Aggregate Crushing Value

1.0 Introduction

The principal mechanical properties required in stones are satisfactory resistance to crushing under the roller during construction and adequate resistance to surface abrasion under traffic.

Aggregates used in road construction, should be strong enough to resist crushing under traffic wheel loads. If the aggregates are weak, the stability of the pavement structure is likely to be adversely affected. The strength of coarse aggregates is assessed by aggregates crushing test. The crushing value provides a relative measure of resistance to crushing under a gradually applied compressive load. To achieve a high quality of pavement, aggregate possessing low aggregate crushing value should be preferred.

2.0 Objective

To ascertain the hardness of the aggregate.

3.0 Apparatus

1. Open ended steel cylinder of nominal 150mm internal diameter with plunger and base plate (plate 7)

Figure 3.1: Open ended steel cylinder

2. A tamping rod with a 16mm diameter and 600mm long.

Figure 3.2: Tamping rod

3. British standard sieves of sizes 14.0mm, 10.0mm and 2.36mm.

Figure 3.3: Sieve size 2.36mm

4. Compression testing machine which capable of applying force of 400kN.

Figure 3.4 Crushing machine

5. Cylindrical metal measures for measuring the sample.

Figure 3.5: Cylindrical metal measure

4.0 Methodology

a)    The cylinder of the apparatus is filled in 3 layers, each layer tamped with 25 blows of a tamping rod.

b)    The weight of aggregates is measured.

c)    The surface of the aggregates is then leveled and the plunger inserted.

d)     The apparatus is then placed in the compression testing machine and loaded at a uniform rate so as to achieve 40kN load in 10 minutes.

e)    After this, the load is released and crushed materials are removed.

f)     The sample is then sieved through a 2.36mm IS Sieve and the fraction passing through the sieve is weighed.

  

5.0 Result

AGGREGATE CRUSHING VALUE (BS 812 PART: 3)

Sample	Weight of size (mm)	Weight if sample before crush (g)	Weight of sample after crushed (g)	Weight passing 2.36mm sieve (g)
A	14 – 10	2870	2207	663
B	14 – 10	2854	2238	616

Percent Wear (Ave)

22.34 %

Calculation

Sample A

 = Weight of sample before crush (g) - Weight of sample after crushed (g)

             =  2870 g – 2207 g

             = 663 g

Sample B

 = Weight of sample before crush (g) - Weight of sample after crushed (g)

             =  2854 g – 2238 g

             = 616 g

Average weight passing 2.36mm = 663 + 616

                                                                   2

                                                          = 639.5 g

Average weight before crush = 2870 + 2854

                                                                 2

                                                    = 2862 g

Percent wear (ave)

x 100 %

            = Average weight passing 2.36mm

x 100 %

               Average weight before crush

            = 639.5

               2862

            = 22.34 %

              

6.0 Discussion

a)    Sample can expel from the mould because the mould not closed mould can affected the error measuring reading.

b)    Heavy crushing mould and machine may not relevance to do the work outside the laboratory.

c)    The crushing machine is damage and can’t do the experiment.

d)    Balance of 3kg minimum capacity are not achieving at this experiment.

7.0 Recommendation

a)    Upgrading the crushing mould to high collar mould to avoid the aggregate to expel from the mould and affected the reading.

b)    These experiments are done at the laboratory after taking the aggregate sample from sites.

c)    Consistence maintenance needs to do to the machine to avoid this kind of problem.

d)    Sample need to be taken double from the balance of 3kg minimum capacity to achieve the 3kg balance.

8.0 Conclusion

From the experiment, we get average percent wear are 22.34% still not exceeding JKR’s standard, <30%. So we can conclude that the aggregate crushing value provides a relative measure of the resistance of an aggregate to crushing under a gradually applied compressive load. The aggregate are mild tough to have the resistance pressure under traffic wheel loads such as car, lorry, motorcycle and etc. These aggregate have the stability of the pavement structure. It’s because the strength of coarse aggregates can effect the capability of the pavement to sustain.

