i) Point to be Noted | Important Points of | Construction Materials

Good Verity of cement contains higher % of:

Tricalcium Silicate (C3S): 3CaO.SiO2

• Supposed to be the best cementing material & well-burnt cement.

Dry Rot:

• Reduces the timber to powder. 
• Dry rot is decomposition of felled timber. It is caused by the action of various fungi.
• The fungus reduces fiber to a fine powder and the timber losses its strength.

Age of a Tree may be ascertained by:

• The number of Annual rings.

Main Ingredients of Portland Cement are:

• Lime (CaO) and Silica (SiO2)

Crushing strength of good building stone should be more than:

• 1000Kg/cm² (100MPa)
• Co-efficient of hardness > 14
• Specific gravity > 2.7
• Toughness index > 13
• % of water absorption after 24 hour < 0.6
• Generally, stones from igneous & metamorphic rocks are heavier & more durable than stones from sedimentary rocks.

Commonly used thinner in oil paints is:

• The solvent of oil paints are used to thin the paints increase, the spread and are also known as thinner.
• Petroleum, Spirit, Naptha & Turpentine oil used for common thinning materials

Moisture content in a well-seasoned timber is:

• 10 to 12%

Commonly used lime in whitewashing:

• Fat Lime is suitable for whitewashing and plastering. 
• Hydraulic lime is used for making mortar & used for masonry construction.

Plywood is obtained by gluing wooden sheets at a pressure of:

• 0.7 to 1.4 N/mm²

Quick Sand is:

• flow condition occurring in cohesionless soil. 

Condition: 

• If the sepage pressure becomes equal to the pressure due to the submerged weight of soil, then evidently the effective pressure is reduced to zero.
• In such a limiting case, the cohesionless soil loses all its shear strength and the soil particles will have a tendency to move up in the direction of flow. This phenomenon of the lifting of soil particles is called the quick condition or boiling condition or quicksand.
• The hydraulic gradient corresponding to this situation is called critical hydraulic gradient.
• ic = (G-1)/(1+r) G = 

specific gravity 

e = void ratio

Bulking:

• The increase in the volume of a given mass of fine agg. caused by the presence of water is known as bulking.
• The extent of bulking depends upon the percentage of moisture present in the sand & its fineness.

In OPC the first one to react with water:

Tricalcium Aluminate (C3A):

• 5-11% of cement.
• it rapidly reacts with water.
• High heat of hydration 
• Responsible for the flash set.