Concrete mixing looks simple, but small errors destroy your project. Whether you’re building a garden path or laying a driveway, getting the concrete mix wrong costs time and money. At Express Concrete, we’ve seen these concrete mixing mistakes happen countless times over our 30+ years in London. Here are the biggest mistakes to avoid.
1. Adding Too Much Water
This is the worst error you can make with your concrete mix. When concrete looks thick and hard to pour, people add extra water. Don’t do this.
Extra water weakens everything. It dilutes the cement that holds your cement and aggregates together. The concrete pours more easily, but once dry, you get weak, crumbly concrete that cracks quickly.
What goes wrong:
- Weak concrete that breaks easily
- Cracks appear everywhere
- Water pools on the surface of the concrete
- Poor-looking finish
The fix: Follow the correct water-cement ratio. Most concrete needs 50kg of water for every 100kg of cement. If mixing feels difficult, use ready mix concrete where ratios are spot-on every time.
2. Wrong Mix Proportions
The basic concrete mix recipe is one part cement, two parts sand, and three parts stone. People try to save money by using less cement or more stone. This always fails.
Cement makes concrete strong. Less cement equals weak concrete. Too much stone creates gaps and makes concrete mixing impossible.
Do this instead: Stick to 1:2:3 exactly. If you’re unsure about the amount of concrete ingredients needed, get professionally mixed concrete delivered.
3. Bad Weather for Concrete Work
Weather conditions matter hugely. Pouring concrete when it’s too hot (above 27°C) or cold (near freezing) creates big problems.
Hot weather makes concrete harden too fast. You rush through concrete finishing and get poor results.
Cold weather can freeze your concrete before it sets properly. Frozen water expands and cracks your concrete slab from the inside. This makes weak concrete that falls apart later.
Best approach: Plan concrete mixing for mild days between 10°C and 27°C. Always check weather conditions before starting.
4. Poor Site Preparation
Rushing to prepare the site ruins many jobs. Your concrete slab needs solid, level ground underneath. Bad preparation means cracks and sinking concrete.
Common preparation errors:
- Not removing grass and soft soil
- Skipping ground compaction
- Missing the gravel base
- Not checking the ground is level
The right way: Take time with preparing the site. Remove all grass and soft soil first. Add compacted gravel, then check everything’s level before concrete mixing.
5. Wrong Mixing Time
Concrete mixing time makes a big difference. Mix too little, and you get lumpy concrete with weak spots. Mix too much, and you weaken the concrete by breaking down the cement.
Signs of poor mixing:
- Visible cement lumps (too little mixing)
- Streaky colours (too little mixing)
- Cement and aggregates separate (too much mixing)
- Mix becomes hard to handle (too much mixing)
Get it right: Mix until your concrete mix looks uniform, then stop. Usually takes 3-5 minutes with proper equipment.
6. Using Poor Materials
Old cement loses strength. Damp cement forms lumps that won’t dissolve. Dirty stone and sand weaken your concrete mix. Poor materials guarantee poor results.
Check everything: Cement should feel powdery and flow freely. Stone and sand should be clean with no mud. Never use cement over a year old.
7. Concrete Finishing Problems
Concrete finishing separates good work from amateur jobs. Many people think pouring concrete is the end. It’s not.
Common finishing errors:
- Starting while water sits on the surface of the concrete
- Using the wrong tools
- Bad timing
The US Environmental Protection Agency’s concrete guidelines emphasise that proper concrete finishing depends on correct material ratios and timing. Starting concrete finishing before the surface of the concrete is ready ruins your project.
Do it properly: Wait until surface water disappears completely. Then use proper tools for smooth concrete finishing.
8. Removing Forms Too Soon
People get excited and remove wooden forms too early. This destroys everything. Your concrete slab needs time to develop full-strength concrete.
The rule: Leave forms for 24-48 hours minimum. Concrete should feel completely firm before removing supports.
9. Calculating the Wrong Amount of Concrete
Getting the amount of concrete wrong causes delays or waste. Too little means visible joints where batches meet. Too much waste of money.
Calculate properly: Measure length × width × depth in metres. Add 5% for waste. When unsure, ask us – we help customers get exactly the right amount of concrete.
Why Ready Mix Concrete Prevents These Mistakes
These concrete mixing mistakes show why smart builders choose ready-mix concrete over site mixing. Professional suppliers like Express Concrete control every part of the concrete mix in perfect conditions.
Ready mix concrete gives you:
- Perfect cement and aggregates ratios
- Consistent strength concrete every time
- No mixing equipment to buy
- Expert advice on the right mix
- Fresh concrete delivered when needed
Our ready mix concrete service removes guesswork. You focus on preparing the site and concrete finishing while we handle the perfect concrete mix.
Working with Concrete Professionals
A concreting specialist understands how weather conditions, site preparation, and concrete mixing work together. They know which concrete mix suits different projects and how to avoid common mistakes.
Express Concrete brings over 30 years of London experience to every job. We’ve delivered thousands of loads, learning what works and what doesn’t.
The Bottom Line
Concrete mixing requires real skill despite looking easy. Small mistakes to avoid in ratios, timing, or technique turn simple projects into expensive disasters.
Professional ready-mix concrete eliminates most concrete mixing mistakes. You get consistent quality, save time, and avoid the stress of perfecting your concrete mix.
At Express Concrete, we’ve helped London builders avoid these problems since 1991. Whether you need advice on preparing the site or want perfectly mixed concrete delivered, we make your project successful.
Remember: good concrete work starts with planning. Take time preparing the site, use quality materials, and don’t rush pouring concrete or finishing concrete. Your project will look better and last longer.