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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.

Typical role:StructureSubstrate and baseExternal surface
Commonly met in:Foundations and groundworksStructural frameFloorsExternal works and landscape

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.

Component forms

Building components commonly formed from this material

Elements this material is commonly used to make, named by the position they occupy in an assembly rather than by what they are bought as. This states common practice only — it is not a statement that this material suits any of these components in a particular building.

Blinding →A weak concrete blinding is a common way of covering a formation and creating a working surface.Benching →Concrete is used to build up the body of the benching where the chamber is large or deep.Cover Zone →The zone is simply the outer part of the concrete delivered and placed; how well it compacts there is what makes it effective.Edge Restraint →A concrete haunching behind the edging is commonly what actually provides the restraint.Kicker →The upstand is cast from the same concrete as the pour it belongs to, which is part of why casting it monolithically is significant.Oversite →A thin concrete oversite is encountered in some construction; whether it is appropriate depends on the design of the void above.Protection Layer →A screed or concrete protection layer is used where heavy loading follows.Thickening →The concrete is placed in one operation with the slab around it in most raft construction.Rodding Eye →A concrete surround is commonly cast around the fitting to hold it and to carry the cover.

Related entries

Alternatives to consider

Entries that may be considered instead of this one for a similar job. Not a statement that they are interchangeable, or equal in any respect.

Precast concrete paving →Factory-made concrete units laid on a prepared base to surface patios, paths and drives, where what sits beneath the paving decides how it performs.

Related entries

Common comparisons

Entries met at the same decision but which behave differently, so the comparison is about the difference rather than a swap.

Precast concrete panels →Concrete units cast in a factory mould and cured under controlled conditions, delivered as finished elements to be lifted and connected rather than poured.Sprayed concrete →Concrete projected onto a face at speed rather than poured into formwork, compacting on impact, and used where forming a surface would be impractical.

Related entries

Often used alongside

Entries commonly encountered together with this one. Co-occurrence only — never a claim that any combination is compatible or suitable.

Acrylic Court Coating →A water based acrylic coating system built up in successive coats, usually with graded sand, over an external asphalt or concrete base and finished with applied line marking.Cement screed →A sand and cement layer laid to a thickness over a structural floor and worked level by hand, forming a true base for the floor finish above it.Concrete Densifier →A reactive silicate solution applied to hardened concrete that works inside the surface pores to reduce dusting, leaving no film and no added thickness on the floor.Concrete kerb & edging →Site-placed concrete is commonly met as the bed beneath and the haunch behind the unit.Crushed rock and unbound fill →A ground-bearing slab is commonly cast over a compacted granular construction, with whatever separating and damp-resisting layers the design calls for between them.Damp-proof membrane →A continuous sheet or liquid-applied moisture-control layer associated with floors and slabs, and a different product from the course built into walling.Dry Shake Hardener →A cement and hard aggregate blend broadcast onto fresh concrete and power floated in, adding a wear layer that becomes part of the slab surface during the pour itself.Extruded polystyrene →Rigid closed cell polystyrene board formed by extrusion, with a smooth skin and profiled edges, used in loaded and moisture exposed positions after professional review.Film-faced plywood →Plywood faced with a bonded resin film and sealed at the edges, made to be struck and reused, and to leave its own face as the surface of the concrete cast against it.Foamed glass aggregate →The layer is placed and compacted before a slab is cast over it; each does a different job and the arrangement between them is designed rather than assumed.Geocell →Concrete is one of the infills used where erosion protection or a channel lining is the purpose.Granolithic Screed →A cement and hard aggregate topping laid over a concrete base and finished as the floor itself, rather than as a levelling layer waiting for a covering to be laid on it.Non-metallic bar →Reinforcement made from glass, basalt, carbon or aramid fibres in a resin matrix: a bar that does not rust, which changes what cover is being asked to do.Polished concrete →A floor produced by grinding and refining an existing concrete slab with progressively finer diamond tooling, so the finish is cut out of the slab itself.Polymer concrete →Units of this kind are commonly bedded and haunched in site-placed concrete, which is generally what carries the load over them.Polyurethane sealant →A tougher and usually paintable elastic jointing sealant associated with construction joints where movement is combined with abrasion or contact wear.Pre-Applied Bonded Membrane →A composite sheet made for concrete to be cast directly against it, developing an adhesive bond so that water cannot travel along the interface between sheet and structure.Precast drainage units →Site-placed concrete is commonly met as the bed, surround or cover-frame haunching around these units, doing a different job from the units themselves.Profiled metal decking →Cold-formed profiled steel sheet spanning between supports as permanent formwork to a concrete floor, or as a structural roof deck carrying the build-up above it.PVC-U drainage pipe →Concrete surrounds and haunching are commonly cast around buried fittings, gullies and access points where the design calls for protection or where cover is shallow.Resin floor coating →Liquid resin systems applied wet and cured in place to form a jointless bonded surface, so preparation of the base and moisture within it largely decide the outcome.Self-levelling compound →A flowable powder-and-liquid mix poured over an existing floor base, spreading to find its own level and correct surface unevenness before a covering is laid.Steel reinforcing bar →Ribbed steel bar cast into concrete to carry tensile forces, protected from corrosion by the alkaline environment of the sound concrete cover surrounding it.Stone Kerb and Edging →Linear stone units worked to a consistent section and set along the edge of paved areas to define edges, form channels and mark changes of level.Void former →Units placed in the ground beneath concrete so that a void exists or appears under it, bought to be crushed or to break down rather than to stay intact.Waterstop →A profiled, hydrophilic or injectable strip cast into concrete joints to interrupt a leakage path inside the structure that no surface-applied membrane can reach.

Related entries

Commonly made using

Entries commonly incorporated into this one. Not a complete bill of materials, and not a statement that any of them suits a particular build-up.

Cement replacements →Ground slag, fly ash, limestone fines and similar powders that stand in for part of the cement in a mix, changing its early life rather than dosing its workability.Concrete admixtures →Materials added in small quantities to a concrete mix to change how it behaves fresh or hardened, dosed by the supplier as part of a designed mix rather than chosen by an owner.Concrete aggregate →The graded stone and sand that makes up most of a concrete or mortar mix by volume, where grading, shape, cleanliness and absorption decide how the mix behaves.Portland cement →The hydraulic binder that sets concrete, mortar, render and screed. It is one ingredient alongside aggregate and water, not the finished material itself.Recycled aggregate →Used as part of the aggregate fraction where a designer has accepted recycled content in the mix; the primary quarried aggregate it stands in for is covered by the library's aggregates and groundworks entries.

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.

Browse all concrete & cement entries →