Category Archives: Building materials

bricks, Building materials

Testing of Bricks – Top 8 Test on bricks to ensure quality

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Testing of bricks is a crucial step both on-site and in laboratories to verify the quality and suitability of bricks for construction. Bricks are one of the oldest and most reliable building materials, valued for their strength, durability, and affordability. Typically made from clay, bricks usually measure 190 mm × 90 mm × 90 mm with sharp, rectangular edges. They serve as essential components in construction, acting as both load-bearing structures and means of load transfer. To ensure their effectiveness, several brick quality tests are conducted, including the compressive strength of bricks, water absorption test, efflorescence test, and brick durability test. These types of brick tests help assess the brick’s resistance, porosity, and overall performance under different conditions. Adhering to these testing methods guarantees that only high-quality bricks are used, leading to safer and more durable construction projects. Understanding the methods for testing bricks is vital for builders, engineers, and quality controllers.

Audio on test on bricks
Audio on test on bricks
  1. Requirement of Good Quality Bricks
  2. Testing of Bricks – Top 8 tests on bricks
    1. Water absorption testing of bricks
  3. Compressive strength of brick/Crushing strength of brick
  4. Efflorescence test on brick – Testing of bricks
  5. Hardness test on bricks
  6. Shape and size Testing of Bricks
  7. Colour test of bricks
  8. Structure Test on Bricks
  9. Soundness test of bricks

Requirement of Good Quality Bricks

Good quality bricks are essential in construction to ensure strong, durable, and safe structures. They provide a stable base and resist environmental stresses, contributing to the longevity of buildings. The requirement for good bricks includes uniformity in size and shape, strength, durability, and minimal water absorption to prevent damage from moisture.

  • Bricks should be homogeneous and compact.
  • They should have equal proportions of clay, sand, and silt. 
  • Bricks should have requisite plasticity.
  • They should be free from defects like lumps and holes. 
  • The shape of the brick should be rectangular. 
  • A good brick should not break if dropped from a one-meter height.
  • Brick should not possess internal cracking and shrinkage.
  • The brick should be fire and scratch-resistant.
  • Water absorption of brick should not exceed 20 per cent of its dry weight. 
  • The compressive strength of the brick should not be less than 3.5N/mm2.
Good quality bricks
Good Quality Bricks

To maintain these qualities, testing of bricks should be done. This article discusses the test on bricks that are carried out to ensure the quality of good bricks.

Testing of Bricks – Top 8 tests on bricks

Bricks must undergo various tests to ensure their quality, strength, and durability for safe and long-lasting construction. Proper testing helps identify defects, assess strength, and confirm compliance with standards, preventing structural failures and ensuring cost-effective use of materials.

  • Water absorption test of brick
  • Compressive strength test of brick/ crushing strength test on bricks
  • Hardness test of brick
  • Shape and size test of bricks
  • Colour test of bricks
  • Soundness test of brick
  • Structure of brick test
  • Efflorescence test of brick

Water absorption testing of bricks

A water absorption test of the brick is performed to determine the amount of moisture absorbed by the brick under extreme conditions. The purpose of the water absorption test of bricks is to determine their durability of the bricks. The water absorption test necessitates the use of a weighing machine and a drying oven.

  • Firstly, the brick specimen is dried in a drying oven 
  • After that, weigh the dry specimen using the weighing machine and mark it as W1.
  • Secondly, immerse the brick in water for 24 hours.
  • Then take the brick out and drain the water.
  • Similarly, measure the weight and mark it as W2.
  • Finally using the formula determine the water absorption.

Water absorption = (W1 -W2) / W1 x 100

The moisture content of the brick is thus determined by the difference between the dry weight and the wet weight. Water absorption for high-quality bricks should be less than 20% of the dry weight. This brick test ensures that the brick is long-lasting and can withstand extreme weather conditions.

Compressive strength of brick/Crushing strength of brick

The ability of the brick to withstand a particular load without failure is the compressive strength of the brick.

A compressive strength testing machine is the apparatus for determining the compressive strength of brick.

  • First, Take three sample specimens and submerge them in water. 
  • After 24 hours, drain the water. Fill the frog and void with mortar in a ratio of 1: 3. 
  • Subsequently, store the brick in jute bags for 3 days. 
  • Place the brick in the compression testing machine with the brick frog area facing upwards. After that apply the load slowly.
  • Note down the load at which the bricks break.
  • Finally, using the formula to determine the compressive strength of brick. 

