When you need to store bulk materials or create a heavy-duty floor for a bunker, a specially designed concrete slab is essential.
We build bunker slabs in Perth that meet the demanding requirements of agricultural and industrial use.
Whether it’s a silage bunker on a farm, a grain storage pad, or a concrete floor for a secure equipment bunker, our slabs are constructed to support huge loads and resist wear from machinery.
With our expertise in heavy concrete works, we deliver thick, reinforced slabs that give you a reliable, easy-to-maintain surface for your bulk storage needs.
The term bunker slab typically refers to a large concrete floor used in open containment areas. Common examples include:
Our focus is on the heavy floor aspect. For example, a dairy farm might request a feed bunker slab of 320m² to store silage, requiring it to handle the weight of several hundred tonnes of feed plus loader operations (we recall cases of around 600 cubic yards of concrete for a feed bunker in one project, highlighting the scale). We deliver such slabs with proper jointing and reinforcement to avoid cracking under those loads.
Unlike a standard driveway or shed slab, bunker slabs are typically much thicker and more reinforced. Here are typical design features: – Thickness: It’s not uncommon for bunker slabs to be 150mm, 200mm, or even 250mm thick, depending on load. For example, a feedlot apron might be 125-150mm for lighter loads, but areas where front-end loaders operate with heavy weights might be specified at 200mm thickness with high-strength concrete. In some U.S. farm guidelines, at least 6 inches (~150mm) is recommended with thicker edges of 300mm to prevent edge breakage. – Concrete Strength: Often 32 MPa or higher. For agricultural use, a higher strength (and low permeability) helps resist attack from silage acids or manure, and reduces wear. We frequently use 40 MPa for commercial grain bunker slabs to ensure durability. – Reinforcement: Heavy mesh (like SL82, SL92) or rebar grid (e.g., N16 bars at 200mm spacing) is used to carry loads and control cracking. If large vehicles or point loads (like jacks or container feet) occur, we design rebar accordingly to spread those loads. – Joints: For expansive slabs, we incorporate contraction joints (sawn or formed) at appropriate intervals (could be 4-6m grids, etc.) to control shrinkage cracks. Construction joints are also planned, as these slabs are large and often poured in sections. We ensure joints are either keyed or dowelled to prevent differential movement if heavy wheels cross them frequently.
Surface Finish: Typically, a broom or textured finish for traction, especially if the slab may get wet or have organic material (slippery). In feed bunkers, a slightly rough finish is good so loader tires have grip and also any liquids drain off rather than pond. Sometimes a brush or swirl finish is used. – Slight Slope: We usually build a gentle slope (1-2%) on the slab to shed water (rain or effluent). For example, a grain bunker slab might slope to one side so rainwater doesn’t pool around stored grain. – Edge Thickening: If open edges will be driven over, we often thicken the slab edges or install a footing beam to avoid edge cracking under wheel loads. Some farm designs call for a 300mm deep edge by 300mm wide “turn-down” footing when slabs transition to grade, preventing undercutting by equipment or erosion. – Integration with Walls: Many bunkers have side or back walls (like concrete push-walls for silage or commodity sheds). We coordinate the slab pour with wall footings: sometimes the slab itself extends under the wall, other times a separate footing and slab, tied with reinforcement. If pre-cast wall panels are used, we often embed anchor points or set keyways in the slab for those panels as recommended by manufacturers.
Constructing a bunker slab is akin to a large industrial floor: 1. Site Prep: The subgrade is crucial. It must be well-compacted and capable of supporting big loads. We often lay a crushed gravel base (100-150mm) compacted to give a stable, uniform support and also to act as a capillary break if moisture is an issue. 2. Formwork: We set forms for the perimeter or use existing walls as forms if present. Given that these slabs can be expansive, we also set interior screed guides (perhaps temporary formwork or use a laser screed) for level control. 3. Rebar Placement: Lay out steel mesh or rebar cage according to design. Support it on chairs so it ends up near the mid-depth of the slab. Overlap laps properly, tie everything securely, because during the big pour, workers and equipment might be moving about. We ensure extra rebar around joints or where heavy loads concentrate (like near walls where loaders might frequently impact). 4. Pouring Concrete: For large slabs, we employ modern methods. Sometimes, a laser screed machine is used for very large pads to achieve flatness quickly. Or we segment pours into strips or bays to manage them. Continuous pours are ideal to minimise cold joints. We use concrete pumps or a direct chute, depending on access. Given Perth’s climate, in hot weather we pour early morning or evening to avoid too-fast setting.
5. Finishing: Typically, we don’t want a slick finish, so we do not over-trowel. We might bull-float to level initially and then apply a broom finish at the right time for texture. On very large surfaces, ride-on power trowels can be used with float blades, then a light broom dragged after, to combine flatness with texture. 6. Curing: We cure diligently. Use of curing compound sprayed on is common for big slabs (white pigmented if under the sun to reflect heat). Or keep the slab wet with covers. This prevents surface shrinkage cracking and ensures the slab reaches full strength, especially important before heavy equipment runs on it. We often advise keeping heavy loads off for at least 7-10 days (depending on concrete strength gain), even if the concrete has hardened, to avoid early micro-cracks.
Because bunker slabs often live outside, we also consider joint sealing if needed. For instance, if storing grain, you might seal joints to prevent grain from getting trapped or moisture from seeping. We can install joint sealants or leave them open per client preference.
We design our Perth bunker slabs to withstand repeated loading. Forklifts, loaders, and trucks impose thousands of cycles of stress. Our use of adequate thickness and reinforcement ensures that cracking is minimised. A slight hairline crack might appear eventually (concrete often cracks minimally), but with our reinforcement, it stays tight and doesn’t shift or spall. The heavy rebar also allows the slab to act as one mat, distributing concentrated loads like loader bucket corners pressing down.
For example, consider a feed bunker where a loader is repeatedly pushing silage across the slab. That introduces friction and impact. We might choose a stronger concrete mix with some fibres to reduce surface wear. Additionally, if acid attack is a concern (from fermented feed), we can use sulphate-resistant cement or add protective coatings. Some farmers will coat their silage pits with epoxy or bitumen, but a properly cured dense concrete often holds up fine; still, we discuss such options with the client for longevity.
Maintenance of a bunker slab built by us should be minimal. Possibly resealing joints or cleaning is all. The slab will be flush and without ridges, so scraping with loader buckets doesn’t catch (however, we do caution users to have rubber blades or not dig too deep with metal buckets directly on concrete to prolong surface life).
These slabs can also double as pads for other purposes off-season, like storing machinery or hay, because of their strength and size.
In sum, we provide a heavy-duty concrete slab solution that fits the rugged use cases of bunkers. We know farmers and industrial operators depend on these floors day in and day out, so we construct them much like a highway pavement, for durability under heavy traffic. We’ve been part of projects pouring hundreds of cubic metres in a day to create these large surfaces, and our team handles it smoothly, coordinating concrete supply and finishers expertly.
