Structural and base materials · Concrete & Cement
Ready-Mixed Concrete (Ready-Mix)
Explains concrete supplied plastic and placed in position, and why the pour, the weather and the site operation form part of the material that ends up in the structure.
Educational reference entry. Suitability depends on the complete assembly, substrate, exposure, installation method, manufacturer documentation, local requirements and qualified professional review.
Overview
What ready-mixed concrete is
Ready-mixed concrete is proportioned and batched at a central plant, then delivered to site in a rotating drum truck while still plastic. The constituents are a cement binder, coarse and fine aggregate, water, and usually one or more admixtures. The drum keeps the mix agitated so it can be discharged, placed and worked before it stiffens.
The defining characteristic is that the material arrives unformed. Its shape comes from formwork erected on site, and its surface comes from whatever is done to it in the period after placing. Site conditions therefore become part of the product: weather, truck access, discharge, compaction and curing all influence the concrete that ends up in the works. Precast concrete inverts this, being cast and cured in a factory and delivered as a finished element.
Mixes are ordered against the performance the designer has asked for rather than by a single fixed recipe, and plants adjust proportions and admixtures accordingly. Two loads described in similar terms can still behave differently in workability, set and finish, which is why the delivery paperwork for each load is worth keeping.
Terminology
Common names and aliases
These names describe the same thing. The library keeps one entry per material so that an acronym, a trade name or a regional spelling never becomes a second, thinner page.
- Ready-mix concrete
- Readymix concrete
- Site-placed concrete
- Truck-mixed concrete
Applications
Common applications
Where this material is typically encountered. A typical application is not a statement that it suits your project.
- Foundations, ground beams and pile caps poured into excavated or formed profiles on site.
- Ground-bearing floor slabs in houses, garages, extensions and outbuildings.
- In-situ walls, columns and suspended slabs cast within temporary formwork.
- Driveways, paths, patio bases and hardstandings in external works.
- Bases and surrounds for structures such as posts, fences and sports court foundations.
- Infill and levelling pours around existing construction where an element is formed in place.
Consideration
Where it is commonly considered
- Where an element has an irregular shape or must be formed to fit existing construction.
- Where the volume required is greater than can sensibly be mixed by hand on site.
- Where a continuous pour without joints is preferred by the designer for a given element.
- Where site access allows a mixer truck to reach the pour, or a pump can be positioned.
- Where the element has to be bonded or tied into work already built in position.
Professional review
Where additional professional review is especially important
These are the situations where the answer depends on the specific building, and where a qualified professional should be involved before anything is decided.
- Where the truck cannot reach the pour and no pumping or barrowing route has been planned.
- Where the pour would take place in freezing or very warm conditions without protection agreed in advance.
- Where the design calls for a factory finish or a tight dimensional tolerance better suited to precast.
- Where the pour is over or against an existing structure whose capacity has not been assessed.
- Where discharge would run past the workable period because of traffic, queuing or limited labour.
Properties
Key properties to discuss
Qualitative topics worth raising. Measured values, classes and grades come from the manufacturer's technical documentation for the specific product, not from a reference page.
- Installation dependency
- Placing, compacting and curing all happen on site within a limited window after batching. Delivery timing, labour numbers, vibration of the pour and protection afterwards all influence the concrete that is actually achieved in the element.
- Documentation
- Each delivery normally arrives with a docket describing the mix supplied, and the supplier holds the technical data behind it. Keeping the dockets gives a record of what went into each part of the works for anyone looking at it later.
- Moisture behaviour
- Fresh concrete carries a large amount of water that continues to leave the slab long after the surface looks dry. Anything laid over it, such as flooring, adhesives or coatings, depends on that drying, and the readiness assessment belongs to the specialist installing the covering.
- Weathering and exposure
- Concrete exposed outdoors is affected by rain, freezing and thawing, de-icing salts and ground moisture. How a particular mix behaves depends on its constituents and on the drainage and detailing around it, so exposure is worth raising with the designer and the supplier.
- Appearance
- The finished look is created on site by the formwork face, the finishing technique and the curing regime. Colour varies between loads and between pours, and patchiness or surface marking is common where finishing conditions changed part way through.
- Substrate dependency
- What the concrete is placed on matters. Ground preparation, sub-base, membranes and any reinforcement fixed in advance all sit under the pour and cannot be corrected once the concrete is in place.
- Repairability
- Local defects can sometimes be cut out and made good, but repairs in a monolithic element rarely match visually, and the structural implications of cutting into one are a matter for a qualified professional.
Exposure
Exposure and environmental conditions
- Will the pour take place in cold, wet or very warm weather, and what protection has been planned?
- Is the element exposed to ground moisture, standing water or run-off once it is in service?
- Will de-icing salts or other chemicals reach the surface in normal use of the site?
- Does any part of the pour sit where freezing and thawing are likely while it is still gaining strength?
- Has the supplier been told about the exposure conditions so the mix can be discussed for that situation?
