Mix Performance and Ordering

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Mix Performance and Ordering

• Inc. EN 206-1 Testing Requirements

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Content

• Mix Specification to BS 8500-12006
• Performance Specification
• Conformity and Identity Testing

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BS 8500 2006
Concrete - Complementary British Standard to BS
EN 206-1
Part 1 Method of specifying and guidance for the
specifier.
Part 2 Specification for constituent materials
and concrete.
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Methods of specifying
A specifier specifies a CONCRETE and a producer
designs a MIX that satisfies all the specified
requirements for the concrete
Designated concrete
Designed concrete
Prescribed concrete
Standardized prescribed concrete
Proprietary concrete
Different producers are likely to have different
MIXES that satisfy the same concrete specification
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Designated Concretes

• Simplified method of specification
• 3rd Party accreditation required
• Suitable for identified end uses
• Limitation on exposure conditions
• RC28/35
• S3, mcc 280, w/c 0.60, range of cement types
  permitted

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Prescribed Concretes

• Specifier prescribes exact composition
• No performance requirements permitted
• Limited applicability
• Limited requests for such concretes

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Standardized Prescribed

• Aimed at on site production
• No requirement for 3rd party certification
• No strength requirement
• Generally uneconomic
• Use Designated or Designed alternative if
  producer has 3rd party accreditation

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Proprietary concrete
Concrete for which the producer assures the
performance, subject to good practice on site,
and for which the producer is not required to
declare the composition On request, the producer
will declare that the proprietary concrete
conforms to the recommendations in BS 8500-1 for
the declared exposure classes The claims made
for proprietary concrete are those of the
producer and BSI has not substantiated any of
these claims
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Designed Concretes

• More flexibility
• More complex
• Specified by
• Strength class
• Limiting values (w/c, mcc, DC-class )
• Consistence class
• Maximum aggregate size
• Chloride Class

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Determine Concrete Quality

• Structural requirements to determine strength
  class
• Identify exposure class or classes
• Intended working life
• Minimum cover
• Other considerations
• eg Lightweight

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Strength Class

• Dual Classification system
• C28/35
• Range from C6/8 to C100/115
• Lightweight strength classes
  
  also included
• LC8/9 to LC 80/88

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Exposure Classes
X0 - No risk of corrosion or attack
XC - Corrosion induced by carbonation
XD - Corrosion induced by chlorides other than
from seawater
XS - Corrosion induced by chlorides from seawater
XF - Freeze/thaw attack
XA - Chemical attack Not used in the UK BRE
SD1 guidance used
With the exception of X0, each class is split
into a number of sub-classes.
Note Specification by exposure class is not
enough!
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Table A.13 Limiting values for composition and
properties of concrete exposed to risk of
corrosion of reinforcement induced by sea water
for an intended working life of at least 50 years.
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(No Transcript)
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Cement and combination types
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Maximum Aggregate Size

• Standard is 20mm
• Generally available 10mm
• Other sizes available on request

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Chloride Content Class
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Consistence Class
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Sustainable Concrete Design

• BRE Environmental Profiles
• Reflect embodied impact of raw materials eg
  cement
• The Green Guide to Specification
• Considers embodied performance of elements for
  Housing
• Code for Sustainable Homes
• Rates the overall performance of dwellings
• BREEAM (BRE Environmental Assessment Method)
• Considers performance of a range of buildings
• Responsible Sourcing
• Considers environmental, social and economic
  impacts in the supply chain
• Building Regulations
• Part L considers energy usage and links to Code
  for Sustainable Homes points methodology

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Sustainable Concrete Design Influence of Cement
Type

• Cement production is energy intensive
• Blended or combination cements reduce CO2 by up
  to 40 in concrete
• For normal construction specify II B-V or IIIA
  cements
• For foundations specify IVB-V or IIIB cements

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Sustainable Concrete DesignImpact of Aggregates

• UK aggregate demand is c.270million Tonnes
• 50million Tonnes is of which is secondary or
  recycled aggregates
• UK already meets EU 2020 target for recycling of
  hard construction waste
• Concrete typically contains up to 2000Kg/m3 of
  aggregate
• Recycled Aggregates have a role to play
• RA Includes a wide range of materials and is
  not generally suitable for use in concrete
• RCA Recycled Concrete Aggregate can contribute
  to a more sustainable concrete

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Impact of RCA
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Specifying RCA Aggregates

