Quality concrete mixes

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About concrete mixes

Concrete can be specified by properties or composition. For composition-based concrete, the producer supplies concrete with a composition set by the customer. For performance-based concrete, the producer is responsible for meeting the specified properties and additional requirements.

Concrete specified by properties is defined by:

  • Compressive strength classes
  • Environmental exposure classes for concrete
  • Maximum aggregate size
  • Chloride content in fresh concrete
  • Consistency
  • Density (lightweight concrete only)

Ecomix Ltd has a professionally equipped testing laboratory for quality control during production and testing. Our experienced operators can develop custom mix designs and provide expert advice.

Our laboratory
ecomix lab
Compressive strength is one of the most important properties of concrete and determines its class, for example C25/30. Testing is carried out after 28 days using cylinders 30 cm high and 15 cm in diameter or cubes with 15 cm sides. Under the national annex, the classes correspond as follows:
Compressive strength class Minimum characteristic cylinder strength Minimum characteristic cube strength
C8/10 8 10
C12/15 12 15
C16/20 16 20
C20/25 20 25
C25/30 25 30
C30/37 30 37
C35/45 35 45
C40/50 40 50
C45/55 45 55
C50/60 50 60
C55/67 55 67
C60/75 60 75
C70/85 70 85
C80/95 80 95
C90/105 90 105
C100/115 100 115
Concrete must resist physical and chemical effects from its environment and use. Exposure classes describe these effects and may be combined. Each designation includes X, the type of damaging action and a number for its intensity, for example XC 3, XD 1, XF 2 and XA. The classification is listed in Table 1 of BDS EN 206.
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Consistency determines the stability and workability of fresh concrete. It is classified by slump-flow diameter (F1-F6), degree of compactability (C0-C3) and slump (S1-S5). BDS EN 12350 describes the methods; the Abrams cone is most commonly used. BDS EN 206 lists other methods. Below is an extract from Table 3 of BDS EN 12350 showing slump classes:
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Classes are designated by Cw and a number for the maximum water pressure in MPa. Dense concrete classes: Cw0.4, Cw0.6, Cw0.8 and Cw1.0.
Classes are designated by Cfr and the minimum number of freeze-thaw cycles. For dense concrete with dense aggregates: Cfr75, Cfr100, Cfr150 and Cfr200.
Chemical admixtures for concrete

We offer chemical admixtures for concrete mixes to meet customer requirements. These substances are dissolved in water and added to concrete, where they change fresh or hardened concrete properties through physical or chemical action, including workability, initial setting, hardening and durability. Examples include anti-freeze and superplasticising admixtures and polypropylene fibres.

Ongoing quality control

Our in-house testing laboratory monitors the production and testing of concrete mixes. Mix designs are approved by CIES Ltd. All concrete classes are certified under Regulation (EU) No 305/2011 and BDS EN 206:2014+A1:2016/NA. Materials for concrete and mortar come from leading suppliers and are accompanied by quality certificates.

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