Method of concrete compression test with 150mmx150mmx150mm cube samples

In concrete compression test, usually 150mmx150mmx150mm concrete cube samples are arranged for performing test. Can 100mmx100mmx100mm concrete cube samples be applied in the test in place of 150mmx150mmx150mm concrete cube samples?

Fundamentally, the force delivered by a concrete compression machine belongs to a definite value. When normal concrete strength is used i.e. under 50MPa, the stress delivered by a 150mmx150mmx150mm cube is adequate for the machine to crush the concrete sample.

However, when the designed concrete strength is 100MPa, under the equivalent force(about2,000kN) delivered by the machine, the stress under a 150mmx150mmx150mm cube inadequate to crush the concrete cube.

So,100mmx100mmx100mm concrete cubes can be utilized in place of 150mmx150mmx150mm cubes to raise the applied stress to crush the concrete cubes. For normal concrete strength, the cube size of 150mmx150mmx150mm is already adequate for the crushing strength of the machine.

Cube Test:

Tools and Materials: Concrete cube mould with size 150mm or 100mm. It is utilized for aggregate size not surpassing 40mm and 25mm. Cube mould for test should be done from steel or cast iron having smooth inside surface. Every mould should contain steel plate to support and to resist leakage.

Compacting steel rod having 16mm diameter and 600mm length.

Compression test machine:

Methods: Mould and base plate should be properly cleansed and used with oil so that the concrete can’t fix to the side of the cube. Base plate is connected with the mould with bolt and nut.

Fill the cube with concrete in three layers.

Each layer should be consolidated for 25 times. This method is performed systematically and compaction is performed consistently to all the surfaces of the concrete. Compaction can also be performed with machine.

The surface of concrete should be flattened to maintain the identical level with the upper side of the mould. The cubes produced at construction site should be covered with plastic cover for a period of 24 hours prior to disassemble the moulds.

Once remoulded is completed, the concrete cubes are drowned in water for curing.

Compression strength test should be conducted for concrete at age 7, 14, and 28 days with compression test machine.

Result: Record the Strength value of each cube and compare with the targeted strength value. The objective of conducting the concrete test on 7 th day and the 14 th day is to forecast whether the concrete could attain the targeted 28 th day strength. Normally, the concrete would have obtained 70% strength on the 7 th day.

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Methods of concrete cube test

In concrete compression test, generally the concrete cube samples with dimensions 150mmx150mmx150mm are utilized. But, in place of 150mmx150mmx150mm concrete cube samples, 100mmx100mmx100mm concrete cube samples are applied for the test.

Fundamentally, the force produced through a concrete compression machine is a definite value. For the use of normal concrete strength, suppose under 50MPa, the stress provided by a 150mmx150mmx150mm cube is adequate for the machine to smash the concrete sample.

However, when the intended concrete strength is 100MPa, under the equivalent force (about2,000kN) delivered by the machine, the stress under a 150mmx150mmx150mm cube is inadequate to crush the concrete cube.

So, 100mmx100mmx100mm concrete cubes are used in place of 150mmx150mmx150mm cubes to raise the used stress to crush the concrete cubes. For normal concrete strength, the cube size of 150mmx150mmx150mm is already sufficient for the crushing strength of the machine.

Cube Test:

Instrument And Material.

Concrete cube mould with size 150mm or 100mm is applied for aggregate size of not more than 40mm and 25mm. Cube mould for test should be formed into steel or cast iron containing smooth inner surface. Each mould should contain steel plate to support and avoid leakage.

Compacting steel rod should be used with 16mm diameter and 600mm length.

The test should be conducted by compression test machine.

Method: Mould and base plate should be cleansed and employed with oil so that the concrete can’t fix to the side of the cube. Base plate is affixed to the mould with bolt and nut.

The cube should be filled with concrete in three layers.

Each layer should be consolidated for 25 times. This process should be accomplished systematically and compaction should be finished equally to all the surfaces of the concrete. Compaction is also done with machine.

