Conclusions & Recommendations – The intent of our effort here is to find out how useful it is for the modern world civilizations to use concrete with reinforcement as two of the fundamental building materials. This project contains reinforced concrete beam bending and strength analysis for 3 different concrete blocks and also gives background and research information about concrete. The comparison of concrete blocks includes different amounts of water/cement ratios and also different sizes of reinforcement. The concrete were tested after a curing period of 15 days. A hydraulic concrete-beam testing machine was used to test the strength performance of the blocks. The maximum strength obtained was 10,040 lbs for the second sample. This was a good result since after 14,000 lbs of compression force concrete blocks are consider as high strength concrete in which the reinforcement rebar had a great contribution for increasing the summing strength. We take advantage of the existing hydraulic concrete-beam testing machine in the science department and began to make 3 concrete beams and test for their compression force. This machine would only test concrete-beam for its flexural force because concrete gives a very impressive amount of compressive strength and rebar gives a very good tensile strength.
This hydraulic compression is acting on both ends of the beam on one side and another force acting in the middle of the beam on the other side. Therefore the compression force of the concrete will push against the bending rebars, which it will contribute to the summing flexural strength. The following figure on the right side is a hydraulic concrete-beam testing machine showing how it would compress the concrete to determine it’s flexural strength. For us to get a sense of the strength of a concrete as well as how the reinforcements help contribute the flexural strength, we made 3 blocks of concretes under 2 different concrete mix proportions and 2 different sizes of rebars as reinforcement. Concrete for the first block contains a ratio 1:2:3 (water: cement: fines with aggregates) and two rebars with diameter 3/8-inch. The second block has the same concrete mix and two larger rebars with diameter 0.5-inch. Concrete for the last block contains a ratio 3:1:9 and two rebars with diameter 3/8-inch. The actual curing period was 15 days before we test the ultimate samples. The resulting flexural strengths for these 3 blocks were 5,980 lbs, 10,040 lbs, and 5,260 lbs respectively. Rounding up these results we can see that the magnitude of the flexural force that concrete with reinforcement can sustain is very huge that we can put trust on it when its used as the building materials.
The Essay on Force And Perfectly Elastic Question
Question no 9) A package is dropped from a helicopter moving upward at 15m/s If it takes16 sec before the package strikes the ground, how high above the ground was the package when it was released if air resistance is negligible? Ans) 1000m Question no. 11) If A -B = 0, then the vectors A and B have equal magnitudes and are directed in the opposite directions from each other. Ans) False Question ...
The real world usage and research of concrete is far more comprehensive than what we have done in this project. Therefore we included some interesting background and useful information about concrete that would help us understand more about the nature and application of concrete as we mention them through out the rest of this project. Our primary objective for this project is to find out how trustworthy it is to use concrete and reinforcement rebar as two of the fundamental building material. We decided to accomplish this mission by testing the concrete beam to determine the magnitude of the flexural strength it can sustain where this strength may or may not be good enough for a range of real world building applications.
Since our scope of work in this project does not contain a wider range of study and experiment for concrete and rebars, we choose to have a secondary objective: include some interesting information about concrete and reinforcements and provide some interesting and must know information about concrete that would be useful for students to have a sense about the usage of concrete and rebar in modern society. Cement, as we know today, the product with less than 200 years of history. Some was used in Europe as a cementing material made by heating naturally accruing mixture of limestone and clay in 1700’s. Greek and Roman builders discovered how to build limestones and make lime, which when we mix with water, formed cement that harden slowly. The invention of reinforced concrete led to use of concrete in buildings. Around 1920, the importance of water cement ratio became known, and many users began specifying a limit of water content and slump. By 1977 the precast concrete industry represented a capital investment of $1.1 billion in plants and facilities consuming thousand tons of cement annually and employing thousands of people. The familiar material that we know as concrete is actually a rather complex mixture of compounds, including Portland cement, sand, gravel or crushed rock, and water.
The Essay on Portland Cement Raw Material
... produced. This is the material that binds cement and concrete together. As hydration proceeds, water and cement are continuously consumed. ... lesser amounts make little direct contribution to strength. Set cement and concrete can suffer deterioration from attack by ... design and curing conditions. Structural properties. The strength developed by portland cement depends on its composition and the ...
