similar to burnt clay bricks and of same size but with high compressive strength free from cracks, flaws and nodules of free base
Uses in heavy engineering work such as bridge and industrial foundation and multi-storey building
Two types- class 400 and class 450 400 indicate compressive strength in 40N/mm2
Bulk density <2500 kg/m3 Efflorescence - Nill Water absorption - < 10%
2.
Burnt Clay Perforated Brciks
IS:2222
have Cylindrical holes throughout theier thickness, have high compressive strength less water absorption area of perforation should not exceed 30 to 45%area of face
3.
Burning clay Facing Bricks
IS:2691
used without any further protection of faces of wall used in corrosive environment and high rise building it is economical class 1 - >100 kg/cmm2 class 2 - >75 kg/mm2
availabe on two sizes 19×9×9 cm and 19×9×4 cm
4.
Burnt Clay paving Bricks
IS:3583
Iron content more than ordinary brick this cause vitrification of bricks burning at low temperature which give natural glaze to brick and more resistant to abrasion
these blocks also known as cellular or cavity blocks used to reduce the dead weight of masonry reduce the transmission of heat, sound and dampness Crushing strength >3.5 N/mm2 Water absorption < 20 %
7.
Sand Lime Bricks
IS:4139
also known as silicate bricks crushed siliceous rock and lime combined by the action of saturated steam under pressure
8.
Sewer Bricks
IS:44885
manufactured from surface clay, fine clay or shale used for lining of walls, roofs and floor of severs
average compressive strength > 175 kg /mm2 water absorption <12%
9.
Acid Resistant Bricks
IS:4860
Resistant to acid and base
10.
Refractory Bricks/Fire clay Bricks
IS:4860
Resist high temperature up 1700 °C
As per IS 1077: 1992, clause 7.3,
The rating of efflorescence shall not be more than 'moderate' up to class 12·5 and 'slight' for classes higher than 12.5.
The common burnt clay bricks shall be classified on the basis of average compressive strength as given by
Class designationAvg compressive strength not less than (N/mm2)
3535
3030
2525
2020
17.5 17.5
1515
12.512.5
1010
7.57.5
55
3.53.5
Types of Bricks based on uses during masonry
(a) Bevelled closer
(b) Queen-closer(half) (c) Queen-closer(quarter)
(d) King closer
(e) Full brick
(f) Mitred closer
(g) Half bat
(h) Three quarter bat
(i) Bevelled bat
What is the maximum allowable water absorption (%) of Indian burnt brick of class 20?
a. 15
b. 5
c.20
d.10
answer a. 15%
As per IS 1077: 1992, clause 7.2, Bricks after immersion in cold water for 24 hours, water absorption shall not be more than 20 percent by weight upto class 12.5 and for the classes above 12.5 water absorption shall be between 12.5 and 15 percent.
Note:
Water absorption for First class brick should not exceed 12-15 % of its dry weight.
comment if any doubt about first and second class brick water absorption
For second class brick it should be between 16 - 20%.
Type of Fire Bricks or Refractory Bricks
These type of bricks are made from fire clay.
In these types of brick generally the amount of sillica is increased and lime is decreased.
In this type of brick earth generally the amount of lime and iron oxide is much less like 2 to 3%
This bricks is made on 1600 to 1700 degree celcius.
Water absorbtion is 5 to 10 % of dry wt of bricks.
The firebricks are classified on the basis of their reactivity or chemical change at high temperatures:
1. Basic Refractory Bricks:
They are resistant to the melts of basic composition. Hence, they will not be suitable for use in those furnaces where acidic melts are being heated.
Examples:
Magnesia bricks, Bauxite bricks.
2. Acid Refractory Bricks:
They are resistant to the melts of acidic composition (but will react with the melts of basic composition).
Example:
Fire-clay bricks, silica bricks.
3. Neutral Refractory Bricks:
They are non-reactive to both the acidic and basic melts. Hence these find applications in heating either type of melts.
