^SfHlfypiJl ^"blfl 3l^LCROW/ GREAT BRITAIN
MMUNICATION No. 2
SECOND CONGRESS ON LARGE DAMS
WASHINGTON,.D. c, 1936
KAy; 'O . EXHHHECKAfl
DAMS BUILT OF PRTOOTTOftCRETE BLOCKS
W. T. Halcrow, M. Inst. C. e., M. I. Mech. e., M. Inst. W. e etc.,
of C. S. Meik & Halcrow .Consulting Civil Engineers, London^ ; England
In view of the difficulties experienced with the formation of cracks in large mass-concrete dams due to shrinkage while the concreteTs setting it was suggested at the Eirst Congress of the International Commission on Large Dams, held % Stockholm in 1933, that dams might be made of precast concrete blocks instead of concrete in the mass as is the most common practice today.
The chief advantage of this method of construction is that all shrinkage due to cooling of the concrete while setting takes place before the concrete blocks are placed in the dam. If the blocks are made to dimensions suitable for handling, the volume of each block will not be great enough to engender cracking of the concrete of which it is made during the time of setting and hardening. In addition to eliminating cracks in the body of the dam the prevention of vertical shrinkage tturing setting would facilitate the fitting of cast-iron guides to the face of the dam for control sluices. In low dams the. initial vertical shrinkage may be considered negligible but in dams of great height it is at present necessary to make allowance for shrinkage when setting such guides, and this cannot be regarded as altogether satisfactory. It may be argued that, although "initial" shrinkage is done away with in block-work dams, volumetric changes due to variations of atmospheric temperature will still remain. This is correct, but the expansion and contraction will tend to take place . mainly in a horizontal direction parallel to the face of the dam and
*Barrages en blocs de beton coulex d'avarice.
■ Iter formierten Gussbetonblöcken errichtete Staudämme.
construidas de bloques de hormigön pre parados por adeLintndo.