Assembly
Substrate and system dependencies
What this material sits on, is fixed to or depends on. This is usually where performance is won or lost.
- Ground preparation and sub-base condition under a slab affect what happens to the concrete afterwards.
- Any damp-proof membrane, insulation or separating layer has to be positioned before the pour and cannot be added later.
- Reinforcement, service ducts, drainage and fixings are set out and secured while the formwork is still open.
- Formwork alignment, support and release treatment shape both the geometry and the visible face.
- Movement and construction joints are located as part of the design rather than decided during the pour.
Appearance
Appearance and finish considerations
- Colour differs between deliveries and between pours, and matching an existing area of concrete is rarely achievable.
- Trowelled, brushed, tamped and exposed-aggregate finishes are produced by different site operations and look quite different.
- Form-face texture, tie positions and panel joints stay visible on walls left as struck.
- Surface blemishes such as blowholes, plastic settlement marks and colour banding are normal features of site-cast work.
- If the slab is later to be ground and polished, that intention changes what needs agreeing before the pour.
Durability
Durability questions
Questions to raise rather than a service life to expect. No material has a universal lifespan — it depends on the assembly, the exposure and the upkeep.
- What exposure has the mix been discussed for, and who is holding that decision?
- How will the concrete be protected and cured in the period immediately after placing?
- Is any surface treatment or sealer intended, and who is responsible for specifying it?
- Where reinforcement is present, how is its cover being controlled during the pour?
- What is the plan for crack control, and which joints are intended to open?
Upkeep
Maintenance and repair considerations
- How will the surface be cleaned, and are there cleaning agents the supplier advises against?
- If a sealer is applied, how often does its manufacturer expect it to be renewed?
- How would a cracked or spalled area be assessed, and who should carry that out?
- Are there records of the mix and the pour that a future repair could refer back to?
- What visual changes should be treated as normal, and what should prompt professional inspection?
Installation
Installation dependencies
What the installation depends on — not how to do it. Method belongs to the manufacturer's instructions and the trades carrying out the work.
- Truck access, standing room and discharge position have to be worked out before the delivery is ordered.
- Where the pour cannot be reached directly, a pump, skip or barrow route becomes part of the plan.
- Enough labour needs to be present to place, compact and finish the whole load within its workable period.
- Formwork has to be strong and tight enough to resist the pressure of wet concrete without moving or leaking.
- Curing and protection arrangements form part of the works rather than an optional extra after the pour.
- Weather forecasts influence whether a pour goes ahead on the planned day.
Documentation
Documentation to request
Ask for these in writing, for the specific product being proposed, and keep them with the project record.
- Delivery dockets for each load, showing the mix supplied and the time of batching.
- The supplier's technical description of the mix and any admixtures included in it.
- The designer's information covering reinforcement, cover and joint positions.
- Any curing, protection and finishing requirements the designer has set for the pour.
- Records of any testing carried out, where testing forms part of the works.
Conversations
Questions for qualified professionals
Bring these to the relevant qualified professional, manufacturer or authority. Requirements vary by project and location.
- Who has specified the mix for this element, and what were they told about its exposure?
- How will the concrete be placed and compacted, and what happens if the load arrives late?
- What curing and protection are planned, and who is responsible for carrying them out?
- Where are the joints, and what movement are they intended to accommodate?
- Is reinforcement required here, and who is confirming its size, position and cover?
- What finish is expected on the visible faces, and how will it be achieved?
- How long should we expect to wait before loading, covering or finishing over this concrete?
- What would you want to see on site before treating the pour as complete?
Blind spots
Commonly overlooked points
- The concrete cannot be improved after discharge, so the decisions have to be made before the truck arrives.
- Drying is not the same as strength gain, and floor coverings depend on the first while structures depend on the second.
- Part-loads and separate deliveries on different days often show as visible colour differences in the finished surface.
- Adding water on site to make a stiff load easier to place changes the material that was ordered.
- Access constraints such as overhead cables, soft ground and gateway width are frequently discovered on delivery day.
What this page does not do
- Where concrete carries load, the mix, reinforcement, sizing and adequacy are engineering decisions for a qualified professional.
- This page does not state whether any mix suits a particular exposure, structure or location, which depends on the design and on local requirements.
- Site safety, chemical handling and placing procedures are matters for the contractor and sit outside the scope of this reference.
- Build Design Hub does not supply, test, approve or endorse concrete or any supplier of it.
Related entries
Related materials
Materials from the same family, an adjacent role in the assembly, or a shared application.
Inspiration
Related Ideas Library pages
Design directions where this material commonly appears.
Preparation
Related planning checklists
Owner-side preparation before the conversation where this material comes up.
Go deeper
Related Build Design Hub guides
Planning guidance and neutral comparisons behind the decisions on this page.
Concrete & Cement Materials
Reference entries for cement-based materials — ready-mixed and precast concrete, screeds, levelling compounds, renders of the cementitious family and the admixtures that modify them.
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