Three Following Types of Perforation or Cavities Bricks :
Perforated bricks
Hollow bricks
Channeled bricks
Perforated Bricks :
These form a modern class of building bricks.
Four perforated bricks of white, yellow and red colors with round and rectangular holes on a pallet with bricks on the background other bricks on a warehouse
In perforated bricks cylindrical, rounded or rectangular holes are made in the bricks after the moulding stage. These holes are called perforations.
They are properly spaced from the side of the brick, minimum distance being 15mm. further, distance between any two perforations is not less than 10mm the volume of the perforations. May be as much as 20-50 percent of the total volume of the brick.
Advantages :
These bricks are light in weight.
Less quantity of clay is required for their manufacture;
Less time is required for drying and burning of perforated bricks.
These offer better resistance against rain penetration and better insulation against heat. As such they are ideally suited for tropical countries.
Efflorescence is least in perforated bricks.
These are specially suitable for construction of brick panels in- multi-storeyed structures.
Hollow Bricks :
A brick also called cavity brick or cellular brick has a few well- defined sets of cavities with specified dimensions made in the body of the brick.
Its net weight may be only one- third to one- half of the solid brick. It is important that the thickness of brick wall near the cavity should not be less than 2 cm. Hence cavity extends throughout the body of the brick.
The hollow bricks are made from special type of brick clay (which should have higher clay content).
Advantages :
Being
light in weight, they can be handled more conveniently and the output of the
mason may be three to four times compared with ordinary bricks.
They
offer better insulation against heat and sound.
They
are ideal and economical for non- load bearing walls, e.g in partition walls.
Channel or Gutter Bricks :
They are actually special purpose bricks having a continuous central semicircular cavity or depression running through their length very often they are glazed to make them impervious.
King Closer : the brick is so cut that it has length and width on one side only.Uses splayed jambs,blunt corners of walls.
Queen Closer : it is also a cut brick. The cut is lengthwise so that brick has only one half of the length of the full bricks. Uses bonding of brick works.
Squint Brick : it is also cut brick.the portion of cut forms angles other than right angle. Uses exterior or interior corners are to be built at some angle and also for ornamental purposes.
Splay Bricks or cant bricks : these have a level or portion taken off, widthwise, lengthwise, or in both directions. Uses for pillars , on top course of plith,on exterior walls etc.
Plinth Header : it has a full length on one face. On the other face, a slope (bevel) is made from 3/4th of the length (D)
Plinth Stretcher : it has slope from one half of the width that extends along the entire length (E).
Plinth Return : it is a combination of both the header and stretcher beveling (F).
Coping Bricks : when a coping is to be provided to a wall, a special shape may be desired. The chamfered brick, the half round brick and the saddle back brick are some common coping bricks.
Bull Nose : it is otherwise a standard brick having one arris or edge rounded. Uses for decoration purposes.
Cow Nose : it is similar to a bull nose but has both edges on the side rounded. It may be called a double bullnose. Use for ornamental purpose.
Miscellaneous Shapes : these include bricks shaped for very specific purpose (not covered above) as for arches and circular walls, chimneys and culvets and wells.
Conventionally , the Bricks are classified in the following two types :
Sun dried or Katcha Bricks :
Burnt or Pucca bricks :
Sun Dried or Katcha bricks :
The bricks dried only in the sun after their moulding are called sun dried or Katcha Bricks.These should not be used at places exposed to heavy rains.
Uses : These are suitable for constructing temporary houses,enclosures etc. in rural area.
Burnt or Pucca Bricks :
These brick burnt in a clamp or klin,after moulding and drying are called burnt or pucca bricks.
These are hard,strong and durable.
Uses : These are generally in permanent works.
These further classified into the following four types :
FIRST CLASS BRICKS :
CHARACTERISTICS :
(i) Well burnt having even surface , perfectly rectangular shape & free from saline deposits.
(ii) When two bricks are struck against each other a ringing- sound is produced.
(iii) Its compressive strength shall not be less than 140kg/cm2 and its absorption after 24 hours, immersion shall not exceed 20 percent.
(iv) It should show a uniform appearance,colour , texture and structure when seen on fracturing.
(v) They shall be clean,smooth & free from cracks,chips,grits,holes , nodules of lime or kankar etc.
(vi) They shall not show any sign of efforescence on surface when dried in the shade.
(vii) They shall not absorb water more than 20% by weight after 24 hours immersion in cold water.
(viii) They shall have a minimum crushing strength of 105kg/sq.cm.
Uses : Every kind of masonry work, flooring etc. Where strength and durability is desired. They are also used for face work,reinforced brick work and as ballast for base concrete work in floors.
SECOND CLASS BRICKS :
CHARACTERISTICS :
Well burnt, even slight over burning is accepted.
Metallic-ringing sound is also a must in this case as well.
In shape, rectangular, but slight irregularity is permitted. Surface may be slightly uneven.