Compressive strength (N/mm2) = Maximum load at bricks fail/ Loaded area of brick

For good quality bricks, the compressive strength should not be less than 3.5 N/mm2. 

Compressive strength of brick/Crushing strength of brick - Apparatus
Compressive strength of brick/Crushing strength of brick – Apparatus

Efflorescence test on brick – Testing of bricks

A good quality brick should be free of soluble salts. However, If soluble salts are present, they form a white substance on the brick surface. Generally, efflorescence on brick is the name given to this white formation. The test procedure for performing the Efflorescence test on brick is as follows.

  • First, take a brick specimen and submerge it in water for 24 hours. 
  • After 24 hours, drain the brick and allow them to dry.
  • Keenly observe the brick surface.
Brick surface conditionDegree of Efflorescence
No white substanceZero efflorescence
10% white substanceSlight efflorescence
50% white substanceModerate efflorescence
More than 50% white substanceHeavy efflorescence
Efflorescence test on brick – Range
Efflorescence Test on Bricks
Efflorescence test on brick

Hardness test on bricks

The hardness test on bricks is a field verification test. Hence they are performed on-site. A good brick should resist scratches against sharp things. The following is the test procedure for the hardness test on bricks.

  • At first, choose a brick randomly from the stack.
  • Using a nail or finger make a mark on its surface. 
  • If there is no scratch, then it is a good quality brick.

Shape and size Testing of Bricks

A good quality brick should be uniform in size and rectangular in shape. In order to check this, measure the brick on the field. The standard size of the brick is 190mm x 90mm x 90mm.

  • Randomly, choose 20 bricks from the stack.
  • Sort them in length, width and height wise.
  • If the sizes are the same, Then they are good bricks.
shape and size test of bricks
shape and size test of bricks

Colour test of bricks

Normally good quality bricks are deep red or copper colour. The colour test is a field test. Therefore, it can be observed visually.

Structure Test on Bricks

Homogeneity and compact structure are the quality of good bricks. 

  • Randomly, pick one brick from the stack.
  • Cut the brick into two pieces at the centre. 
  • Then observe its inner side.
  • They should be free from defects such as lumps, holes etc. 

Soundness test of bricks

The soundness test of bricks is a field test used to determine the strength of the bricks.

  • In this test, choose two bricks randomly without damage or break.
  • Hit the bricks with each other. 
  • Then, listen to the sound the brick produce. 
  • If a metal ringing sound is produced, then it is good quality bricks. 
Building materials, CEMENT

Cement tests – Laboratory tests and field tests

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Cement tests are significant because cement is the most important and highly recognized binding material used in construction. Cement is an integral part of all types of construction ranging from huge skyscrapers, bridges, tunnels, etc to small residential buildings. For industrial structures like power plants, refineries, steel plants, cement plants, bridges, roads, etc. cement is the main component. Cement, when mixed with sand and aggregates, forms concrete and with sand makes mortar. The serviceability, strength, and durability of a structure are related to cement used in various works.

This article is about various tests conducted on cement to check its quality.

Cement tests – Categories

Cement is one of the oldest and most used binding materials and an integral ingredient used in the construction sector. The quality, serviceability, and stability of a structure are directly related to the quality of cement used in it. Hence it is required to analyse the quality of cement before using it for works. The tests for determining cement quality are split into two major categories.

Cement got physical as well as chemical properties. Normally lab tests are conducted to ascertain the properties of cement. Lab tests require time, special equipment, and professionals for testing and interpreting the results. It may not be possible to check all the properties of cement at the site. To overcome this difficulty cement tests are categorised into field tests and laboratory tests.

Cement tests

Field tests on Cement

The quality of cement is determined using some simple field tests. These tests do not require any sophisticated types of equipment and professional skills and get the results very quickly. By conducting these simple tests and analyzing the results we will get an idea about the cement quality and can immediately decide on accepting or rejecting it.
Following are the common field tests conducted to ensure the quality of cement.

These are first look tests and quality of cement is ensured by its smoothness to touch, the colour of cement, etc.

  • Checking manufacturing date
  • Visual checking of lumps
  • Feel test
  • Heat of cement
  • colour
  • Water float test
  • Setting test

These basic tests give an approximate characteristic of cement. These are easy and quick but not accurate, however help in concluding the acceptance of cement for works.

