Shakes are nothing but cracks which separates the wood fibres partly or completely. There is a longitudinal separation in the wood between the annual rings.
Different types of shakes are:
i) Star Shakes: This type of shake starts propagating from the bark towards the sapwood and sometimes even towards the heartwood along the lines of medullary rays. Cracks are wider on the outer edge or bark and narrower on the inside.
ii) Ring shakes: When the crack separates the annual ring completely, it is called ring shakes.
iii) Heart shakes: heart shakes start propagating from the pith to the sapwood along the lines of medullary rays. Shrinkage of the interior part of the timber causes this crack.
Sedimentary Rocks ⇒ Rocks formed by accumulation, compaction, and consolidation of sediments are sedimentary rocks. It is also known as secondary rocks.
Examples: Breccia, Limestone, Sandstone, Shale
Metamorphic Rocks ⇒ Rocks formed due to metamorphism (process responsible for all the changes that take place in an original rock under the influence of changes in the surrounding, conditions of temperature and pressure) are known as metamorphic rocks.
Examples: Quartzite, Marble, Slate, Phyllite, Schist, Gneiss
Igneous Rock ⇒ Rocks formed due to cooling or solidification of magma or lava is known as igneous rocks.
There are two types of igneous rocks:
Intrusive Igneous Rocks → These rocks are formed due to cooling/solidification of magma within the crust of a planet. It is also known as Plutonic Rock.
Examples: Dike, Sill, Granite, Laccolith, Pegmatite, etc.
Extrusive Igneous Rocks → These rocks are formed due to cooling/solidification of magma at the crust’s surface. It cools faster than the intrusive one.
Examples: Basalts, Traps, Black Smokers, etc.
The crushing strength (MPa) of good stone used for construction of a building must not be less than
10
50
100
120
Crushing strength should be greater than 100 N/mm2
A good building stone has the following properties:
Percentage of wear in the attrition test should not be more than 3
Specific gravity should be at least 2.7
Coefficient of hardness should be greater than 17
Percentage of water absorption by weight of stone should be less than 5
Toughness index should not be less than 13
Crushing strength should be greater than 100 N/mm2
For self-compacted concrete water/powder ratio by volume should be
0.80 to 1.0
1.2 to 1.4
0.6 to 0.8
1.0 to 1.2
.8 to 1;
Indicative proportions of materials are shown below for self-compactible concrete:
1) Water/powder ratio by volume is to be 0.80 to 1.00
2) Total powder content to be 160 to 240 litres (400-600 kg) per m3
3) The sand content may be more than 38% of the mortar volume.
4) Coarse aggregate content should normally be 28 to 35% volume of the mix.
5) Water/cement ratio is selected based on the strength required. In any case, water content should not exceed 200 litres/m3.
CORRECT decreasing order of rate of hydration of Portland cement compounds
C3A
C4AF
C3 S
C2 S
C4AF > C3A > C3S > C2S
The setting and hardening of cement after addition of water is due to hydration of some of the constituent compounds of cement such as Tricalcium aluminate, Tricalcium silicate, Dicalcium silicate, and Tetra calcium aluminoferrite.
These compounds are known as Bogue’s Compounds.
Hydration of Bogues Compounds
Tricalcium aluminate (C3A): Celite is the quickest one to react when the water is added to the cement. It is responsible for the flash setting. The increase of this content will help in the manufacture of Quick Setting Cement. The heat of hydration is 865 J/Cal.
Tricalcium silicate (C3S): This is also called as Alite. This is also responsible for the early strength of the concrete. The cement that has more C3S content is good for cold weather concreting. The heat of hydration is 500 J/Cal.
Dicalcium Silicate (C2S): This compound will undergo reaction slowly. It is responsible for the progressive strength of concrete. This is also called as Belite. The heat of hydration is 260 J/Cal.
Tetra calcium Alumino ferrite (C4AF): This is called as Felite. The heat of hydration is 420 J/Cal. It has the poorest cementing value but it responsible for long-term gain of strength of the cement.