The surface of concrete should be leveled to retain the equivalent level with the upper side of the mould.

Cubes which are produced at construction site should be wrapped with plastic cover for a period of 24 hours prior to remove the moulds.

After remoulded, the concrete cubes should be drowned in water for curing.

Compression strength test should be conducted for concrete at age 7, 14, and 28 days through compression test machine.

Result: The Strength value of each cube should be noted and compared with the targeted strength value. The reason for conducting the concrete test on 7 th day and the 14 th day is to anticipate whether the concrete could attain the targeted 28 th day strength. Normally, concrete can obtain 70% strength on the 7 th day.

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Specifications of cement concrete in detail

Cement, fine aggregates, coarse aggregates and water are mainly used to form cement concrete. While writing detailed specifications, explain The specifications of every single component should be narrated briefly at the time of formulating detail specifications.

CEMENT: Cement belongs to the elementary and most vital component of cement concrete. The quality of cement should be fresh while utilizing it for construction work and it should satisfy the standard specifications.

FINE AGGREGATE: Sand is utilized as fine aggregate in cement concrete. Sand particles should comprise of coarse, sharp and angular edges. Size of sand particles should be maintained in such a manner that it can move through 4.75mm sieve. Sand should be clean and does not contain dust and organic matters. Sea sand should not be applied for construction work due to extreme salt contents.

Stone dust is also applied as fine aggregate in cement concrete, but prior to application, check that it adheres to specifications.

COARSE AGGREGATE: Normally, pieces of feverous rocks are applied as coarse aggregates. These stones should be solid, strong, long-lasting and clean. The shapes of aggregates should be cubic or closed to cubic shape. The shape of coarse aggregates should not be laminated and elongated. It should be clean and does not contain from any irrelevant organic matters.

The size of coarse aggregates should satisfy the approved construction work requirements. It should not move through the sieve size of 5mm and coarse aggregates should be graded. Voids should not go beyond 42%.

PROPORTIONING: Based on their fixed ratios, cement, sand and coarse aggregates should be calculated. Prepare a standard measuring box as per the volume of one cement bag. Volume of one cement bag is 1.25 cubic foot.

When, it is required to calculate the ratio of sand, bulking of sand should be taken into consideration. Choose dry sand at the time of making calculation of proportioning. Work out the moisture content in sand and include extra volume of sand. Constantly work out moisture content throughout construction work and include extra volume of sand based on the amount of moisture. It is suggested not to compact coarse aggregates at the time of proportioning.

CONCRETE MIXING: Mixing machine is suitable for large scale construction works whereas hand mixing is chosen since it is cost-effective for smaller concrete works.

CONCRETE CONSISTENCY: Concrete consistency is based on water to cement ratio. Surplus amount of water reduces the strength of concrete and also concrete constituents can be easily detached. The quantity of water given below should be applied against 50kg cement bag.

Concrete Ratio - Amount of Water
1:3:6 - 34 liters
1:2:4 - 30 liters
1:2:3 - 27 liters
1:1:2 - 25 liters

If vibrator is utilized for concrete compaction, then the amount of water should be reduced as per suggestion of engineer in charge.

 
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How bubble deck technology is used in construction work

Bubble Deck belongs to the original combination method of connecting air, steel and concrete in two-way structural slab. Hollow plastic balls is embedded into the slab and reinforced with steel. The end result eliminates up to 35% of concrete that contains carrying effect at the time of restoring the two-way span strength. It can be used with most of the buildings particularly open floor design : educational, commercial, hospital and other organizational buildings.

Bubble Deck contains the following properties :-

Shear strength - 80% of solid deck slab
Deflection - Similar to solid slab
Weight - 40% below solid slab
Fire Resistance – 65% of solid slab

Bubble Deck slab belongs to a biaxial voided concrete slab in which high density polythene hollow sphere substitute the incompetent concrete in the middle of concrete slab.