When properly produced, the mixture gets hard and becomes a material with high strength, excellent durability, fire resistance, and water tightness. Cement and concrete are not the same. The difference between cement and concrete is, cement is a dry powder, it becomes a paste that binds the aggregate (sand and gravel) particles in to the solid when mixed with water. The fresh concrete is concrete in a plastic state. The cement has not hydrated, or set. The concrete has no definite shape; it can be molded or shaped with ease. One of the most important properties of fresh concrete is workability, which can be defined as the ease with which the concrete can be handled and placed in the forms with a minimum loss of homogeneity. Cementitious Materials of Different Types Categorization of cementitious materials: Originally, concrete was made using a mixture of only three materials: cement, aggregate, and water; almost invariably, the cement was Portland cement. Later on, in order to improve some of the properties of concrete, either to make it fresher or more hardened, small quantities of chemical products were added into the mix. These materials are called chemical admixtures.
The Essay on Arizona Concrete Portland Cement
Arizona Concrete John McCollamGeology 101, Section 12262 Randy Porch 20 November 1996 According to the Mine Faculty at the University of Arizona, cement is manufactured primarily from suitable limestone and shale rocks. Arizona had two dry-process cement plants in 1969, namely the Arizona Portland Cement Company plant in Pima County, near Tucson, and the American Cement Corporation plant ...
Other materials that are inorganic in nature were also introduced in the concrete mixture. The reason for the use of these materials was usually economic, since they were cheaper than Portland cement. Some of these materials were also byproducts or industrial wastes. Some of these materials are blast furnace slag, fly ash, and silica fume. According to ASTM if cement consists of two or more inorganic constituents, which contribute to the strength gaining properties, it is called hydraulic cement. (ASTM C 1157-94a) However, the American Concrete Institute does not use this terminology. Another terminology is that, if cement consists of Portland cement and one or more appropriate inorganic materials, it will be called blended cement. All of these materials called inorganic constituents or components have one in common that they contribute to the strength-gaining properties of the cement. All these cementitious materials are at least fine as the particles of Portland cement and sometimes even much finer. This is by far the most common cement that is used. About 90% of all cement used in the United States is ordinary Portland cement. Ordinary Portland (Type I) cement is admirably suitable for use in general concrete construction when there is no exposure to sulfates in the soil or groundwater.
The standard requirements for this kind is that it is made from 95 to 100 percent of Portland cement clinker and 0 to 5 percent of minor additional constituents, all by mass, the percentages being those of the total mass except calcium sulfate and manufacturing additives such as grinding aids. (Refer to attachment 1) This cement comprises Portland cement subclasses of 32.5 and 42.5 Mpa as prescribed by BS 12:1991. Rapid-hardening Portland cement (Type III), as its name implies, develops strength more rapidly, and should, therefore, be correctly described as high early strength cement. The increased rate of gain of strength of the rapid hardening is achieved by a higher C3S content (higher than 55 percent, but sometimes as high as 70 percent) and by a finer grinding of the cement clinker. (Refer to attachment 1) 3.Special very rapid-hardening Portland Cements: There exist several specially manufactured cements, which are particularly rapid hardening. One of these is so-called ultra high early strength cement. This type of cement is not standardized but rather supplied by individual cement manufacturers. Ultra high early strength cement has been used successfully in a number of structures where early pre-stressing or putting into service is important. (Refer to attachment 1) The rise in temperature in the interior of a large concrete mass due to heat development by the hydration of cement, coupled with a low thermal conductivity of concrete, can lead to serious cracking. For this reason, it is necessary to limit the rate of heat evolution of the cement used in this type of a structure: a greater proportion of the heat can then be dissipated and a lower rise in temperature results. Cement having such a low rate of heat development was first produced for use in large gravity dams in the United States, and is also known as low heat Portland cement (Type IV).
