPS Lightweight Fill Design Checker (geofoam)

Enter the pavement/slab build-up, surcharge and groundwater level: the checker returns the sustained stress arriving at the top of the block, the grade whose compressive resistance @1% strain covers it, and the uplift/flotation check. The grade properties in the tool are the PROVISIONAL datasheet ladder — the project design must be signed off by the geotechnical engineer.

Open the tool → Write the spec clause

On site

Installation

The limits

Where not to use this

A material specified for the wrong job fails you, then us.

Where fuel, oil, solvent or hot bitumen can reach the blocks and no impermeable membrane is provided (fuel forecourts, workshops, hydrocarbon-contaminated ground, oil-filled cable trenches)
EPS is dissolved by hydrocarbons and organic solvents. Contact destroys the block and the lost volume appears as sudden local settlement — there is no slow warning.
→ Designed geomembrane encapsulation for the spill case, or a mineral lightweight fill (foamed concrete, expanded clay aggregate) where the exposure cannot be reliably excluded.
Below the design groundwater or flood level, or anywhere the fill can be submerged, without ballast designed for uplift
At 12–30 kg/m3 the blocks float; buoyancy, not strength, governs. A fill that is safe under wheel loads can be lifted bodily by a rising water table. Prolonged immersion also lets EPS take up moisture, adding weight and degrading the (already incidental) thermal value — the same mechanism that makes plain EPS a poor choice in an inverted/protected-membrane roof.
→ Raise the fill above the water table, design permanent overburden ballast, or use a heavier lightweight fill (foamed concrete) below water.
Where the sustained design stress would exceed the grade's compressive resistance @1% strain — including anyone sizing off the @5%/@10% numbers
Beyond about 1% strain EPS creeps under permanent load. The @10% values (60–200 kPa) are failure-region strengths, not working loads; designing to them produces a fill that keeps settling for the life of the structure.
→ Move up the grade ladder (EPS24/EPS30), thicken the load-distribution slab to spread the stress, or use structural lightweight concrete where the load cannot be spread far enough.
As permanently exposed fill, or under a surface that will be left open — no slab, pavement or soil cover
EPS is combustible (fire-retardant grades are treated, not non-combustible), UV-degradable and mechanically soft. Geofoam has NO fire-resistance (E/I/R) rating; the only current reaction-to-fire result on file (B-s1,d0, IT 23-08-00009) was established on a 60 mm FRCel 20DV sheet and is not extended to the buried block grades — and a reaction-to-fire class is not a fire-resistance rating in any case.
→ Design a permanent slab/pavement/soil cover as part of the works, or use a non-combustible mineral fill where cover cannot be guaranteed.
In direct contact with heat — hot-applied bitumen poured onto the blocks, steam or hot-process pipework, boiler and flue penetrations, hot works during construction
EPS softens and melts well below the temperature of hot-applied bitumen and hot service lines; the melted zone becomes a void and the fill loses support locally.
→ Interpose the load-distribution slab and base course before any hot-applied surfacing; sleeve or box hot services in a mineral material (stone wool, concrete).
As the answer to a thermal requirement — claiming geofoam toward a SANS 10400-XA roof/ceiling total R-value (3.7 m2K/W in all zones under XA:2021; Zone 5 humid-coastal retains 2.7 with roof ventilation) or a wall requirement
No R-value or U-value per thickness is published for geofoam and its lambda is a PROVISIONAL grade-span datasheet figure with no declared-value test. Separately, most masonry walls need nothing added at all — double-skin cavity masonry and plastered single leaf >=140 mm are deemed-to-satisfy under XA (only lightweight / non-qualifying walls need a minimum total R >= 0.35 m2K/W).
→ Use a board product with a declared lambda and thickness for under-slab or envelope insulation and confirm the requirement in the free SANS 10400-XA compliance checker (../../technical/xa-compliance/).
Where the specification demands an Agrement SA certificate for the fill
Agrement SA 2020/609 covers the LiteCore Building System only, as a non-load-bearing wall. There is no Agrement certificate for geofoam, and another system's product certificate must never be offered as cover for this one.
→ Specify to ASTM D6817 / D7180 / D7557 with a project-specific geotechnical design, plus batch verification of the delivered grade where the client requires it.
Where it has been used

