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Fire Group meeting @ Edinburgh, October 2013

Presented at the Fire Group meeting on 2 October 2013
by

Cristian Maluk

on 16 September 2014

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Transcript of Fire Group meeting @ Edinburgh, October 2013

Luke Bisby, Giovanni Terrasi,
Michal Krajcovic, José Luis Torero,
Guillermo Rein, Tim Stratford,
Lukas Bäurle, and others...

Technical and Research Staff

PhD and MEng students

Interns

Visitors
Effects of Polypropelene Type on Occurrence of Heat-Induced Concrete Spalling
c.maluk@ed.ac.uk
BRE Centre for Fire Safety Engineering
Why?
Furnace Tests
2009-2010
"Step back"
Novel Test
Results

H-TRIS is an opportunity...

Test at a negligible economical and temporal cost relative to the standard fire resistance test

Quantifiable and "proper" thermal loading

Design for “real” fire (or fires!)

Move away from a pass-fail testing environment

Better “understanding” of materials’ and systems’ behaviour in fire
Acknowledgments
60 min
16.36 kJ/m2
7.9 min
10.6 min
16.3 min
1.61
kJ/m2
2.22
kJ/m2
3.64 kJ/m2
Past Research
A "plan"
H-TRIS
Effects of Polypropylene Fibre Type on Occurrence of
Heat-Induced Concrete Spalling
3rd International Workshop on Concrete Spalling due to Fire Exposure
Paris, France
H
eat
-T
ransfer
R
ate
I
nducing
S
ystem
Cristián Maluk
Luke Bisby
Giovanni Terrasi
Radiant panels
Loading rig
Linear motion system
Control
thermal energy!
BRE Centre for Fire Safety Engineering
Size of the test specimen
Identical cross section as the full size element
500 mm in length

Mechanical loading
Replicate mechanical conditions near the anchorage zone

Thermal loading
Get the radiant panel as hot as possible and as close as possible
Inverse Heat Transfer Model
Experimental Validation of the Inverse Heat Transfer Model
?
Inverse Model
High-performance concrete design...

High performance SCC (110 MPa)

CFRP tendons (non-corrosive, high strength)

High prestress conditions (12 MPa)

Slender structural elements (45mm thick)

Addition of microsilica and fly ash

2 kg/m3 of monofilament PP fibres

High slump flow (750 mm)
Heat-induced concrete spalling
Longitudinal splitting cracks and loss of bond
3 m long span
Cold overhangs
Simply supported
Four-point bending (decompression at the tension fibre in the central region)
200x45 mm2 cross section
Standard fire resistance test...
One of the following methods should be provided:

Method A: Add an extra reinforcement mesh.

Method B: Demonstrate (by local experience or by testing) that no spalling of concrete occurs under fire exposure.

Method C: Add protective layers.

Method D: Include 2 kg/m3 of monofilament propylene fibres.
EN 1992-1-2:2004
"...the risk of spalling shall be taken into account."

"Explosive spalling shall be avoided, or its influence on performance requirements (R and/or EI) shall be taken into account."

"Properties and recommendations are given for fire exposure corresponding to
standard temperature-time curve only
."
25-27th September 2013
Factors related to the occurrence of spalling
"Define a concrete mixture for which
we can assure that no spalling will occur"
What's going on in the furnace which I'm not replicating?
Why is concrete
not spalling?
?
Assess the effect of PP fibre type (cross section, diameter, length and supplier) and dose.

11 concrete mixtures
(casted at SACAC)
Study on heat-induced concrete spalling

Effect of PP fibres' type (cross section, diameter, length, supplier) and dose

11 concrete mixtures

With and without compressive stress

Each test done in triplicate

30 days
Quantifiable thermal boundary condition

High repeatability

High statistical confidence

Low economical and temporal cost
No spalling!
Through-thickness data
- Furnace tests
- "Real" fires

Develop H-TRIS 2.0
- Higher heat flux
- Larger exposed surface
- Higher mechanical loading

Large experimental parametric program

And...
2nd International Workshop on Concrete Spalling due to Fire Exposure
Delft, Netherlands
5-7 October 2011
Inclusion of PP fibres avoid the occurrence of spalling

An equal dose of PP fibres does not imply an equal behaviour
- Length, diameter of the fibre are also relevant

Dependency on the time-history of imposed heat flux (i.e. dynamic of the fire)

When spalling occurs at an early stage of the test, the mass spalled is considerably lower than when it occurs at a later stage

Concrete mixtures that spalled under load tend to spall when free to expand
Results' discussion...
Next step...
"Define a concrete mixture for which
we can
assure
that no spalling will occur"
½
60 kW/m2
50 kW/m2
40 kW/m2
30 kW/m2
Imposed
heat flux
Inclusion of PP fibres avoid the occurrence of spalling

An equal dose of PP fibres does not imply an equal behaviour
- Length, diameter of the fibre are also relevant

Dependency on the time-history of imposed heat flux (i.e. dynamic of the fire)

When spalling occurs at an early stage of the test, the mass spalled is considerably lower than when it occurs at a later stage

Concrete mixtures that spalled under load tend to spall when free to expand
Inclusion of PP fibres avoid the occurrence of spalling

An equal dose of PP fibres does not imply an equal behaviour
- Length, diameter of the fibre are also relevant

Dependency on the time-history of imposed heat flux (i.e. dynamic of the fire)

Concrete mixtures that spalled under load tend to spall when free to expand

When spalling occurs at an early stage of the test, the mass spalled is considerably lower than when it occurs at a later stage
(mainly near the anchorage zone)
Hydraulic Jack
Load Cell
70 kW/m2
"Never before, we had so much information, and so little knowledge."
And that was it...
...or was it?
George Steiner 2010
Ackoff's content of the human mind
Data
Information
Knowledge
Understanding
Wisdom
"knowledge is the
appropriate
collection of information, such that it's intent is to be
useful
."
One more BIG test
Go back to the furnace

Use our "best" concrete mix

Hope to avoid spalling

Measure all the "cool" things
Longitudinal splitting cracks
Bond degradation
February 2013
Ready for it...
Bond degradation
Transient slip of the tendon
Pi-gauges

Through-thickness temperature measurements
Steel
Concrete
Ceramic
Aircrete
Almost there...
BBQ day
?
Back to H-TRIS
New plan...
Test identical specimens for the
"highest" and "lowest" time-history
of absorbed heat flux.
Are we ever going to "understand" spalling?
Do we
need
to?
Is the occurrence of spalling that
sensitive
to the
inherent scatter
of the thermal loading imposed in a fire resistance test?
Spalling
No spalling
Finding answer to the
important questions
It can happen...
Prof
Dr
PhD
Post-docs
Technicians
Design for spalling
How should the solution look like?
deliver the right information at the right time
favour comprehension over precision
avoid complexity
comprehensible
simple
Age
Moisture content
Compressive and tensile strength
Type and size of aggregate
Type of cement
Water/cement
Admixtures inclusion (e.g. fly ash, silica fume)
Polypropylene and steel fibres inclusion
Casting technique (e.g. vibrated concrete, SCC, spun concrete)
Air-entrainment

Internal reinforcement (e.g. type, ratio, tie configuration)
Structural form (e.g. shape, size, thickness, span)
In-service mechanical stress condition

Heating rate
Heating technique (e.g. gas-fired or electric-powered furnace, etc.)
Single or multi-surface exposure
An highly stochastic
thermo-hygro-chemo-mechanical
phenomenon!!!
...nobody cares
One size fits all
What the &%*# just happened...
Full transcript