You order concrete by the cubic metre, a mixer truck arrives on site, and the concrete slides down the chute ready to pour. What happens before that truck arrives plays a major part in how the finished concrete performs. Ready-mix concrete is batched at a plant to a set specification, then delivered ready to place instead of being mixed by hand on site. Learning how ready-mix concrete works helps you order the right grade, plan the pour, and end up with a foundation or floor that performs for years.
Concrete is the most used material on earth after water, with 3 tonnes per year used for every person in the world. Most of that reaches sites as ready-mix, batched under controlled conditions for an accuracy that hand mixing cannot match. The parts that make up the mix, the way it hardens, and the grade you choose all affect the result.
What Is Ready-Mix Concrete
Ready-mix concrete is concrete made at a batching plant to a specific grade, then delivered to your site in a rotating drum ready to pour. The alternative is site mixing, where the materials are combined by hand or in a small mixer at the point of use.
Batching at a plant gives much tighter control over the proportions, which means the concrete that arrives matches the grade you ordered. That accuracy is the core of how ready-mix concrete works, and the reason it is used on commercial and domestic pours alike.
What Goes Into Ready-Mix Concrete
Every batch comes down to four ingredients, each doing a specific job in the mix. The proportions change with the grade, but the components stay the same.
Cement as the Binder
Cement is the binder that holds everything together. Once water is added, the cement forms a paste that coats the aggregates and hardens as the batch cures. The cement content and water-to-cement ratio both influence the final strength, alongside the aggregate blend and other mix properties.
Aggregates for Bulk and Strength
Aggregates make up the bulk of the mix and give the concrete its body. Two sizes go into a standard batch:
- Fine aggregate, usually sharp sand, fills the gaps between the larger pieces
- Coarse aggregate, such as gravel or crushed stone, carries much of the load
The blend of the two affects how workable the wet concrete is and contributes to the strength of the hardened mix. Getting that balance right is part of what the plant controls.
Water That Starts the Reaction
Water does more than make the mix pourable. Once water meets the cement, a chemical reaction called hydration begins, and that reaction hardens the concrete. Too much water weakens the final result, and controls the water-to-cement ratio as part of the mix design.
Admixtures for Extra Performance
Admixtures are optional additives that adjust how the concrete behaves. Retarders slow the setting time for long transits or hot weather, while accelerators speed it up in cold conditions. Plasticisers improve workability without adding water. The plant adds these only where the job calls for them.
How Ready-Mix Concrete Is Batched and Delivered
Batching is where the raw materials become concrete. The plant weighs each ingredient to the mix design, combines them, and loads the result into a mixer truck for transport.
The process runs in a few controlled stages:
- Materials are weighed to the exact proportions of the ordered grade
- Cement, aggregates, water, and any admixtures are combined at the plant
- The mixer drum keeps turning in transit to help keep the concrete from separating
That constant rotation keeps the mix uniform and workable until it reaches you. At Pro-Mix Concrete, our ready-mix concrete delivery process covers each stage in full, from the order through to the moment the drum stops turning.
What Happens When Ready-Mix Arrives On Site
Getting the concrete to site is only part of the process. The area needs to be prepared before delivery, with the formwork, reinforcement and access ready for the pour. Once the truck arrives, the concrete can be discharged through the chute or directed through a pump where access is more difficult.
The basic process looks like this:
- The mixer truck is positioned as close as practical to the pour area
- Concrete is discharged through the chute or into a line or boom pump
- The fresh concrete is placed into the prepared formwork or slab area
- The concrete is compacted and levelled where required
- The surface is finished to the specification of the project
The timing matters because fresh concrete has a limited workable period. Once placement and finishing are complete, the concrete needs suitable conditions to set and cure properly. This final stage connects the controlled batching at the plant with the finished foundation, floor, driveway or other structure on site.
How Ready-Mix Concrete Sets and Gains Strength
Fresh concrete does not simply dry out. The mix hardens through hydration, a reaction between cement and water that builds strength over time.
Setting Stage
Setting is the short stage right after the pour, when the concrete stiffens from a liquid into a solid. It usually begins within a few hours, though the exact timing shifts with temperature and any admixtures in the mix.
Once set, the concrete holds its shape but carries very little load. That strength only comes with the curing that follows, which is why a fresh pour needs protecting during this early window.
Curing Process
Curing is the longer stage after setting, where the hydration reaction keeps running, and the concrete steadily hardens. This stage does the real work, and it stretches over weeks rather than hours.
A few conditions help the concrete cure properly:
- Steady moisture, so the reaction has the water it needs to continue
- Protection from wind, direct heat, and frost while the mix is young
- Enough time before the surface takes any heavy load
Rush this stage and the concrete ends up weaker and more likely to crack later on. Giving it the time and moisture it needs is what turns a fresh pour into a durable one.
