Properties and uses of white cement concrete

White cement concrete has similarity with grey Portland cement but the main difference lies in fineness and color. The white color of this cement is obtained by its manufacture system and its raw materials. There are wide array of color options in this type of cement for developing architectural and structural concrete.

This cement is formed with raw materials with little or no iron or manganese. Normally, china clay is utilized in white cement along with with limestone or chalk.

The cement should be white Portland cement with adherence to the standard specification ASTM C150.

The compressive strength of white cement is less as compared to OPC cement.

A large amount of iron and manganese are added in its manufacturing process to enhance the whiteness of the cement and becomes more expansive. White cement concrete is called as snow Crete. With white cement, a homogenous concrete is produced with exact color for a structure.

To develop white cement, 40% higher energy is necessary as compared to the normal grey cement and it makes the white cement expensive. Light colored sand along with whitest chalk is provided in the production of white cement.

HOW TO CHOOSE PROPER RAW INGREDIENTS:

Cement: The delivery of white cement in both bulks and bagged. The storage of the white cement bagged should not get in touch with the ground. If storing is made in the concrete floor then the cement should be stored up against the exterior walls. White cement bags should be preserved in pallets and it should be safeguarded from weather and maintain them off the ground. Due to the low content of soluble chromium, white cement should be preserved for minimum of 6 months when provided in proper dry condition.

Aggregates: The selection of aggregates for white should comprise of the white marble, white granite, and crushed calcinated flint. The color choice of coarse aggregates is crucial to the final appearance of white concrete. The selection of fine aggregates especially the filler particles should be lower than 0.25mm. Precautions should be taken to make sure that the mix of aggregates remain as constant as possible among batches to avoid in shading of finished products.

Water: Water to be mixed in white concrete should be clean and does not contain organic impurities. The water-cement ratio remains high in white concrete with regards to normal concrete and is critical in finding out the final strength of concrete.

CHARACTERISTICS OF WHITE CEMENT CONCRETE:

1. The initial setting time of white cement should 100 minutes.
2. The fineness of white cement should be 395 kg/m2.
3. The brightness of white cement should remain 87%.
4. The compact density of white density should be 3150 kg/m3.
5. Bulk density of white cement is 110 kg/3.
6. Compressive strength after 1 day 21 Mpa, after 2 days 38 Mpa, 7days 61 Mpa and after 28 days 74 Mpa.

APPLICATIONS OF WHITE CEMENT:

1. White cement is effective for decorative works as well as prestige construction projects.
2. White cement is applied to develop brightly colored concrete and mortars.
3. It is suitable for interior and exterior decoration due to its whiteness.
4. White cement is frequently applied in roads to enhance the visibleness to highway medians.
5. It is useful for huge numbers of manufacturing precast members.

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Steps involved in cement concrete works

Given below, brief specifications for executing cement concrete works for different objectives :-

1. Materials for Cement Concrete: Different types of materials cement, aggregates and water are required for cement concrete works. The aggregates are categorized as fine aggregates (sand) and coarse aggregates. The aggregates should comprise of inert material and should be clean, dense, hard, robust, long-lasting, non-absorbent. Besides, it should have the ability to make superior bond with the cement mortar.

Cement - Fresh Portland cement or pozzolana Portland cement (PPC) should be used according to requirement or specification and should contain the necessary tensile and compressive strength and fineness.

Fine Aggregates - Course sand with hard, sharp and angular grains should be utilized as fine aggregate or sand and it should get through 5mm (3/16”) square sieves or mesh. It should contain standard quality and does not contain dust, dirt and organic matters. Sea sand is not recommended for concrete works. Fine aggregates should comprise of crushed stone or manufactured sand if indicated.

Coarse Aggregates - These should comprise of hard broken stone of granite or similar stone and does not contain dust, durst and other foreign materials. The size of stone ballast should remain 20mm (0.75 inches) and less and should be arranged on 5mm (0.25 inch) square mesh. These should be well grades to retain voids under 42%.

The size of coarse aggregate is based on the thickness of concrete and nature of work. As for instance, size of coarse aggregates for building works should remain 20mm and 40mm to 60mm sizes are applied for road work and mass concrete works.

Water - The quality of water should be same as drinking water and it does not contain alkaline and acid matters.

2. Proportioning of Cement Concrete: The proportions in cement concrete should be according to the design and strength requirements. The proportion can be 1:2:4 (M15 concrete) or 1:1.5:3 for M20 concrete. The proportions of 1:2:4 concrete include the ratio of cement: sand: coarse aggregates by volume until indicated. Least compressive strength of concrete of 1:2:4 mix proportion should be 140 kg/sq.cm or 2000 lbs/sq.in on 7 days.

