Superplasticizers, also known as high range water reducers, are chemical admixtures used where well-dispersed particle suspension is required. These polymers are used as dispersants to avoid particle segregation(gravel,coarse and fine sands), and to improve the flow characteristics (rheology) of suspensions such as in concrete applications. Their addition to concrete or mortar allows the reduction of the water to cement ratio, not affecting the workability of the mixture, and enables the production of self-consolidating concrete and high performance concrete.This effect drastically improves the performance of the hardening fresh paste. The strength of concrete increases when the water to cement ratio decreases. However, their working mechanisms lack a full understanding, revealing in certain cases cement-superplasticizer incompatibilities.[1] The addition of superplasticizer in the truck during transit is a fairly new development within the industry. Admixtures added in transit through automated slump management systems, such as Verifi, allows concrete producers to maintain slump until discharge without reducing concrete quality.
Tuesday, 20 October 2015
Superplasticizer
Superplasticizers, also known as high range water reducers, are chemical admixtures used where well-dispersed particle suspension is required. These polymers are used as dispersants to avoid particle segregation(gravel,coarse and fine sands), and to improve the flow characteristics (rheology) of suspensions such as in concrete applications. Their addition to concrete or mortar allows the reduction of the water to cement ratio, not affecting the workability of the mixture, and enables the production of self-consolidating concrete and high performance concrete.This effect drastically improves the performance of the hardening fresh paste. The strength of concrete increases when the water to cement ratio decreases. However, their working mechanisms lack a full understanding, revealing in certain cases cement-superplasticizer incompatibilities.[1] The addition of superplasticizer in the truck during transit is a fairly new development within the industry. Admixtures added in transit through automated slump management systems, such as Verifi, allows concrete producers to maintain slump until discharge without reducing concrete quality.
AGGREGATE IMPACT VALUE
This test is done to determine the aggregate impact value of coarse aggregates as per IS: 2386 (Part IV) – 1963. The apparatus used for determining aggregate impact value of coarse aggregates is
Impact testing machine conforming to IS: 2386 (Part IV)- 1963,IS Sieves of sizes – 12.5mm, 10mm and 2.36mm, A cylindrical metal measure of 75mm dia. and 50mm depth, A tamping rod of 10mm circular cross section and 230mm length, rounded at one end and Oven.
Preparation of Sample
i) The test sample should conform to the following grading:
– Passing through 12.5mm IS Sieve – 100%
– Retention on 10mm IS Sieve – 100%
ii) The sample should be oven-dried for 4hrs. at a temperature of 100 to 110oC and cooled.
iii) The measure should be about one-third full with the prepared aggregates and tamped with 25 strokes of the tamping rod.
A further similar quantity of aggregates should be added and a further tamping of 25 strokes given. The measure should finally be filled to overflow, tamped 25 times and the surplus aggregates struck off, using a tamping rod as a straight edge. The net weight of the aggregates in the measure should be determined to the nearest gram (Weight ‘A’).
aggregate-impact-value
Procedure to determine Aggregate Impact Value
i) The cup of the impact testing machine should be fixed firmly in position on the base of the machine and the whole of the test sample placed in it and compacted by 25 strokes of the tamping rod.
ii) The hammer should be raised to 380mm above the upper surface of the aggregates in the cup and allowed to fall freely onto the aggregates. The test sample should be subjected to a total of 15 such blows, each being delivered at an interval of not less than one second.
Reporting of Results
i) The sample should be removed and sieved through a 2.36mm IS Sieve. The fraction passing through should be weighed (Weight ‘B’). The fraction retained on the sieve should also be weighed (Weight ‘C’) and if the total weight (B+C) is less than the initial weight (A) by more than one gram, the result should be discarded and a fresh test done.
ii) The ratio of the weight of the fines formed to the total sample weight should be expressed as a percentage.
Aggregate impact value = (B/A) x 100%
iii) Two such tests should be carried out and the mean of the results should be reported
STONE
CLAASSIFICATION OF STONE
Origin - How was it made?
•Sedimentary
•Metamorphic
•Igneous
•Man-Made
Composition - What is it made of?
