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Concrete is a mixture of cementious material, aggregate, and water. Aggregate is commonly considered inert filler, which accounts for 60 to 80 percent of the volume and 70 to 85 percent of the weight of concrete. Although aggregate is considered inert filler, it is a necessary component that defines the concrete’s thermal and elastic properties anddimensional stability. Aggregate is classified as two different types, coarse and fine. Coarse aggregate is usually greater than 4.75 mm (retained on a No. 4 sieve), while fine aggregate is less than 4.75 mm (passing the No. 4 sieve). The compressive aggregate strength is an important factor in the selection of aggregate. When determining the strength of normal concrete, most concrete aggregates are several times stronger than the other components in concrete and therefore not a factor in the strength of normal strength concrete. Lightweight aggregate concrete may be more influenced by the compressive strength of the aggregates.

Other physical and mineralogical properties of aggregate must be known before mixing concrete to obtain a desirable mixture. These properties include shape and texture, size gradation, moisture content, specific gravity, reactivity, soundness and bulk unit weight. These properties along with the water/cementitious material ratio determine thestrength,workability, anddurabilityof concrete.

The shape and texture of aggregate affects the properties of fresh concrete more than hardened concrete. Concrete is more workable when smooth and rounded aggregate is used instead of rough angular or elongated aggregate. Most natural sands and gravel from riverbeds or seashores are smooth and rounded and are excellent aggregates. Crushed stone produces much more angular and elongated aggregates, which have a higher surface-to-volume ratio, better bond characteristics but require more cement paste to produce a workable mixture.

The surface texture of aggregate can be either smooth or rough. A smooth surface can improve workability, yet a rougher surface generates a stronger bond between the paste and the aggregate creating a higher strength.

The grading or size distribution of aggregate is an important characteristic because it determines the paste requirement for workable concrete. This paste requirement is the factor controlling the cost, since cement is the most expensive component. It is therefore desirable to minimize the amount of paste consistent with the production of concrete that can be handled, compacted, and finished while providing the necessary strength and durability. The required amount of cement paste is dependent upon the amount of void space that must be filled and the total surface area that must be covered. When the particles are of uniform size the spacing is the greatest, but when a range of sizes is used the void spaces are filled and the paste requirement is lowered. The more these voids are filled, the less workable the concrete becomes, therefore, a compromise between workability and economy is necessary.

Themoisture contentof an aggregate is an important factor when developing the proper water/cementitious material ratio. All aggregates contain some moisture based on the porosity of the particles and the moisture condition of the storage area. The moisture content can range from less than one percent in gravel to up to 40 percent in very porous sandstone and expanded shale. Aggregate can be found in four different moisture states that include oven-dry (OD), air-dry (AD), saturated-surface dry (SSD) and wet. Of these four states, only OD and SSD correspond to a specific moisture state and can be used as reference states for calculating moisture content. In order to calculate the quantity of water that aggregate will either add or subtract to the paste, the following three quantities must be calculated: absorption capacity, effective absorption, and surface moisture.

Most stockpiled coarse aggregate is in the AD state with an absorption of less than one percent, but most fine aggregate is often in the wet state with surface moisture up to five percent. This surface moisture on the fine aggregate creates a thick film over the surface of the particles pushing them apart and increasing the apparent volume. This is commonly known as bulking and can cause significant errors in proportioning volume.

The density of the aggregates is required in mixture proportioning to establish weight-volume relationships. Specific gravity is easily calculated by determining the densities by the displacement of water. All aggregates contain some porosity, and the specific gravity value depends on whether these pores are included in the measurement. There are two terms that are used to distinguish this measurement; absolute specific gravity and bulk specific gravity. Absolute specific gravity (ASG) refers to the solid material excluding the pores, and bulk specific gravity (BSG), sometimes called apparent specific gravity, includes the volume of the pores. For the purpose of mixture proportioning, it is important to know the space occupied by the aggregate particles, including the pores within the particles. The BSG of an aggregate is not directly related to its performance in concrete, although, the specification of BSG is often done to meet minimum density requirements.

For mixture proportioning, the bulk unit weight (a.k.a. bulk density) is required. The bulk density measures the volume that the graded aggregate will occupy in concrete, including the solid aggregate particles and the voids between them. Since the weight of the aggregate is dependent on the moisture content of the aggregate, a constant moisture content is required. This is achieved by using OD aggregate. Additionally, the bulk density is required for the volume method of mixture proportioning.

