Following tests are conducted on bricks to determine its suitability for construction work.
Absorption test
Crushing strength test
Hardness test
Shape and size
Color test
Soundness test
Structure of brick
Presence of soluble salts (Efflorescence Test)
WATER Absorption Test on Bricks - 3495 PART 2
Absorption test is conducted on brick to find out the amount of moisture content absorbed by brick under extreme conditions.
Apparatus:
Oven,
Weight balance,
Tray
PROCEDURE
Take any five random bricks from a lot of brick as a specimen.
Dry the specimen in a ventilated oven at a temperature of 105°C to 115°C till it achieves considerably constant mass.
Cool the specimen to room temperature and take its weight (M1).
Testing:
When the specimen is completely dry, then immerse it in the clean water at the room temperature (27 ±2°C) for 24 hours.
Remove the specimen from the water after 24 hours and wipe out water with a damp cloth and weigh the specimen.
Take the weight (M2) of the specimen after 3 minutes of removing from the water.
Points to be Taken Care:
When you take M1, If the Specimen is warm while touching, it shall not be used for the test. Test it when you feel it cool.
Result:
Note down the M1 and M2.
Percentage of Water absorption of brick by its mass, after 24-hour immersion in cold water is calculated by the following formula
(M2-M1)/M1*100
For a good quality brick the amount of water absorption should not exceed 20% of weight of dry brick.
TYPE WATER ABSORBTION
FIRST CLASS < 20% OR 15% AVERAGE
SECOND CLASS < 22.5% OR 20% AVERAGE
THIRD CLASS < 25% OR 25% AVERAGE
Crushing Strength or Compressive Strength Test on Bricks - IS 3495 PART 1
Place the specimen with flat face s horizontal and mortar filled face facing upwards between plates of the testing machine.
Apply load axially at a uniform rate of 14 N/mm2 (140 kg/cm2) per minute till failure occurs and note maximum load at failure.
The load at failure is maximum load at which the specimen fails to produce any further increase in the indicator reading on the testing machine.
Compressive Strength of Bricks = Maximum Load at Failure (N)/Average area of bed face (mm2)
The average of result shall be reported.
Crushing strength of bricks is determined by placing brick in compression testing machine.
After placing the brick in compression testing machine, apply load on it until brick breaks.
Note down the value of failure load and find out the crushing strength value of brick.
compressive strength in N/mm2
>10.5 first class
7.5 second class
5.5 third class
compressive strength of common bricks should not be used if it is less than 3.5N/mm2
Bricks Class Designation
Average compressive strength of Bricks
Not less than (N/mm2)
Less than (N/mm2)
350
35
40
300
30
35
250
25
30
200
20
25
175
17.5
20
150
15
17.5
125
12.5
15
100
10
12.5
75
7.5
10
50
5
7.5
35
3.5
5
Efflorescence Test on Bricks - IS 3495 PART - 3
A good quality brick should not contain any soluble salts in it.
If soluble salts are there, then it will cause efflorescence on brick surfaces.
Type
area affected
Nill Effloresence
Very Low
Slight
0-10%
Moderate
10-50%
Heavy
>50%
Serious
>50% + deposit are
present in powder forms
Heavy Flakes
WARPAGE TEST - IS 3495 PART 4
check the bricks for warpage of brick like concave and convex warpage with the help of glass or stell surface
Hardness Test on Bricks
A good brick should resist scratches against sharp things.
So, for this test a sharp tool or finger nail is used to make scratch on brick.
If there is no scratch impression on brick then it is said to be hard brick.
for any doubt finger nail means
Shape and Size Test on Bricks (dimension test) - IS 1077
Shape and size of bricks are very important consideration. All bricks used for construction should be of same size. The shape of bricks should be purely rectangular with sharp edges.
Standard brick size consists length x breadth x height as 19cm x 9cm x 9cm.
To perform this test, select 20 bricks randomly from brick group and stack them along its length , breadth and height and compare.
So, if all bricks similar size then they are qualified for construction work.
Dimension Test
Dimension should not greater than below value
Length -19×20= 380 ± 12 cm
Breadth - 9×20 = 180 ± 6 cm
Height - 9×20 = 180 ± 6 cm
here 20 indicate 20 no of bricks used in sample
Color Test of Bricks
A good brick should possess bright and uniform RED color throughout its body.
Soundness Test of Bricks
Soundness test of bricks shows the nature of bricks against sudden impact.
In this test, 2 bricks are chosen randomly and struck with one another.
Then sound produced should be clear bell ringing sound and brick should not break.
Then it is said to be good brick.Soundness Test of Bricks
Structure of Bricks
To know the structure of brick, pick one brick randomly from the group and break it.
Observe the inner portion of brick clearly. It should be free from lumps and homogeneous.Structure of Bricks
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.
Which of the following is the main reason to provide frog in the bricks?
Print manufacturer’s name.
Form keyed joint between brick and mortar.
Improve thermal insulation
Reduce the weight of brick.
Form keyed joint between brick and mortar.
Frog: It is an indentation or depression on the face of a brick made with the object forming a key for the mortar. This prevents displacement of the brick above.
∴ The term frog means a depression on a face of bricks.
Some other definitions:
1. Quoins is the exterior angle of a wall.
2. Closer is the portion of brick cut in such a manner that its one long face remains un-cut.
3. Bat is the portion of brick cut across width.
4. Perpend is that vertical joint on the face of wall, which lies directly above the vertical joints in alternative course.
5. Stretcher: Bricks are laid along its length.
6. Header: Bricks are laid perpendicular to the face of wall.
Basic Runway Length Correction for Elevation, Temperature and Gradient Correction for Elevation Corrections in runway length (i) correction ...
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