Pozzolanic Cement Concrete Volume, Weight & Cost Estimator — 2026 Specifications & Pricing Guide
CEM V concrete is concrete manufactured using a pozzolanic composite cement — the most advanced blended cement family defined in BS EN 197-1, combining Portland clinker with both a latently hydraulic material (ground granulated blast furnace slag, GGBS) and a pozzolanic material (siliceous fly ash, PFA, or silica fume) simultaneously. This dual-SCM approach distinguishes CEM V from the single-addition blended cements of the CEM II family, and results in a cement with a significantly lower Portland clinker content — typically 20–64% clinker versus 65–94% for CEM II — and correspondingly greater reductions in embodied carbon, heat of hydration, and long-term permeability.
Under BS EN 197-1, CEM V is divided into two sub-types based on the total proportion of supplementary cementitious materials (SCMs): CEM V/A, where the combined GGBS and pozzolan (PFA or silica fume) additions total 36–60% of the cement mass (clinker 40–64%); and CEM V/B, where the combined additions total 61–80% of the cement mass (clinker content as low as 20%). The most common UK variant is CEM V/A (S-V), which combines granulated blast furnace slag with siliceous fly ash, each in proportions of 18–30% by mass of the cement, alongside 40–64% Portland clinker.
In the UK construction industry in 2026, CEM V concrete occupies a specialist niche — it is not the everyday default cement like CEM II/A-L, but rather a deliberately chosen specification for projects where very low embodied carbon, very low heat of hydration, or exceptional long-term durability in aggressive environments are primary design drivers. Its use has grown significantly since 2020 as the UK construction sector accelerates its response to embodied carbon targets, and it is increasingly specified on infrastructure projects, large commercial developments, and sustainability-led residential schemes where whole-life carbon reporting under PAS 2080 or BREEAM Outstanding credits are required.
The naming convention for CEM V cements follows the same systematic approach used throughout BS EN 197-1. The principal designations relevant to UK construction practice in 2026 are:
CEM V/A (S-V) — Portland-slag-fly ash cement with 18–30% GGBS and 18–30% siliceous PFA, with clinker content between 40–64%. This is the most widely available and most commonly specified CEM V type in the UK. The combination of GGBS and PFA provides a synergistic effect: the GGBS accelerates the pozzolanic reaction of the PFA, and the PFA's finer particle size helps fill the pore structure created by GGBS hydration. The result is a concrete with excellent long-term durability, moderate early strength development, very low heat of hydration, and embodied CO₂ approximately 45–55% lower than equivalent CEM I concrete.
CEM V/B (S-V) — Portland-slag-fly ash cement with 31–50% GGBS and 31–50% PFA, with clinker content of only 20–38%. This very low clinker content gives CEM V/B the lowest embodied CO₂ of any standard cement family in BS EN 197-1 — typically 55–70% lower than CEM I — making it the preferred choice for projects with the most demanding embodied carbon reduction targets. The tradeoff is very slow early strength development (7-day cube strength may be only 40–55% of 28-day) and high sensitivity to temperature — cold weather significantly extends strength gain and formwork striking times must be managed carefully. CEM V/B is not suitable for applications requiring early loading or formwork removal and should only be used where the design programme allows the extended curing regime it requires.
CEM V/A (S-D) — Portland-slag-silica fume cement with 18–30% GGBS and 18–30% silica fume, with clinker 40–64%. Silica fume (condensed silica fume, CSF or microsilica) is a highly reactive pozzolan — individual particles are approximately 100 times finer than Portland cement particles — that dramatically reduces concrete permeability and significantly increases strength. CEM V/A (S-D) concrete offers the best combination of strength and durability in the CEM V family, approaching or matching CEM I at 28-day strength while providing far superior resistance to chloride ingress and sulfate attack. Its use in the UK is more limited than CEM V/A (S-V) due to the high cost of silica fume (typically £400–£800 per tonne versus £25–£60 per tonne for PFA), but it is the preferred CEM V variant for marine structures, underground infrastructure, and high-durability applications where silica fume's pore-filling effect is particularly valuable.
