How to Mix Concrete — Step-by-Step UK Guide

Mix Ratios by Application

What You'll Need

Before You Start

• Calculate the volume of concrete you need — length × width × depth. Add 10% for waste and spillage.
• For volumes over 1m³, consider ordering ready-mix concrete — it is more consistent and saves a huge amount of labour.
• Use our Concrete Mix Calculator to work out exact quantities of cement, sand and aggregate, and our Concrete Volume Calculator for the total volume needed.
• Store cement bags off the ground and under cover — wet cement sets in the bag and is wasted.
• Wear gloves — wet cement is alkaline and burns skin on prolonged contact. Wash any splashes off immediately.

Step-by-Step Instructions

Method 1: Mixing by Machine (Cement Mixer)

Step 1: Set Up the Mixer

Position the cement mixer on firm, level ground close to where the concrete will be placed. Ensure it is stable and will not tip when loaded. Connect to power (electric) or fuel (petrol/diesel).

Step 2: Add Half the Water

Start the mixer and add approximately half of the water you think you will need. Adding water first prevents dry material from sticking to the drum.

Step 3: Add the Aggregate

Shovel in the coarse aggregate (gravel). Use a bucket to measure consistent quantities — one full bucket = one "part" of the ratio. Let it tumble for 30 seconds with the water.

Step 4: Add the Sand

Add the sharp sand in the correct ratio. For C20 (1:2:4), add two buckets of sand for every four buckets of aggregate. Let it mix for another 30 seconds.

Step 5: Add the Cement

Add the cement (one bucket per batch for the ratios above). If using plasticiser, add it to the remaining water now. Let it mix for 1-2 minutes.

Step 6: Adjust the Water

Add the remaining water gradually. The mix should be uniform in colour, hold its shape when formed, and slide cleanly off the shovel. It should not be sloppy or crumbly. A good test: form a ridge with the back of a shovel — it should hold without slumping or cracking.

Step 7: Pour and Compact

Tip the concrete into your formwork or trench. Spread it evenly with a shovel and tamp it down with a tamping beam to remove air pockets. For slabs, use a screed board across the formwork rails to level the surface. For foundations, a rough tamp is sufficient.

Method 2: Mixing by Hand

Step 1: Measure the Dry Materials

On a clean, hard surface (mixing board or old sheet of plywood), measure out the dry materials using a bucket. For C20: four buckets of aggregate, two of sand, one of cement. Form a mound.

Step 2: Mix Dry

Turn the pile over with a shovel at least three times until the colour is uniform throughout. There should be no streaks of unmixed cement or sand.

Step 3: Form a Crater and Add Water

Make a well in the centre of the pile. Pour water into the well gradually. Fold the dry material into the water from the edges, turning and mixing continuously. Add water in small amounts until you reach the correct consistency.

Curing

Concrete must be kept moist during curing to develop full strength. In warm or windy weather, cover with polythene sheet or damp hessian for at least 7 days. In cold weather, protect from frost with insulating blankets. Do not pour concrete if the temperature is below 3°C or frost is forecast within 48 hours.

Common Mistakes to Avoid

• Too much water: The most common mistake. Excess water makes the mix easier to work but dramatically reduces strength. Halving the water-to-cement ratio roughly doubles the strength.
• Inconsistent measuring: Guessing quantities with a shovel gives inconsistent results. Always use a bucket for accurate ratios.
• Not compacting: Air pockets (honeycombing) weaken concrete. Always tamp or vibrate to remove trapped air.
• Pouring in freezing conditions: Water in the mix freezes before the cement sets, resulting in very weak, crumbly concrete.
• Using building sand instead of sharp sand: Building (soft) sand is for mortar, not concrete. Sharp (concreting) sand has angular grains that interlock with the aggregate for strength.
• Not curing properly: Concrete left to dry out too quickly cracks and does not reach full strength. Keep it moist for at least 7 days.

Cost Estimate (2026 UK Prices)

Use our Concrete Mix Calculator and Concrete Volume Calculator for exact quantities for your project.