Materials for building up the bubble deck

Steel: The steel reinforcement of MS or HYSD is applied.

Plastic Sphere: Void sphere formed with recycled high density polyethylene. It contains adequate strength & rigidity. It does not make any reaction.

Concrete: The concrete is formed with standard Portland cement with highest aggregate size of ¾ inch.

Bubble Deck Manufactured Components: It stands for a structural vacuumed smooth slab system that reduces dead weight of a floor slab by 33% facilitating longer span among column supports and forms an entire range of other cost and construction benefits.

The system acts as an alternative of all other supporting structure like beams or walls. The entire floor slab extents in two directions directly into pre-cast or in-situ reinforced concrete column.

Benefits of Bubble Deck:

Structural:
a. Less weight
b. No beams are necessary
c. Only few columns are essential
d. Make your choice for shape
e. Bigger Span

Construction
a. Fewer work on job site
b. Light weight, less equipment is necessary
c. Simple and does not require heavy jobsite work

Economy:
a. Huge savings for materials (slabs, beams, columns, foundation), up to 50%
b. Needs fewer carrying cost
c. Requirement of concrete is reduced up to 35%
d. Lower workforce, no carpentry, no beams and workers with less skill can be employed

Environmental:
a. Less material consumption (cement, aggregate, steel)
b. Less energy consumption (throughout production, transportation and lifting on construction site)



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Details about High Performance Concrete (HPC)

Now-a-days, High Performance Concrete (HPC) is gaining popularity. HPC denotes superior concrete performance throughout wet stage (mixing & placing process); with greater strength in hardened stage together with a greater strength in long-run as compared to normal concrete.

The HPC is comprised of different chemical cum mineral admixtures and fibres. In HPC, the proportions are designed, or engineered, to create the strength and durability required for the structural and environmental requirements of the project.

High-strength concrete contains a specified compressive strength of 8000 psi (55 MPa) or higher. Special mixing, placing, and curing practices are required to develop and manipulate high-performance concrete. Normally, comprehensive performance tests are essential to show compliance with specific project requirements.

High-performance concrete is mainly utilized in tunnels, bridges, and tall buildings due to its strength, stability, and high modulus of elasticity. It is also been applied in shotcrete repair, poles, parking garages, and agricultural applications.

High-performance concrete characteristics are developed for particular applications and environments; some of the properties that may be required include:

• High strength
• High early strength
• High modulus of elasticity
• High abrasion resistance
• High strength and permanence in rigorous environments
• Low permeability and diffusion
• Defiance against chemical attack
• High resistance against frost and deicer scaling damage
• Toughness and impact resistance
• Volume stability
• Ease of placement
• Compaction devoid of segregation
• Inhibition of bacterial and mold growth

High-performance concretes are developed with cautiously chosen high-quality materials and optimized mixture designs; these are batched, mixed, placed, compacted and cured with reference to the superior industry standards.

Normally, such concretes will contain a low water-cementing materials ratio of 0.20 to 0.45. Plasticizers are normally utilized to produce these concretes fluid and workable. High-performance concrete almost always contains a greater strength as compared to normal concrete.

High-early-strength concrete, also known as fast-track concrete, attains its specified strength at an initial age as compared to normal concrete. The time period in which a specified strength should be attained may vary from a few hours (or even minutes) to several days. High-early-strength is achieved by employing conventional concrete ingredients and concreting practices, although sometimes special materials or techniques are necessary.



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Characteristics of polymer-Modified Mortar

Mortar is considered as one of the vital components in masonry construction. It is normally formed by mixing water with portland cement, hydrated lime and sand. If the proportions of each of these ingredients are changed, strength and other characteristics may differ. Mortar with polymeric admixtures is applied extensively and inexpensively in definite situations.