Also read : Field tests for cement

Laboratory tests for Cement

The laboratory tests are conducted to define the physical and chemical properties of cement. It is not possible to check all the cement properties at the site. The main laboratory tests conducted on cement is as follows.

  • Fineness Test
  • Compressive Strength Test
  • Consistency Test on cement
  • Setting time
  • Soundness Test
  • Tensile strength Test
  • Heat of hydration

Lab tests require time. But it provides accurate results.

Fineness test

The fineness test determines the size of the cement grains. Smaller the diameter of grains finer the cement is. Finer cement grains enhance the strength and cohesiveness of concrete.
The fineness of cement grains plays an important role in the hydration process and directly impacts the strength of concrete. Cement fineness is determined with the help of the following tests.

  • Sieve test
  • Blain’s air permeability test
  • Wagner turbidimeter method.

Blain’s air permeability test is the more reliable than sieve analysis test. The apparatus for this test is the permeability apparatus.

Finer cement grains above the permissible limits are also not preferred because excess finer grains increase the surface area. An increase in the surface area requires more water and results in the quick setting of cement. The standard guidelines for the Fineness test are IS 4031-PART1-1996, IS 4031(Part2)-1999, ASTM-204-05, ASTMC-115-96a (re-approved 2003).

Compressive Strength Test

The compressive strength of cement is the prime data to be determined before selecting the cement at the site. Concrete imparts strength to the structure and cement is the main ingredient in concrete. The apparatus for this test is a Compression testing machine. Gradual load is applied to the cement specimen. The load at which the specimen breaks and the area of the specimen define its strength. Certain factors like improper mixing, curing, proportioning, etc also affect the strength of cement. The cement with low compressive strength is not recommended in construction. The standard guidelines available for this test are IS4031 (Part 6)-1988, ASTM C 109, BS EN 196 – 1:2005.

Consistency test on cement

The consistency test is performed to determine the water necessary for attaining standard consistency or normal consistency. Water content is an important factor in making cement mortar. On mixing water with cement the chemical reaction or hydration is initiated. Excess water in cement results in an increase in the water-cement ratio. An increase in the water-cement ratio leads to a loss of strength when cement hardens. Less water content reduces the hydration process leads to loss of strength. Vicat apparatus is used to determine the consistency. The standard consistency of cement is when the Vicat plunger penetrates to a point 5 to 7 mm from the bottom of the Vicat mould. The consistency of cement ranges from 26% to 33%.

Vicats apparatus-Consistency test on cement
Vicats apparatus-Consistency test on cement

An increase in the amount of water content creates problems like bleeding, segregation in concrete. The standard guidelines about cement consistency are available in IS 4031 (Part 4)-1988, ASTM C 187, BS EN 196-3:2005, etc.

Setting time

Setting time is the time at which the cement hardens after gaining strength. It is necessary for the transportation, placing, and compaction of cement. The setting time of cement is measured at two stages – Initial and final. The time at which the setting begins is the initial setting time. At this stage, the cement loses its plasticity. The time at which the setting completes is the final setting time. This helps in the removal of scaffolding. We use the Vicat apparatus for determining setting time. The initial setting time of cement is 30 minutes and the final setting time is 600 minutes. The code which gives the guidelines about this test are IS 4031 (Part 5)-1988, ASTM C 191, BS EN 196-3:2005.

Soundness Test

A soundness test determines the capacity of cement to retain its volume after hardening. It also determines the additional lime present in the cement. Lime is one of the main ingredients of concrete. The deficiency of lime affects the setting time of cement. If the amount of lime is high, the cement will become unsound. Large expansion in the cement may produce cracks in concrete. Thus the disintegration, corrosion, and distortion occur in the concrete. So unsound cement should not be used in construction. This test can be done using the Le Chateler method and Autoclave method. The standard guidelines about this test are available in IS4031 (Part 3)-1988, ASTM C 151-09, BS EN 196-3: 2005.

Cement tests - Le Chatelier apparatus
Cement tests – Le Chatelier apparatus

Tensile strength Test

The tensile strength test is done using the Briquette test method or by the split tensile strength test. The tensile strength of cement is less compared to the compressive strength. Tensile cracking occurs due to dynamic loading and temperature variation. In this test, uni axial loading is done to determine the tensile strength. The standard guidelines for this test are available in ASTM C307 and EN 196-1.