3. Measurement of Materials: Sand and coarse aggregates are calculated by volume with boxes. Cement should not be calculated by box, one bad of cement of 50kg weight should be treated as 1/30 cu.m or 1.2 cu.ft volume. Size of measured boxes may be 30 cm x 30 cm x 38 cm or 35 cm x 35 cm x 28 cm similar to the content of one bag of cement.

All materials should be dry and in case of utilizing damp sand, compensation should be done with extra quantity sand to the extent necessary for bulking of sand.

4. Mixing of Cement Concrete: Mixing of concrete should be done with machine to attain superior quality. For small works, hand mixing by batches is suitable.

5. Checking for Concrete Slump: Slump test should be conducted constantly to control the addition of water and to retain the desired consistency. A slump of 7.5cm to 10 cm (3 inches to 4 inches) is perfect for building work and 4 cm to 3 cm (1.5 inch to 2 inches) is ideal for road work.

6. Formwork for Concrete Works: Formwork centering and shuttering should be arranged as per need and the standard specifications prior to place concrete to confine or to support or to retain the concrete in exact location. The inside surface of the concrete should be oiled with formwork oils so that the concrete can’t stick to it.

Before placing concrete, water should be sprinkled over the base and formwork where the concrete will be arranged. Forms should not be detached prior to 14 days in general, side forms may however be detached after 3 days of concreting.

7. Placing of Concrete: It is necessary to place concrete gently in layers not surpassing 15cm or 6 inches and it should be consolidated by pinning with rods and tamping with wooden tampers or with mechanical concrete vibrating machines unless a solid concrete is produced.

Concrete should be placed constantly. If the placing of concrete is postponed for rest of the day or for the following day, the end should be sloped at an angle of 30 degrees and made rough for jointing again.

Curing of Concrete: After about two hours of placing when the concrete starts to become solid gradually, it should be retained moist by covering with wet gunny bags or wet sand for 24 hours and then curing by flooding with water making mud walls of 7.5 cm or 3 inches high or by covering with wet sand or earth and kept damp constantly for 15 days.



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Some vital guidelines to build up a raft foundation

A raft foundation alias mat foundation refers to a continuous slab that stands on the soil that expands over the whole footprint of the building, thus provides strong support to the building as well as transmits its weight to the ground.

A raft foundation is mostly suitable when the soil becomes weak, since it allows to allocate the weight of the building over the whole area of the building, and not over shorter zones (like individual footings) or at individual points (like pile foundations). It minimizes the stress on the soil.

Stress is merely the weight divided with area. As for instance, when a building measures 5 x 5 weighs 50 tons, and contains a raft foundation, then the stress on the soil is weight / area = 50/25 = 2 tons per square meter.

When the similar building is supported by 4 individual footings with dimension 1 x 1m each, then the entire area of the foundation should be 4 m2, and the stress on the soil should be 50/16, that is around 12.5 tons per square meter. Therefore, if the entire area of the foundation is raised, the stress on the soil is significantly reduced, that means the weight per square meter.

A raft foundation is also effective for basements. Foundations are built up with excavation of soil with the purpose of retaining strong, compact, undisturbed natural soil that remains a few feet underneath ground level.

This soil contains more strength as compared to the loose soil at the surface. When a raft foundation is built up 10 feet under ground, and the concrete walls remain around the boundary to form a sound basement.

GUIDELINES TO BUILD UP A RAFT OR MAT FOUNDATION
Initially, excavate the ground to consistent, flat level to build up a raft foundation.

After that, place a waterproof plastic sheet over the earth, and pour a thin 3" layer of plain cement concrete (PCC) to form a rightly flat and level base for the foundation.

Then, a waterproofing layer is set up, and then reinforcement steel for the raft slab is secured in place. Once all the steel are arranged in exact location, concrete is poured to the required thickness that normally remains in the range of 200mm (8") to 300mm (12") thick for small buildings. The thickness will be increased when it is required to combat heavy loads.

To get more details, click on the link.

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Types of plasticizers commonly used and their benefits

Plasticizers & super-plasticizers facilitate concrete to enhance it's workability.

Due to it’s strong fluidity, shotcrete is highly beneficial. When the homogeneous mix is applied pneumatically, it simply conforms with even rugged surfaces whereas maintaining the initial resistance to compression to offer good structural support from the beginning.