Basics and function: Polymer-modified mortar is developed by interchanging a part of the conventional binders with polymers. Polymers are included with mortar to enhance the characteristics which may contribute to adhesion, toughness, flexural or tensile strength, and resistance to chemicals.

The purpose of the polymers is to make the capacity of work and adhesion of non hardened mortar better and often need fewer quantity of extra water as compared to conventional mortar. It leads to less pores and high capacity cements, consequently the immersion of water & and penetrability to salts are decreased.

Types of Polymers: Polymer-modified mortar is commercially obtainable with all constituents already provided in the mixture. Conversely, polymer additives separated into classes, are included with mortar mix. Redispersible polymer powders like ethylene vinyl acetate are normally included with dry mortar mix.

Water-soluble polymers like polyvinyl alcohol belong to powders but are added to wet mortar mix. Aqueous latex suspensions comprise of latex particles hanged up in water to coat hydrating cement particles. At the end, liquid polymers as epoxy resins or unsaturated polyesters are included throughout mixing to develop a network of cemented polymer hydrate and thus the strength of the mixture is raised significantly.

Application: Polymer-modified mortar is employed in a wide array of mortar and concrete repair and primary construction applications. Low water level and salt infiltrations transform polymer-modified mortar suitable for masonry prone to weathering and other exterior conditions. The main objective of polymer-modified thinset mortar is to bind tile to concrete and cement board substrates devoid of immersing the tiles earlier. Polymer-modified mortars are frequently applied for repairing purposes due to their low shrinkage and capacity to tie with even solid surfaces.

Supplementary Possible Admixtures: Besides, polymers, other types of materials can be included with mortars to attain required characteristics. Color pigments may be included with mortar to change the look of the mortar. If accelerators and retarders are included, these can decrease or raise the length of time necessary for the mortar to be cured, a vital characteristic to control in severely cold or warm, humid weather. Other mortar additives range from mineral additions, like silica fume, aggregates and inert fillers, plasticizing chemical admixtures and fibers to manage shrinkage efficiently.



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Some vital tests for checking compressive strength of cement

If water is included in the cement, the compressive strength of the hardened cement is considered as the vital factor. Cement hydrates and exposes cohesion and consistency. It joins all the components like cement, sand, aggregate etc. collectively. The hardiness of cement-based compound like mortar/concrete is based on the type and nature of cement.

Owing to strength, nature of cement, both mortar and concrete contain high strength against compression and less strength against tension. Therefore, testing of cement for compressive strength is very crucial. Cement is examined for compressive strength so that the strength and stability of the structure is retained.

Initial strength gain is affected by high lime or high alumina content. The firmness of cement is also impacted with the degree of burning, the fineness of grinding, and the aeration it obtains once the final grinding is completed.

Under the strength test, cement mortar is applied since neat cement produces shrinkage and cracking and it becomes complicated for testing.

Primarily, cement is recognized with its compressive strength. Cement is designated with its grade like 53 grade, 43 grade, 33 grade of cement. This grade signifies the compressive strength of cement, i.e. 53 grade of cement species that compressive strength of cement cube after 28 days of curing should be 53 N/mm2 (MPa) or 530 kg/cm2.

Compressive Strength Test of Cement according to IS 4031 (Part 6) 1988.

The following equipments are required for conducting the test :

• Compression Testing Machine or Universal Testing Machine.
• Cube Mould: 70.6 mm*70.6 mm*70.6 mm size
• Vibrating Machine
• Weighing Machine
• Gauging Trowel
• Measuring Cylinder
• Tray

Method: Arrangement Of Test Samples

• Testing material is cement, sand and water.
• The necessary material for each cube is as follows:

1. Cement – 200gm,
2. Sand – 600gm,
3. Water quantity (P/4 + 3) % of the total mass of cement and sand. Where P denotes the standard consistency of cement.
• Initially, blend cement and sand in dry condition with a trowel for one minute and then include water and blend unless homogeneous colour is produced.
• The time of mixing should not be under 3 minutes and not in excess of 5 minutes.

