Lignite in Sand: What’s Actually Lurking in Your Sand?

Lignite in sand is probably something you’ve never heard of, because most people haven’t.

When most people think about sand, they imagine it’s all the same. Clean, simple, and ready to use. But when it comes to concrete and screed, that assumption can lead to costly surprises.

Sometimes, what’s hiding in your sand can cause real problems for your project. One small impurity, known as lignite, can make a big difference to the quality and durability of your mix.

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Flowmix Tewkesbury: Tel: 01684 217888 Flowmix Walsall: Tel: 01922 741731

What Is Lignite?

Lignite is a soft, brownish type of coal that can sometimes occur naturally in sand deposits, especially if the sand source has become contaminated. It looks harmless enough, but in concrete and screed production, lignite behaves very differently from standard sand particles.

Because it’s light, porous and organic, lignite tends to absorb water during mixing. Later, as the concrete or screed dries out or becomes wet again, it expands and contracts. This constant movement can cause visible surface damage and weaken the integrity of the finished material.

Why Lignite Is a Problem in Concrete and Screed

Even small traces of lignite in sand can cause noticeable issues once the concrete has hardened. Some of the most common problems include:

• Pop-outs and craters – small holes or blemishes that appear on the surface
• Uneven colour or dark patches – caused by lignite reacting within the mix
• Weak spots or poor bonding – reducing the overall strength of the concrete or screed

While these issues may seem cosmetic at first, lignite in sand can lead to long-term durability issues. Surfaces may become more prone to cracking, and the overall finish may lose its smooth, professional appearance.

Need Expert Advice?

Speak to the team at Flowmix Tewkesbury or Walsall. We are happy to help with all your concrete requirements.

Flowmix Tewkesbury: 01684 217888 Flowmix Walsall: Tel: 01922 741731

How Flowmix Prevents Lignite Contamination

At Flowmix Tewkesbury, Gloucestshire and Aldridge, Walsall, quality control begins with the materials we source. We use only high-quality sands and aggregates, thoroughly tested to ensure they’re clean, consistent, and free of impurities such as lignite.

If a sand quarry shows any sign of contamination, our team identifies and rectifies the issue immediately through our extensive network of trusted suppliers. This proactive approach guarantees that every batch of concrete and screed we deliver meets the highest possible standards.

Our goal is simple: to provide strong, smooth, and reliable mixes that perform exactly as they should, every time.

✅ Order ready-mix or volumetric concrete today
✅ Free, fast quote within 24 hours
✅ Call, message or complete our simple online form

Flowmix Tewkesbury: Tel: 01684 217888 Flowmix Walsall: Tel: 01922 741731

Why Quality Control Matters

Quality concrete starts with quality materials. Even a small amount of lignite in sand can impact the appearance and performance of a finished surface, so it’s essential to know where your materials come from.

When you order from Flowmix, you can rest assured that we have produced your mix using clean, carefully tested materials, giving you confidence that your project will stand the test of time.

It’s just one of the details that make a big difference in the quality and reliability you get from Flowmix.

If you’re sourcing concrete or screed elsewhere, it’s worth asking your supplier a simple question:
Does your sand contain lignite?

Because when it comes to concrete, the smallest details often make the biggest difference.

How Flowmix Can Help With Your Project

Flowmix has two plants, Gloucester and Walsall. We provide the following services (with time slots):

• Ready-mix concrete, mix on-site (volumetric concrete)
• Traditional and liquid screed.
• Concrete line pump Hire to reduce manual labour and associated costs, increase efficiency, reduce wastage and clean up.
• Interlocking concrete blocks for temporary or permanent barriers.
• Mini mix deliveries up to 4 cubic metres.

Flowmix has the BSA-approved Ready Mix Concrete Kitemark KM683844, a certification that “confirms a product or service’s claim has been independently and repeatedly tested by experts” (source BSI).

Flowmix Tewkesbury: 01684 217888 Flowmix Walsall: Tel: 01922 741731

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