Poured concrete, also called cast-in-place or in-situ concrete, is concrete placed as a fluid mix into formwork, where it stays until it has gained enough strength to be self-supporting. It’s the default placement method for foundations, slabs, columns, retaining walls and most above-ground structural elements, and on the right project it remains the most efficient way to build.
It isn’t, however, the only method. On schemes with restricted access, irregular geometry, or a live environment where formwork simply can’t go up, it isn’t the right one. This guide covers what poured concrete is, how it compares to sprayed concrete (shotcrete), and how to work out which one your project actually needs.
What Is Poured Concrete?
Poured concrete involves placing a fluid concrete mix into a pre-built formwork system, typically timber, steel or engineered plywood, which holds the mix in shape until it cures enough to be struck (removed) or stripped back. The formwork can then be reused or, on smaller jobs, discarded.
This is the traditional method behind:
- Foundations, footings and ground slabs
- Columns, beams and suspended floors
- Retaining walls and basement structures
- Most above-ground structural concrete in buildings and civil engineering schemes
Poured concrete is sometimes confused with precast concrete, which is cast off-site in a controlled factory environment and delivered ready to install. Poured (in-situ) concrete is mixed and placed on site, inside formwork built for that specific pour.
What Is Sprayed Concrete?
Sprayed concrete, also known as shotcrete or gunite, is applied pneumatically through a nozzle at high velocity. The force of impact compacts the material as it lands, which removes the need for formwork on the receiving face. It bonds directly to the substrate and can be built up in layers to reach the required thickness and reinforcement cover.
There are two delivery methods: wet mix, where the concrete is pre-batched and pumped to the nozzle, and dry mix (gunite), where water is introduced at the nozzle itself. Both are used across tunnelling, geotechnical works, structural repair and water feature construction.
Poured Concrete vs Sprayed Concrete: The Key Differences
| Factor | Poured Concrete | Sprayed Concrete |
|---|---|---|
| Formwork | Full containment required on all faces | One face or none, suiting open-face and underground work |
| Speed | Formwork erect/strike adds programme time | Excavation and support can proceed almost simultaneously |
| Strength | High, consistent, well understood | Comparable, and can exceed poured mixes when applied by an accredited nozzleman |
| Shape adaptability | Best for flat, regular geometry | The only practical option for curves, domes, irregular rock faces |
| Waste | Formwork waste, minimal rebound | Rebound (material that doesn’t adhere), kept under 10% with wet-mix and experienced crews |
| Best suited to | Slabs, columns, walls with reusable formwork | Underground, confined-access, irregular or time-critical structures |
Neither method is universally cheaper. It depends on the application. For simple, regular structures where formwork can be reused across multiple pours, poured concrete is usually the more economical choice. For complex, irregular or underground structures, sprayed concrete typically wins on total cost once formwork elimination and programme time are factored in.
When to Specify Poured Concrete
- The structure is regular, above ground, and formwork can be reused
- Finish quality and mix consistency are the priority
- The geometry and volume suit conventional batching and placement
When to Specify Sprayed Concrete
- Access is restricted or the work face is irregular
- Programme is critical and early strength gain matters
- The structure is underground, submerged, or exposed to aggressive ground conditions
- Formwork isn’t practicable or economically viable
- The profile involves complex curves or variable thickness
Why This Decision Isn’t Academic: Farnworth Railway Tunnel
In 2015–16, Fineturret carried out reinforcement and shotcrete lining of an existing 370m, 8.00m-internal-diameter tunnel beneath the A666 dual carriageway at Farnworth, for J Murphy & Sons and United Utilities. The work had to fit around 10 weekend rail possessions, run in double shifts, with 90 skilled operatives across a 7-and-4 shift pattern.
Poured concrete wasn’t an option here. There was no possession window long enough to erect formwork, pour, and wait for strike strength before handing the line back. Sprayed concrete let excavation and lining proceed within the same possession, in an open-faced drive, with the tunnel needing to be self-supporting almost as soon as the material was applied. It’s the kind of constraint that decides the method before cost or finish even enter the conversation, and it’s why the placement method has to be part of the specification discussion at design stage, not an afterthought once formwork has already been drawn.
Getting the Specification Right
Whichever method suits your structure, the outcome comes down to the contractor’s skill and the rigour of the specification. Mix design, application technique (for sprayed concrete, a competent, accredited nozzleman) and curing regime all need to be controlled properly for either method to perform to design intent.
Fineturret has specified and delivered both placement methods across 50+ years of civil engineering work, from flood alleviation schemes to national infrastructure including Sellafield and Hinkley Point C. Where sprayed concrete is the right call, our sprayed concrete contractors team can advise from early design (including Early Contractor Involvement) through to delivery. For the full technical picture on tunnel applications specifically, see our guide to sprayed concrete lining (SCL).
If you’re weighing up poured versus sprayed concrete for an upcoming scheme, get in touch for independent technical advice and a quotation.
Frequently Asked Questions
Is poured concrete the same as cast-in-place concrete?
Yes. Poured concrete, cast-in-place concrete and in-situ concrete all describe the same method: concrete mixed and placed on site into formwork, as opposed to precast concrete, which is cast off-site and delivered ready to install.
How long does poured concrete need to cure before formwork can be struck?
It depends on the mix design, ambient conditions and the structural element. Formwork is typically struck once the concrete has reached sufficient strength to be self-supporting, while full design strength takes longer (commonly around 28 days) to develop.
Can sprayed concrete achieve the same strength as poured concrete?
Yes. When applied by an experienced, accredited nozzleman, sprayed concrete can match, and in some cases exceed, the compressive strength of an equivalent poured mix, producing a dense, low-permeability matrix.
Which method costs less?
Neither is universally cheaper. Poured concrete is usually more economical for simple, regular structures where formwork is reused. Sprayed concrete is typically more cost-effective once formwork elimination and programme time are factored in for complex, irregular or underground structures.