For the rate of hydration is highest for C4AF and heat of hydration is highest for C3A.
From the above, the decreasing order of rate of hydration of Portland cement compounds is
C4 AF > C3 A > C3 S > C2 S.
For the heat of hydration, decreasing order of heat of hydration of portland cement is
C3 A > C3 S > C4 AF > C2S
Note: Heat of Hydration and Rate of Hydration is different
Which of the following is the main reason to provide frog in the bricks?
Print manufacturer’s name.
Form keyed joint between brick and mortar.
Improve thermal insulation
Reduce the weight of brick.
Form keyed joint between brick and mortar.
Frog: It is an indentation or depression on the face of a brick made with the object forming a key for the mortar. This prevents displacement of the brick above.
∴ The term frog means a depression on a face of bricks.
Some other definitions:
1. Quoins is the exterior angle of a wall.
2. Closer is the portion of brick cut in such a manner that its one long face remains un-cut.
3. Bat is the portion of brick cut across width.
4. Perpend is that vertical joint on the face of wall, which lies directly above the vertical joints in alternative course.
5. Stretcher: Bricks are laid along its length.
6. Header: Bricks are laid perpendicular to the face of wall.
all of correct : Three most important advantages of seasoning have already been made apparent:
1. Seasoned timber lasts much longer than unseasoned. i.e. durability Since the decay of timber is due to the attacks of wood-destroying fungi, and since the most important condition of the growth of these fungi is water, anything which lessens the amount of water in wood aids in its preservation.
2. Seasoning increases the strength of the timber.
3. In the case of treated timber, seasoning before treatment greatly increases the effectiveness of the ordinary methods of treatment, and seasoning after treatment prevents the rapid leaching out of the salts introduced to preserve the timber.
4. The saving in freight where timber is shipped from one place to another.
5. The resilience which the ability to store the stress-energy per unit volume reduces after seasoning.
i. Expanding cement is used for filling the cracks
ii. White cement is mostly used for decorative works
iii. Portland Pozzolana cement produces less heat of hydration
iv. High strength Portland cement is produced from the special materials
All correct Expanding Cement: It is obtained from mixing sulpho-aluminate. It has a property to expand, thus used in the elimination of shrinkage cracks. It is used in the treatment of expansion joints and for grouting.
White Portland cement: The white colour of this cement is due to less proportion of iron oxide, which is replaced by Sodium Alumino Ferrite. Colouring agents can be added to white cement to produce coloured cement.
Portland Pozzolana Cement: It is formed by inter grinding of OPC clinker to 10% to 25% of pozzolanic material. It produces less heat of hydration and offers greater resistance to the attack of aggressive water than OPC. It is useful in marine and hydraulic constructions.
High strength Portland cement: This cement is produced by a special technique called Macro Defect Free (MDF) innovation. In this process 4-7% of one of several water-soluble polymers (such as hydroxypropyl methylcellulose, polyacrylamide of hydrolyzed polyvinyl acetate is added for generating high strength.
Cubical aggregate has maximum strength in concrete as it has good packing and strength in all direction.
Rounded aggregate is not suitable for concrete.
Flaky means have less thickness, elongated means having more length. These aggregate can be easily crushed and having a minimum strength.
Reasons:
Generally, in normal concrete loads are taken by aggregates only and cement acts as a binder, therefore, a normal concrete can have maximum strength till the aggregates are not broken.
If the aggregates fail under a load before failure of cement sand matrix. The concrete produced with that aggregates will not achieve the desired strength.
So using flaky and elongated aggregates might lead to failure of concrete and hence should be avoided.
Classification of aggregates on basis of shape –
Rounded aggregates / spherical - Rounded aggregates result the minimum percentage of voids (32 – 33%) hence gives more workability. They require lesser amount of water-cement ratio. They are not considered for high strength concrete because of poor interlocking behaviour and weak bond strength.
Irregular or partly rounded aggregates - Irregular aggregates may result 35- 37% of voids. These will give lesser workability when compared to rounded aggregates.