Heat of Hydration

Hydration is an exothermic chemical reaction between cement and water involving the release of Heat. The hydration process increases the strength of cement. The heat of hydration is signified in terms of kilo joules per kilogram.
A calorimeter is an apparatus used for determining the hydration of cement. Important factors that influence the heat of hydration are the proportion of C3S and C3A, water-cement ratio, the curing temperature, fineness of cement, etc. An increase in heat of hydration produces undesirable stresses. The standard guidelines for this test are available in ASTM C 186 and IS4031 (Part 9 ) – 1988.

Conclusion

Tests on cement is the most essential activity to be included before starting any construction activity. The quality of cement determines the strength, serviceability, stability and life of a structure. Any compromise on quality can lead to serious construction defects and failures.

CONCRETE, Stone

Stones || Quality tests on stones ||Types and procedures

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Stones are the form of rocks from the earth’s crust. They find their application in the construction of residential and public buildings, dams, harbours, face-work of structures, road metal, and railway ballast. Besides, stones have good strength and durability.

Quality tests on stones are crucial for construction projects. Testing stone ensures that it meets the necessary standards for strength and durability. There are various tests for stones that assess different properties. These tests for stones include crushing strength, water absorption, and abrasion resistance. By performing these tests, engineers can decide the suitability of the stone for specific uses. Properly testing stone helps prevent structural failures and ensures long-lasting constructions. In this blog, we will explore the different types of stones and the procedures for each quality test. This information is essential for anyone involved in construction and material choice.

  1. Types of Stones Used in Construction
  2. Acid test
  3. Attrition test on stones
  4. Crushing test on stones
  5. Stone Crystalline test
  6. Freezing and Thawing Test
  7. Hardness Test
  8. Impact test
  9. Water absorption test
  10. Microscopic tests on stones
  11. Smiths tests

Types of Stones Used in Construction

Granite is a hard, durable stone, ideal for high-stress applications. Tests on stones, like crushing strength tests, highlight its robustness. Limestone is versatile but porous, requiring water absorption tests. Marble is prized for aesthetics, with abrasion resistance tests ensuring durability. Sandstone, used in paving and walls, needs strength and porosity tests. Slate, known for durability, is tested for impact resistance and is used in roofing and flooring. Proper testing stone ensures suitability for construction.

Qualities of Good Stone

We consider good-quality stones for the construction of important engineering structures. The next are the prime requirements of good-quality stones.

Also read : 9 lab tests for flexible pavements

  • The heavy stones have less porosity and high compactness. Thus the specific gravity of stones should be high.
  • Uniform and appealing colour stones are employed for decorative works.
  • Should have a homogeneous composition and should have less water absorption.
  • It should have the ability to get good polish.
  • Moreover, it should be free from iron oxides and calcium carbonate to resist fire.
  • The dense compaction of rocks can withstand the consequences of external agencies.
  • A good stone must be free from quarry sap.
Stones : Quality tests
Stones - Quality tests

Test on stones

Testing stone is essential to make sure durability and strength in construction. These tests for stones assess various properties. Proper tests on stones prevent structural issues.To conclude the strength, durability and other engineering properties of the stone, the following tests are performed. 

  • Acid test
  • Attrition test
  • Crushing test
  • Crystalline test
  • Freezing and thawing test
  • Hardness Test
  • Impact test
  • Water absorption test
  • Microscopic Test
  • Smith’s Test

Acid test

The acid test is a crucial procedure in testing stone for quality. Tests on stones help to determine the durability and suitability. Proper tests for stones ensure reliable construction materials.The acid tests determine the presence of calcium carbonate in rocks. The test method is as follows,

  • Take some 50 to 100g specimen randomly.
  • Then place them in the solution of sulphuric acid and hydrochloric acid having 1% strength for about one week.
  • Frequently mix the solution and immerse the specimen fully.
  • Subsequently, observe the specimen. 
  • Specimen with high lime content causes efflorescence due to the presence of an acid solution.
Quality tests on stones -Acid test

Attrition test on stones

The attrition test indicates the rate of wear of the stone under the sudden impact of loads. Another name of the attrition test is the abrasion test. The apparatus for the attrition test is Devel’s testing machine.

