20–40 mm Diabase Crushed Stone: Road Base & Drainage Aggregate

The 20–40 mm fraction is a coarse, robust crushed stone that excels as a supportive base and drainage medium in construction. Each stone is roughly 2–4 cm, derived from hard diabase rock that resists crushing under heavy loads. This fraction’s strength class (M1400) and frost durability (F300) remain on par with our smaller aggregates hkc.kz, so you get the same long-term performance in a larger size. What sets 20–40 mm aggregate apart is how it behaves in large-fill scenarios: the stones form a stable matrix with significant void space. Those voids are beneficial in applications like drainage and frost protection, as they allow water to pass through freely, preventing water buildup and ice expansion under structures.

Key application areas for 20–40 mm crushed stone include:

• Road base and subbase layers: This fraction is commonly used to build up the lower layers of roadways and highways. A layer of 20–40 mm diabase acts as a strong foundation that distributes vehicle loads over a wide area. It is often placed above even coarser fill and compacted to form the road subbase. Because the stones are large and hard, the road base remains stable over time, even under heavy truck traffic. Contractors use 20–40 mm aggregate to stabilize dirt roads, highway bases, and airport runways, ensuring minimal deformation under load.

• Drainage beds and backfill: Thanks to its coarse nature, 20–40 mm gravel is ideal for drainage applications. It’s used in drainage layers around foundations, behind retaining walls, and in French drains or soakaway pits. The large voids between stones facilitate quick water runoff, which prevents water pressure buildup and mitigates issues like frost heave. For example, before pouring a concrete foundation, a layer of 20–40 mm stone is often laid as a drainage and capillary break (“foundation cushion”).  This keeps the foundation dry and stable over seasons.

• Railway sub-ballast and embankment fill: While main railway ballast typically uses slightly smaller fractions, 20–40 mm diabase can serve as a sub-ballast layer beneath the primary 25–60 mm ballast. It provides additional load distribution and drainage under the tracks. Additionally, this aggregate is used in general embankment fills and leveling of large areas, where its sheer weight and volume help form a solid platform for further construction.

One of the main benefits of using 20–40 mm diabase is the combination of strength and drainage it offers. The rock’s high compressive strength means it won’t pulverize under compacting equipment or traffic, and its frost resistance ensures longevity in outdoor use. At the same time, when layered, it creates a permeable structure that handles water well – a critical factor in preventing damage to roads and foundations from water and ice. B2B clients, such as road builders and civil engineering firms, appreciate that our diabase is uniformly graded and clean (low fines), which makes compaction more predictable and prevents clogging of drainage intended voids.

From a supply perspective, we offer direct quarry sourcing in the large volumes that big projects demand. Our rail delivery system is capable of moving tens of thousands of tons efficiently, lowering the cost per ton delivered for customers building long highway stretches or extensive facility foundations. Using 20–40 mm diabase crushed stone from us means you’re investing in a stable, well-drained foundation for your project – and doing so with a reliable partner who will keep that material flowing to your site as needed.