The most commonclassification of aggregateson the basis of bulk specific gravity is lightweight, normal-weight, and heavyweight aggregates. In normal concrete the aggregate weighs 1,520 – 1,680 kg/m3, but occasionally designs require either lightweight or heavyweight concrete. Lightweight concrete contains aggregate that is natural or synthetic which weighs less than 1,100 kg/m3and heavyweight concrete contains aggregates that are natural or synthetic which weigh more than 2080 kg/m3.

Although aggregates are most commonly known to be inert filler in concrete, the different properties of aggregate have a large impact on the strength, durability, workability, and economy of concrete. These different properties of aggregate allow designers and contractors the most flexibility to meet their design and construction requirements.

can u explain in short

Cement is a glue. It holds aggregates to withstand compression. 100 % aggregate would theoretically limit the compression to that of aggregate itself. In reality, good compaction of concrete can not be done with larger aggregates in over abundance using traditional vibratory methods . There would be large number of air pockets as these aggregates get stuck due to their sizes. Therefore, one needs an optimal distribution of aggregates of different sizes, which would slip seamlessly into the smaller and smaller gaps. When everything flows correctly during compaction, one can obtain a dense concrete with least amount of water:cement ratio, with little voids. That's the secret of obtaining higher compressive strength. W:C ratio is so important, that a small number of air voids and bug holes (at outer surface) are considered acceptable, removing them by increasing water content would actually make the concrete weaker. The answer to your question lies in proportion of the coarse aggregate in overall mix (assuming it has uniform size), and it's relation to size distribution of smaller ‘particles’ . An overabundance of coarse aggregate would generally produce a weaker concrete as it would be difficult to compact in real life using vibration.

This should not apply as rigidly when using super plasticizers, they are otherwise reserved for crowded places using higher content of smaller aggregate or sand. Primary reason for limiting their use to such applications is cost. I would hypothesize, using super plasticizers one should be able to use a mix with larger aggregates in relative excess, especially in applications like making a floor. Pushing content of coarse aggrgates to extreme, one may be able to harness superior compression approaching closer and closer to that of coarse aggregate itself, but this material would not flow well around densely set rebars, thus may end up being weaker if applied without forethought.

On another note, if I have an excess of large aggregates, and the project is a small homely one, there is a way to obtain optimal results making something like a floor. At the very bottom pour a good mix, then, manually sprinkle large aggregate or chunks (such as pieces of old concrete) on the top, bury this with good concrete, srinkle again, and repeat as needed. Top with good concrete. Here we are visually ensuring that larger aggregate is getting surrounded by good concrete. Excellent compaction can be achieved with vibration. If cost is not an issue, such as spare superplasticizer laying around, it can make it very easy utilizing any remaining excess of coarse aggregate.

Velocity = dispacement / timeSpeed = distance / time

a) when he jogs from A to B on a straight road,displacement = distance = 300mtime = 2 minutes 30 seconds = 150 s

velocity = 300/150 = 2 m/sspeed = 300/150 = 2m/s

b)when he jogs from A to B and turns back to C,displacement = 300-100 = 200mdistance = 300+100 = 400mtime = 3 minute 30 second = 210 s

velocity = 200/210 = 20/21 m/sspeed = 400/210 = 40/21 m/s

I)A=Bit)A=Biii)A is not=Bif)A=Bv)A is not=B

1. A=B

2.A=B

3.A is not B

4.A=B

5. A is not B

option d is write answer

H=i^2Rthence heat produced is directly proportional to resistancehence if resistance is tripled heat will be tripledand if resistance is one third then heat will be one third

Angular velocity of earth is

2πr/time of day in seconds

r = radian subtended by radius of earth

2π r/ 86400 =

7.25 × 10 ^ -5

Radians / sec

It stays the same, no matter how long or thick your conductor is. That is not to say thatresistivitycannotchange. Itvarieswith temperature. So there is nochange with lengthinresistivitybut resistancechangesin direct proportion withlengthof the conductor

10 = 1.6 * 10^-8 * l/(π*25*10^-8)l=250π/1.6=2500π/16=625π/4 m

b. R is proportional to 1/d^2thus Resistance is one fourth

i) The Resistance Will increase by 4ii) There Will be no change in resistivity because resistivity does not depend on leng th and area of cross section.

