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MARSHALL STABILITY TEST FOR SDAC (Semi Dense Asphalt Concrete )

Description of Test

The Marshall Method for hot-mix asphalt concrete mix design is a rational approach to

selecting and proportioning two materials, asphalt cement and mineral aggregates to

obtain the specified properties in the finished asphalt concrete surfacing structure. The

method is intended for laboratory design of asphalt hot-mix paving mixtures.

1.2.

Application of the Test

The objective to be achieved using the Marshall Method for hot-mix asphalt concrete mix

design is to determine an economical blend and gradation of aggregates (within the limits

of project specifications) and asphalt that yields a mix having;

1. Sufficient asphalt cement to ensure a durable asphalt concrete surface course.

2. Sufficient mix stability to satisfy the demands of traffic without distortion or

displacement.

3. Sufficient voids in the total compacted mix to allow for a slight amount of

additional compaction under traffic loading without flushing, bleeding and loss of stability, yet low enough to keep out harmful air and moisture.

4. Sufficient workability to permit efficient placement of the mix without segregation.

5. Characteristics which allow normal construction operating variations without

falling outside of the specified requirements.

1.3.

Units of Measure

The units of measure will be as specified in the individual procedures that are used in the

Marshall Mix Design analysis.

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2.

APPARATUS AND MATERIALS

2.1.

Equipment Required

Refer to:

STP 204-8 Preparation of Marshall Compaction Specimens

STP 204-9 Theoretical Maximum Specific Gravity

STP 204-11 Marshall Stability and Flow

STP 204-15 Stripping Potential

STP 204-19 Asphalt Film Thickness Determination

STP 204-20 Hveem Stability

STP 204-21 Marshall Compaction Specimens - Density and Void Characteristics

Determination

STP 204-22 Retained Marshall Stability

STP 206-4 Plasticity Index Coarse Grained Soils

STP 206-5 Sand Equivalent

STP 206-7 Specific Gravity - Bulk, Apparent

STP 206-9 Lightweight Pieces in Aggregate

STP 206-14 Percent Fractured Faces in Aggregate

STP 206-15 Clay Lumps and Friable Particles in Aggregate

2.2.

Materials Required

Refer to the Standard Test Procedures as outlined in 2.1 above.


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2.3.

Sample to be Tested

Representative samples of all aggregate components to be used on the project and asphalt

cement of the same grade and from the same manufacturer as will be used for the field

work.

2.3.1.

Obtaining Required Gradation For Each Aggregate Component

Dry the samples of aggregate in the oven for approximately 18 hours at 105

o

C to

110

o

C. Separate aggregate into individual sieve sizes by dry sieving. Select the

sieve sizes corresponding to the specifications for the "type" of

Recombine individual aggregate fractions in correct proportions to obtain the

average stockpile gradation which is submitted from the field along with the

sample. Use a trial and error method as described in the following paragraph.

Combine trial percentages of each size, then run a wet sieve and compare the

result to the stockpile average. Adjust the proportions of each size and repeat the

procedure until the desired gradation is achieved. Use the final percentages of

each size to produce specimens as required later in the procedure.

2.4.

Data Required

The following data is required for each proposed aggregate gradation when preparing a

Marshall Mix Design;

Lightweight Pieces in Aggregate

Plasticity Index of the Aggregate

and Equivalent of the Aggregate

Percent Fractured Faces in the Aggregate

Clay Lumps and Friable Particles in Aggregate

Theoretical Maximum Specific Gravity for each asphalt/aggregate combination

Specific gravities for all aggregate fractions

Density, air voids and voids in mineral aggregate determination for each asphalt/aggregate

combination

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Marshall stability and flow for each asphalt/aggregate combination

Stripping Potential Analysis on the recommended mix design

Hveem stability on the recommended mix design

Retained stability for the recommended mix design

Asphalt film thickness determination for the design aggregate gradation at each asphalt

content evaluated.

3.

PROCEDURE

3.1.

Test Procedure

Prepare two or more initial trial specimens as described in STP 204-8 at an estimated

optimum asphalt content. Use the combined stockpile gradation of the natural split for

one set of molds.

Determine the Marshall Mix Design characteristics using STP 206-7, 204-21, 204-9 and

204-11.

Compare the Marshall properties for the trial molds with SHT specified properties for that

aggregate type and asphalt type.

If the Marshall properties for one of the chosen gradations are satisfactory, proceed with

the full design procedure. If the properties are obviously outside the range, make further

adjustments by changing split combinations or adding blenders/fillers. Estimate by

plotting the gradation on an e

.45

graph and comparing to the theoretical maximum density

line (a line drawn between the origin and the point where the gradation line crosses 90%

passing). Continue until the properties are satisfactory.

Using the procedures previously described, prepare a series of Marshall specimens in

triplicate at four asphalt contents (by weight of dry aggregate) to bracket optimum.

Determine the Marshall properties for each specimen and average the results of the

triplicates at each asphalt content.

On a graph MR-71 or EPS-71, plot the Marshall properties (density, air voids, VMA and

Marshall stability) as a function of asphalt content.

Select optimum asphalt for each property; for density and stability use the peak of the

curves and for VMA use the low point. For air voids, select the optimum asphalt content

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where air voids are 0.5 to 0.75% above the minimum specified value for that particular

asphalt type.

After selecting optimum asphalt from each graph average the values and use this new

asphalt content for further design requirements (Stripping Potential, Hveem stability,

Retained Stability, Asphalt Film Thickness).

4.

RESULTS AND CALCULATIONS

4.1.

Reporting Results

Marshall Mix Designs shall be reported on Form MR-71 or Form EPS-71 whichever is

applicable. Additional information on other options evaluated should be attached to the

formal design as an Appendix

St

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

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.

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.