There are three compelling reasons why structural engineers, concrete technologists, and sustainability-focused clients are increasingly specifying CEM V concrete on UK projects in 2026:
Embodied carbon reduction: With clinker content of only 20–64% versus 95–100% for CEM I, CEM V cements deliver the greatest embodied CO₂ reduction of any standard cement family available in the UK. CEM V/A (S-V) concrete typically carries approximately 45–55% of the embodied carbon of equivalent CEM I concrete; CEM V/B reduces this further to 30–45%. On large pours — raft foundations, mat foundations, basement walls, and thick structural slabs — these reductions are substantial in absolute terms. A 500m³ basement raft in CEM V/B concrete saves approximately 70–85 tonnes of CO₂e compared to the same pour in CEM I, equivalent to the annual carbon footprint of several UK households.
Heat of hydration reduction: The very low clinker content of CEM V cements dramatically reduces the heat generated during concrete curing. In thick concrete pours — typically anything over 500mm — the heat generated by cement hydration can raise the internal concrete temperature to 60–80°C, creating a significant differential with the cooler surface that causes thermal cracking. Using CEM V instead of CEM I or CEM II can reduce peak temperature differentials by 15–30°C in thick sections, eliminating or dramatically reducing the risk of thermally induced cracking without the need for chilling of mix water or aggregates. This makes CEM V the natural specification for large pile caps, raft foundations, transfer slabs, and dam or reservoir concrete in the UK.
Long-term durability: The combined GGBS and PFA additions in CEM V produce a significantly denser, less permeable concrete matrix than CEM I or CEM II/A-L at equivalent strength classes. The rate of chloride ion diffusion — the key durability parameter for reinforced concrete in marine, coastal, and de-icing salt environments — is dramatically lower for CEM V concrete than CEM I, potentially extending the time to onset of reinforcement corrosion from the 50–75 years typical for CEM I to 100–150 years or more for CEM V. This exceptional durability makes CEM V concrete particularly appropriate for marine structures, tunnel linings, underground infrastructure, and any application where the consequences of reinforcement corrosion are severe and the design service life is long.
Unlike CEM II/A-L which is the default production cement at virtually every UK ready-mix plant, CEM V is a specialist product that requires advance planning when ordering. In 2026, CEM V concrete is available from most major UK ready-mix producers — Hanson, Aggregate Industries, Tarmac, and CEMEX all produce CEM V mixes — but typically as a non-standard product requiring 2–5 working days' notice while the specialist cement blend is sourced and a validated mix design is prepared.
Before ordering CEM V concrete, confirm the following with your supplier: the specific CEM V sub-type available (CEM V/A or CEM V/B; S-V or S-D); whether the mix design has been validated for your target strength class and exposure class; the expected 7-day and 28-day cube strengths for the specific mix (given the slow early strength development of CEM V, this is critical for formwork striking decisions); the slump class available and whether superplasticiser is included as standard in the mix; and the cold weather protocol — at what ambient temperature the supplier recommends switching to a CEM V/A or a CEM II/B mix to manage the slow early strength development risk.
For projects requiring conformity documentation — particularly public sector, infrastructure, and BREEAM-assessed commercial projects — request a Declaration of Performance (DoP) confirming the cement designation, clinker content range, and the manufacturer's environmental product declaration (EPD) for the specific CEM V product. The EPD provides the accurate embodied carbon data (kg CO₂e per tonne of cement) needed for PAS 2080 reporting and whole-life carbon assessments, and is increasingly required as part of project handover documentation.
Professional Resources 2026: CEM V technical guidance at The Concrete Centre | Embodied carbon data from Mineral Products Association | Standards at BSI Group | PAS 2080 at UK Green Building Council | Sustainability at IStructE | Ready-mix at Aggregate Industries
The single most important site management consideration when using CEM V concrete is the slower early strength development compared to CEM I or CEM II/A-L. The extent of this delay depends on the specific sub-type: CEM V/A (S-V) typically reaches 60–70% of its 28-day cube strength at 7 days; CEM V/B (S-V) with its very low clinker content may reach only 40–55% at 7 days. At 28 days, both sub-types achieve their specified characteristic strength — and beyond 28 days, CEM V concrete continues to gain strength as the SCM reactions proceed, often reaching 115–130% of the 28-day characteristic by 90 days.
For formwork striking and construction sequencing, the following practical guidance applies to CEM V concrete in the UK in 2026. For soffit formwork supporting structural elements (beams, slabs) where the concrete must carry its own weight: do not use generic age-based striking rules derived from CEM I experience — always use in-situ cube testing to confirm that the minimum stripping strength (typically 75% of specified characteristic strength) has been achieved before striking. For vertical formwork (walls, columns) where the concrete carries no load on stripping: CEM V/A can typically be struck at 48–72 hours in normal UK weather (above 10°C); CEM V/B may require 5–7 days before stripping in cool weather. In cold weather below 5°C, all CEM V concrete requires extended protection and cube testing before any formwork is removed.
