GUIDES
Concrete Mix Design Guides
Practical guides to strength classes, exposure classes and mix specification, grounded in BS 8500 and EN 206. Each guide links through to the calculator so you can apply what you read.
All guides
Strength Classes ExplainedWhat C25/30, C32/40 and similar mean under EN 206Designated vs Designed ConcreteThe two ways concrete is specified under BS 8500, and when each appliesExposure Classes & DurabilityHow BS 8500 exposure classes can set stricter limits than strength aloneThe EN 206 MethodStep-by-step walkthrough of the calculationMaterial Cost CalculatorCost of concrete per m³ from your ratesCarbon Impact CalculatorEstimate carbon per m³ from cement type and quantitiesConsistence Classes S1–S4Slump and flow classes, and how they set water contentWater-Cement RatioThe strength and durability ceilings, and which winsFree Water ContentHow Dmax, shape and consistence set water demandCement ContentMinimum cement content by exposure classCoarse AggregateEN 12620 sizing, Dmax and grading categoryFine AggregateThe absolute-volume closure and EN 12620 finesTrial Mixes & Initial TestingConfirming a design before full-scale useTarget Mean Strengthfcm = fck + margin, and conformity criteriaAdmixturesBS EN 934-2 types and dosageAir EntrainmentXF freeze-thaw classes and minimum air contentCommon Mix Design MistakesExposure limits, site water, skipped trialsCement CombinationsCEM I, CIIA-V, CIIB-V, CIIIA, CIIIB explainedBS 8500:2023 ChangesWhat changed from the 2015+A2:2019 editionDesignated Concrete CatalogueGEN, RC, FND and PAV designations explainedC20/25 ConcreteTypical uses and GEN equivalentC25/30 ConcreteTypical uses and RC25/30 equivalentC30/37 ConcreteTypical uses and RC30/37 equivalentC35/45 ConcreteTypical uses and RC35/45 equivalentC40/50 ConcreteTypical uses and RC40/50 equivalent
Frequently asked questions
Are these guides a substitute for the standard?
No. These guides explain the concepts in plain language, but the current applicable BS 8500 and EN 206 editions — and your project specification — are always the reference for a real project.
Do I need to be an engineer to use them?
No. They are written to be useful to practising engineers as well as site staff and students who need a clear explanation of a term or a step.