Moulding Samples
• Once the blending is completed, mortar is provided in the cube mould. Prior to arrange the mortar, use oil on the inside surface of cube mould.
• To discharge the entrained air and get rid of honeycombing, the mortar should be stimulated 20 times in about 8 s and then consolidated with vibration.
• The vibration period should be 2 minutes at the certain speed of 12 000 ± 400 vibrations per minute.
• Then, the top surface of the cube in the mould should be completed by leveling the surface with the blade of a trowel.

Curing Samples
• Once the vibration is finished, retain the filled moulds in a moist closet or moist room for 24 hours.
• As soon as that period is ended, detach mortar cube from the moulds and instantly immerse in clean, fresh water and put there unless it is removed before testing.
• The cubes should not get dried once they are removed and unless they are tested.

Testing
• The testing is done with compression testing machine or universal testing machine.
• Test 3 cubes for compressive strength for every time period according to detailed specifications. As for instance 3 cubes for 3 days test, 3 cubes for 7 days test and 3 cubes for 28 days test.
• The cubes testing should be performed on their sides. No packing among the cube is allowed and the steel plates of the compression testing machine while testing is going on.
• The load shall be gradually and consistently employed and the rate of loading should remain 35 N/mm2/min.

Points to be considered
• Clean appliances should be applied for the tests.
• Test for temperature and humidity should be carried out at 27 ± 2°C temperature and 65 ± 5 percent of the relative humidity of the laboratory.
• The water in which the cubes are immersed should be changed every 7 days and retained at a temperature of 27 ± 2°C
• While determining the compressive strength, the faulty samples should not be utilized.
• The samples which produce strength differing by above 10 % from the average value of all the test samples.



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The role of Viscosity Modifying Admixture (VMA) in Concrete

Viscosity Modifying admixtures or VMAs belong to the admixtures which are applied to modify various properties of fresh concrete ranging from viscosity, workableness, cohesiveness etc.
The functionality and uses of VMA for several types of concrete are given below.

Function of Viscosity Modifying Admixture (VMA) in Concrete

The prime objective of viscosity modifying admixture in a concrete mix is to modify the rheological properties of concrete- particularly the plastic viscosity of fresh concrete. If VMA is added to concrete mix, the plastic viscosity of concrete is raised and a slight surge in yield point is observed.

Yield point is another rheological property of concrete that should also be improved together with the plastic viscosity to attain perfect concrete rheology. The yield point of concrete is not impacted with VMA.

Therefore, besides, VMAs plasticizers or super plasticizers are also included to modify the yield point of concrete mix.

Advantages of Viscosity Modifying Admixtures (VMAs)

Given below, the details of various types of concretes which show different behavior with the inclusion of viscosity modifying admixture to their design mixes:

1. Self-compacting Concrete, 2. Pumped Concrete, 3. Under Water Concrete, 4. Light weight concrete, 5. Semi-dry Concrete, 6. Sprayed Concrete, 7. Porous Concrete, 8. Concrete with Poorly Graded Aggregates

1. Self-compacting Concrete: When Self-compacting concrete blends with less powder content, it remains unsafe against moisture variations and as a result segregation may take place.

Inclusion of viscosity modifying admixture to self-compacting concrete raises the segregation resistance as well as enhances the strength to moisture variations.

VMAs improve the strength of self-compacting concrete mixes.

VMAs also minimize bleeding from concrete mix.

Pumped Concrete

a. Obstacle of aggregates at bends in pipe is the issue found in general that occurs for pumped concrete.
b. When Viscosity modifying admixture is included, pumped concrete turns out to be more consistent and segregation while pumping can’t occur.
c. The friction among pump-wall and concrete mix while pumping is minimized by lubricating effect resulting from VMA.

Sprayed Concrete
a. Use of viscosity modifying admixture reduces the rebound of aggregates from sprayed concrete by enhancing the cohesion of concrete mix.