CEM V concrete is particularly well suited to mass concrete applications — deep pile caps, thick raft foundations, transfer slabs, and dam or reservoir concrete — where the risk of thermally induced cracking from high heat of hydration is a primary engineering concern. The UK guidance on mass concrete thermal control is set out in BS EN 13670 (Execution of concrete structures) and the Concrete Society Technical Report TR 74, which recommends that the temperature differential between the hottest point inside a concrete pour and its surface or exposed edges should not exceed 20°C.
In a typical 1,000mm deep raft foundation poured in CEM I concrete, peak internal temperatures of 65–80°C are common, creating temperature differentials of 40–50°C that significantly exceed the 20°C guideline and require expensive thermal management measures — insulated formwork, heated or chilled mix water, staged pours, or post-pour cooling pipes. Using CEM V/B (S-V) for the same pour reduces peak temperatures to 35–50°C and temperature differentials to 10–20°C, eliminating or dramatically reducing the thermal management requirement. On large infrastructure projects, the saving in thermal management costs — which can run to tens of thousands of pounds per pour — often justifies the specialist cement cost and planning overhead of CEM V by a substantial margin.
The price of CEM V concrete in the UK in 2026 reflects its specialist status. CEM V/A (S-V) ready-mix concrete is typically priced approximately £5–£18 per m³ above equivalent CEM II/A-L mixes of the same strength class — a modest premium for a product that delivers 45–55% lower embodied carbon and dramatically reduced heat of hydration. CEM V/B is sometimes priced at a slight discount to CEM V/A for the same nominal strength class, reflecting the lower clinker content, though the slower strength development and need for extended curing may add to overall project cost if not managed carefully.
The total project cost of specifying CEM V concrete versus CEM I or CEM II/A-L must be evaluated on a whole-project basis, not just by comparing per-m³ concrete prices. For mass concrete pours, CEM V typically reduces or eliminates the cost of thermal management measures (insulated formwork, cooled aggregates, post-pour cooling systems) — savings that can easily exceed the per-m³ concrete premium on large pours. For sustainability-driven projects, CEM V may contribute to BREEAM credits, public sector embodied carbon compliance, or planning condition fulfilment that has a commercial value well above the per-m³ price differential. Always evaluate the full cost-benefit picture rather than selecting cement type on raw material cost alone.
| Designation | Clinker % | GGBS % | PFA / Silica Fume % | Early Strength (7d) | 28d Strength | Heat of Hydration | Chloride Resistance | CO₂ vs CEM I | Price vs CEM I |
|---|---|---|---|---|---|---|---|---|---|
| CEM I 42.5N (baseline) | 95–100% | 0% | 0% | Very high | Highest | High | Standard | — | Baseline |
| CEM II/A-L (reference) | 80–94% | 0% | 0% (limestone) | Near CEM I | High | High | Standard | –10–20% | Same |
| CEM III/A (reference) | 35–64% | 36–65% | 0% | Moderate | Very high | Low | Very good | –38–55% | –£3–8/m³ |
| CEM V/A (S-V) ★ | 40–64% | 18–30% | 18–30% PFA | Moderate–good | Very high | Very low | Excellent | –45–55% | +£5–18/m³ |
| CEM V/B (S-V) ★ | 20–38% | 31–50% | 31–50% PFA | Slow | High–very high | Extremely low | Outstanding | –55–70% | +£2–12/m³ |
| CEM V/A (S-D) ★ | 40–64% | 18–30% | 18–30% silica fume | Moderate | Very high | Very low | Outstanding | –42–52% | +£15–40/m³ |
★ CEM V types are the focus of this page. Price premiums versus CEM I are per m³ of finished concrete (not per tonne of cement). CO₂ reductions are approximate based on MPA ICE Database v3.0 and manufacturer EPD data. Silica fume (CSF) in CEM V/A (S-D) significantly increases cost due to its high raw material price (~£400–800/tonne vs ~£25–60/tonne for PFA).