A family of chemical polymers like plasticizers and super-plasticizers are liable for the material’s fluidity. These are also called water reducers to minimize the total water-to-cement ratio, providing it a more ‘liquid’ consistency devoid of diluting the mix with water.

These additives are normally added all through the mixing process and allow the concrete mix to become yielding until application keeping its consistency unchanged.

Plasticizers and super-plasticizers provide a temporary dispersing effect, that produces a comprehensive hydration of each cement particle, making the fluidity of the mix better.

This mix is amalgamated with volcanic fly ash to form the type of hydraulic concrete, a fully hardy and weatherproof material along with extremely erosive salt water.

Plasticizers: first steps - First generation of plasticizers is known as Lignosulphonates. It belongs to a byproduct originated from wood processing that is frequently applied in recent times to form a workable mix with only basic raw materials.

These additives, known as Mid-Range Water Reducers [MRWR] affix themselves to the surface of a cement particle, that bears both positive and negative charges. Plasticizer polymers, which are negatively charged, neutralize the positive charges on the cement surface, transforming the entire surface completely negative.

It causes a physical effect that allows the negatively charged cement particles to keep away each other, providing a dispersing effect to develop better water infiltration. This mix can now function well devoid of adding more water, and allows for a cutback in the overall amount of water necessary, reducing the water-cement ratio by around 10%.

But these additives can defer the curing process, which may sequentially produce further complicacies. If curing is not done within a certain timeframe, a greater amount of hydrostatic pressure could amass in a formwork column over a long lasting period, causing the formwork to burst.

The second generation: Plasticizers 2.0: This type of plasticizer can significantly lessen the water-to-cement ratio of around 25%. Polysulfonates like naphthalene and melamine offer same type of working mechanism to the first generation of plasticizers, producing an electrical dispersing albeit of superior intensity.

These polymers conform to the cement particles, charging them negatively to form repulsion among related particles, allowing water to flow and hydrate the mix in an efficient manner.

This similar repulsion activity also activates major air occlusion, raising the workability of the mix but at the same time developing pockets of air that reduces its resistance and settle its structural integrity.

This type of polymer may also put other challenges, since it provides a very narrow window of ‘workability’: as soon as the cement is hydrated, it is likely to develop a crust-like byproduct that makes application complicated.

Super-plasticizers: the third generation - Super-plasticizers stands for the additives which bring huge benefits along with a water-to-cement ratio curtailment of around 40%.

Polycarboxylates alias High Range Water Reducers (HRWR) function on the base of sterical in spite of electrostatic repulsion. A major steric effect is steric hindrance for which a chemical reaction can’t occur. In this case it stops cement particles from agglomerating.

Polycarboxylates stands for complex co-polymers which are applied to satisfy several functions, and comprise of a negatively charged ‘backbone’ molecule with polymeric side chains.

Most of these additives can be amalgamated jointly, and blended with other types like air-entraining, accelerating and retarding additives
​

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Plain cement concrete – Uses and formation method

The objective of plain cement concrete alias PCC is to arrange a firm impermeable bed to RCC in the foundation where the soil is soft and flexible. It is mostly applied over brick flat soling or devoid of brick flat soling.

It is also known as Cement Concrete (CC) or Blinding Concrete.

When, any reinforcement is not used inside the concrete, it is defined as the plain cement concrete. It’s just a blend of concrete ingredients.

Characteristics of Plain Cement Concrete - Given below, some vital characteristics of plain cement concrete:

• Compressive strength: 200 to 500 kilogram/square centimeter
• Tensile strength: 50 to 100 kilogram/square centimeter
• Density: 2200 to 2500 kilogram/cubic meter
• Stability: Outstanding

Applications of Plain Cement Concrete: PCC is mostly found in footings, grade slabs, and concrete roads. When the underlying soil is weak and flexible, brick flat soling is provided under PCC.

To form PCC, the following materials are utilized :-

Cement: Normally, the Portland cement is utilized as bonding material in PCC.

Fine Aggregate: Sand is employed as fine aggregate. The fineness modulus (FM) of sand should remain 1.2 to 1.5. FM stands for an index number that demonstrates the mean size of particles in sand. It is measured by carrying out sieve analysis.

Coarse Aggregate: Usually, the brick chips are utilized for developing PCC. It is also possible to utilize stone chips in these conditions. The size of the coarse aggregate remains 20mm downgrade.

Water: Pure drinkable water should be provided in PCC.

How to build up PPC?

With the following methods, plain cement concrete is formed.