9.0 Reference:

a)    Civil Engineering Portal. Aggregate Crushing Value Test. 1(1): [7 screen]. Available from: URL: http://www.engineeringcivil.com/aggregate-crushing-value.html

b)    Aggregate Crushing Value Apparatus. 1(1): [7 screen]. Available from: URL: http://www.thetestequipment.com/aggregate-crushing-value-apparatus.html

c)    LYS. Aggregate Crushing Value Test (BS 812: Part 3). Editted October 28, 2010.  1(1): [8 screen]. Available from: URL: http://scienceray.com/technology/aggregate-crushing-value-test-bs-812-part-iii/

d)    Aggregate Crushing Value. 1(1): [8 screen]. Available from: URL: http://civil-online2010.blogspot.com/2010/02/aggregate-crushing-value_10.html

e)    Muniandy R., Radin Umar Radin Sohadi. Highway Materials, A Guide Book For Beginners. University Putra Malaysia: Penerbit Universiti Putra Malaysia; 2010.

f)     Paul H.W., Karen K.D. Highway Engineering [Seventh Edition]. USA: John Wiley & Son; 2003.

Highway Lab report

Highway Engineering Laboratory Report

Aggregate Crushing Value

Aggregate Impact Value

Basic Concept of Electric Circuit

Subdivision in Electrical Engineering

•Communication systems

•Computer systems

•Control systems

•Electromagnetic

•Electronics

•Photonics

•Power systems

•Signal processing

Electric Current

•The time rate of flow of electrical charge passing through a predetermined area of a conductor.

•The unit is in Ampere [A]

•Constant current of 1[A]=1[C/s]

Fluid Flow Analogy

•Electrical circuits are analogous to fluid flow systems.

•Battery = Pump

•Charge=Fluid

•Conductors (Copper wires)=pipes

•Current=Flow rate of the fluid

•Voltage=Pressure difference between points in the fluid circuit

Switches=Valves

Kirchhoff’s Current Law(KCL)

•A node in an electrical circuit is a point at which two ore more circuit elements are joined together.

•The net current entering a node is zero.

•Current entering---------- (+)

•Current leaving------------ (-)

•I1+I2-I3=0

•Another way to state KCL: The sum of currents entering a node equals the sum of currents leaving a node.

•I1+I2=I3

•No current is lost around the closed circuit

•The sum of the currents at a node must equal to zero

How voltage, current, and resistance relate

An electric circuit is formed when a conductive path is created to allow free electrons to continuously move. This continuous movement of free electrons through the conductors of a circuit is called a current, and it is often referred to in terms of "flow," just like the flow of a liquid through a hollow pipe.

The force motivating electrons to "flow" in a circuit is called voltage. Voltage is a specific measure of potential energy that is always relative between two points. When we speak of a certain amount of voltage being present in a circuit, we are referring to the measurement of how much potential energy exists to move electrons from one particular point in that circuit to another particular point. Without reference to twoparticular points, the term "voltage" has no meaning.

Free electrons tend to move through conductors with some degree of friction, or opposition to motion. This opposition to motion is more properly called resistance. The amount of current in a circuit depends on the amount of voltage available to motivate the electrons, and also the amount of resistance in the circuit to oppose electron flow. Just like voltage, resistance is a quantity relative between two points. For this reason, the quantities of voltage and resistance are often stated as being "between" or "across" two points in a circuit.

To be able to make meaningful statements about these quantities in circuits, we need to be able to describe their quantities in the same way that we might quantify mass, temperature, volume, length, or any other kind of physical quantity. For mass we might use the units of "kilogram" or "gram." For temperature we might use degrees Fahrenheit or degrees Celsius. Here are the standard units of measurement for electrical current, voltage, and resistance:

The "symbol" given for each quantity is the standard alphabetical letter used to represent that quantity in an algebraic equation. Standardized letters like these are common in the disciplines of physics and engineering, and are internationally recognized. The "unit abbreviation" for each quantity represents the alphabetical symbol used as a shorthand notation for its particular unit of measurement. And, yes, that strange-looking "horseshoe" symbol is the capital Greek letter Ω, just a character in a foreign alphabet (apologies to any Greek readers here).

Each unit of measurement is named after a famous experimenter in electricity: The amp after the Frenchman Andre M. Ampere, the volt after the Italian Alessandro Volta, and the ohm after the German Georg Simon Ohm.