| Cement | Clinker % | Main SCMs | CO₂ vs CEM I | Heat of Hydration | Sulfate Resistance | Typical Price (concrete per m³) | Primary UK Application |
|---|---|---|---|---|---|---|---|
| CEM I 42.5N | 95–100% | — | Baseline | High | Standard | £125–£215+ | Precast, PT, rapid strength |
| CEM II/A-L | 80–94% | Limestone 6–20% | –10–20% | High | Standard | £125–£215+ | UK default for all GEN/RC mixes |
| CEM II/B-V | 65–79% | PFA 21–35% | –25–38% | Moderate | Improved | £120–£205+ | Mass concrete, sustainable RC |
| CEM II/B-S | 65–79% | GGBS 21–35% | –22–35% | Moderate | Good (AC-2) | £120–£205+ | RC foundations, moderate sulfate |
| CEM III/A | 35–64% | GGBS 36–65% | –38–55% | Low | Very good (AC-3) | £120–£205+ | FND3/FND4, marine, durability |
| CEM III/B | 20–34% | GGBS 66–80% | –60–75% | Very low | Excellent (AC-4) | £120–£205+ | FND4 highly aggressive ground |
| CEM IV/A | 45–64% | PFA or silica fume 18–30% | –30–45% | Low–moderate | Good | £130–£210+ | Mass concrete, durability RC |
| CEM V/A (S-V) | 40–64% | GGBS 18–30% + PFA 18–30% | –45–55% | Very low | Excellent | £133–£230+ | Mass concrete, marine, low carbon RC ★ |
| CEM V/B (S-V) | 20–38% | GGBS 31–50% + PFA 31–50% | –55–70% | Extremely low | Excellent | £130–£225+ | Net zero target pours, BREEAM Outstanding ★ |
★ CEM V types shown in bold. Concrete prices shown are the full range across all standard BS 8500 strength classes (GEN3 to RC35+). The CEM V concrete price premium over CEM I for the same strength class is typically £5–£40/m³ depending on sub-type — but thermal management savings on mass pours and BREEAM/carbon credit value can far outweigh the premium.
| BS 8500 Class | Strength | Binder (kg/m³) | Max w/c | 7-Day Strength (CEM V/A) | 7-Day Strength (CEM V/B) | CEM V Price per m³ (2026) | Key Applications |
|---|---|---|---|---|---|---|---|
| GEN3 | C20/25 | 260–290 | 0.65 | ~65–70% | ~42–50% | £130–£158 | Mass foundations, oversite (CEM V/A preferred) |
| RC25 | C25/30 | 290–320 | 0.60 | ~65–72% | ~44–52% | £140–£170 | RC slabs, raft foundations, pile caps |
| RC28 | C28/35 | 330–360 | 0.55 | ~68–74% | ~46–54% | £148–£182 | RC structural elements, marine, tunnel |
| RC30 | C30/37 | 320–350 | 0.55 | ~68–75% | ~48–55% | £155–£190 | Exposed RC, marine XS2/XS3 |
| RC32 | C32/40 | 355–385 | 0.50 | ~70–76% | ~50–58% | £165–£205 | Very high durability — underground, marine severe |
7-day strength percentages are indicative for UK curing temperatures of 12–18°C. In cold weather (<5°C), CEM V/B 7-day strength may be as low as 30–40% of 28-day — formwork striking must be confirmed by cube testing, not assumed from age. In warm conditions (>20°C), strength development is faster. Always obtain mix-specific data from your supplier before planning the construction programme.
Peak temperature rise in mass concrete pours is directly related to cement type. CEM V's very low heat of hydration is one of its most important technical advantages for large-section pours. The following table gives indicative peak temperature rises for common cement types in a 1,000mm deep raft foundation at 20°C ambient temperature.
| Cement Type | Clinker % | Approx. Peak Temp (1m raft) | Approx. Max Differential | Thermal Cracking Risk | Thermal Management Needed? |
|---|---|---|---|---|---|
| CEM I 42.5N | ~97% | 65–80°C | 40–55°C | Very high | Yes — extensive |
| CEM II/A-L | ~85% | 60–75°C | 35–50°C | High | Yes — significant |
| CEM II/B-V | ~70% | 50–65°C | 28–42°C | Moderate | Likely — assess by calculation |
| CEM III/A | ~50% | 40–55°C | 20–35°C | Low–moderate | Sometimes — assess by calculation |
| CEM V/A (S-V) | ~52% | 35–50°C | 15–28°C | Low | Rarely — monitor and insulate |
| CEM V/B (S-V) | ~30% | 25–40°C | 8–20°C | Very low | Rarely needed |
Values are indicative for a 1,000mm deep raft with 300 kg/m³ binder at 20°C ambient. Peak temperatures and differentials scale with binder content, section thickness, and ambient temperature. Always perform a thermal analysis using BS EN 13670 or Concrete Society TR 74 guidance for all pours exceeding 500mm depth. A concrete technologist should be involved for large mass pours.