•Silicates
•Calcium Carbonates
Classification of Rocks
Rocks Classification
Mineral Composition
Silicates
These stones are made mostly of quartz-like particles called silica. They are very hard, durable and generally acid resistant. Examples: granite, sandstone, slate and quartzite.
Calcium Carbonates
The minerals in these stones were formed under pressure over millions of years from the bodies of tiny fossilized creatures. These stones are softer, less durable than silicates and acid sensitive.
Examples: limestone, marble and travertine
Origin - How was it made?
•Sedimentary
•Metamorphic
•Igneous
•Man-Made
Composition - What is it made of?
•Silicates
•Calcium Carbonates
Classification of Rocks
Rocks Classification
Mineral Composition
Silicates
These stones are made mostly of quartz-like particles called silica. They are very hard, durable and generally acid resistant. Examples: granite, sandstone, slate and quartzite.
Calcium Carbonates
The minerals in these stones were formed under pressure over millions of years from the bodies of tiny fossilized creatures. These stones are softer, less durable than silicates and acid sensitive.
Examples: limestone, marble and travertine
Wednesday, 7 October 2015
CONCRETE CURING COMPOUND
Concrete curing compound consists essentially of waxes, natural and synthetic resins, and solvents of high volatility at atmospheric temperatures. The compound forms a moisture retentive film shortly after being applied on fresh concrete surface. White or gray pigments are often incorporated to provide heat reflectance, and to make the compound visible on the structure for inspection purpose. Curing compound should not be used on surfaces that are to receive additional concrete, paint, or tile which require a positive bond, unless it has been demonstrated that the membrane can be satisfactorily removed before the subsequent application is made, or that the membrane can serve satisfactorily as a base for the later application.
The compound should be applied at a uniform rate. The usual values for coverage range from 0.20 to 0.25 m2/lit. Curing compound can be applied in two applications at right angles to each other by hand or power sprayer usually at about 0.5 to 0.7 MPa pressure. For small areas, the compound can be applied with a wide, soft-bristled brush or paint roller.
For maximum beneficial effect on open concrete surfaces, compound must be applied after finishing and as soon as the free water on the surface has disappeared and no water is visible, but not so late that the liquid curing compound will be absorbed by the concrete.
When forms are removed, the exposed concrete surface should be wetted with water immediately and kept moist until the curing compound is applied. Just prior to application, the concrete should be allowed to reach to a uniformly damp appearance with no free water on the surface and then application of the compound should begun at once.
USES
Curing compound can be used with advantage where wet curing is not possible. It is very suitable for large areas of concrete which are directly exposed to sunlight, heavy winds and other environmental influences. It can be used for curing of:
•Concrete pavements, airport runways, bridge decks, industrial floors.
•Canal linings, dams and other irrigation related structures.
•Sport arenas and ice ring.
•Precast concrete components
•Roof slabs, columns and beams
•Chimneys, cooling towers and other tall structures.
TESTING OF CURING COMPOUND
The curing compound should be tested in accordance to ASTM for the following tests:
a) Water retention – The test should be conducted in accordance with test method C 156.
b) Reflectance – Determine the daylight reflectance of white – pigmented compound in accordance with test method E 97.
c) Drying time – The test should be conducted in accordance to ASTM C 309 clause 10.3
d) Long term setting – For routine testing use test method D 1309. In case of dispute use method D 869.
e) Nonvolatite content – Test in accordance with test method D 1644 method 4.
Saturday, 3 October 2015
RAPIGROUT CEMENT IN REPAIR WORK
Imagine a scenario: enemy aircraft penetrates air defence systems, fly over airfield and drop bombs on the runway. Craters are formed on the runway making it non-operational. Pilots cannot take off to defend or attack the enemy. Worthy war machines remain idle. The same runway needs to be attended to, repaired and rehabilitated at breakneck speed — usually overnight — to put it back into use.
War inventory, today, has indigenous supportive technology for such, expected contingencies. Helipads too can be built overnight. Commercially available Rapid Acting cement is used only for construction and cannot be used for runway repair. This indigenous technology is for civil use as well.