The Term Paper on Concrete Material
The exterior of the Guggenheim Museum is a stacked white cylinder of reinfored concrete swirling towards the sky. The museum’s dramatic curves of the exterior, however, had an even more stunning effect on the interior. Inside Wright proposed “one great space on a continuous floor,” and his concept was a success. Walking inside, a visitor’s first intake is a huge atrium, rising 92′ in height to an ...
However, for some time now, Type IV cement has not been produced in the United States. (Refer to attachment 1) There is a reaction between C3A and gypsum and of the consequent formation of calcium sulfo-aluminate. A second type of reaction is that of base exchange between calcium hydroxide and the sulfates, resulting in the formation of gypsum. These reactions are known as sulfate attack. Sulfate attack is greatly accelerated if accompanied by alternating wetting and drying. The remedy lies in the use of cement with a low C3A content, and such cement is known as sulfate-resisting Portland cement. (Refer to attachment 1), (Picture 2) For architectural purposes, white concrete or a pastel color is sometimes required. To achieve best results it is advisable to use white cement with, of course, a suitable fine aggregate and, if the surface is to be treated, also an appropriate coarse aggregate. White cement has also the advantage that it is not liable to cause staining because it has a low content of soluble alkalis. Cements of this name consist of an intimate mixture of Portland cement and ground granulated blastfurnace slag. This slag is a waste product in the manufacture of pig iron, about 300 kg of slag being produced for each tone of pig iron. Chemically, slag is a mixture of lime, silica, and aluminum, that is, the same oxides that make up Portland cement but not in the same proportions.
The Essay on The Information Age Is Upon Us The Raw Materials Are
The information age is upon us. The raw materials are ones and zeros. The technology used to transport the ones and zeros provides numerous opportunities for entrepreneurs, scientists, and engineers. Telecommunications is dynamically changing the way we work, learn, communicate, and view society. At no other time in history have so many people been given the ability to exchange ideas, sell their ...
Supersulfated cement is made by intergrinding a mixture of 80 to 85 percent of granulated blastfurnace slag with 10 to 15 percent of calcium sulfate and up to 5 percent of Portland cement clinker. The cement has to be stored under very dry conditions as otherwise it deteriorates rapidly. Description of Cementitious Materials: Pozzolanas: On of the common materials classified as cementitious is pozzolana, which is natural or artificial material containing silica in a reactive form. A more formal definition of ASTM describes pozzonola as a siliceous and aluminious material, which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties. Fly ash, also known as pulverized-fuel ash, is the ash precipitated electro statically or mechanically from the exhaust gases of coal-fired power stations; it is the most common artificial pozzonola. (Attachment 5) Silica fume: This is a recent arrival among cementitious materials. It was originally introduced as a pozzonola. However, its action in concrete is not only that of a very reactive pozzonola but is also beneficial in other aspects.
It is a byproduct of the manufacture of silicon and ferrosilicon alloys from high-purity quartz and coal in a submerged-arc electric furnace. Silica in the form if glass is highly reactive, and the smallness of the particles speeds up the reaction with calcium hydroxide produced by the hydration of Portland cement. The very small particles of silica fume can enter the space between the particles of cement, and thus improve packing. (Attachment 5) Fillers: A filler is a very finely-ground material, of about the same fineness as Portland cement, which, owing to its physical properties, has a beneficial effect on some properties of concrete, such as workability, density, permeability, capillarity, bleeding, or cracking tendency. Fillers can be naturally occurring materials or processed inorganic mineral materials. What is essential is that they have uniform properties, and especially fineness. (Attachment 5) The wide variety of cement Types (in American nomenclature) and cement Classes (in European classification) and, above all, of cementitious and other materials used in blended cements, may result in a bewildering impression. Which cement is best? Which cement should be used for a given purpose? There is no simple answer to these questions but a rational approach will lead to satisfactory solutions.
Compare And Contrast Sample Essay
H2>SAMPLE ESSAY 1: Columbia, Athlete and Musician (sailing and bass guitar) Write a chapter from your autobiography. Chapter 34: One Memorable Sailing Practice The suns glare off the water forces my watery eyes to close even more. Spray leaps over the bow and blocks my vision as it slams into me like hundreds of little pebbles. The salt water has irritated my eyes enough already, but I am only ...