CEM V is the fifth and final main cement family defined in BS EN 197-1, combining Portland clinker with both a latently hydraulic material (GGBS) and a pozzolanic material (PFA or silica fume). It is the only standard cement family using two different SCM types simultaneously.
CEM V/A (S-V) reduces embodied CO₂ by approximately 45–55% versus CEM I; CEM V/B reduces it by 55–70% — the greatest carbon reduction of any standard cement family in BS EN 197-1. On a 1,000m³ structural pour, CEM V/B saves approximately 130–180 tonnes of CO₂e.
CEM V/B in a 1,000mm deep mass concrete pour generates peak internal temperatures of only 25–40°C — versus 65–80°C for CEM I — dramatically reducing thermal cracking risk and eliminating or greatly reducing the need for costly thermal management measures.
CEM V/A (S-V) reaches approximately 65–72% of 28-day cube strength at 7 days. CEM V/B reaches only 42–55% at 7 days. Never use age-based formwork striking rules from CEM I experience — always confirm by cube testing before striking soffit shuttering.
CEM V concrete develops a very dense, low-permeability matrix through the combined pozzolanic and latent hydraulic reactions of PFA and GGBS. Chloride diffusion coefficients are typically 3–6× lower than CEM I at the same strength class — dramatically extending time to reinforcement corrosion onset.
CEM V is not a standard stock product at most UK batching plants. Contact your ready-mix supplier at least 2–5 working days in advance to confirm availability of the specific CEM V sub-type, validate the mix design, and arrange delivery. Always get confirmation in writing.
CEM V concrete makes a significant contribution to BREEAM Materials credits and to whole-life embodied carbon targets under PAS 2080. Always request a manufacturer EPD for the specific CEM V product to provide accurate A1-stage carbon data for project reporting.
CEM V's slow early strength development makes it unsuitable for precast prestressed concrete where tendons must be stressed in 12–24 hours. Post-tensioned construction requiring stressing at 3–5 days is also generally not suitable for CEM V/B — use CEM I or CEM II/A-L for these applications.
CEM V/B concrete is highly sensitive to cold weather — below 5°C, strength development may be extremely slow and extended frost protection (minimum 7–14 days) is needed. Consider switching to CEM V/A or CEM III/A for pours in autumn and winter when temperatures are unpredictable.
CEM V/A (S-D) — using silica fume rather than PFA — provides the best chloride resistance of any standard CEM V sub-type, making it the preferred choice for marine XS3 structures, tunnel linings in saline ground, and any application where maximum impermeability is the primary design driver.
CEM V/A (S-V) carries a premium of approximately £5–£18/m³ over equivalent CEM I mixes. CEM V/A (S-D) with silica fume carries a larger premium of £15–£40/m³ due to the high cost of silica fume as a raw material. CEM V/B is sometimes priced £2–£12/m³ above CEM II/A-L equivalent.
Conformity cube testing per BS EN 12350-1 is essential for all CEM V structural pours. The slow strength development of CEM V means 28-day results are critical — and 56-day supplementary testing is recommended for CEM V/B applications to confirm the full long-term strength potential has been achieved.
CEM V is a pozzolanic composite cement defined in BS EN 197-1 that combines Portland clinker with both granulated blast furnace slag (GGBS) and a pozzolanic material (typically siliceous fly ash, PFA) simultaneously — the only standard cement family to use two different supplementary cementitious materials together. CEM II cements use a single addition (limestone, fly ash, or GGBS alone) and retain a higher clinker content (65–94%). CEM III cements use GGBS alone in high proportions (36–80% clinker replacement). CEM V's dual-SCM approach gives it a unique combination of very low heat of hydration (from the combined GGBS and PFA additions), very high long-term durability (from the synergistic pozzolanic reactions of both materials), and very low embodied carbon — making it the most carbon-efficient and thermally benign of all standard cement families in BS EN 197-1.
