dallas scc march 2012

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High-Temperature Behavior of SCCSelf-Compacting/Self-Consolidating

ConcretePatrick Bamonte and Pietro G. Gambarova

Dept. of Structural Engineering

Politecnico di Milano, Milan - Italy

ACI Spring Convention 2012 - Dallas

Committee 237 Self-Consolidating Concrete

March 19, 2012


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ACI Committee 237 Dallas (TX), March 19, 2012

Introduction

1. Question : Why should SCC behave differently from ordinary

vibrated concrete VC at high temperature and in fire ?2. Answer : Because of the somewhat different microstructure:

the amounts of cement, water and fine aggregates are similar tothose in VC (70-80% by mass), but SCC typically contains:

less medium and coarse aggregates (30% vs. 50% in VC).

ultrafines (up to 10-15% by mass).

relatively large amounts of chemical admixtures (superplasticizers,

viscosity agents, ).

3. Hence , the cementitious matrix is more compact, with lessinterconnected pores, higher vapor-pressure build-ups in the pores athigh temperature, higher tensile stresses around the pores and moremicrostructural damage

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4VC mechanical behavior (2)Hot tests on stressed/unstressed specimens Residual tests on unstressed specimens


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ACI and FIB provisions for the mechanicaldecay of vibrated concrete: High temperature - Past cooling Calcareous-siliceous aggregates

Stressed-unstressed specimens

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Different thermal ramps and specimensgeometry

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7/16ACI Committee 237 Dallas (TX), March 19, 2012

7Test results examined in this study (1)

9 experimental campaigns (2004-2011); only SCC mixes; f c20 = 40-90MPa, v

f 0.2% (pp fibers); unstressed specimens

Milan (2008-2011): , hot and residual tests, T = 20, 200, 400,600C; cylindrical specimens ( = 100 mm, h = 200 mm); f c = 52, 82,90 MPa; 3 mixes; no fibers; limestone powder and mixed aggregates .

Persson (2004): hot and residual tests; T = 20, 200, 400, 600,800C; cylindrical specimens ( = 100 mm, h = 200 mm); f c = 40-88 MPa; number of the mixes examined here 10 with/without pp.fibers; limestone powder and siliceous aggregates .

Sideris (2006): residual tests ; T = 20, 100, 300, 500, 700C; cubic

specimens (side = 100 mm); R c = 42-75 MPa; number of the mixesexamined here 2 (f c = 43 and 54 MPa) without fibers; siliceousaggregates .



Test results examined in this study (2)

Noumow, Carr, Daoud and Toutanji (2006): residual tests ; T =

20, 400C; cylindrical specimens ( = 160 mm, h = 320 mm); f c = 75-81 MPa with/without pp fibers; one mix examined here (f c = 76 MPa, v f = 0.2%); silica fume and calcareous aggregates .

Reinhardt and Stegmaier (2006): residual tests T = 20-650C;short cylindrical cores ( = 100 mm; h = 100 mm); f

c = 33-76 MPa;

number of the mixes examined here 5 (f c = 50-76 MPa); siliceousaggregates, fly ash and calcareous powder .

Fares, Noumow and Remond + (2009): residual tests ; T = 20,150, 300, 450 and 600C; cylindrical (160 320 mm) and prismaticspecimens (100 100 400 mm); number of the mixes examinedhere 2 (f c = 37 and 54 MPa); limestone filler and 70-75% siliceousaggregates.

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Test results examined in this study (3)

Annerel and Taerwe (2010): residual tests ; T = 20, 200, 300,

550C; cylindrical specimens ( = 106 mm, h = 320 mm); f c =63,46 MPa; one mix examined here (f c = 63 MPa); siliceousaggregates and limestone powder ; no fibers.

Tao, Yuan and Taerwe (2010): hot tests ; T = 20, 200, 400, 600,800C; cylindrical specimens ( = 150 mm, h = 300 mm); f

c = 22-

70 MPa; number of the mixes examined here 2 (f c = 70 and 53 MPa,the latter with fibers); calcareous aggregates and limestone powder .

Khaliq and Kodur (2011): hot tests ; T = 20-800C with T = 100or 50C; cylindrical specimens ( = 75 mm; h = 150 mm); f c = 70 MPa(average value); number of the mixes examined here 2 (one with ppfibers); calcareous aggregates, slag and fly ash .

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SCC mechanical properties (1)Compressive strength

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SCC mechanical properties (2)Elastic modulus

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12SCC mechanical behavior (3)Compressive strength



13SCC mechanical behavior (4)Compressive strength



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f c20 = 50, 80, 90 MPa ; D = v hd2 / (16 T)

SCC vs. VC thermal behaviorThermal diffusivity



Conclusions

No systematic differences between VC and SCC ( no fibers or minimal

amounts of pp fibers ), in terms of uniaxial compressive/tensilestrength, elastic modulus, fracture energy.

Minor differences in the stress-strain curves in compression (in SCCmore linear loading branches and steeper softening branches below

400C).

No differences in terms of thernal diffusivity (which controls heattransfer by conduction).

ACI provisions for the hot/residual properties of VC ( no pre-loading inthe heating phase ) seem to apply also to SCC.

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Open questions

Effect of the confinement on SCC behavior in compression: somedata are already available.

Effect of fiber reinforcement : pp fibers against spallingsteel fibers for toughness

Some data are already available.

Spalling sensitivity (typical of highly-unsteady thermal conditions ):

some data are available, but there are no normalized methods toassess concrete sensitivity to spalling.

dallas scc march 2012

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