The following tools are utilized for the production of PCC

• Wooden or Steel rammer
• Mixture machine (if any)

The Thickness of PCC: The thickness of PCC is normally 50mm over Brick Flat Soling (BFS). If you don’t use BFS below PCC then the thickness should be 75¬mm. When the PCC is used in car parking area then the thickness should be 75mmover BFS.

Ration of materials in PCC: The ratio of cement, sand and brick chips in foundation or basement should be 1:3:6. But, if it is applied in the car parking area, the ratio will be changed to 1:2:4.

The production method for PCC: If ready-mix concrete is applied, this step should be omitted. If PCC is produced through mixture machine then click “How to mix concrete by mixture machine”. If the concrete is mixed manually, get help by clicking on this link “how to mix concrete by hand”.

Placing and Compaction of PCC:

• Ensure that brick soling/sand bed level is perfect for PCC.
• Create formwork for PCC with wooden planks according to stipulated dimensions.
• There should be no dust and foreign materials in concreting area.
• The bed of PCC should be covered with polythene.
• Create level pillars of fresh concrete in the area at proper spacing but not in excess of 2m c/c both ways.
• Set the concrete softly from one side. Apply the mixed concrete within 45 minutes once the water is added.
• For compaction and finishing of PCC, wooden rammer should be used.
• The surface of PCC should be rough to combine future work prior to solidification of the concrete.

Curing of PCC: After PCC is placed for 24 hours, wet the concrete surface with water. Alternatively moist gunny bags can be used to cover the surface for minimum seven days.



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Advantages of microsillica in concrete

Microsilica alias silica fume or condensed silica fume stands for is a mineral admixture that is formed with very fine solid glassy spheres of silicon dioxide. Most microsilica particles remain under 1 micron (0.00004 inch) in diameter, normally 50 to 100 times finer as compared to average cement or fly ash particles. Microsilica belongs to a by-product of the industrial manufacture of ferrosilicon and metallic silicon in high-temperature electric arc furnaces.

Microsilica may be suitable in managing heat formation in mass concrete. It can also be combined with fly ash to provide superior result.

If pozzolanic materials are integrated with concrete, the existent silica in these materials makes a reaction with the calcium hydroxide produced throughout the hydration of cement and develops supplementary calcium silicate hydrate (C – S – H) that enhances the strength and the mechanical properties of concrete.

Types of Microsilica: Microsilica is categorized as follow -

1. Powdered microsilica, 2. Condensed microsilica, 3. Slurry microsilica

Impacts of Microsilica on Concrete

1. Fresh Concrete

a. It decreases the scope of segregation, so it is applied as pumping aid.
b. It almost reduces bleeding, as a result finishing work commences before time.
c. Workability and uniformity of concrete reduces.

2. Hardened Concrete: The inclusion of microsilica enhances the following characteristics of hardened concrete -

a. Improves compressive strength that leads to improve flexural and tensile strength.
b. Bond strength
c. Abrasion resistance
d. Lessens permeability; consequently, it safeguards reinforcement steel against corrosion.
e. Impact and cavitations resistance.
f. Sulphate Resistance
g. Heat Reduction
h. Chemical Resistance

Properties of Microsilica:

1. Microsilica belongs to a grey; almost white to black powder.
2. Spherical particles remain under 1mm in diameter.
3. The mass density of microsilica is dependent on the degree of densification and differs from 130 to 600 kg/m3.
4. The specific gravity of microsilica differs among 2.2 to 2.3

Benefits:

a. Minimizes thermal cracking resulting from the heat of cement hydration.
b. Enhance the strength to resist against sulphate and acidic waters.
c. Minimizes the growth of temperature in preliminary stage.
d. Silica fume is cheap; therefore, it is inexpensive.
e. It minimizes the entire slab weight and cost.
f. Inclusion of microsilica reduces efflorescence caused by the refined pore structure and increased consumption of the calcium hydroxide.



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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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Raft foundation construction details

This construction article provides the detail construction methods for raft foundation of a building. The raft foundation is conducted for the multistory buildings or building having heavy loads.

Step 1: Initially, the surveyor should begin exaction and as soon as the survey is completed then exaction is carried out to the desired level on the basis of the validated shop drawings.

Throughout excavation, precaution for safety should be undertaken, the entire area should be guarded and everybody should utilize PPE at site.

Step 2: As soon as the final phase of the exaction is completed then the surface should be consolidated with plate compacter as the area is small and it is not difficult to apply the roller compacter. But 95% compaction should be performed with compaction test.