Angular aggregates -
Angular aggregates result maximum percentage of voids (38-45%) hence gives less workability
Flaky aggregates -
When the aggregate thickness is small when compared with width and length of that aggregate it is said to be flaky aggregate. Or in the other, when the least dimension of aggregate is less than the 60% of its mean dimension then it is said to be flaky aggregate.
Elongated aggregates -
When the length of aggregate is larger than the other two dimensions then it is called elongated aggregate or the length of aggregate is greater than 180% of its mean dimension.
Flaky and elongated aggregates -
When the aggregate length is larger than its width and width is larger than its thickness then it is said to be flaky and elongated aggregates. The above 3 types of aggregates are not suitable for concrete mixing
Important Point:
Split tensile strength(fct) = 0.66 × Modulus of Rupture
Due to the difficulty in applying uniaxial tension to a concrete specimen, the tensile strength is determined by indirect methods.
It is the standard test to determine the tensile strength of concrete indirectly as per IS: 5816-1970
A standard test cylinder of a concrete specimen of 300 mm × 150 mm diameter is placed horizontally between the loading surfaces of the compression testing machine.
The compression load is applied diametrically and uniformly along the length of the cylinder until the failure of the cylinder along vertical diameter.
Modulus of rupture:
It is a measure of the tensile strength of concrete beams or slabs.
Flexure strength of concrete is determined as a modulus of rupture. Flexural strength of concrete/ Bending tensile strength of concrete/Modulus of rupture of concrete (fcr) is given by,
fcr = 0.7×√fck
Compressive strength of concrete:
It is determined by the compressive strength test on a standard 150 mm concrete cube in a compressive testing machine as per IS 516: 1959. The test specimens are generally tested after 28 days of casting and continuous curing.
In USA standard cylinder of height to diameter ratio of 2 is taken. (150 mm diameter, 300 mm height) for determining.
It is observed that the Cube strength of concrete is nearly 1.25 times the cylinder strength.
1. Pith : It is the inner most part of tree consist of cellular tissue which is used for nourishment of tree in young age.
2. Sapwood : It is outer annual rings between heartwood and cambium layers. It is the living, outermost portion of a woody stem or branch.
3. Heartwood : It is the dead, inner wood, which often comprises the majority of a stem's cross-section.
4. Cambium Layer : It is a thin layer of sap between sapwood and inner bark.
A good building stone has the following properties:
Percentage of wear in the attrition test should not be more than 3
Specific gravity should be at least 2.7
Coefficient of hardness should be greater than 17
Percentage of water absorption by weight of stone should be less than 5
Toughness index should not be less than 13
Crushing strength should be greater than 100 N/mm2
Chemical composition: The various tests are carried out to determine the chemical constituents of cement. Following are the chemical requirements of ordinary cement as per IS: 269- 1998:
Ratio of percentage of alumina to that of iron oxide: This ratio should not be less than 0.66.
Ratio of percentage of lime to those of alumina, iron oxide, and silica: This ratio is known as the lime saturation factor (LSF) and it should not be less than 0.66 and it should not be greater than 1.02, when calculated by the following formula:
Total loss on ignition: This should not be greater than 4 percent.
Total sulphur content-The sulphur content is calculated as SO3 and it should not be greater than 2.75%.
Weight of insoluble residue-This should not be greater than 1.5%.
Weight of magnesia-This should not exceed 5%.
Note:
As per IS 12269: 2013, the loss on ignition for OPC 53 should not be greater than 4%.
As per IS 8112: 2013, the loss on ignition for OPC 43 & 33 should not be greater than 5%.
Colored cement:
Colored pigment is manufactured by mixing of color pigments (5-10 %) with OPC.
The pigment is mixed in a finest powdered state.
The main modern white hiding pigment is Titanium dioxide. Zinc oxide is a weaker white pigment with some important usages.
Some pigments are toxic, such as those used in lead paint. Paint manufacturers replaced lead white with a less toxic substitute, which can even be used to colour food titanium white (titanium dioxide).