The mathematical symbol for each quantity is meaningful as well. The "R" for resistance and the "V" for voltage are both self-explanatory, whereas "I" for current seems a bit weird. The "I" is thought to have been meant to represent "Intensity" (of electron flow), and the other symbol for voltage, "E," stands for "Electromotive force." From what research I've been able to do, there seems to be some dispute over the meaning of "I." The symbols "E" and "V" are interchangeable for the most part, although some texts reserve "E" to represent voltage across a source (such as a battery or generator) and "V" to represent voltage across anything else.

All of these symbols are expressed using capital letters, except in cases where a quantity (especially voltage or current) is described in terms of a brief period of time (called an "instantaneous" value). For example, the voltage of a battery, which is stable over a long period of time, will be symbolized with a capital letter "E," while the voltage peak of a lightning strike at the very instant it hits a power line would most likely be symbolized with a lower-case letter "e" (or lower-case "v") to designate that value as being at a single moment in time. This same lower-case convention holds true for current as well, the lower-case letter "i" representing current at some instant in time. Most direct-current (DC) measurements, however, being stable over time, will be symbolized with capital letters.

One foundational unit of electrical measurement, often taught in the beginnings of electronics courses but used infrequently afterwards, is the unit of the coulomb, which is a measure of electric charge proportional to the number of electrons in an imbalanced state. One coulomb of charge is equal to 6,250,000,000,000,000,000 electrons. The symbol for electric charge quantity is the capital letter "Q," with the unit of coulombs abbreviated by the capital letter "C." It so happens that the unit for electron flow, the amp, is equal to 1 coulomb of electrons passing by a given point in a circuit in 1 second of time. Cast in these terms, current is the rate of electric charge motion through a conductor.

As stated before, voltage is the measure of potential energy per unit charge available to motivate electrons from one point to another. Before we can precisely define what a "volt" is, we must understand how to measure this quantity we call "potential energy." The general metric unit for energy of any kind is the joule, equal to the amount of work performed by a force of 1 newton exerted through a motion of 1 meter (in the same direction). In British units, this is slightly less than 3/4 pound of force exerted over a distance of 1 foot. Put in common terms, it takes about 1 joule of energy to lift a 3/4 pound weight 1 foot off the ground, or to drag something a distance of 1 foot using a parallel pulling force of 3/4 pound. Defined in these scientific terms, 1 volt is equal to 1 joule of electric potential energy per (divided by) 1 coulomb of charge. Thus, a 9 volt battery releases 9 joules of energy for every coulomb of electrons moved through a circuit.

These units and symbols for electrical quantities will become very important to know as we begin to explore the relationships between them in circuits. The first, and perhaps most important, relationship between current, voltage, and resistance is called Ohm's Law, discovered by Georg Simon Ohm and published in his 1827 paper, The Galvanic Circuit Investigated Mathematically. Ohm's principal discovery was that the amount of electric current through a metal conductor in a circuit is directly proportional to the voltage impressed across it, for any given temperature. Ohm expressed his discovery in the form of a simple equation, describing how voltage, current, and resistance interrelate:

In this algebraic expression, voltage (E) is equal to current (I) multiplied by resistance (R). Using algebra techniques, we can manipulate this equation into two variations, solving for I and for R, respectively:

Let's see how these equations might work to help us analyze simple circuits:

In the above circuit, there is only one source of voltage (the battery, on the left) and only one source of resistance to current (the lamp, on the right). This makes it very easy to apply Ohm's Law. If we know the values of any two of the three quantities (voltage, current, and resistance) in this circuit, we can use Ohm'sLaw to determine the third.

In this first example, we will calculate the amount of current (I) in a circuit, given values of voltage (E) and resistance (R):

What is the amount of current (I) in this circuit?

In this second example, we will calculate the amount of resistance (R) in a circuit, given values of voltage (E) and current (I):

What is the amount of resistance (R) offered by the lamp?

In the last example, we will calculate the amount of voltage supplied by a battery, given values of current (I) and resistance (R):

What is the amount of voltage provided by the battery?