It started with a need in the armed forces felt to repair runway that gets damaged due to enemy bombing which leaves craters. Indian Air Force bought a mixer cum dispenser from a French company at an enormous cost. Since then, an alternative was looked at. In 1990 the DRDO sanctioned the concept of a Rapid Repair of Runway. Seven scientists and engineers set about making ‘Runway Rehabilitation using Quick Setting Cement’ a reality. Research and Development Establishment (Engineers) have since announced Rapigrout Cement — produced indigenously.
Rapigrout
On an average, a crater in the runway is of 12 metre diameter and is two metre deep at the deepest point. Rapigrout is of a special variety that does not need conventional reinforcement with steel mesh or rods of steel or tor-steel. The shelf life of the French Mix is one year. Which means, if left unused, the ingredients go waste. But Rapigrout is claimed to have two years shelf life.
Rapigrout does not need the typical curing period. In fact, Rajendra Kumar Gupta, the scientist at Composite Research Center at R&D E(Engrs) claims that it is a non-curing cement. It gains in strength without conventional curing. It contains a ultra rapid hardening hydraulic binder. The cement is effective in the temperature range between minus 20 degree Celsius to 50 degree Celsius with additives. Additive C is used in cold weather and additive H is used in hot weather.
Setting time
The scientists recommend use of hot water at just 28 degree C mixed with Additive L, a lime-based compound. The chemical reaction due to lime mixing with water produces heat and Rapigrout uses this indigenous heat to set rapidly.
It is well known that normal cement used in construction takes 7 days to reach normal level of curing provided it is constantly kept wet. A total of 28 days are needed for the cement concrete to set fully. Further, as authenticated by Border Roads Organization, at Himalayan heights, curing takes much longer due to sustained low temperatures.
On the other hand, Rapigrout takes just 10 minutes for initial setting and in 25 minutes, it sets finally.
Laboratory tests after 100 minutes reported results with the test blocks able to withstand 100 kilo gram per square centi metre load.
A crater of 12 m diameter and having 2 m depth at the deepest point needs about 12,000 cubic metre of slurry. Water content needed varies - in cold weather it is less than 28 per cent of the total weight of Rapigrout used; in hot weather 32 per cent water content is sufficient. Pre-packed aggregate of 47 milli metre size — a little less than two inch size — is mixed with this very finely powdered cement. Fineness of the cement particles
is better than in normal
cement. The finer it is the faster it strengthens.
Rapigrout has a shelf life of two years and can be stored at a temperature range of minus 20 degree C and plus 50 degree C in
airtight containers. Cost of Rapigrout is estimated to be five or six times the Rapid Acting cement.
R&D E does not want to give away full details and commercialisation is still some time away. A leading cement manufacturing company has signed a Memorandum of
Understanding with DRDO to facilitate research, trial and manufacture.
Building a Helipad or helicopter landing ground, using Rapigrout is yet to be tried - or, if it has been tried - is not admitted to.
The minimum area needed to land and take off with Helicopter is a circle of 15 m diameters.
Just 24 hours!
Preparing the slurry with appropriate additive will take some time, to be spread evenly on the
prepared site. The mix sets in less than two hours and is ready for operation. The whole helipad can be built in 24 hours.
War inventory, today, has indigenous supportive technology for such, expected contingencies. Helipads too can be built overnight. Commercially available Rapid Acting cement is used only for construction and cannot be used for runway repair. This indigenous technology is for civil use as well.
It started with a need in the armed forces felt to repair runway that gets damaged due to enemy bombing which leaves craters. Indian Air Force bought a mixer cum dispenser from a French company at an enormous cost. Since then, an alternative was looked at. In 1990 the DRDO sanctioned the concept of a Rapid Repair of Runway. Seven scientists and engineers set about making ‘Runway Rehabilitation using Quick Setting Cement’ a reality. Research and Development Establishment (Engineers) have since announced Rapigrout Cement — produced indigenously.
Rapigrout
On an average, a crater in the runway is of 12 metre diameter and is two metre deep at the deepest point. Rapigrout is of a special variety that does not need conventional reinforcement with steel mesh or rods of steel or tor-steel. The shelf life of the French Mix is one year. Which means, if left unused, the ingredients go waste. But Rapigrout is claimed to have two years shelf life.