Portland slag cement:
This cement is prepared by mixing granulated blast furnace slag, hard burnt gypsum, and cement clinkers in suitable proportions.
This cement offer:
The heat of hydration of Portland slag cement is lower than OPC. Therefore, this cement can be used in mass concreting.
Higher resistance against the attack of chlorides and sulfate.
Better refinement of pore structure.
Higher water tightness. so this cement can be used in the marine structures.
Rapid hardening cement:
It is the type of cement that developed a higher rate of gain of strength and must not be confused with quick setting cement which only set quickly.
The cement attains the strength at the age of 3 days equivalent to that attained by OPC in 7 days.
This Higher strength in the initial stage is attributed to the higher fineness of the cement and increases the proportion of C3S (specific surface area should not be less than 3250 cm2/gm and C3S is approximate 56%).
Application
Pre-fabricated construction
Cold weather concreting
Emergency repair work
Pavement construction
High alumina cement:
This cement is obtained by fusing a mixture, in suitable proportions, of alumina and calcareous materials and grinding the resultant product to a fine powder. The raw material used for the manufacture of high alumina cement is limestone and bauxite.
The proportion of alumina in the cement must not less than 32% and the ratio of the percentage of alumina to that of lime is in the range of 0.85 to 1.3.
The cement offers a higher initial setting time (3.5 hours) and a lower final setting time (5 hours), hence more time is available to work with the cement along with speedy construction.
The cement can also resist high temperatures.
It can resist the action of acid up to a greater extent.
It also offers a higher rate of gain of strength.
When Water and Cement mix, heat is generated. This process is known as Hydration.
Hydration is a chemical reaction in which the major compounds in cement form chemical bonds with water molecules and become hydrates or hydration products.
Major compounds of cement clinker (also known as Bogues compounds) are:
Tricalcium aluminate (C3A): Celite is the quickest one to react when the water is added to the cement. It is responsible for the flash setting. The increase of this content will help in the manufacture of Quick Setting Cement. The heat of hydration is 865 J/Cal.
Tricalcium silicate (C3S): This is also called as Alite. This is also responsible for the early strength of the concrete. The cement that has more C3S content is good for cold weather concreting. The heat of hydration is 500 J/Cal.
Dicalcium Silicate (C2S): This compound will undergo reaction slowly. It is responsible for the progressive strength of concrete. This is also called as Belite. The heat of hydration is 260 J/Cal.
Tetra calcium Alumino ferrite (C4AF): This is called as Felite. The heat of hydration is 420 J/Cal. It has the poorest cementing value but it responsible for long term gain of strength of the cement.
Non-destructive Tests
Non-destructive tests are used to ascertain the quality of hardened concrete (strength, durability, elastic properties), generally following test are characterized as non-destructive test are:
1. Schmidt Rebound hammer test
2. Ultrasonic Pulse velocity test
3. Penetration method
4. Pull out Test method
5. Radioactive and nuclear test method
Destructive Test
In the case of destructive tests, the concrete specimens (cube, cylinder, etc) are loaded till destruction in the laboratory, and strength properties are determined from the tests. The following test are characterized as destructive test are:
1. Compressive strength
2. Tensile strength
Splitting tensile test
Modulus of rupture test
3. Bond strength
Different type of strength of timber:
Compressive strength:
The compressive strength is found to be the highest when acting parallel to the axis of growth.
The compressive strength perpendicular to the fibers of wood is much lower than that parallel to fibers of the wood.
Tensile strength:
Tensile strength along a direction parallel to the grains is found to have the greatest strength that can be developed under any kind of stress.
Tensile strength parallel to fibers is of the order 80.0 to 190.0 N/cm2.
Shearing strength:
Resistance to shear in across direction is found 3 to 4 times greater than that along fibers.
The shear strength along the fiber is found of the order 6.5 to 14.5 N/mm2.
Explanation:
The strength of timber is the highest parallel to the grains and minimum perpendicular to grains.
Timber:
The wood that is going to use for the building. The structure of the wood is:
Pith:
The innermost central portion or core of the tree is called the pith or medulla.