No single cement is the best one under all circumstances. Even if the cost is ignored, pure Portland cement is not the all-around winner. What is really important is that the appropriate cement should be used for a given purpose. More than one type or class of cement can be used. The choice depends on availability, on cost-that important element in engineering decision making- and on the particular circumstances of equipment, skilled labor force, speed of construction and, of course, on the exigencies of the structure and its environment. (Attachment 2) Because at least three-quarters of the volume of concrete is occupied by aggregate, it is not surprising that its quality is of considerable importance. Not only may the aggregate limit the strength of concrete, as aggregate with undesirable properties cannot produce strong concrete, but the properties of aggregate greatly affect the durability and structural performance of concrete.
Aggregate was originally viewed as an inert material dispersed throughout the cement paste largely for economic reasons. It is possible, however, to take an opposite view and to look on aggregate as a building material connected into a cohesive whole by means of the cement paste, in a manner similar to masonry construction. In fact, aggregate is not truly inert and its physical, thermal, and sometimes the chemical properties influence the performance of concrete. Aggregate is cheaper than cement and it is, therefore economical to put into the mix as much of the former and as little of the latter as possible. But economy is not the only reason for using aggregate: it confers considerable technical advantages on concrete, which has a higher volume stability and better durability than hydrated cement paste alone. General classification of aggregates: The size of aggregate used in concrete ranges from tens of millimeters down to particles less than one-tenth of a millimeter in cross-section. The maximum size actually used varies but, in any mix, particles of different sizes are incorporated, the particle size distribution being referred to as grading. In making low-grade concrete, aggregate from deposits containing a whole range of sizes, from the largest to the smallest, is sometimes used; this is referred to as all-in or pit-run aggregate.
The alternative, always used in manufacture of good quality concrete, is to obtain the aggregate in at least two size groups, the main division being between fine aggregate, often called sand not larger than 5 mm or 3/16 in., and coarse aggregate, which comprises material at least 5 mm or 3/16 in. in size. The design of concrete mixes has been made much more complex by the availability of many different cementitious materials as well as admixtures to reduce water requirement, entrain air, accelerate or retard setting, and reduce permeability or shrinkage. It may help to start with the old fashioned idea that the concrete consists of cement, coarse aggregate, fine aggregate and water. Historically the problem of mix design has been seen as to select suitable aggregates and determine their optimum relative proportions and the cement requirement to produce a given strength at a given slump. Early investigators tended to be concerned with how to define and produce ideal concrete. Frequently this meant trying to determine the ideal combined grading of the coarse and fine aggregate and therefore how these materials should be specified and in what proportions they should be combined.
Today, the consideration of concrete mix should be: Use available aggregates rather than searching for ideal aggregates. Recognize that there is no concrete ideal for all purposes, but rather define what is required for particular purpose. Understand that there will be competition based on price While strength is often not the most important requirement, the reason for its use as a criterion is shown by the step following its selection in most mix design procedures. This is to convert the strength requirement into a water/cement (w/c) ratio. The relationship between strength and w/c ratio is generally attributed to Abram’s in the United States. (Attachment 2) As a measure of the quality of concrete the compressive strength has become one of the most important standards, all strengths of concrete- compression, tension, shear and flexure – being related. The compressive strength is usually employed as a relative measure of strength under other loading, such as shear or tension. In nearly all-structural applications, the concrete is required to resist compressive stresses. However, some cases in which the concrete carries a load other than compressive.
For example, a beam is in flexure and will break in the middle because the bottom fibers are in tension and concrete is weak in tension. We overcome this weakness by inserting reinforcing steel in the bottom of the beam to provide resistance to flexural loading or bending, the steel having a high tensile strength. In concrete beam loaded in flexure, or bending, the bottom fibers are in tension. Reinforcing steel placed in the bottom of the beam gives it tensile strength to enable it to support such a load. The commonly accepted strength test is made when the concrete is 28 days old, because, concrete reaches its final strength on the 28th day. (Attachment 6) A durable concrete is one that will withstand, to a satisfactory degree, the effects of service conditions to which it will be subjected, such as weathering, chemical action, and wear. Numerous laboratory tests have been devised for measurement of durability of concrete, but it is extremely difficult to obtain a direct correlation between service records and laboratory findings. (Attachment 2) a) Weathering Resistance: Disintegration by weathering is caused mainly by the disruptive action of freezing and thawing and by expansion and contraction, under restraint, resulting from temperature variations and alternate wetting and drying. Concrete can be made that will have excellent resistance to the effects of such exposures if careful attention is given to the selection of materials and to all other phases of job control. The purposeful entertainment of small bubbles of air also helps to improve concrete durability by decreasing the water content and improving placeability characteristics.