Rapigrout does not need the typical curing period. In fact, Rajendra Kumar Gupta, the scientist at Composite Research Center at R&D E(Engrs) claims that it is a non-curing cement. It gains in strength without conventional curing. It contains a ultra rapid hardening hydraulic binder. The cement is effective in the temperature range between minus 20 degree Celsius to 50 degree Celsius with additives. Additive C is used in cold weather and additive H is used in hot weather.
Setting time
The scientists recommend use of hot water at just 28 degree C mixed with Additive L, a lime-based compound. The chemical reaction due to lime mixing with water produces heat and Rapigrout uses this indigenous heat to set rapidly.
It is well known that normal cement used in construction takes 7 days to reach normal level of curing provided it is constantly kept wet. A total of 28 days are needed for the cement concrete to set fully. Further, as authenticated by Border Roads Organization, at Himalayan heights, curing takes much longer due to sustained low temperatures.
On the other hand, Rapigrout takes just 10 minutes for initial setting and in 25 minutes, it sets finally.
Laboratory tests after 100 minutes reported results with the test blocks able to withstand 100 kilo gram per square centi metre load.
A crater of 12 m diameter and having 2 m depth at the deepest point needs about 12,000 cubic metre of slurry. Water content needed varies - in cold weather it is less than 28 per cent of the total weight of Rapigrout used; in hot weather 32 per cent water content is sufficient. Pre-packed aggregate of 47 milli metre size — a little less than two inch size — is mixed with this very finely powdered cement. Fineness of the cement particles
is better than in normal
cement. The finer it is the faster it strengthens.
Rapigrout has a shelf life of two years and can be stored at a temperature range of minus 20 degree C and plus 50 degree C in
airtight containers. Cost of Rapigrout is estimated to be five or six times the Rapid Acting cement.
R&D E does not want to give away full details and commercialisation is still some time away. A leading cement manufacturing company has signed a Memorandum of
Understanding with DRDO to facilitate research, trial and manufacture.
Building a Helipad or helicopter landing ground, using Rapigrout is yet to be tried - or, if it has been tried - is not admitted to.
The minimum area needed to land and take off with Helicopter is a circle of 15 m diameters.
Just 24 hours!
Preparing the slurry with appropriate additive will take some time, to be spread evenly on the
prepared site. The mix sets in less than two hours and is ready for operation. The whole helipad can be built in 24 hours.
Friday, 2 October 2015
SILT TEST FOR SAND
Silt test.
The silt test is carried out to determine the amount of silt, clay or other fine dust that may be present in a sand sample. The presence of such in a sand used in concrete will reduce the strength of the hardened concrete if exceeds a permitted limit. The permitted limit is 8 percent.
Equipment used:
Sample of sand, Saline solution (one per cent common saltwater), graduated cylinder and calculator.
Method:
•Put 50 ml of saline solution into the graduated cylinder.
•Continue to add sand up the 100 ml mark.
•Add more saline solution until the 150 mark is reached.
•Shake well covering the top of the graduated cylinder with your hand.
•Allow to settle for three hours.
•Measure the heights of both sand and silt respectively.
•Calculate the amount of silt as a percentage of the amount of sand.
Calculating the percentage using the following formula:
Height of silt layer X100 = percentage of silt present
Height of sand layer
( Er. Ashish Srivastava )
The silt test is carried out to determine the amount of silt, clay or other fine dust that may be present in a sand sample. The presence of such in a sand used in concrete will reduce the strength of the hardened concrete if exceeds a permitted limit. The permitted limit is 8 percent.
Equipment used:
Sample of sand, Saline solution (one per cent common saltwater), graduated cylinder and calculator.
Method:
•Put 50 ml of saline solution into the graduated cylinder.
•Continue to add sand up the 100 ml mark.
•Add more saline solution until the 150 mark is reached.
•Shake well covering the top of the graduated cylinder with your hand.
•Allow to settle for three hours.
•Measure the heights of both sand and silt respectively.
•Calculate the amount of silt as a percentage of the amount of sand.
Calculating the percentage using the following formula:
Height of silt layer X100 = percentage of silt present
Height of sand layer
( Er. Ashish Srivastava )
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