As the plant becomes old, the pith dies up and decays.
Sap Wood:
Outer annual rings between the heartwood and cambium layer are the sapwood.
It is light in color and weight.
It takes an active part in the growth of the trees.
It does not impart any strength.
Cambium Layer:
A thin layer of sap in between the sapwood and inner bark is referred to as the cambium layer.
It indicates the portion of the sap which is yet to be converted into the sapwood.
Bark:
The Outer protective layer or covering provided around the cambium layer is referred as bark.
Bulking of Sand:
The increase in the volume of sand due to an increase in moisture content is known as the bulking of sand. A film of water is created around the sand particles which forces the particles to get aside from each other and thus the volume is increased.
The increase in moisture in sand increases the volume of sand. The volume increase in dry sand is known as the bulking of sand. Bulking of sand depends on the quantity of moisture in the sand and also the size of the particles. Five to eight percent of the increase in moisture in the sand can increase the volume of sand up to 20 to 40 percent. Again the finer the sand is more will be the increase in volume and the increase in volume will be relatively less for coarser sand.
So, From the figure, We can say that With an increase in moisture content, the bulking of sand First increases to a certain maximum value and then decreases.
Fineness modulus of an aggregate is an indicator of the mean size of particles. The coarser the particle, the higher the fineness modulus.
Type of SandFineness Modulus Range
Fine Sand2.2 – 2.6
Medium Sand2.6 – 2.9
Coarse Sand2.9 – 3.2
Resins:
The resin is a natural or synthetic compound that begins in a highly viscous state and hardens with treatment
Many different kinds of resins may be used to create a varnish
Natural resins used for varnish include amber, kauri gum, dammar, copal, rosin, sandarac, balsam, elemi, mastic, and shellac
Varnish may also be created from synthetic resins such as acrylic, alkyd, or polyurethane
Typically, it is soluble in alcohol, but not in the water
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Vee - Bee Consistometer
It is the method used to determine the workability of very dry mixes with low workability.
It measures the time required for complete remoulding of concrete in seconds after placed in the mould with a slump cone.
It is expressed in seconds.
Note:
As slump increases, Vee - bee time decreases, and the compaction factor increases as it becomes easier for concrete to flow.
The degree of workability in Vee - Bee test is classified based on the time taken in seconds as shown below:
Degree of workability Vee - Bee degree (seconds)
Extremely low > 20
Very low 12 - 20
Low 6 - 12
Medium 3 - 6
High 0 - 3
Pointing is the finishing of the joints in brick masonry using either cement mortar (1 (cement): 3 (sand)) or lime mortar (1 (fat lime): 2 (sand)).
Facing is an outer layer or coating applied to a surface like brick wall for protection or decorative purpose.
Guinting is the process of repairing the already damaged concrete surface. In this method, cement is mixed with sand in 1: 3 or any other specified proportion and this mixture is applied over damaged concrete surface with a cement gun under some pressure. By doing so, a highly impervious surface is achieved.
Plastering is the process of covering rough walls and uneven surfaces in with a material, called plaster, which is a mixture of lime or cement and sand along with the required quantity of water.
Efflorescence:
It is a whitish coloured powdered deposition of salts on the concrete surface that is formed due to evaporation of water from the concrete.
It is caused when water soluble salts are present in the concrete material, which comes on to the surface while evaporation of water from the concrete.
These salts are sulphate and carbonate salts of calcium and sodium and can come from bricks, cement, aggregates, water, or admixtures.
The following water soluble salts are generally leads to efflorescence:
∴ Sulphates and carbonates of sodium, and calcium leads to efflorescence, but not due to those of iron.
Stones
Quarrying is the process of removing the rock, sand, gravel or other minerals from the ground in order to use them to produce materials for construction or other uses.
Natural bed of stone is the plane along which stone can easily be split. It thus indicates the plane or bed on which the sedimentary stone was originally deposited.