Ohm's Law is a very simple and useful tool for analyzing electric circuits. It is used so often in the study of electricity and electronics that it needs to be committed to memory by the serious student. For those who are not yet comfortable with algebra, there's a trick to remembering how to solve for any one quantity, given the other two. First, arrange the letters E, I, and R in a triangle like this:

If you know E and I, and wish to determine R, just eliminate R from the picture and see what's left:

If you know E and R, and wish to determine I, eliminate I and see what's left:

Lastly, if you know I and R, and wish to determine E, eliminate E and see what's left:

Eventually, you'll have to be familiar with algebra to seriously study electricity and electronics, but this tip can make your first calculations a little easier to remember. If you are comfortable with algebra, all you need to do is commit E=IR to memory and derive the other two formulae from that when you need them!

• REVIEW:
• Voltage measured in volts, symbolized by the letters "E" or "V".
• Current measured in amps, symbolized by the letter "I".
• Resistance measured in ohms, symbolized by the letter "R".
• Ohm's Law: E = IR ; I = E/R ; R = E/I

source: How voltage, current, and resistance relate

COMPETITIVE MARKET

COMPETITIVE MARKET:

A market with a large number of buyers and sellers, such that no single buyer or seller is able to influence the price or control any other aspect of the market. That is, none of the participants have significant market control. A competitive market achieves efficiency in the allocation of scarce resources if no other market failures are present.

A competitive market is a market with a sufficient number of both buyers and sellers such than no one buyer or seller is able to exercise control over the market or the price. Efficiency is achieved because competition among buyers forces buyers to pay their maximum demand price and competition among sellers forces sellers to charge their minimum supply price for the given quantity exchanged.

Working the Market Model

Competitive Market

The market model presented here depicts a typical competitive market that has achievedequilibrium. The market demand curve is labeled D and the marketsupply curve is labeled S. Competition among buyers forces the market price up to the maximum demand price on the demand curve. Competition among sellers forces the market price down to the minimum supply price on the supply curve. With competition among both buyers and sellers, the market price is simultaneously on both the demand curve and the supply curve.

This result is illustrated by the market equilibrium achieved at price Po and quantity Qo. The competitive forces of demand and supply automatically generate this market equilibrium. If the going market price is higher or lower than Po, creating a shortage or surplus, then competitive forces eliminate the imbalance and restores equilibrium.

The Invisible Hand of Efficiency

A competitive market is efficient because equilibrium is achieved where the demand price and supply are price equal.

• Competition on the demand side forces buyers to buy a good at the maximum demand price that they are willing and able to pay. The demand price is the value society places on the good produced based on the satisfaction received.
• Competition on the supply side forces sellers to sell the good at the minimum supply price that they are willing and able to accept. The supply price is the opportunity cost of production, which is the value of goods NOT produced.

Equality between the demand and supply prices means that the economy cannot generate any greater satisfaction by producing more of one good and less of another.

Competitive markets are the cornerstone of capitalism and a market-oriented economy. They efficiently address the scarcity problem and answer the three questions of allocation automatically (as if guided by aninvisible hand) with little or no government intervention.

Uncompetitive Markets

The real world contains some markets that come close to this competitive ideal and other markets that fall short. These real world markets can be grouped into three distinct market structures.

• Monopolistic/Monopsonistic Competition: The most competitive real world markets are termed monopolistic competition or monopsonistic competition, depending on whether the focus is on the sellers (monopolistic) or the buyers (monopsonistic).
• Oligopoly/Oligopsony: Real world markets with a modest amount of competition, but not a lot, are termed oligopoly or oligopsony, depending on whether the focus is on the sellers (oligopoly) or the buyers (oligopsony).
• Monopoly/Monopsony: Real world markets that have no competition are termed monopoly, if there is only one seller, or monopsony, if there is only one buyer.

Other Market Failures

Competitive markets achieve an efficient allocation of resources as long as other market failures are not present. The lack of competition, also termed market control, is one key market failure. Three noted market failures are externalities, public goods, and imperfect information.

• Externalities arise if the demand price does not fully reflect the value generated by the good or if the supply price does not fully reflect the opportunity cost production. As a result, the market equilibrium does not include all of the information about value and cost needed to achieve efficiency.
• Public goods are goods characterized by nonrival consumption and the inability to exclude nonpayers. The use of the good by one does not impose a cost on others and no one can be prevented from consuming the good.
• Imperfect information occurs if buyers or sellers do not know as much about the good as they should for an efficient allocation. In other words, buyers are not aware of the full value they obtain from consuming the good or sellers are not aware of all opportunity cost incurred in production.

source: Competitive Market