Hollow Block, Hexagonal Paver & Revetment Block Moulds

Hollow blocks, hexagonal pavers and hollow hexagonal revetment blocks are three of the highest-volume products in precast concrete — and three of the easiest to order incorrectly. Each is measured in a different way, and in each case one parameter quietly controls whether the finished unit works: hole geometry for hollow blocks, thickness for pavers, and wall taper for revetment blocks.

This guide covers all three: hollow block moulds, hexagonal paver moulds and hollow hexagonal revetment block moulds.

1. Hollow block moulds: hole geometry decides everything

A hollow block mould casts a masonry unit with internal cores. The cores cut block weight, save concrete, improve insulation and give mortar somewhere to key into. The trade-off is compressive strength, which is why hole shape and the wall thickness between cores are the first two things an engineer checks.

Square holes give the largest void for the least concrete and are the default for boundary walls and partitions. Round holes leave thicker material at the corners, so they hold up better where blocks are handled roughly or where rebar passes through. Angled and arched holes exist mainly for appearance where a block face stays visible, and ventilation blocks push open area as far as it will go for airflow.

Format matters commercially too. 20×20×10cm is the workhorse size and where multi-cavity moulds pay off: a three-in-one ABS mould casts three blocks per pour instead of one. The 30×30×10cm double-sided S30 series is finished on both faces, so blocks can be laid either way round — useful for freestanding walls where both sides are seen.

• Ask for: finished block length × width × height, hole shape, hole count and minimum wall thickness between cores.
• Watch out for: multi-cavity moulds need a flat, level casting bed — an uneven bed produces blocks of inconsistent height across the same pour.
• Cost lever: moving from single-cavity to three-in-one cuts labour per block roughly to a third at the same mould price band.

2. Hexagonal paver moulds: measure the side, not the diagonal

Hexagonal pavers interlock on six sides. That spreads wheel load better than a square slab and stops the paving creeping under traffic, which is why hexagons stay standard on pavements, parking aprons and park walkways decades after they were introduced.

The sizing trap is simple and expensive: hexagon pavers are quoted as side length × thickness, not across the corners. A 20×8cm paver has 20cm sides and is 8cm thick — but it measures roughly 40cm diagonally. Buyers who order "40cm hexagons" from a site measurement usually receive units twice the intended size.

Thickness is the load decision, and it is worth being conservative. Use 6cm for footpaths and garden paths, 8–10cm for car parks and light vehicle traffic, and 12–15cm for heavy vehicle aprons, slope surfaces and water-conservancy works. Surface type follows the environment: anti-slip and concave-base faces are specified for wet slopes and drainage surfaces, while chamfered edges reduce spalling where vehicles turn.

One detail that saves real money on site: order matching half-hexagon moulds at the same time. Without them, every paving edge has to be cut from full pavers — slow, wasteful, and it leaves a ragged line along the kerb.

• Ask for: side length and thickness, plus expected traffic load.
• Watch out for: the diagonal-vs-side confusion — always confirm which dimension your drawing refers to.
• Cost lever: half-hexagon edge units cost far less than the labour and breakage of cutting full pavers on site.

3. Hollow hexagonal revetment blocks: read the wall taper

Hollow hexagonal revetment blocks are the open-cored units laid across river banks, canal slopes, highway embankments and reservoir edges. The hexagon keeps the mat keyed together against water flow, and the open core is planted with grass or filled with gravel so the slope becomes vegetated erosion control rather than bare concrete.

These blocks are specified as side length × block height, plus wall thickness — and wall thickness is usually written as a range like 6–5cm. That is not a tolerance and not a choice: it is a taper, 6cm at the wide face and 5cm at the narrow face, so the cast block releases cleanly from the mould. Treating it as a tolerance leads to arguments over blocks that were actually made correctly.

Side length 14.5–18cm suits canal linings, garden slopes and low-flow banks. 20cm is the most widely used revetment size, with block heights from 6cm to 30cm depending on the design concrete volume per square metre. 22–25cm is specified for main river banks and high-flow channels. As with pavers, half-hexagon and semi-hollow units finish the mat edge without cutting.

• Ask for: side length, block height, and wall thickness including the taper if specified.
• Watch out for: reading a tapered wall spec as a tolerance range — confirm which face each figure refers to.
• Cost lever: block height drives concrete volume per square metre far more than side length does; check it against the slope design before fixing the mould size.

4. Why buyers often order these three together

These families look unrelated but frequently land in the same container. A municipal or water-conservancy contract commonly needs revetment blocks for the slope, hexagonal pavers for the walkway on top of it, and hollow blocks for the boundary or retaining walls around the site. Because all three are plastic moulds in similar size bands, they pack efficiently together and share the same freight.

Mixing families in one order also smooths the tooling spend. Mould cost per design is modest compared with the labour and concrete you will spend using it, so it is usually better to buy a wider set of designs once than to reorder in small batches as each work package starts.

5. What to send when asking for a quote

The fastest quotes come from a drawing or a photo with dimensions marked. If neither exists, send these:

• Hollow blocks: block length × width × height, hole shape and count, wall thickness between cores, and your target output per day.
• Hexagonal pavers: side length, thickness, traffic load, paved area, and whether half-hexagon edge units are needed.
• Revetment blocks: side length, block height, wall thickness with taper, slope area, and whether cores are planted or gravel-filled.
• All three: quantity, destination country, and whether mixed designs can share one container.

Typical service life is 300+ pour cycles with normal release-agent use and careful demoulding, and OEM moulds can be produced from drawings or sample photos when a project specification does not match a catalogue size.