Step 3: After getting the passable results of compaction test, 75mm or 100 mm blinding concrete is arranged. Blinding concrete should be garde 20/20 SRC (Sulphate Resisting concrete).

The blinding concrete facilitates to arrange a solid and flat surface for the reinforcement of raft foundation.

The curing polythene sheets should be arranged instantly after finishing and when the concrete is set, it should be substituted with hessian cloth and should be retained wet unless the surface becomes fully dry.

Once the blinding surface becomes dry, water proofing of surface should be started according to sanctioned specification.

Step 4: Once water proofing is done, perfect planning should be undertaken for the shuttering work, all material should be retained on a plate form and steel bars should be installed with adherence to sanctioned shop drawings of the surrounding. All working space should maintain neat & clean to get rid of accidents at site.

Upon the completion of the reinforcement work, the contractor should sanction it from the supervision consultants for pouring the concrete.



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How to estimate cement bags in 1 cubic meter

Suppose the proportion of nominal mix is 1:2:4 (one part cement, 2 part sand and 4 part aggregate)

Wastage of cement is taken as 2%
Output of mix is provided as 67%.

For 1 cum output, the requirement of dry mix is 1/0.67 = 1.49 say 1.50 cum.
After including the wastage (2%), the output will be (1.50 + 0.02) = 1.52 cum.
Volume of cement = (cement/cement+sand+aggregate) × Total material

= (1/1+2+4) × 1.52
=0.2171 cum
The density of cement is 1440 kg/cum and
Weight of 1 bag cement = 50 kg.

So, volume of 1 bag cement = 50/1440
=0.0347 cum.
No. of cement bags essential in 1 cubic meter = 0.2171/0.0347
= 6.25 bags.
The above formula can be utilized for measuring cement for other nominal mixes.

To get more details, watch the following video tutorial.

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Definition of M20 grade of concrete

In construction, there should be individual strength for each building element.

To maintain the strength of concrete for different elements, various types of concrete grades are required. The strength needed for foundation, beam, slab etc. will be different.

IS 456-2000 has specified the concrete mixes into a number of grades as M10, M15, M20, M25, M30, M35 and M40. In the following construction video tutorial, brief explanation is given on M20 grade of concrete.

In M20, M denotes Mix and 20 refers to the characteristic strength (fck) of that mix i.e. 20mpa. Cement, sand and aggregates are used for mixing in the ratio of 1 : 1.5 : 3. M20 signifies mixture of cement, sand and aggregate which are prepared in such a manner that a cement concrete cube of size 15 cm x 15 cm x 15 cm is formed with characteristic strength (fck) of 20mpa while examining it after being cured for 28 days.

The characteristic strength (fck) signifies the strength under which not over 5% of test results are predictable to fail.

Cement is always calculated with weight. Commonly it is applied in terms of bags. The weight of one bag of cement is 50 kg and it contains a volume of 35 litres (or, 0.035m3). A gauge box is employed for batching of fine and coarse aggregate by volume.

To get more brief information, watch the following video tutorial.

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Setting Process of Cement

The reaction of cement starts immediately when the water is mixed. In it’s pure and finely ground form, it is extremely sensitive to water. Out of the three main compounds of cement, i.e. C3A, C3S, C2S, reacts quickly with water. They produce a jelly-like mixture that starts solidifying. This changing action from fluid to solid is called ‘Setting’ (not ‘hardening’).

In the next stage of hydration, cement paste starts hardening itself to the reaction of C3S and C2S with water. After that it become more harden and dominant. Once initial stiffing has taken place, it should be hardened or gain strength as soon as possible so the risk of frost damage in frozen climate is minimized. The exact timing should always be followed.

“Initial setting time” is defined the period elapsing between the times when water is added to the cement and the required section fails to pierce the test block to a depth from the bottom of the mould.

“The final setting time” is defined as the period elapsing between the time when water is added to cement and the time at which the needle of certain section with required attachment makes an impressive on the test block.

The compressive strength test is based on two functions to fulfill. 1. Final check on the quality of the cement. 2. In case of any doubt, it also helps to classify the cements according to their strength.

The difference between setting and hardening cement is: cement is said to harden when the paste further reacts with water into action. Hardening is associated with the development of strength.

Source: theconstructor.org

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Rajib Dey

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Detailed methods for slump test to check the consistency of fresh concrete

This construction video briefly explains the importance of Slum Test and how it is used to examine the workability and conformity of fresh concrete.

