Print

CONCRETE UPGRADE

Concrete has always maintained an advantage over steel as a construction material because of its inherent fire resistance. This has been the conventional wisdom but one which has been challenged with recent findings and research into the performance of concrete elements under fire loads, both actual and simulated, when taking into account spalling incidents in rapid rise fires (hydrocarbon fires). In comparing the loss of strength with rising temperatures, findings are that the two materials differ little in this context. The below table summarises the physio-chemical changes and the consequent damage in concrete at various temperatures.

 

Physio-chemical changes in concrete with temperature

Temperature

Effect

70 to 80oC

Some loss of strength, however it is reversible. When temperature is reduced, strength is restored. This is due to the weakening of the physical van Der Waal forces due to the expanding water particles pushing the CSH layers apart.

100oC

Loss of all free water. Loss of chemically bound water begins.

200oC

No change in morphology or microstructure.

300oC

Ca(OH)2 crystals are dissociated and deformed. Start of siliceous concrete strength loss. CSH gels undergo irreversible changes and cause loss of strength and elasticity.

Also see discussion below on explosive spalling.

400oC

Start of dehydration of CH, 5-15% loss in strength.

500 to 600oC

Development of micro-cracking. Marked increase in basic creep with 30% loss in strength.

700oC

Significant changes in concrete morphology due to increase in micro-cracks, voids, porosity and disrupted CSH phase boundaries. Dissociation of Calcium Carbonate.

800oC

Total loss of water of hydration, 70-80% strength loss.

1000oC

Rapid deterioration and total loss of strength.

 

All Portland cement based concrete therefore begins to lose their load bearing capacity when temperatures reach in excess of 350oC.

Cementitious coatings perform well in Hydrocarbon as well as Cellulosic fires and during fires initially rely on the combined water of crystallization to hold its internal temperature at approximately 95°C, maintaining low interface temperatures for extended periods of time. Once the water of crystallization has evaporated the vermiculite’s excellent refractory properties continue to protect the concrete. This slower heating allows for moisture to be driven out of the concrete thus totally eliminating the phenomenon of spalling. All Portland cement based concrete therefore begins to lose their load bearing capacity when temperatures reach in excess of 350°C.All Portland cement based concrete therefore begins to lose their load bearing capacity when temperatures reach in excess of 350°C.

Vermitex TH specifically designed for passive fire protection has now been used for many decades and is of proven performance.

 

LAF VALUE ENGINEERING

Products:

Vermitex® TH

Test Reports:

FSH 0981

FS 3049/1696  TEST DATA FROM VERMIDUCT AND REIN PANEL FIRE TEST IN ACCORDANCE WITH AS1530.4

FSP-1161 – FIRE TEST ON VERMITEX TH PROTECTION SYSTEM (BS476:APP.D, UL-1709, EN1363-1)

FSP-1071 – FIRE TEST ON VERMITEX TH PROTECTION SYSTEM IN ACCORDANCE WITH BS 476 PART 20; 1987 APPENDIX D

FSP-1070 – FIRE TEST ON VERMITEX TH PROTECTION SYSTEM

Assessments:

FCO-2290 – VERMITEX TH & HX PROTECTION OF CONCRETE ELEMENTS

FCO2543 – VERMITEX TH & HX FIRE PROTECTION SYSTEMS

FCO 2819 – VERMITEX TH SYSTEM FOR UPGRADING THE FIRE PERFORMANCE OF HORIZONTAL AND VERTICAL CONCRETE ELEMENTS EXPOSED TO ISO/BS/AS/ASTM CELLULOSIC FIRE TYPEAND RAPID RISE HYDROCARBON TO BS(APPENDIX D), UL1709, RABT(TRAIN), RWS, HCinc, MODIFIED HEATING CONDITIONS