Compressive strength shall not be less than 70kg/cm2 and absorption value between 20-22 percent.
Slight difference in structure on fractured surface is admissible.
They have fine , compact ,uniform texture.
They may have slightly chips , flaws or surface cracks but shall be free from lime & kankar nodules.
They are not so hard & strong.
They shall have a minimum crushing strength of 70 kg/sq.cm.
They shall not absorb water more than 22% by weight after 24 hours immersion in cold water.
They shall not show any sign of efflorescence on surface either in wet or in dry state.
Uses : These used in unimportant situations where bricks are hidden from front views as in the case of interior walls. They are never used in reinforcement brick work or face works of building.
THIRD CLASS BRICKS :
CHARACTERISTICS :
Poorly and unevenly burnt, that is, may be over burnt or under burnt.
On striking a dull thud (rather than metallic sound) is produce.
Appearance, shape and size are also non- uniform and irregular.
Compressive strength lies between 35- 70 kg/cm2 and absorption between 22-25 percent.
Yellowish in colour & may be distorted and have round edges.
They are soft & weak in strength.
They shall not absorb water more than 25% by weight after 24 hours immersion in cold water.
Uses : These used in inferior and temporary buildings & in place not subjected to heavy rains . They are sometimes used for scaffolding and centring in the construction of building.
JHAMA OR FOURTH CLASS / OVER BURNT BRICKS :
CHARACTERISTICS :
Irregular in shape and dark in colour, which is due to over burning.
Quite strong in compressive strength, generally above 150kg/cm2 and low in porosity and absorption.
They shall be over burnt , vitrified & distorted bricks.
They shall be dark in colour.
They shall be irregular in shape & size and may be available in the form of lumps.
They shall be hard & strong.
Produce metallic sound when struck with one another.
Uses : They are used as aggregates for making base for concrete to be used in foundations, floors etc. and as road metal for soling coats.
The process of drying timer(removing moisture or sap, Present in a freshly felled tree, under more or less controlled conditions timber is called Seasoning of Timber.
Seasoning is the first step in the efficient utilization of timber.Tree contain a large quantity of moisture roughly From 100% to 200%, based on dry weight of wood.A well seasoned piece of wood may contain about 10% to 12 % moisture.
Purpose Of Seasoning of Timber :
To minimize the tendency to shrink, warp & split. To reduce the weight for transport purposes , Handling and thereby reduction in cost. To increase strength, durability and electrical resistance. To improve the wood working qualities in timber including gluing, Painting and polishing. To make it capable to a certain degree for protection from attack by insects and fungus.To make it fit for effective preservation treatment, otherwise the protective coat will close the outside pores and induce decay on the timber member.
Classification of Seasoning of Timber :
A)Prevention of drying of log:
The drying of the log should be induced by storing Them under water , which is incorrectly known as water seasoning.
b) End coating for
preventing Splitting in Wood :
This can be prevented or minimized by coating the ends of logs and thick sections of all timbers with some kind of moisture proof substance , upto a distance of 80mm from the ends.
Some of the effective composition for end coating are given below :
1)Thick coat tar or bituminous
paint.
2)Rousin and Lamp Black melted, mixed & applied hot.
3)Hardened Gloss Oil.
4) Paraffin Wax.
5) Molasses and lime (3:1).
Methods of Seasoning of Timber :
1)Air Reasoning or
Natural Seasoning :
Provide free circulation of air so as to allow moisture to evaporate.This method consists in stacking the sawn timber in a dry place, should be made 300 to 450mm above ground level.
Long beam of strong timber, having cross section 100x 100mm, should be placed above the floor to serve as frame work for the stacking of timber.Air Seasoning is a slow process. Time Period depend Upon the size & type of timber, and season variations of climate.
a)Railway Sleepers :
The one and nine method is suitable for moderately heavy timber. The close crib method gives slower seasoning as it reduces the air circulation.This is recommended for stacking sleepers of refractory timber hot & dry localities. Containing about 100 sleepers
but center to center distance of crossers shall not exceed 1.5m.
B) Poles :
Poles should be stacked either in closed heaps or with crossers.The center to center distance of crossers should not exceed 3m.
“Open Crip Method “ in which case, the alternative layers of poles are at right angle to each other ,leaving a space more than 8cm between adjacent pole in the layer.
The convenient height is kept 3m. The center to center distance is kept 1.5m.
C) Bamboos :
These should be stacked in close heaps on foundation to any convenient height.
D) Scantlings and
Squares:
Stacked should be Crossers 50mm x40mm in cross section, which are kept 2.5 to 3m apart.The height of stack may be kept upto 3m.
E) Planks :
Stacking of planks should be thickness And cross section 40x25mm for planks upto 50mm Thickness. The center to center distance of crossers in each layer should be 60cm for planks upto 50mm thickness.
