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Greg van Rooyen | Technical Director - Material Technology
Challenges in material specification
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Introduction
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Challenges in material specification CIA 2018
Introduction
1. Shortfalls in the standards – Why specify
2. Understanding local constraints
3. Supply chain issues
4. Types of specifications
5. Durability and sustainability
6. Common issues
7. Discussion
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Australian Standards
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Challenges in material specification CIA 2018
Standards for concrete
• AS 1379 Specification and supply of concrete
• AS 1012 Methods of testing concrete
• AS 1141 Methods for sampling and testing
aggregates
• AS 1289 Methods of testing soils for
engineering purposes
• AS 3550 Methods for the analysis of water
• AS 1478.1 Admixtures for concrete
• AS 2758.1 Concrete aggregates
• AS 3582.1 SCM’s Fly ash
• AS 3582.2 SCM’s Slag
• AS 3582.3 SCM’s Amorphous silica
• AS 3972 Portland and blended cements
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Challenges in material specification CIA 2018
Standards for concrete
• Lets take a closer look as AS 1379
• Density range 2100 to 2800 kg/m3
• Chloride content below 0.8 kg/m3
• Sulfate content below 50 g/kg of cement
• Drying shrinkage below 1000 microstrain
• Minimum 7 day strength
• Cement and aggregate comply to relevant
standards
•Standard N-grades
• N20, N25, N32, N40, N50
• Slump 20 to 120 mm in 10 mm increments
• Maximum nominal aggregate 10, 14 or 20 mm
• Air content up to 5.0%
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Challenges in material specification CIA 2018
Standards for concrete structures
• AS 2159 Piling
• AS 3600 Concrete structures
• AS 5100.5 Bridge design – Concrete
• AS 3735 Concrete structures retaining liquids
• AS 4997 Guidelines for the design of maritime
structures
• AS 2876 Concrete kerbs and channels (gutters) –
manually or machine placed
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Challenges in material specification CIA 2018
Standards for concrete structures AS3600
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Challenges in material specification CIA 2018
Standards for concrete AS5100.5
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Challenges in material specification CIA 2018
Types of specifications
• Drawings
• Reference to standards
• Supplementary Specifications
• Reference to Client / Authority standards
• Comprehensive Specifications
• Stand alone documents with limited
external references
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Challenges in material specification CIA 2018
Types of specifications
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Understanding local constraints
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Challenges in material specification CIA 2018
Material availability
A common problem facing specifiers is
knowing what local materials are available.
Consider airport pavement
Traditionally this required:
• Basalt aggregate, then
• Basaltic aggregate + performance
requirements, then
• Performance requirements only.
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Challenges in material specification CIA 2018
SCM’s are a critical material with regard
durability
Queensland is fortunate in availability of
SCM’s
Not everything is available everywhere
The specifier should work with the
supplier – Early engagement to
establish availability and options.
This does require the specification to be
broad.
Material availability – SCM’s
High performance precast boats
70 MPa GP + FA + SF
Low heat, late age infill
40 MPa GP + FA
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Challenges in material specification CIA 2018
What performance is achievable
Generally avoid issues by specifying
N-grades or as per relevant standard.
As noted this is not always possible or
desirable.