Dressing of Stone is the working of quarried stone into the shape and size required for use. This can be necessary as stones obtained from quarrying generally do not have the exact required dimensions or finish.
Seasoning of stone means to expose the stone in the open air for a period of 6 to 12 months. It removes quarry sap and makes the stone-hard and compact.
The strength of any timber is highest in direction of
an angle of 60 degree to grains
an angle of 0 degree to grains
an angle of 90 degree to grains
an angle of 120 degree to grains
An angle of 0 degree to grains; Wood has three principal axes namely longitudinal, tangential and radial axes. Since it is orthogonal material m it has three values of modulus of elasticity varying by as much as 150 to 1, three shear moduli varying from 20 to 1, and six Poisson’s ratios varying by 40 to 1.
For different strength:
a) Compressive strength: The compressive strength is found to be highest when acting parallel to the axis of the growth. However compressive strength perpendicular to fibres of wood is much lower than that parallel to fibres of wood. Compressive strength parallel to fibre varies from 30.0 to 77.5 N/cm2.
b) Tensile strength: Tensile strength along direction parallel to the grain is found to have greatest strength that can be developed under any other kind of stress. Tensile strength parallel to fibres is of the order 80.0 to 190.0 N/cm2.
c) Shearing strength: Resistance to shear in across direction is found 3 to 4 times greater than that along fibres. The shear strength along fibre is found of the order 6.5 to 14.5 N/mm2.
∴ The strength of timber is highest in the direction of an angle of 0° to the grains.
Quick Lime ; Calcination or calcining is a thermal treatment process to bring about a thermal decomposition. The process takes place below the melting point of the product. The name calcination is derived from the Latin word ‘Calcinare’ which mean to burn lime.
CaCO3→heatCaO+CO2(Limestone)→(Lime)+(Carbondioxide)CaCO3→heatCaO+CO2(Limestone)→(Lime)+(Carbondioxide)
The lime which is obtained by the calcination of comparatively pure limestone is known as quick lime or caustic lime. It's chemical composition is (CaO) oxide of calcium and it has great affinity for moisture.
The quick lime as it comes out from kiln is also known as lump limes.
Sodium carbonates in deionised water accelerates the initial as well as final setting times whereas the other compound sodium bicarbonates retards the initial and final setting times in all concentrations. Sodium carbonates and sodium bicarbonates in deionised water decrease the compressive and tensile strength of concrete specimens significantly at 28 days and 90 days.
Important points:
The two most popular type of admixture added in concrete are as follows:
Retarder:
It is added in concrete in order to delay the chemical process of hydration so as to keep the concrete plastic and workable for longer duration in comparison to the concrete without retarder.
Example: Calcium Sulphate, Sugar, starch, cellulose etc.
Accelerators:
It is used to increase the rate of gain of strength in the concrete.These admixtures find their application in cold weather concreting, pre - fabricated concrete construction, emergency road repair work and where formwork is to be reused for speedy construction.
Example: calcium chloride, silicates, Fluorosilicates, Triethanolamine etc.
The impurity of mixing water which affects the setting time and strength of concrete is _____.
sodium sulphates
sodium chlorides
sodium carbonates and bicarbonates
calcium chlorides
Sodium Carbonates and Bicarbonates. Explaination:
Sodium carbonates in deionised water accelerates the initial as well as final setting times whereas the other compound sodium bicarbonates retards the initial and final setting times in all concentrations. Sodium carbonates and sodium bicarbonates in deionised water decrease the compressive and tensile strength of concrete specimens significantly at 28 days and 90 days.
Clay bricks are classified as first-class, second class, third class and fourth class based on their physical and mechanical properties.
First Class Bricks:
1. These are thoroughly burnt and are of deep red, cherry or copper color. 2. The surface should be smooth and rectangular, with parallel, sharp and straight edges and square comers. 3. These should be free from flaws, cracks, and stones. 4. These should have a uniform texture. 5. No impression should be left on the brick when a scratch is made by a fingernail. 6. The fractured surface of the brick should not show lumps of lime. 7. A metallic or ringing sound should come when two bricks are struck against each other. 8. Water absorption should be 20% of its dry weight when immersed in cold water for 24 hours. 9. The crushing strength of the brick should not be less than 10 N/mm2. This limit varies with different Government organizations around the country. Uses: First class bricks are recommended for pointing, exposed face work in masonry structures, flooring and reinforced brickwork.