  • Take some sample specimen and break them into small pieces having 60mm size.
  • Now take 50N of stones and place them in the cylinder of the testing machine. 
  • Then close the cylinder and rotate them for 5 hours at a rate of 30 rpm. 
  • After 5 hours, take the samples outside and sieve them through a 1.5 mm mesh.
  • Weigh the amount of material retained in the sieve and calculate the percentage of wear using the following formula.

Percentage of wear = ( Loss in weight / Initial weight ) x 100

Thus, we get the percentage of wear.

Attrition test on stones
Stones

Crushing test on stones

The crushing test gives the strength of the stones. These tests are performed for stones to be used at the bottom of heavy structures.

  • For this test, cut the stone specimens into 40mm x40mmx 40mm and dress the sides.
  • Minimum of three specimens are needed for this test.
  • Before starting, place the specimen in water for 72 hours.
  • Then cover the load-bearing surface of the specimen with a plywood layer.
  • Now place the specimen in the testing machine.
  • Simultaneously, apply load axially at a rate of 13.7 N/mm2 per minute.
  • Note down the load at which the stone breaks. Calculate the strength using the following formula.

Crushing strength = Maximum load at which stone breaks / Loaded area 

However even weak stone possess high compression strength. For example, the crushing strength of stone for ordinary building works should not exceed 1N/mm^2. 

Stone Crystalline test

This test defines the weathering nature of stones. To conduct this test we need at least 4 cubes with 40mm size. The crystallisation of Calcium sulphate causes eroding of stones

  • To start with first, immerse the samples in a solution of sodium sulphate at normal room temperature.
  • After that dry them at 100 degree Celsius and repeat these steps 5 times.
  • Then note down their difference in weight in the percentage of the original weight.
  • The difference in weight shows the weathering quality of the stones. 

Freezing and Thawing Test

As stones in the construction work are exposed to sunlight, wind, rain etc. This test is necessary to carefully study the behaviour of stone. The test procedure is as follows.

  • Take the specimen and immerse it in water for 24 hours.
  • Then place it in a freezing mixture at 12 degree Celsius for 24 hours.
  • Frequently repeat the above two steps and observe the stone quality. 

Besides, perform this test only in the shade to prevent the consequences of rain, sunlight, etc.

Hardness Test

The hardness of the stone is its ability to resist scratch or rebound.

  • For this test, we use a penknife. This can not make a scratch on pard stones like granite.
  • Moh’s scale value determines the hardness of the specimen.
  • For example, Moh’s scale value is 1. Since it is easily scratchable.
  • Likewise for Quartz, Moh’s scale value is 7. Since it cannot be scratched with a knife.

Impact test

The impact test determines the toughness of the stone. The impact testing machine is the apparatus used for this test. The test procedure is as follows.

  • Take a specimen in a cylindrical shape with 25mm diameter and 25mm height. 
  • Then place it on the cast iron anvil of the machine
  • After that, allow a steel hammer of 20N to fall vertically over the specimen
  • The first blow height is at 1cm. For the second blow height, it is 2cm and so on. 
  • Gradually increase the height of the blow. Finally, note down the height at which the specimen breaks. 
  • The height at which the specimen breaks is the toughness index.

Water absorption test

Through this test, we can determine the porosity as well as moisture content. The water absorption test is as follows

  • Prepare a stone sample and record its weight asW1
  • Then immerse the cube in distilled water for 24 hours. 
  • After that wipe the water with a damp piece of cloth. Again weigh the sample as W2.
  • Now suspend the cube freely in water and record its weight as W3.
  • Subsequently, place the cube in boiling water for five hours. Again weigh the cube and record its weight as W4.
  • From the above data, we can also calculate the percentage absorption of water and saturation coefficient using the formula.

Percentage absorption by weight after 24 hours = (W2- W1)/ W * 100

Percentage absorption by volume after 24 hours = (W2 – W1)/( W2 – W1) * 100

Saturation coefficient = Water absorption / Total porosity = (W2- W1) – ( W4- W1)

Microscopic tests on stones

This test helps to study the geology of the stone. The sample is placed for microscopic examination to analyse the below properties.

  • Mineral components
  • Texture and nature of stones
  • Presence of malicious substance
  • Determining defects and pores
  • Size calculation, etc.

Smiths tests

Smith’s test calculates indicates the presence of earth matter in stones. 

  • In this test firstly, break the specimen into small pieces.
  • Then take a test tube with clear water and place these pieces in it.
  • Vigorously shake the test tube. The muddy colour of the water shows the presence of earthy matter.