Strength at 28 Days
Concrete is tested at 28 days because that is when it reaches its specified strength under standard conditions. Most of the gain happens early in the process. Research on strength development found that concrete reached almost 75% by the seventh day, with the rest building across the rest of the 28-day period.
Even after that point, the mix keeps hardening slowly for years. The 28-day mark is simply the benchmark the grade is measured against, not the end of the reaction.
Concrete Grades and How the Mix Is Specified
Concrete is sold by grade, a number that states its strength. The grade tells the plant exactly what mix to batch for your job. Each grade is measured in newtons per square millimetre, written as C10 up to C40 and beyond. Higher numbers mean a stronger mix built for heavier loads.
| Grade | Strength (N/mm²) | Typical use |
| C10 to C15 | 10 to 15 | Blinding, kerb bedding, non-structural fill |
| C20 to C25 | 20 to 25 | Foundations, footings, domestic slabs, driveways |
| C30 to C35 | 30 to 35 | Heavy-duty slabs, external paving, structural work |
| C40 | 40 | Structural and commercial pours under heavy load |
Grades are specified under UK standards such as BS 8500 and BS EN 206. These standards set out how each mix is designed and tested. Choosing the right one depends on the load, the exposure and the ground conditions.
If you cannot decide which grade your job needs, talk to our experts at Pro-Mix Concrete about what you are building, and we will work out the right grade and the volume before you order a single load.
Ready-Mix vs On-Site Mixing
We supply concrete two ways, and the right choice depends on the size and access of your job. Both come batched to the grade you need.
Ready-Mix Delivered to Site
Ready-mix concrete arrives fully batched in a mixer truck, poured straight from the drum on arrival. This route suits medium to large pours where you know the volume in advance. The mix stays consistent from the first barrow to the last, with no mixing work on your part.
Concrete Mixed Fresh on Site
Site mixing combines the materials at your location, giving you concrete made fresh at the point of use. This works well where access is tight, or the exact volume is hard to judge before the day. You get a workable mix without waiting on a full delivery load.
Both routes deliver the same batched quality to the grade you ordered. The difference comes down to volume, access, and how your site is set up.
When Ready-Mix Concrete Is the Right Choice
Ready-mix suits almost any pour beyond the smallest repair. The scale and accuracy make it the practical choice for most projects.
Ready-mix is the right call in these cases:
- Foundations, footings and ground slabs that need a reliable grade
- Driveways, patios and larger domestic pours
- Any job where consistency across the whole pour matters
- Pours too big to mix by hand in the time available
For a very small job, a few bags mixed by hand may be enough. Once the volume climbs or the grade matters, a batched supply saves time and gives a dependable result.
How long does ready-mix concrete stay workable after delivery?
Ready-mix concrete usually stays workable for around two hours after batching, though heat, distance, and admixtures affect the window. Retarders can extend it for longer transits. Placing and finishing the pour promptly gives the best result.
Can ready-mix concrete be pumped to where it is needed?
Ready-mix concrete can be pumped with a line or boom pump. This reaches over buildings and into spots a truck cannot access. Pumping suits upper floors, back gardens and tight sites where the chute will not stretch far enough.
What happens if too much ready-mix concrete is ordered?
Ordering a little over is common, and the surplus is usually taken back with the truck or placed elsewhere on site if you have a use for it. Working out the volume accurately beforehand keeps waste and cost down.
Final Takeaway
Ready-mix concrete works because every batch is measured to a set grade, mixed under controlled conditions, and delivered ready to place before it cures into its full strength over the following weeks. The ingredients decide the mix, the grade matches it to the job, and the curing turns a fresh pour into a lasting one. Understanding how ready-mix concrete works puts you in a far better position to order the right grade, plan the pour around it, and end up with a foundation or floor that performs for years.
Concrete only performs when the mix is matched to the job, and that match is the part we take off your hands. At Pro-Mix Concrete, we batch every grade from C10 to C40 to your specification and supply it across London and the surrounding areas, delivered ready-mixed or mixed fresh on site, then pumped straight to where the pour needs to reach.
Tell us the job, and we will help you settle on the grade, work out the volume, and get a workable mix to site on your date.
- Dennis Broderick is the founder and owner of Pro-Mix Concrete Company, a trusted name in ready-mix concrete solutions across the UK. With over 20 years of hands-on experience in the construction and concrete industry, Dennis brings unmatched expertise, practical insights, and a commitment to quality on every project - from residential driveways to large-scale commercial developments.
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