Second Class Bricks are supposed to have the same requirements as the first-class ones except that
1. Small cracks and distortions are permitted.
2. A little higher water absorption of about 22% of its dry weight is allowed.
3. The crushing strength should not be less than 7.0 N/mm2.
Uses: Second class bricks are recommended for all important or unimportant hidden masonry works and centering of reinforced brick and reinforced cement concrete (RCC) structures.
Third Class Bricks are under burnt. They are soft and light-colored producing a dull sound when struck against each other. Water absorption is about 25 percent of dry weight.
Uses: It is used for building temporary structures.
Fourth Class Bricks are over burnt and badly distorted in shape and size and are brittle in nature.
Uses: The ballast of such bricks is used for foundation and floors in lime concrete and road metal.
Ferro
cement developed by P.L. Nervi, an Italian architect, and engineer, in
1940. It consists of closely spaced wire meshes which are impregnated
with rich cement mortar mix.
The wire mesh is usually
of 0.5 to 1.0 mm diameter wire at 5 mm to 10 mm spacing and cement
mortar is of the cement-sand ratio of 1: 2 or 1: 3 with water/cement
ratio of 0.4 to 0.45.
The ferro cement elements are
usually of the order of 2 to 3 cm in thickness with 2 to 3 mm external
cover to the reinforcement. The steel content varies between 300 kg to
500 kg per cubic meter of mortar.
The basic idea behind
this material is that concrete can undergo large strains in the
neighbourhood of the reinforcement and the magnitude of strains depends
on the distribution and subdivision of reinforcement throughout the mass
of concrete.
It is impervious in nature, has the capacity to resist shock and no formwork is required to gain initial strength.
The
main advantages are the simplicity of its construction, a lesser dead
weight of the elements due to their small thickness, its high tensile
strength, fewer crack widths compared to conventional concrete, easy
repairability, noncorrosive nature and easier mouldability to any
required shape.
In-depth Knowledge of Ferro-cement
Definition
Ferrocement is a construction material that consists of a combination
of cement mortar and a mesh of metal, usually steel, which can be used
to create thin-section structures.
Here are some key points about
ferrocement:
Composition:
Ferrocement is composed of a mortar mix (cement, sand, and water) reinforced with layers of mesh or metal.
The
mesh used in ferrocement is typically made of metal, such as steel, and
is carefully arranged to form a strong and durable structure.
Applications:
Ferrocement
is versatile and can be used in various construction applications,
including boat building, water tanks, pipes, roofs, and even sculptural
elements.
Its ability to form thin and complex shapes makes it
suitable for applications where traditional materials might be less
practical.
Advantages:
Ferrocement structures are known for their strength and durability.
They are relatively lightweight compared to traditional concrete structures.
The construction process allows for intricate shapes and designs.
Ferrocement structures can be more resistant to cracking than conventional concrete due to the distributed reinforcement.
Construction Process:
The construction of ferrocement involves layering the mesh and applying cement mortar.
The layers are built up gradually, with each layer allowing for the incorporation of the reinforcement into the structure.
Proper curing is essential to achieve the desired strength and durability.
Uses in Water-related Structures:
Ferrocement is commonly used in the construction of water tanks, boats, and even swimming pools.
Its ability to resist corrosion makes it suitable for applications involving water exposure.
Challenges:
Quality control in construction is crucial to ensure uniform thickness and proper bonding between the mortar and reinforcement.
Proper curing and workmanship are essential to achieving the desired structural integrity.
Ferrocement
offers a unique set of properties that can be advantageous in specific
applications, and its use requires careful consideration of the intended
structure and appropriate construction techniques. If you have more
specific questions or if there's a particular aspect of ferrocement
you'd like to ask further in comment section, feel free to ask!