Key Takeaways

Quality tests on stones are essential for ensuring their suitability in construction projects. Testing stone involves various tests, including crushing strength, water absorption, and abrasion resistance. Each test stone procedure is designed to assess specific properties, such as strength, durability, and weather resistance. Granite, limestone, marble, sandstone, and slate are commonly used stones that undergo these tests for stones. Procedures like the acid test, attrition test, and freezing and thawing test help determine the stone’s durability and resistance to environmental factors. Proper tests on stones prevent structural issues and ensure long-lasting constructions. Understanding these tests for stones is crucial for anyone involved in construction and material selection.

Conclusion

In conclusion, performing quality tests on stones is a fundamental step in construction to ensure the materials’ strength and durability. Testing stone through various procedures, such as crushing strength, water absorption, and impact tests, provides critical information about the stone’s properties. These tests for stones help in selecting the right material for different construction purposes, ensuring safety and longevity. Types of stones like granite, limestone, marble, sandstone, and slate each require specific testing methods. Therefore, incorporating these tests on stones into the construction process is vital for achieving reliable and robust structures. Properly testing stone materials guarantees their performance and enhances the overall quality of construction projects.

aggregate, Building materials

Shape tests on Coarse Aggregates- Flakiness index test and Elongation Index Tests.

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Shape test on coarse aggregates constitutes flakiness Index and elongation index tests. The particle size and shape of aggregate is one of the major factors affecting the quality of the concrete.

Shape test on Coarse Aggregates

  • Flakiness index test
  • Elongation index test

Must read : Aggregate crushing test- Strength of aggregate

Must read : Bitumen – 9 lab tests on bitumen for flexible pavements.

Shape test on coarse aggregate – Flakiness index test

The particle shape of aggregates is determined by the percentages of flaky and elongated particles contained in it. for concrete and construction of bituminous works the presence of flaky and elongated particles are not suitable and cause failures and breaking during heavy loads.

The Flakiness index of aggregates is the percentage by weight of particles whose least dimension (thickness) is less than three- fifths (0.6times) of their mean dimension. This test is not applicable to sizes smaller than 6.3mm

The Elongation index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than nine-fifths (1.8times) their mean dimension. This test is not applicable for sizes smaller than 6.3mm.

Flake materials may cause voids in concrete and has to be kept under limit to ensure the quality of the concrete.

Relevant IS codes: 

  • IS:2386(PartI)-1963

Apparatus used

  • Weighing machine
  • Metal gauge
  • IS sieve

Test procedure

First we have to find the flakiness index.

Dimensions of thickness and length gauges
Dimensions of thickness and length gauges
  • For finding the flakiness index, we have to test at least 200 pieces of any fraction and weigh them.
  • Then sieve the sample through IS sieves according to the table below.
  • After that to determine the flakiness index separate the aggregate retained in the sieve.
  • Then pass each aggregate through the corresponding slot in the thickness gauge.
  • Finally, we calculate the flakiness index.
  • The flakiness index is the total weight of material passing through the gauge to the total weight of the sample. It is expressed in terms of percentage. Weigh the flaky material passing the gauge to an accuracy of at least 0.1 per cent of the test sample.
  • The formula for flakiness index is

F.I = (Weight of aggregate passing through the slot of the thickness gauge / Total weight of the sample) * 100

Thickness gauge
Thickness gauge

Must read : Los Angeles abrasion test on aggregates

Shape test on Coarse Aggregates- Elongation index test

The presence of elongated particles in the aggregate is undesirable for construction. Also, this shape test is made in coarse aggregate. The elongation shape test is not applicable for aggregates with a smaller size than 6.3 mm.

Relevant IS codes: 

  • IS:2386(PartI)-1963

Apparatus used

  • Weighing machine
  • Metal gauge
  • IS sieve

Test procedure

  • For finding the flakiness index, we have to test at least 200 pieces of any fraction.
  • Then sieve the sample through IS sieves according to the table below.
  • After that pass, each fraction through the gauge individually.
  • Now using a weighing machine, weigh the total amount of fraction retained.
  • Finally, we calculate the elongation index.
  • The elongation index of an aggregate is the weight of the particle whose greatest dimension is greater than 1.8 times its mean dimension.
  • The formula for elongation index is 
Shape test on aggregates
Shape test on aggregates

E.I = Weight of the aggregate retained on length gauge / Total weight of aggregate x 100

Conclusion

The shape tests give only a rough idea of the relative shapes of aggregates. Flaky and elongated particles should be avoided in pavement construction, particularly in surface course.