The term ‘Slump’ can be defined as following two ways :-
1. A measurement of workability or fluidity of concrete
2. An indirect measurement of the conformity or rigidity of the concrete

Slump Test refers to the way of availing the conformity and & workability of fresh concrete. It is also utilized indirectly as a way of verifying whether exact amount of water is added to the concrete mix or not.

The test computes consistency of concrete in that particular batch. Consistency means the smoothness with which concrete flows. It is utilized to specify degree of wetness.

It belongs to the physical specifications of concrete that can impact the finesse, strength and durability.

ASTM C143 - Standard Test Method for Slump of Hydraulic-Cement Concrete.

It stands for a test necessary for passing the American Concrete Institute (ACI) Field Technician Certification Program -- "Concrete Field Testing Technician—Grade I."

A Concrete Field Testing Technician—Grade I refers to an individual who has validated the knowledge and capacity to properly execute and record the results originated from seven basic field tests on freshly mixed concrete.

The program needs a working knowledge of the various ASTM test methods and practices which are described below:

• C1064/C1064M - Temperature of Freshly Mixed Hydraulic-Cement Concrete
• C172 - Sampling Freshly Mixed Concrete
• C143/C143M - Slump of Hydraulic-Cement Concrete
• C138/C138M - Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete
• C231 - Air Content of Freshly Mixed Concrete by the Pressure Method
• C173/C173M - Air Content of Freshly Mixed Concrete by the Volumetric Method

Watch the following video to view the detailed slum test process.

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Rajib Dey

www.constructioncost.co

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Different types of foundation and their usefulness

Maximum structures are built with two parts like super structure and sub-structure of the foundation. Super Structure is located over the ground and the other sub-structure of the foundation is located beneath the ground level. Foundation alias footing of a structure associates and transfers the load from the structure to the ground soil. The foundation is developed on the solid ground and it is called as the foundation bed. The foundation transfers the load of the structure and it’s self-weight to the soil with the purpose of keeping the final bearing capacity of the soil under control (the shear failure does not occur) as well as keeping acceptable settlement.

All the structures have foundation at the base that offers the following functionalities:

• To disperse the load of the structure across an extensive bearing area.
• To load the bearing surface equally to get rid of asymmetrical settlement.
• To resist the lateral movement of the supporting material.
• To enhance the strength of the structure all together.

Foundation is based on the following points :-

Foundation is categorized depending on the dispersion of load to the ground into two sub-categories like shallow foundation and deep foundation.

Shallow Foundation

Shallow foundation belongs to the foundations where depth of the foundation remains below the width of the foundation (D < B). Shallow foundations are usually known as spread footing because they transfer the load of the super structure laterally into the ground.

Categorizarion of Shallow Foundation:

Based on the design, the shallow foundation is classified as:

• Wall Footing
• Isolated column or Column Footing
• Combined Footing
• Cantilever (Strap) Footing
• Mat (Raft) Foundation
• Wall Footing

This type of foundation runs consistently along the direction of the wall and facilitates transferring load of the wall into the ground. Wall footing are mostly applicable where transferable loads are small and cost-effective in compact sands and gravels. For this type of foundation, the width remains 2-3 times the width of the wall at ground level. Wall footing is built up with stone, brick, plain or reinforced cement concrete.

Column Footing

Column footing are useful and inexpensive for the depth surpassing 1.5m. For this type of foundation, the base of the column is distended. Column footing comes in the shape of of flat slab and is developed with plain or reinforced concrete.

Combined Footing

Combined footings belong to the foundations which are built in common for two or more columns in a row. It is generally formed if the footing for a column is spreaded outside the property line. It is applicable if the two columns are placed narrowly and the soil on which the structure is developed contains low bearing capacity. The shape of the combined footing appears as rectangular or trapezoidal.

Strap Footing

If an edge footing fails to spread outside the property line, it is connected with the other interior footing through a strap beam. Such footings are defined as strap footing. or sometimes cantilever footing.

Mat Foundation

A mat foundation belongs to a combined footing that covers the whole area below a structure and supports all the walls and columns. It is also called as raft foundation. Mat foundation is mostly suitable for the following reasons:

Permissible bearing pressure is low.

The structure is weighty.

The site is located with highly compressible layer.

The mat foundation is categorized into following types:

Flat slab type.

Flat Slab thickened under column.

Two way beam and slab type.

Flat slab with pedestals.

Rigid frame mat.

Piled mat.

To read the complete article, visit civileblog.com

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Rajib Dey

www.constructioncost.co

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