Building Material (Part-III) (GENERAL ENGINEERING) (SSC JE)

• Final setting time is referred as the time which is measured from the instant water is added in to the cement up to the extent it completely looses its plasticity and attain sufficient firmness to resist definite loading.

• Initial setting time is referred as the time which is measured from the instant water is added into the cement upto to the extent start loosing its plasticity.

Texture– The coarseness of the grains of a mineral is known as texture.

Luster– Luster is the way light interacts with the surface of a crystal, rock or mineral.

Fracture– A fracture is any separation in a geologic formation, such as a joint or a fault that divides the rock into two or more pieces.

Deforestation–

• Deforestation can be defined as the large scale removal of trees from forests (or other lands) for the facilitation of human activities.

• The right time of deforestation from plain area is winder season.

Supplementary cementitious material is fly ash, rice husk ash, silica fume.

Artificial pozzolana, materials are a supplementary cementitious material like fly ash, ground blast-furnace slag, silica fume, surkhi, rice husk ash.

Hydration of cement–

• The chemical reaction between cement and water is known as hydration of cement.

• The reaction takes place between the active components of cement C4AF, C3A, C3S and C2S and water.

According to chemical classification, the rocks may be classified as follows– 

Siliceous rocks–

• The principal constituent of these rock is silica. They are hard and durable and are not easily affected by weathering action.

• Example of such rocks are granite, map, sand stones etc.

Argillaceous rock–

• The rocks which contain clay or alumina as a main constituent is called argillaceous rocks. Example– Slate, laterite and kaolin.

Calcareous rocks–

• The main constituent of these rocks is calcium carbonate.

• The durability of these rocks depends upon the constituents present in the surrounding atmosphere.

• Lime stone is a calcareous rock of sedimentary origin while marble is a calcareous rock of metamorphic origin.

English Bond, Flemish Bond, Dutch Bond are related to masonry work.

• Dutch Bond:- The Dutch bond is the modified version of the English bond where the corners of the walls are straightened.

Gypsum use in grouts:-

• Gypsam retard the setting time of cement.

• The paste of cement remain in mobile condition for 3 to 4 hour without setting.

• It control the rate of hydration and retard initial setting time

Calcareous Rock– In this rock calcium is predominate. eg : Marble and limestone.

Argillaceous rock– In this rock, alumina or clay predominates these are brittle and can't with stand shock. eg : slates, laterite

Siliceous rock– In this rock silica is predominate these are hard and durable.

eg : Granite and sandstone, quartzite.

 Fire-clay bricks or refractory bricks–

• Fire-clay bricks are made from fire-clay the process of manufacturing is as of an ordinary brick, burnt at very high temperatures in special kilns (Hoffman's kiln).

• These are used for lining blast furnaces, ovens, kilns, boilers and chimneys.