Building materials, timber

Timber – 5 Important Quality Tests and Procedures.

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Timber is wood suitable for construction purposes. In order to find the quality and sustainability of the Timbers, Various Quality tests are performed.

They are natural polymeric material that nearly does not age. Moreover, the structure of the wood ensures efficient strength and load capacity.
Wood can be split into two classes. They are natural and man-made. Hence some examples of man-made timber are plywood, fibreboard, impregnated wood, etc.

PROPERTIES OF GOOD QUALITY TIMBER

The timber should posses the following qualities.

  • It should have a good uniform dark colour.
  • Timber should be free from defects such as shakes, flaws, dead knots, etc.
  • It should possess regular annual rings.
  • The freshly carved surface of the wood should have a sweet smell.
  • Moreover, It should have a heavyweight.
  • The cellular tissue and fibres should be compact and hard.
  • A good timber should be durable and possess elasticity. 
  • It should be resistant to fungus, insect, etc.
  • Also, timbers with compact texture have good resistance to fire. 
  • It should be inert from mechanical, chemical and physical agencies.
  • A good quality wood should hold loads from structures.
qualities of good timber
qualities of good timber

Also Read : Bitumen – 9 lab tests on bitumen on flexible pavement

Also Read : Bricks – 8 Reliable tests to ensure quality.

TEST ON TIMBER

In order to find the quality and sustainability of the Timbers, Various Quality tests are performed. In this article, we have listed a few test procedures.

  • Moisture content test
  • Tensile strength test
  • Compressive strength test
  • Shear strength test
  • Bending test

MOISTURE CONTENT TEST OF TIMBER

This test determines the moisture content in wood. However, wood contains a small amount of moisture content. A weighing machine and a drying oven are important apparatus for the water absorption test. 

moisture content test of timber
moisture content test of timber

Relevant IS codes:

IS I 2380 ( Part VI ) – 1977

Test procedure

  • Initially, Take the specimen with a size of 5cm x 5cm x 2.4cm.
  • Then using a weighing machine weigh the specimen. Mark it as W1.
  • After that oven-dry the timber at a temperature of 103-degree celsius. 
  • Later, take out the specimen when becomes dry.
  • Again weigh and mark the weight of the dry specimen as W2.
  • Finally, calculate the percentage of moisture content by

% of moisture content = Weight of moisture in sample/ Dry weight of sample = (W1 – W2)/ W2

TENSILE STRENGTH TEST OF TIMBER

The tensile strength test defines the strength and ability to withstand breaking. Also, we can determine the load-carrying capacity of the wood.

Relevant IS codes:

IS I 2380 ( Part VI ) – 1977

Test procedure

Tensile test on timber
Tensile test on timber
  • Firstly, take a specimen with 5cm x 5cm and 20cm in length.
  • Then place the specimen on the base plate of the instrument. 
  • After that apply load either parallel or perpendicular to the grains. 
  • Mark the load at which the wood breaks.
  • Finally, calculate the tensile strength of the wood.

Tensile strength = Maximum load applied / Cross sectional area

COMPRESSIVE STRENGTH TEST

The compressive strength test defines the crushing strength of the timber. Furthermore, this test determines the load which the wood can support over a period.

Relevant IS codes:

IS I 2380 ( Part VI ) – 1977

Test procedure

Compressive test
Compressive test
  • Initially, take a specimen with a size of 5cm x 5cm x 20cm. 
  • Then place the specimen in the compressive testing machine.
  • Following this, apply load parallel to the grains.
  • The specimen should be free from defects. Gradually increase the load.
  • Then note down the load at which the timber breaks. 
  • Lastly, calculate the compressive strength from the below formula.

Compressive strength = Load at which the specimen breaks/ Total area of the specimen

SHEAR STRENGTH TEST

The shear strength is important when timber is used as slabs. The load should be applied parallel to the grains. 

Relevant IS codes:

IS I 2380 ( Part VI ) – 1977

Test procedure

Shear test apparatus
Shear test apparatus
  • The size of the specimen for shear strength is 5cm x 5cm x6.25 cm. 
  • Then cut the corner of the specimen.
  • Thus it produces failure on 5cm x 5cm surface.
  • However, this failure occurs tangentially or radially. 

