During the last few years, concrete structures are becoming massive. It is essential to cast raft, slabs, dams, massive structures, etc without construction joints in single pour.
Such pour would involve large volume of concrete to be poured continuously without stoppages leading to monolithic structures.
Mass concrete can be defined as any large volume of cast-in place concrete with dimensions large enough to require measures to cope with the generation of heat and attendant volume change to minimize cracking.
For general considerations any concrete structure having lateral dimensions of 0.75 meter or more, may need appropriate mass concreting practices
PROBLEMS FACED DURING MASS CONCRETING:
Thermal cracks appear in mass concrete due to rise in peak temperature of the inner core concrete. The development of high temperature at the core becomes critical if the thickness of the structure is 500mm or more. The temperature difference leads to differential thermal expansion.
The surface of concrete should be insulated by appropriate materials like polyethylene sheet, thermocol sheet, plastic coated tarpaulin or quilts etc.
Large columns may be wrapped with plastic coated quilts or such other materials for at least three or four days.
Accelerators shall be used as admixture for increasing strength of concrete at early ages.
Air entry agent used for improving the quality and workability of concrete.
Water use shall confirm the specifications as per IS CODE.
Concrete work should be suspended during excessively hot, cold or rainy weather.
Finishing of concrete surface should be done as desired for mass concrete.