Thursday, February 04, 2016

RCC Concrete specifications

  • Concrete in one layer should not be more than 15 cm.
  • Hacking of surface should be done immediately after removal of centering and shuttering.
  • When concrete is placed especially in floors and pavements, solid particles of the ingredients of concrete begin to settle down by gravity action and water rises to surface. This process is known as 'bleeding' it should be ensured that the evaporation of water is lower than the rate of bleeding. This can be achieved by covering the top by wet burlab (a coarse canvas), especially during hot seasons.
  • Shrinkage cracks can be controlled by using temperature reinforcement with about 0.12% (if high strength deformed bars are used, refer clause of IS: 456-2000) of cross sectional area of concrete both horizontally and vertically. It is perferable to use bars of smaller diameters at closed intervals.
  • Curing of concrete should be commenced immediately after the setting has taken place and proper curing should be done for 28 days, but concrete members (slabs/ columns) must be completely immersed in water for at-least 10 days and should be kept wet by repeated spraying for the balance period.
  • For vertical fascias, RCC vertical projections are to be provided and not brick masonry. This applies for sun- shades also. This is to avoid horizontal cracks at the joint between slab surface and the masonry.
  • Catwalk should be provided to prevent disturbance to reinforcement as well as already laid concrete.