Advantage :
1)Simple & Economical method. ● 2)It does not require much skill and attention in the process of seasoning.
3)Slow Process, the chance of seasoning defects in the timber are comparatively less.
Disadvantage :
1)Slow Process.
2)Large Space required for stacking timber.
3)More Capital investment is required which is otherwise blocked till the seasoning is complete.
4)The moisture contents cannot be reduced less than 15 to 18%. So timber ,seasoned by this method cannot used on certain jobs for which the moisture contents required is less.
5) The timber can easily attacked by insects and fungi due to long period of seasoning even under favorable conditions.
Klin or Artificial Seasoning :
Seasoning of timber in a Klin. It is a quick method of seasoning. The moisture
content by this method can be reduced to the extent of 8 to 12 % and timber can be used in a short time and according to the climate conditions of the locality.
Construction of klin :
It is usually a masonry chamber equipped with arrangement for heating , humidifying and circulating air in the klin.
Construction of klin :
Steam is generally used for heating & humidifying the air in modern klins through furnace gases are also used for supplying heat.It is also provided with propeller fans inside the chamber for rapid circulations of air.
Kiln seasoning
Method :
The stack of timber is made as for air seasoning and the trolley containing stacked wood is driven inside kiln and the doors are closed tightly .
A boiler for heating and power for driving the fans are also used steam is injected through the steam Pipes in the chamber while the heating pipes are kept At low temperature.Full Humidity is maintained by the steam and evaporation from the surface of the timber members is prevented in spite of the heat which gradually reaches inside the timber members.
This process is also known as
desiccating.
Proper circulation of hot air is maintained by driving the fans.
Started at a comparatively low temperature & higher Humidity. Conditions Gradually when temperature of air inside the kiln is fairly high and humidity is low or reduced.
Special instrument such as moisture meter etc. are used for testing some pieces of wood periodically to check the per moisture content.The period of kiln seasoning is also variable Accordingly To thickness and species of timber (4 to30days for 25mm thick planks).
Advantage :
1)Shortest time under controlled process. ● 2)The wood can be used immediately as and when required.
3)It renders the timber less liable
to shrinkage.
4) It renders the timber les liable to be attacked by insects and fungi.
5) Moisture content reduce as per requirement.
Disadvantage :
1)It is a costlier method through space required is less.
2) Skilled labour is
required.
3)Being a quick process of drying, a continuous Attention and watch is required, otherwise the Timber Is liable to seasoning defects such as end splits, Surface cracks, warping , internal cracks etc.
Timber derived from Timberian which mean to build.The wood used for building or other engineering purpose is called timber.
It is a first construction material used by a man since pre-historic ages.
Timer is a natural material. Trees provide shelter from sun and the rain.
Tree: Maple Tree
Trees conserves soil moisture. It precipitate rainfall & lower temperature .A single Tree can cool the summer heat better than 20 Air conditioners.
It prevents depletion of the ozone layer of the atmosphere. It prevents soil erosion.
Trees produces oxygen and purifies the air.
Timber :
Timber
Timber obtained from trunk of a tree. There are many varieties of timber available all over the world.
Advantages :
Timber is strong than any other material. Timber can be easily worked to any size & shape. It can be jointed to required form.
Timber can used for furniture & decoration fittings. Structural connections can be easily made in timber. Timer are light in weight, quite durable.
Its resale value is good. Its non conductors of heat & sound.
Timber uses in construction
Classifications of Timber :
1)Exogenous Trees
2)Endogenous Trees
Exogenous Tress :
Trees which grow outwards and increase in bulk by the formation of successive annual rings are known as exogenous trees.
Exogenous Trees Structure
Timber which is used for building engineering works,Is Mostly obtained from exogenous trees. Examples : Deodar, Kail, Sal, Teak, Shishum, Chir etc .
Exogenous trees are further divided into following two types:-
1)Conifers or Evergreen Trees
2)Deciduous or Broad – Leaf Trees
Conifers or Evergreen Trees : Soft Wood
Trees which remain evergreen & bear fruits.These trees usually yield soft wood & show distinct annual rings. They are light in color & weight.
They can easily split & are resinous. They are comparatively weak in strength. Example :Pine, Deodar, kail, Chir,walnut etc
Deodar – Conifers Tree
Deciduous or Broad Leaf Trees : Hard Wood
Trees which shed their leaves in the autumn &put on new leaves in the spring season are known as deciduous or broad leaf trees.
These trees usually yield hard wood & dark in color, Hard, close grained and strong.They are useful for important engineering works. Example :Sal, Teak, Shishum, Babul, Ash, Mahogany etc.
Deciduous or Broad Leaf Trees
Endogenous Trees :
Endogenous trees which grow end wards in a longitudinal fibrous mass are known as endogenous trees.
These trees are too flexible & aren’t suitable for engineering works.Example : Canes, Bamboos , palms etc
Tanya Decor 