Thursday, May 13, 2010

Types of Contracts

  • Fixed Fee or Lump sum Contracts (with provision for change orders)
  • Item Rate Contracts
  • Cost Plus Contracts with GMP
  • Percentage Rate Contracts with Guaranteed Maximum Price (GMP) 
  • Contract between a Govt body and a private organizations is called PPP or Public Private Partnership.
  • Supply and Erection Contracts

Components of a Centralized Air Conditioning System:

  1. Chillers

  2. AHU
  3. Ducts

  4. Water Pipes

  5. Pumps

  6. Cooling Towers

  7. Diffusers, Grills, Registers etc

  8. Mechanical Dampers, Fire Dampers, Smoke Dampers, Thermostats

Tendering Cycle Sequence

   1) Notice Inviting Tender Date

   2) Date of Bid Submission

   3) Date of Bid Opening

   4) Award of Contract

   5) Date of Notice to Proceed

   6) Date of Onsite Construction Presence

About Bricks

Indian Standards in Brickwork
  • Nominal Size of Brick (in mm) = 230 x 115 x 75
  • Nominal Size of Brick (in inches) = 9 x 4.5 x 3
  • Number of bricks per cum of brickwork = 1/(0.230 x 0.115 x 0.075) = 504 bricks
  • Number of bricks per sqm of half-brick thick wall = 1/( 0.230 x 0.075) = 58 bricks 
  • Mortar required per cum of brickwork = 0.25 cum
Brick Types:
  • Normal Bricks
  • Fly-ash Bricks 
  • Cement Hollow Blocks ( 400mm x 200mm x 200mm) (These blocks are generally hollow, else they would be very heavy to lift)

Basics of Concrete

Concrete Mix Ratios - Cement : Fine Aggregate : Coarse Aggregate
  • M10 =1:3:6
  • M15= 1:2:4
  • M20 = 1:1.5:3
  • M25 = 1:1:2
The numbering denotes strength of the concrete. The higher the number the higher the strength.
For M30 and above, only design mixes are used.

  • These mixes are based on OPC 43 cement. If OPC 53 or any other grade of cement were to be used then these ratios would change.

  • M10 means that the concrete mix should have a compressive strength of 10N/mm2 and so on

  • These ratios are based on a volumetric mix and not a mix based on weights of the ingredients

  • IS Code 456 deals with the various grades of concrete

  • RMC is Ready Mix Concrete supplied by the RMC plants to the construction site in transit mixer trucks

  • Cost of Ready-Mix-Concrete including transportation is Rs 3000 per cum

  • As the water to cement ratio increases, the strength and durability of concrete decreases. However adequate water to cement ratio must be used for workability of concrete.
Concrete is tested by:
  1. Cube Test for strength
  2. Slump Test for workability