Specify CEM V concrete when one or more of the following apply: you need the maximum possible embodied carbon reduction (CEM V/B provides 55–70% CO₂ saving vs CEM I — greater than CEM III/B); you are pouring mass concrete over 500mm deep and want to minimise or eliminate thermal cracking risk without expensive thermal management measures; the project requires very long service life in aggressive environments — particularly marine, underground, or chloride-rich conditions — where the dense, low-permeability matrix of CEM V provides superior performance to CEM II or even CEM III; or your project requires compliance with a specific embodied carbon target (PAS 2080, BREEAM Outstanding, planning conditions) where the marginal carbon reduction of CEM V over CEM III/B is worth the additional cost and planning overhead. For standard domestic applications, CEM II/A-L or CEM III are more widely available and less expensive, and CEM V provides greater performance than these applications typically require.
CEM V/A (S-V) concrete typically reaches 65–72% of its 28-day characteristic cube strength at 7 days under UK curing temperatures of 12–18°C. CEM V/B with its very low clinker content reaches only 42–55% at 7 days — and in cold weather below 5°C, 7-day strength may be as low as 30–40% of 28-day. At 28 days both sub-types achieve their specified characteristic strength, and beyond 28 days they continue to gain — typically reaching 115–130% of the 28-day characteristic at 90 days as the SCM reactions continue. This extended strength gain means CEM V concrete should always be assessed at 28 days for conformity purposes, with supplementary 56-day or 90-day testing specified for applications where it has engineering significance. Never use age-based formwork striking rules derived from CEM I experience when placing CEM V concrete.
In 2026, CEM V/A (S-V) ready-mix concrete is typically priced approximately £5–£18 per m³ above equivalent CEM II/A-L mixes of the same strength class. CEM V/A (S-D) with silica fume carries a larger premium of £15–£40/m³ due to the high raw material cost of silica fume (approximately £400–£800/tonne versus £25–£60/tonne for PFA). CEM V/B is sometimes priced slightly lower than CEM V/A for the same nominal strength class, reflecting the lower clinker content, though this varies between suppliers. The CEM V price premium is usually a minor fraction of total project cost, especially when the savings from reduced thermal management on mass pours and the commercial value of BREEAM credits or embodied carbon compliance are included in the cost-benefit analysis. Always confirm current pricing with your local ready-mix supplier — CEM V is a specialist product and prices can vary significantly.
CEM V concrete can technically be used for domestic foundations and will produce structurally adequate results, but it is generally over-specified for standard domestic strip foundation applications where GEN3 / C20/25 with CEM II/A-L is perfectly adequate. The main barriers to CEM V use in domestic construction in 2026 are: it is not a standard stock product at most local batching plants and requires advance notice; the slow early strength development can affect construction programme on small domestic sites where building on the foundation proceeds quickly; and the cost premium is not justified by any performance benefit in the non-aggressive ground conditions typical of domestic applications. CEM V is most cost-effective and technically appropriate for large-volume, sustainability-driven, or technically demanding pours — not standard domestic strip foundations or slab work.
The designation CEM V/A (S-V) decodes as follows: CEM V = the fifth main cement family in BS EN 197-1 (pozzolanic cement); /A = A-type, meaning the total supplementary cementitious material (SCM) additions are 36–60% by mass; (S-V) = the two specific SCMs used are S (granulated blast furnace slag, GGBS) and V (siliceous fly ash, PFA). So CEM V/A (S-V) is a pozzolanic composite cement with 40–64% Portland clinker, 18–30% GGBS, and 18–30% PFA. CEM V/B (S-V) is the B-type version: 20–38% clinker, 31–50% GGBS, 31–50% PFA — the very low clinker content giving the greatest carbon reduction. CEM V/A (S-D) substitutes silica fume (D) for fly ash (V) alongside the GGBS addition.
Yes — raft foundations are one of the ideal applications for CEM V concrete. The thick section of a concrete raft (typically 300–600mm for domestic rafts, 600–1,500mm for commercial and infrastructure rafts) generates significant heat during cement hydration when using CEM I or CEM II/A-L, risking thermal cracking that can compromise the structural integrity and waterproofness of the raft. CEM V/A (S-V) or CEM V/B (S-V) dramatically reduces peak temperatures and temperature differentials, typically eliminating the need for chilled aggregates, cooled mix water, or post-pour cooling pipes on all but the very thickest domestic raft sections. For commercial and infrastructure rafts above 1,000mm depth, CEM V/B remains the safest choice for thermal management even at additional cost. Always conduct a thermal analysis per Concrete Society TR 74 before specifying cement type for rafts above 500mm depth.