Contractual problems
• Unclear specification
• Creating partnership
• Dealing with non-conformance
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Supply chain issues – a consultants view
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Challenges in material specification CIA 2018
Development of the specification
Client requirements (SWTC)
Design requirements
Durability requirements
Review panel requirements
Final Specification
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
A project required remediation of several concrete elements (near Brisbane)
The structural design identified three concrete mixes for various elements
The mix requirements table from the Specification looked like this:
Class N20 S32 S40
Use Mass infill General
concrete
Structural &
Mass
concrete
Max w/c
ratio
0.5 0.5 0.5
Min fly ash 25% 25% 25%
Min cement 190 320 390
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
After review by the review panel and client concerns with high in-situ
strength (as experienced on another project and heat of hydration
were raised). The requirements were amended as follows:
Class N20 S32 S40
Use Mass infill General
concrete
Structural &
Mass concrete
Max w/c ratio 0.5 0.5 0.5
Min fly ash 25% 25% 25%
Min cement 190 320 390
Minimum strength
(28 days)
20 32 40
Maximum strength
(56 days)
28 38 48
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
Issues – Part 1
Class N20 S32 S40
Use Mass infill General
concrete
Structural &
Mass concrete
Max w/c ratio 0.5 0.5 0.5
Min fly ash 25% 25% 25%
Min cement 190 320 390
Minimum strength
(28 days)
20 32 40
Maximum strength
(56 days)
28 38 48
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
Issues – Part 2
Class N20 S32 S40
Use Mass infill General
concrete
Structural &
Mass concrete
Max w/c ratio 0.5 0.5 0.5
Min fly ash 25% 25% 25%
Min cement 190 320 390
Minimum strength
(28 days)
20 32 40
Maximum strength
(56 days)
28 38 48
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
Neither the design nor expert panel specified the actual required
performance.
But wait things get worse….
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
Concrete supplier mix performance:
N20 – 220 kg cementitious 30% fly ash – 24 to 28 MPa
S32 – 0.55 w/c 320 kg/m3 cementitious – 45 to 50 MPa
S40 – 0.45 w/c 390 kg/m3 cementitious – 55 to 60 MPa
In short the current mix performance exceeds all of the nominated
criteria.
However the client cannot ignore expert panel advise therefore
designer has to relax requirements.
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
After discussion with client, consultant, contractor and supplier
the following was agreed:
Class N20 S32 S40
Use Mass infill General
concrete
Structural &
Mass concrete
Max w/c ratio 0.85 0.70 0.55
Min fly ash 25% 25% 25%
Min cement 190 320 390
Average strength (28
days)
20 32 40
Maximum strength
(56 days)
28 38 48
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Challenges in material specification CIA 2018
Case Study – Concrete requirements
To actually achieve the required performance the following
could have been specified:
Class N20 S32 S40
Use Mass infill General
concrete
Structural &
Mass concrete
Max w/c ratio - 0.60 0.50
Min fly ash - 25% 25%
Min / Max cement - 320 / 380 380 / 420
Maximum in-situ
peak temperature
- 80 80
Characteristic
strength
- 32 MPa at 28
days
40 MPa at 56
days
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Durability, sustainability and performance
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Challenges in material specification CIA 2018
Durability
• Specifying performance criteria
• Chloride testing
• Special testing
• Mix design “deemed to comply” criteria
Cement Admixture Rebar Surface Electrochem
PC Plasticisers Carbon Steel Rebar Extended Curing Chloride Monitoring
Micro-silica Self-compacting agents Non-reinforced Design Controlled Permeability
Formwork
Corrosion Monitoring
FA / SFA Water-proofers Stainless Steel Rebar Penetrating Sealers Provision for Future CP
GGBFS Corrosion Inhibitors GRP reinforcement Surface Coatings Cathodic Prevention
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Challenges in material specification CIA 2018
Sustainability
Current requirements focus on CO2 or embodied
energy reduction.
Most easily achieved through use of SCM’s
Great deal of research into alkali activated /
geopolymer concrete.
This has not translated into standards yet.
Development ongoing.
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Common areas of concern
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Challenges in material specification CIA 2018
Standard testing
Data availability
Data never (hardly ever) available but:
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Challenges in material specification CIA 2018
Standard testing
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Challenges in material specification CIA 2018
Heat of hydration and temperature control
• Common issue is dealing with temperature control
• Requirements not allowed for – becomes contractual cost issue
• How do we get the right technical soluton
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Challenges in material specification CIA 2018
Heat of hydration and temperature control
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Challenges in material specification CIA 2018
Water addition to concrete
• AS1379 Specification and
supply of concrete
• Need to consider the
conditions
• Large number of variables
involved, simplest solution is
to not permit water additions
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Challenges in material specification CIA 2018
Concrete placement time
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Discussion
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Challenges in material specification CIA 2018
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