Examples:
Chromite bricks, Chrome-magnesite bricks.
Tolerances limit of Bricks
As per IS 1077 (1992), clause 6.2, Tolerances
The dimensions of bricks when tested in accordance with 6.2.1 shall be within the following limits per 20 bricks:
a) For modular size
Length 3720 to 3880 mm (3800 ± 80 mm)
Width 1760 to 1840 mm (1800 ± 40 mm)
Height 1760 to 1840 mm (1800 ± 40 mm)
(For 90 mm high bricks)
760 to 840 mm (800 ± 40 mm)
(For 40 mm high bricks)
b) For non - modular size 23 *11*7
Length 4520 to 4680 mm (4600 ± 80 mm)
Width 2240 to 2160 mm (2200 ± 40 mm)
Height 1440 to 1360 mm (1400 ± 40 mm)
(For 70 mm high bricks)
640 to 560 mm (600 ± 40 min)
(For 30 mm high bricks)
Test on Brick Earth
Ball of about 8 cm diameter are moulded with hands and allow it for sun dry. If the dry ball get deformed and crumble easily, it indicates that soil has sand particles in it.
Well kneaded soil of plastic consistency which is capable of being rolled in threads of 3 mm in diameter. This test is done to determine shrinkage cracks.
English bond
In this bond, the alternate courses consist of headers and stretchers.
This is considered to be the strongest bond.
Hence it is a commonly used bond for walls of all thicknesses.
Flemish Bond
In this type of bond, each course comprises of alternate header and stretcher.
Alternate courses start with stretcher and header.
Every header is centrally supported on the stretcher below it.
Construction of Flemish bond needs greater skill.
Used to get a good aesthetic view.
To break the continuity of vertical joints
In English bond - Queen closer is used in the beginning and end of a wall after the first header.
In Flemish bond - Queen closers are required if a course starts with a header and in walls having their thickness equal to odd number of half bricks, bats are essentially used to achieve the bond.
In Header bond - 3/4 brick bat as a quoin brick in alternating courses.
Stretcher bond - 1/2 brick bat is provided in alternating courses.English bond
In this bond, the alternate courses consist of headers and stretchers.
This is considered to be the strongest bond.
Hence it is a commonly used bond for walls of all thicknesses.
Flemish Bond
In this type of bond, each course comprises of alternate header and stretcher.
Alternate courses start with stretcher and header.
Every header is centrally supported on the stretcher below it.
Construction of Flemish bond needs greater skill.
Used to get a good aesthetic view.
To break the continuity of vertical joints
In English bond - Queen closer is used in the beginning and end of a wall after the first header.
In Flemish bond - Queen closers are required if a course starts with a header and in walls having their thickness equal to odd number of half bricks, bats are essentially used to achieve the bond.
In Header bond - 3/4 brick bat as a quoin brick in alternating courses.
Stretcher bond - 1/2 brick bat is provided in alternating courses.
Angularity is a measure of angularity of aggregate sample. It gives a general idea of shape, void ratio, denseness, packaging and compactness of the aggregate sample.
Angularity Number = (67−W×100)/(w×G)
where
W = Aggregate weight filled in the cylinder
w = Weight of the water filled in the cylinder
G = specific gravity of aggregate
The angularity number ranges from 0 to 11 for aggregates suitable for making concrete.0
Important Points:
If the angularity number is zero, the solid volume of aggregate is 67% and if angularity number is 11, the solid volume of the aggregate is 56%. Angularity number represents the most practicable rounded aggregates and the angularity number 11 indicates the most angular aggregates that can be tolerated for making concrete which is not so unduly harsh and uneconomical.
In this process, timber surface is cleaned and it is coated with a dilute solution of sodium silicate. A cream-like paste of slaked fat lime is then applied and finally, a concentrated solution of silicate of soda is applied on the timber surface. This process is quite satisfactory in making the timber fire- resistant.
Basic Runway Length Correction for Elevation, Temperature and Gradient Correction for Elevation Corrections in runway length (i) correction ...
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