It is also common in UK practice to add GGBS as a separate component to a CEM I or CEM II base cement at the batching plant — this is sometimes called a "CEM III equivalent" mix even though the cement itself may be CEM I or CEM II. The advantage of this approach is flexibility — the GGBS addition level can be varied per pour — and it can be cheaper than a pre-blended CEM V where no pre-blended stock is available. However, CEM V (factory blended to BS EN 197-1) has the advantage of a fixed, certified composition with a traceable Declaration of Performance and EPD — important for BS 8500 conformity, BREEAM documentation, and PAS 2080 reporting. Many structural engineers and specifiers prefer certified factory-blended CEM V over site-blended combinations for this reason, particularly on infrastructure and sustainability-driven projects where precise carbon reporting is required.
Yes — CEM V concrete, particularly CEM V/B, requires more rigorous curing than CEM I or CEM II/A-L. The pozzolanic reactions of both PFA and GGBS require the presence of moisture to proceed — if the concrete surface dries out too early, these reactions stop and the potential long-term strength and durability benefits of the CEM V blend are not fully realised. Apply curing compound immediately after surface finishing, or cover with wet hessian under polythene for a minimum of 7 days. In warm, dry, or windy conditions, extend curing to 10–14 days for CEM V/B. Never allow the surface to dry and rewet repeatedly in the first week — each drying event disrupts the ongoing pozzolanic reaction. For mass pours, insulated blankets serve double duty — controlling the temperature gradient and maintaining surface humidity simultaneously.
Yes — concrete made with CEM V cement that is designed to a BS 8500 strength class (GEN3, RC25, RC28 etc.) and appropriate exposure class is fully compliant with BS 8500 and BS EN 206. The BS 8500 designated mix system does not prescribe a specific cement type — it defines the performance requirements that the concrete must meet, and CEM V concrete can be formulated to meet those requirements across the GEN and RC designation range. For applications requiring specific cement type compliance (such as FND4 requiring ≥80% GGBS content, which falls into the CEM III/B range rather than CEM V), check BS 8500-1 Table A.2 carefully and confirm the CEM V mix design against the specific exposure class requirements with your concrete technologist. Always obtain a conformity certificate confirming the specific CEM V mix design complies with the required BS 8500 designation.
CEM V concrete is available from major UK ready-mix producers including Hanson, Aggregate Industries, Tarmac, and CEMEX, but it is a specialist product requiring advance notice — typically 2–5 working days — at most plants. Not all regional batching plants stock CEM V as a standard product. Contact the technical team at your preferred supplier rather than placing a standard online order, as CEM V concrete requires a validated mix design, confirmed availability of the specific CEM V cement sub-type, and appropriate quality documentation. For CEM V/A (S-D) with silica fume, additional lead time of up to 5–10 working days may be required. In London and major urban centres, availability tends to be better than in rural areas.
Yes — CEM V concrete is an excellent choice for below-ground basement walls and waterproof structures. The very low permeability of the dense, well-reacted CEM V concrete matrix provides excellent resistance to water and chloride ingress — one of the key requirements for below-ground waterproofing. When used as part of a Type B waterproofing system (structural integral waterproofing, per BS 8102) with appropriate mix design, cover to reinforcement, and careful pour-joint detailing, CEM V concrete can form a fully effective waterproof membrane without additional tanking or membrane systems on projects where ground aggressivity is not beyond the CEM V exposure class capability. Always work with a waterproofing specialist and structural engineer when designing basement waterproofing — the choice of concrete mix is only one component of an integrated waterproofing strategy that must also address construction joints, penetrations, and ground water pressure.
Additional Resources 2026: CEM V guidance at The Concrete Centre | Carbon data from Mineral Products Association | Standards at BSI Group | Sustainability at UK Green Building Council | Concrete Society TR 74 (Mass Concrete) at The Concrete Centre | Ready-mix at Hanson | Aggregate Industries | Structural engineers at IStructE
© 2026 CEM V Concrete Calculator UK. All prices are indicative May 2026 estimates. CEM V concrete is a specialist product — availability, mix design validation, and BS 8500 compliance must be confirmed with your ready-mix supplier and concrete technologist before specifying or ordering. Always involve a structural engineer for structural CEM V applications.