Resistance=resistivity*length/areahence if length is doubled are area halvedresistance will become 4 timesand resistivity will become 1/4th times

It is because of the inertia of motion. The lower part of our body is in contact with the bus. As the bus is moving our whole body is moving along with it. As the bus stops, our lower body also stops with it as it is in contact whereas our upper body tends to remain in the state of motion due to inertia of motion and we fall forward. By the way nice question

can answer this question in malayalam

no we answer only in English

ok tnkzzz nice answer

how we identify it is inertia of mation or inertia of rest

what u didn't understand...what to identify about

how will identify the question is inertia of motion or inertia of rest

can u answe this question in manglish

c is the right answer

option (c) is correct.

can I please elaborate

thank u

Tree age measurement- When you make cross section of the trunk you'll see some rings. This annual ring formation is so regular, for this reason the age of a tree may be accurately calculated simply by counting the rings "each ring represents one year of growth". Because the vascular cambium suspends its activity during fall and winter when the tree becomes dormant, ring growth occurs only during spring and summer. Each annual ring consists of several layers of large xylem cells, referred to as springwood, followed by progressively smaller cells, the summerwood.

Tree volume measurement-1-Tree climbers can physically measure the height and circumference of a tree using a tape. The distance from the highest climb point and the top of the tree is measured using a pole that extends from the tree top to the anchor point of the tape. This height is noted and the diameter of the tree is measured at that point. The climber then rappels down the tree measuring the trunk circumference by tape wrap at different heights with the height of each measurement referenced to the fixed tape running down the trunk.

2-Remote measurements of trunk volume are usually made from a position on the ground where the observer has a clear view of the entire length of the trunk. Measurements may be made using professional surveying equipment such as a total station

thank you so much mam

mam I need a notes

Thepower of a lensis the reciprocal ofitsfocal length in meters. It is represented by the letter P. ThepowerP of alensof focal length f is given by f = 1/P. TheSI unitofpoweris dioptre .

Drawbacks/Demerits of Mendeleev's periodic table :-

1) Hydrogen's positionHydrogen resembled the properties of both alkali metals(like lithium) and also that of halogens(like iodine). Hence, the position of hydrogen(whether hydrogen is to be placed with halogens or alkali metals) was not specified.

2) Position for IsotopesIsotopes are those with same atomic no: and different mass no:s.Mendeleev'speriodic table was based on arranging elements in increasing order of atomic masses. But isotopes were not included in his periodic table.

3) Certain elements were arranged in reverse order. Elements having higher atomic mass were placed in front(or before) the elements with less atomic mass. Example - Cobalt and NickelCobalt being more heavier than Nickel ,was placed before Nickel , in the Mendeleev's periodic table.

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b)

Lunar Exploration Module (LEM) nick-named ‘Eagle’

the answer is odometer

The answer will be Odometer.

the correct answer is odometer

Ans :- The major features of the model are as follows.

1 All protons are present inside the nucleus, which is situated at the center of the atom.

2. Electrons reside outside the nucleus and revolve around the nucleus in well-defined orbits.

3. The size of the nucleus is very small in comparison to the size of an atom. As per Rutherford’s calculations, the size of the nucleus is 105times smaller than an atom.

Force on a current carrying conductor in the presence of a magnetic field is explained using Fleming's Left Hand Rule According toFleming’s left-hand rule, if we stretch the thumb,forefinger and middle finger of our left handsuch that they are mutually perpendicular to each other,If the first finger points in thedirection of magnetic field and the secondfinger in the direction of current, then thethumb will point in the direction of motion (the force acting on the conductor.)

In electrostatics free charges in a goodconductorreside only on the surface. So the free chargeinsidetheconductoris zero. So thefieldin it is caused by charges on the surface. Since charges are of the same nature and distribution is UNIFORM, theelectricfields cancel each other.

In electrostatics free charges in a goodconductorreside only on the surface. So the free chargeinsidetheconductoris zero. So thefieldin it is caused by charges on the surface. Since charges are of the same nature and distribution is UNIFORM, theelectricfields cancel each other.

When a charge is moved from one point to another along some equipotential surface, it is true that the work done on the chargeby the electric fieldis zero. Additional work done on the particle over this path depends on how the particle is moved. If the particle is initially moving in the correct direction, then obviously no work is required. This is why the Moon is able to maintain its motion along an (approximate) gravitational equipotential without an army of angels diligently pushing it on it's path.

But if you are moving a particle from one position at rest to a second position at rest, along the equipotential, some external agent supplying work is needed to start and stop the particle. However, you in principle you could make this motion arbitrary slow over arbitrarily long times, so that at any point along the path it's kinetic energy is indistinguishable from zero, hence zero change in kinetic energy along the path, hence zero work necessary.