HOW HOT IS YOUR CONCRETE & DOES IT REALLY MATTER?
HEAT EVOLUTION & ITS EFFECTS ON CONCRETE CAST
ON CONSTRUCTION SITES IN ASIA
30th Our World in Concrete and Structures (OWICs) - 2005
Christopher Stanley*, Concrete Consultant, Hong Kong.
The chemical reaction between cement & water, known as the hydration process, is an
exothermic reaction. That is, heat is liberated during both the setting & hardening process
of the concrete.
The concrete expands as the temperature rises, & restraint against contraction on
subsequent cooling, unless properly controlled, leads to cracking. The cracks that form
usually pose a durability problem, because they often pass through the full section of the
concrete. A lack of a proper understanding of the mechanism of thermal contraction
cracking often results in the formation of such cracks being incorrectly attributed to other
causes such as plastic or drying shrinkage.
Thermal contraction cracking is a very common occurrence on construction sites
throughout South East Asia. However it is little understood & the appearance of even the
smallest cracks often leads to prolonged disputes on site.
A number of factors combine to influence the magnitude & extent of thermal contraction
cracking in Asian concrete & these are addressed together with case studies of examples
of the temperature rise in hydrating pre-cast & in situ concrete on Asian construction sites