• Choice of RCA will depend on
• Aggregate quality
• Aggregate availability
• Transport distance
• Impact on cement content
• Environmental and cost implications
• Some limitations on end use
• Eg DC2 and above, some Exposure Classes
• Early liaison with all parties is recommended to
  ensure most effective use

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Use of Admixtures
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General guidance on concrete design for
sustainability

• Specify use of combination type cements
• Permit the use of admixtures
• Work with suppliers on appropriate use of
  aggregates
• Avoid unnecessary over specification

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Information Exchange

• From Specifier
• In addition to concrete specification
• Delivery date , time and rate
• Any special methods of placing and finishing
• Any special method of transport on site
• Any limitations on delivery vehicles
• Details of intended on site testing regime
• Details of non-accredited laboratories (if used)
• No proscribed format

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Information Exchange

• From supplier (on request)
• Type and strength class of cement
• Type of aggregate
• Target water cement ratio
• Results of previous tests on the concrete
• Strength development data
• Source of materials
• Further specific information available on request
• Method for minimising ASR
• Freeze thaw information where porous flint is
  used
• Chemical information on RA
• Type and source of RA or RCA
• Evidence of suitability of RCA
• Information on proprietary concrete

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Supply

• Based on specified requirements the producer will
• Select appropriate materials
• Design a mix to meet the requirements
• Modify mix proportions to ensure conformity

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Conformity and Identity Testing
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Conformity

• An assessment by the producer to verify that the
  claims for the product are valid
• 3rd party certification bodies such as QSRMC or
  BSI provide independent audit on conformity
• BS 8500-1 strongly recommends that producers hold
  3rd party certification

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Properties subject to conformity checks

• Strength
• Water cement ratio
• Cement content
• Air content
• Chloride content
• Density (L/weight or H/weight)
• Consistence

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EN 206-1 Table 13 Minimum rate of sampling for
assessing conformity
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EN 206-1 Table 14 Conformity criteria for
compressive strength
Identified non conformities to be advised to
specifier
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Table 17 Conformity criteria for properties
other than strength (and consistence)
a Unless limits are specified
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Table 18 Conformity criteria for consistence
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Identity Testing

• Testing to determine if selected batches come
  from a conforming population
• When is it useful?
• Where there is doubt about quality
• To carry out spot checks
• Where there is no 3rd party accreditation
• For critical elements or structures
• Identity tests do not form part of conformity

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Identity testing
BS EN 206-1, Annex B (Normative)
Concrete is deemed to come from a conforming
population if both the criteria in Table B.1 are
satisfied for n results derived from strength
tests on samples taken from the defined volume of
concrete.
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Identity testing
BS EN 206-1, Annex B (Normative)
B.3 Identity criteria for compressive strength
B.3.2 Concrete not under production control
certification.
From the defined volume of concrete at least 3
samples shall be taken for testing.
The concrete is deemed to come from a conforming
population if the conformity criteria in 8.2.1.3
and Table 14 for initial production are satisfied.
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BS 8500-1 Table B.1 - Identity criteria for slump
specified as a slump class
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Low cube results

• Can be due to many reasons
• Administration
• Production issues
• Raw material issues
• Sampling issues
• Testing
• Statistics
• Irrespective of cause
• Major distraction
• Contributes to poor image of concrete

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Actions in the case of strength non-conformity or
identity test failure

• Review sampling and testing procedures
• Audit supplier records
• Raw materials and batch records
• For confirmed non conformities
• Carry out NDT
• Carry out coring
• Consider design effects

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Sometimes its obvious.
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Defective Cubes ?
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Defective cubes

• Incorrect sampling
• Excessive mould oil
• Insufficient mould oil
• Moulds out of tols.
• Poor compaction
• Poor curing
• Fins on cubes

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Use your supplier

• Assess testing facilities and sampling regime
• Some suppliers can carry out UKAS accredited
  testing
• Always use UKAS laboratories

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Actions in the case of strength non-conformity or
identity test failure

• Review sampling and testing procedures
• Audit supplier records
• Raw materials and batch records
• For confirmed non conformities
• Carry out NDT
• Carry out coring
• Consider design effects

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Summary

• Concrete specification can be complex
• Early sharing of information between User and
  Producer can lead to economic and sustainability
  benefits
• Improvements in conformity and identity testing
  will improve the image and share of concrete as a
  construction material