Porous Concrete
a. Viscosity modifying admixtures resist the discharge of cement paste from porous concrete mix.
b. VMA makes the bond better among cement paste and aggregate thereby raises the strength of concrete.

To get more details, go through the following link theconstructor.org



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How to repair concrete with Dry Pack Mortar Method

The purpose of dry pack mortar is to repair the concrete surfaces with cracks or holes of depth greater than or equal to the minimum dimension of the repair area. The holes usually discovered on concrete surfaces are cone bolt holes, she bolt holes, holes formed with ties etc.

Dry pack mortar should not be used for shallow cracks, fully extended holes i.e., from one side to other side, space behind reinforcement etc.

Dry pack method involves the following steps for executing repairing work to concrete.

1. Arrangement of Hole Inner Surface
2. Arrangement of Dry Pack Mortar
3. Using Dry Pack Mortar
4. Curing of Dry Pack Repair Area

1. Preparation of Hole Inner Surface

a. Prior to use dry pack mortar, the surface or hole to be repaired should be cleansed, washed and dried perfectly. Also they should not contain any damaged pieces of aggregates.
b. The inside surface of hole should have been rough to create superior bond. If the surface is smooth, it should be roughened with tapered reamer or star drill.
c. Usually, there exist three methods to develop the inside surface area of holes for maintaining superior bond with dry pack mortar.

Method – 1

a. Bonding grout is used to brush the inside surface of hole. Bonding grout is made of cement and fine sand in the proportion 1:1.
b. Now, the dry pack mortar is applied prior to bonding mortar becomes dry to make superior bond among mortar and surface.
c. When bonding grout is used, ensure that no free surface water exists in the hole so that the hole remains fully dry.

Method – 2

a. By applying wet rags or burlap, the hole is pre-soaked all night with and permitted to dry.
b. When the hole is partly dried or comprises of some amount of surface water, then spray dry cement on to the surface with small brush.
c. The cement will consume free water and develops a layer on the surface. Extra cement still in dry form is eliminated with jet of air so that dry pack can be applied on the surface.

Method – 3

a. Under this method, superior bond among dry pack mortar and surface is formed with epoxy bond resins
b. Epoxy resin is blended and used on the surface with brush.
c. Ensure that the concrete temperature should not exceed at the time of using epoxy or else it may burn or dry up the epoxy promptly.
d. As soon as epoxy is used, instantly use the dry pack mortar prior to epoxy gets dried out.
e. Epoxy bond resin can resist the hydration of water to adjacent concrete surface.

To get more details about dry pack mortar, go through the following link theconstructor.org

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How temperature plays an important role on concrete

The concrete is extended with the rise in temperature and contracted with reduction in temperature. The range in difference in temperature differs from areas to areas, seasons to seasons and day to day.

The crack may happen in concrete because of contraction integrated with the impact of shrinkage.

Sometimes, big and injurious stress may produce owing to deformation that takes place for temperature variation.

The coefficient of thermal expansion of contraction is dependent on the type and quantity of cement, aggregate, proportionate humidity and sizes of section.

In high temperature, the concrete is influenced by the following factors :-

1. The elimination of evaporable water
2. The elimination of combined water
3. Modification in cement paste
4. Disruption (of beam) from discrepancy of expansion and resultant thermal stresses
5. Modification of aggregate
6. Alteration of bond among aggregate and paste

Cycles of temperature can provide a gradual impact on the curtailment of strength and even long-lasting curing can’t improve the loss.

Tensile strength of concrete is mostly affected with temperature.
If the heating is adequately fast, high stresses can be added and therefore, failure and instability may occur.

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Mechanical properties of building materials

All the building structures are developed with various types of materials. These materials are either known as building materials or materials of construction. The cost of material in a building varies from 30 to 50 percent of entire building cost.