Worldwide use of Ferro-cement
While ferrocement is not as widely used as some other construction
materials in large-scale structures, it has found application in various
projects around the world. Here are a few examples:
Pleasure Island Boats (Italy):
In
Venice, Italy, ferrocement has been used in the construction of some
boats navigating the city's canals. These boats are known for their
lightweight construction and durability, which are important qualities
for navigating the narrow waterways of Venice.
Ferrocement Yachts:
Ferrocement
has been used in the construction of yachts and small boats. The material's versatility and ability to create complex shapes make it
suitable for designing lightweight yet strong hulls for water vessels.
Ferrocement Water Tanks:
Ferrocement
is commonly used in the construction of water tanks, especially in
regions where there is a need for reliable and cost-effective water
storage. The material's resistance to corrosion makes it suitable for
such applications.
Boat Hulls and Marine Structures:
Ferrocement
has been employed in the construction of boat hulls and other marine
structures due to its ability to resist corrosion in a saltwater
environment. While not as prevalent as other materials, it has been used
in certain niche applications.
It's important to note that
ferrocement, while offering advantages in specific situations, is not as
commonly used in large-scale structures as materials like reinforced
concrete. The examples mentioned typically involve smaller-scale
applications where ferrocement's unique properties, such as its ability
to form complex shapes and resistance to corrosion, are particularly
beneficial.
Some additional key points
Here are some additional key points that may contribute to a deeper understanding of ferrocement:
Thin-Section Construction:
One
of the defining characteristics of ferrocement is its ability to create
thin-section structures. This is achieved by using a relatively small
thickness of mortar reinforced with a mesh. The thin sections contribute
to the material's flexibility and versatility.
Flexibility and Shaping:
Ferrocement
allows for the construction of structures with intricate shapes and
curves. This is particularly advantageous in applications such as boat
building, where streamlined and customized designs are often desired.
Reinforcement Mesh Types:
Various
types of mesh can be used as reinforcement in ferrocement, including
chicken wire, hexagonal wire mesh, and woven steel mesh. The choice of
mesh depends on the specific requirements of the project.
Construction Techniques:
The
construction process typically involves layering the reinforcement mesh
and applying mortar to each layer. The layers are built up gradually,
with attention to proper compaction and bonding between layers to ensure
structural integrity.
Corrosion Resistance:
Ferrocement
exhibits good resistance to corrosion, making it suitable for
applications in marine environments and water-related structures. This
property is attributed to the protective alkaline environment created by
the cement.
Applications in Developing Countries:
Ferrocement
has been explored as a cost-effective building material in developing
countries. Its affordability, ease of construction, and durability make
it a potential solution for housing, water storage, and other
infrastructure needs.
Research and Advancements:
Ongoing
research and advancements in materials science continue to explore ways
to enhance the properties of ferrocement, including improving its
strength, durability, and crack resistance.
Combination with Other Materials:
In
some cases, ferrocement is used in combination with other materials to
create hybrid structures that leverage the benefits of both. For
example, combining ferrocement with foam insulation can result in
lightweight yet sturdy panels.
Energy Efficiency:
The relatively low
thermal mass of ferrocement can contribute to energy efficiency in
buildings. It may respond quickly to temperature changes, potentially
reducing the need for extensive heating or cooling.
Remember
that ferrocement, while offering unique advantages, is not a
one-size-fits-all solution. Its suitability depends on the specific
requirements of the project, and proper construction practices are
essential to realizing its full potential.
13. Density of high-density concrete is about ________
2400 kg/m3
2750 kg/m3
3000 kg/m3
3360 kg/m3
3360 kg/m3. The density of normal concrete is about 2400 kg/m3. The density of light-weighted concrete is about 1900 kg/m3.
For concrete to be termed as high-density concrete, it must have a unit weight ranging about 3360 kg/m3 to 3840 kg/m3, which is about 50% higher than the weight of conventional concrete. The high-density concrete is used in the construction of radiation shields.
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