BENDING STRENGTH TEST

The Bending strength test is necessary when we use timber as a beam. Through this test, we can find the modulus of rupture and modulus of elasticity.

Relevant IS codes:

IS I 2380 ( Part VI ) – 1977

Test procedure

Bending test on timber
Bending test on timber
  • For this, take a specimen of 5cm x 5cm x 7.5 cm in size
  • The specimen should be free from defects and deterioration.
  • Then drop a hammer with specific weight from a certain height.
  • Thus we get the impact bending.
  • Lastly using the load and deflection, calculate bending strength.

Also Read : Los Angeles abrasion test on aggregates

aggregate, Building materials

Aggregate crushing test to find Strength of aggregate

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Aggregate crushing test is done to find out the strength of aggregate which is the fundamental and essential components of concrete, flexible pavements, etc. More than 70 to 80 per cent of the volume of concrete is aggregate. Aggregates are a very important component of concrete, so the quality really matters when it comes to aggregates. Furthermore, their uses include flexible pavements, railway ballast, etc.

Different tests are to be performed to ensure the quality requirements of aggregates for the specific uses.

Tests on aggregates

Different types of tests are done to determine their properties like

  • Strength
  • Toughness
  • Hardness
  • Shape
  • Water Absorption etc.

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Must Read : Bitumen – 9 Lab tests on bitumen for flexible pavements

Following are the types of aggregate tests conducted to ascertain the suitability of aggregates.

  • Aggregate Crushing test
  • Abrasion test
  • Impact test
  • Water absorption test
  • Flakiness index test
  • Elongation index test
  • Bulk specific gravity test
  • Polishing test

Aggregate Crushing test (IS 2386(Part 4):1963 & BS 812–110:1990)

Aggregate crushing test values indicates the strength of aggregate and hence it is very significant. Similarly we can say crushing value is the relative measure of resistance of an aggregate under gradually applied compressive loads. Higher crushing strength means lower crushing value and vice versa. If the aggregate crushing value is less than 10, means an exceptionally strong aggregate, Whereas crushing value of 35 and above means a weak aggregate.

Relevant codes for aggregate crushing test

  • IS 2386(Part 4):1963
  • BS 812–110:1990

Apparatus required

  • Compressive Testing Machine
  • Crushing Mould: A steel cylinder 15 cm diameter with plunger and base plate.
  • Weighing machine,
  • Sieve: Size of 12.5 mm, 10 mm and 2.36 mm
Aggregate crushing value test apparatus
Aggregate crushing value test apparatus

Aggregate crushing Test procedure

  • Oven dry the aggregates
  • Firstly, sieve the aggregate using Indian standard sieves.
  • Then collect the specimen passed through 12.5 mm and retained on a 10mm sieve.
  • Thus is the test sample of aggregate.
  • Then put the cylinder on the base plate and weight it (W). 
  • The aggregate sample should be filled in 3 layers , each layer is subjected to 25 strokes using tamping rod.
  • After that weigh the materials with cylinder and record as (W1)
  • Weight of aggregate will be (W1-W). ie : (Weight of cylinder with aggregates – Weight of cylinder)
  • Level the aggregate surface carefully before inserting the plunger so that it rests horizontally over the surface.
  • Place the cylinder with plunger below a compression testing machine.
  • Apply load at a uniform rate so that a total load of 40T is applied in a span of 10 minutes.
  • Then release the load and remove the material from the cylinder.
  • Following, sieve again on 2.36mm IS sieve. 
  • Then weigh the material passing through the sieve and record it as W2. 
  • Finally, calculate the specimen crushing value using the formula below. 

Aggregate crushing value = (W2 x 100) / (W1-W)

W1-W = weight of dry sample

W2 = Weight of fraction passing through the sieve after application of load.

For a good quality aggregate, the crushing strength value is low.

Recommended crushing values

Flexible pavementsCrushing value
Soling50
Water bound Macadam40
Bituminous macadam40
premix carpet30
Dense mix carpet30
Rigid pavements
Other than wearing course45
Surface or Wearing course30

The aggregates used in roads and pavement construction must be strong enough to withstand crushing under roller and traffic. If the aggregate crushing value is 30 or higher’ the result may be anomalous and in such cases the ten percent fines value should be determined instead.