Given below, the detail mechanical properties of materials :-

Strength:

a. Strength is defined as the strength of material to resist the load.
b. Strength of materials – Capacity to resist an applied stress devoid of failure.
c. Compressive strength – Capacity to resist axially directed pushing forces.
d. Tensile strength – Highest stress at the time of being expanded or dragged prior to necking.
e. Shear strength – The capacity to resist shearing.
f. Elasticity – In a material if exterior load is employed it experiences deformation and on elimination of the load, it gets back to it’s actual shape.

Plasticity: If a material fails to retrieve it’s actual shape while eliminating the exterior load, it is defined as plastic materials.

Ductility: When a material experiences a significant deformation devoid of rupture, it is known as ductile materials.

It experiences a large deformation throughout tensile test. It is considered as the most perfect material for tension member. Steel, copper, wrought iron, aluminum alloys belong to ductile materials.

Elongation is in excess of 15%

Brittleness:

a. If a material can’t experience any deformation if some external force functions on it and it collapses with rupture.
b. Brittleness means powerful in compression and poorer in tension.
c. Brittleness is found in C.I, glass, concrete, bricks etc.
d. Elongation remains under 5%

Malleability: Malleability is the capability of a material to distort under pressure (compressive stress). After being malleable, a material is flattened into thin sheets through hammering or rolling. Several metals with high malleability also contain high ductility.

Malleable materials are gold, silver, copper, aluminum, tin, lead steel etc.

Toughness: Toughness means the capability of a material to consume energy prior to rupture is known as toughness.

Toughness is found in mild steel, wrought iron etc.

Hardness: Hardness means the resistance of materials against abrasion, indentation, wear and scratches.

C.I is stronger material.

Stiffness: Stiffness refers to force that is necessary to create unit deformation in a material.

Creep: Creep means inelastic deformation because of sustained load.

Physical properties of materials

Bulk density = ρ = M/V
Water absorption
Permeability
Stability

Specific gravity (G): Mass of solids of specified volume / Mass of equal volume distilled water

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How to check the workability of concrete with flow table test

Workability belongs to a vital factor of concrete that directly affects the strength, quality and look of concrete as well as finds out how easily freshly produced concrete is blended, set, compacted and finished by retaining its consistency as it is.

To examine the functionality of the freshly mixed concrete, the following tests are generally conducted on field and lab.

Slump test, Kelly ball test, K slump test, Vee bee consistometer test, Flow table test

In this article, detail information is given on flow table test of concrete.

Flow table test of concrete: Under this test method, the functionality of concrete is established by checking the flowing property of concrete.

With Flow table test of concrete, the quality of concrete is found based on the uniformity, cohesiveness and the susceptibility to segregation.

This flow table test is adhered to BS 1881 part 105 of 1984 and DIN 1048 part I.

The following equipments are required for Flow Table Test:

Flow table is built up with metal with thickness 1.5mm and dimensions 750mmx 750mm, tamping rod constructed with hardwood, Scoop, Centimeter Scale, Metal Cone or mould (Lower Dia = 20cm, upper Dia = 13 cm, Height of Cone = 20cm). The central part of flow table is pointed with a concentric circle of dia 200mm to arrange a metal cone on it.

Flow table test is conducted with the following methods :-

Get concrete ready according to mix design and set the flow table on a horizontal surface.

Cleanse the dust or other gritty material on flow table and spray a hand of water on it.

Now, set the metal cone at the central part of the flow table and rest on it.

Pour the freshly mixed concrete in the mould containing two layers; each layer is tamped with tamping rod for 25times. Once the last layer is tamped, the overflowed concrete on the cone is jammed with a trowel.

Gradually, raise the mould upright & allow concrete to rest on its own devoid of any support.

The flow table is elevated at the height of 12.5mm and dropped. The same procedure is reiterated for 15times in 15secs.

Calculate the spread of concrete in diameter with centimetre scale horizontally and vertically. The arithmetic mean of the two diameters should be the calculation of flow in millimetres.



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