Project references

2D Shapes & Sheets

Riverstone Mall, Meyerton

Meyerton · Retail

Geofoam Lightweight Fill

Sun International Times Square

Menlyn, Pretoria · Casino / hotel

Geofoam Lightweight Fill

SA Reserve Bank

Institutional / banking

Geofoam Lightweight Fill

Liberty Life

Commercial

Questions

Specifier FAQ

Does geofoam need compaction?
No. It is placed dry as rigid blocks in staggered, mechanically inter-connected courses — no compaction, no moisture conditioning, no layer-by-layer density testing. That is exactly why it is used where a compacted fill would surcharge soft ground or a buried structure.
How do I choose the grade?
Work out the sustained stress arriving at the top of the block once the load-distribution slab has spread it, then pick the grade whose compressive resistance @1% strain exceeds it. The @1% ladder is 15 / 17 / 45 / 70 / 100 kPa for EPS12 / 15 / 20 / 24 / 30 (PROVISIONAL datasheet figures, ASTM D7180). Never size against the @10% strengths (60–200 kPa) — those are failure-region values and designing to them causes long-term creep.
Will it float?
Yes, if you let it. At 12–30 kg/m3 the fill is far lighter than water, so uplift is often the governing check. Keep the base above the design groundwater level, drain the surrounds, and confirm the permanent overburden exceeds the buoyant force at the design flood level with the engineer's factor of safety. The geofoam design checker runs this check alongside the stress check.
Can trucks and plant drive on it?
Not on the bare blocks. Traffic loads must be spread by the load-distribution slab and base course above; plant running on exposed EPS crushes and gouges it. Place the cover before any construction traffic.
What happens if diesel or petrol reaches it?
It dissolves the EPS. Wherever a hydrocarbon or solvent spill is credible a continuous impermeable geomembrane must be designed into the build-up — a requirement, not a precaution. If the exposure cannot be reliably excluded, use a mineral lightweight fill instead.
What is the fire rating?
There is no fire-resistance (E/I/R, minutes) rating for geofoam and none should be quoted. The only current reaction-to-fire result on file is Class B-s1,d0 to SANS 53501-1 (report IT 23-08-00009, FIRELAB, valid to ~2028), established on a 60 mm FR-grade EPS FRCel 20DV sheet — that is a reaction-to-fire classification, not a fire-resistance rating, and it is not formally extended to the buried geofoam grades. All EPS is combustible (fire-retardant grades are treated, not non-combustible), so the permanent works must keep it covered by slab, pavement or soil and clear of flues and hot works.
Is geofoam Agrement certified?
No. Agrement SA certificate 2020/609 covers the LiteCore Building System only (as a non-load-bearing wall) and does not extend to geofoam or any other Technopol product. Geofoam is specified against ASTM D6817 / D7180 / D7557 with a project-specific geotechnical design. Technopol's ISO 9001:2015 certification (Reg. Q 2016024, valid to 2028-06-02, scope includes EPS blocks and sheets) is a manufacturing quality-system credential — not a product performance approval.
Does the fill also insulate the ground below it?
Incidentally. The datasheet lambda span is 0.033–0.045 W/m.K (PROVISIONAL, grade-dependent), but no R-value or U-value per thickness is published for geofoam and none may be claimed toward SANS 10400-XA. If insulation is the objective rather than a by-product, specify a board product with a declared lambda and check the requirement in the XA compliance checker (../../technical/xa-compliance/).
How is it cut and detailed on site?
Blocks are field-cut with hot-wire or fine-tooth saws for edges, tapers and service penetrations; complex profiles (battered abutment faces, transition wedges) are better hot-wire cut in the factory to a cutting schedule. Gaps between blocks are packed with cut EPS, never with soil — soil in the joints reintroduces the very mass the design removed.
How long does it last?
Buried, drained, protected from hydrocarbons and loaded within its @1% limit, EPS block fill is chemically stable and does not rot or decompose. The durability risks are all detailing risks: solvent contact, submergence, over-stress creep, UV and heat on exposed block. Every one of them is designed out in the build-up above.

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