b) Resistance to Chemical Deterioration: Concrete deterioration, attributable in whole or in part to chemical reactions between alkalies in cement and mineral constituents of concrete aggregates, is characterized by the following observable conditions Cracking, usually of random pattern on a fairly large scale (Pictures 1,2) Excessive internal and overall expansion Cracks that may be very large at the concrete surfaces (openings up to 1.5 in. have been observed) but which extend into the concrete only a distance from 6 to 18 inches c) Resistance to Erosion: The principal causes of erosion of concrete surfaces are; cavitation, movement of abrasive material by flowing water, abrasion and impact of traffic, wind blasting, and impact of floating ice. (Pictures 3,4) Permeability is the ease with which liquids or gases can travel through concrete. There are three avenues by which water can penetrate concrete: Gross voids arising from incomplete compaction, often resulting from segregation. Micro (or macro) cracks resulting from drying shrinkage, thermal stresses or bleeding settlement. Pores or capillaries resulting from mixing water in excess of that which can combine with the cement.
Gross voids may be regarded as too obvious a cause to be included. However, they are worth mentioning because they may be made more likely by action which would otherwise reduce porosity, i.e. harsh, low slump mix will have a low water content and a richer mortar (higher cement/sand ratio) than a sandier mix of equal strength. Obviously a low permeability concrete must be such that it will be fully compacted by the means available. It must not depend on unrealistic expectations of workmanship. A concrete that can be readily compacted is said to be workable, but to say merely that workability determines the ease of placement and the resistance to segregation is too loose a description of this vital property of concrete. The desired workability in any particular case would depend on the means of compaction; likewise, workability suitable for mass concrete is not necessarily sufficient for thin, inaccessible, or heavily reinforced sections. For these reasons, workability should be defined as a physical property of concrete alone without reference to the circumstances of a particular type of construction. This is a test used extensively in site all over the world. The slump test does not measure the workability of concrete, although it is described as a measure of consistency, but the test is very useful in detecting variations in the uniformity of a mix of given nominal proportions. The mould for the slump test is a frustum of a cone, 300 mm (12 in.) high. It is placed on a smooth surface with the smaller opening at the top, and filled with the smaller opening at the top, and filled with concrete in three layers. Each layer is tamped 25 times with a standard 16-mm (5/8 in.) diameter steel rod, rounded at the end, and the top surface is struck off by means of a sawing and rolling motion of the tamping rod. The mould must be firmly held against its base during the entire operation; this is facilitated by handles or foot-rests brazed to the mould.
Immediately after filling, the cone is slowly lifted, and the unsupported concrete will now slump- hence the name of the test. The decrease in the height of the slumped concrete is called slump, and is measured to the nearest 5 mm (1/4in.).
In order to reduce the influence on slump of the variation in the surface friction, the inside of the mould and its base should be moistened at the beginning of every test, and prior to lifting of the mould the area immediately around the base of the cone should be cleaned of concrete which may have dropped accidentally. (Attachment 4) For the concrete mix: Scup, bucket, shovel, and pre-constructed wooden mould (6” x 6” x 3’).
(The steel make concrete mould on the right side is similar to our wooden mold, which is also open top) For the slump test: Slump cone, inspection scale, base plate, scoop, trowel, brush, and tamping rod. For testing: hydraulic concrete beam test machine. (This test machine shown is similar to the one we used, shown here for visualization purpose only) 3/8” diameter by 3’ Rebar 1/2‘ diameter by 3’ Rebar 2 pieces Concrete Recipe: Make 2 blocks of concrete (sample 1 and 2) with the following proportions. 90 lbs of aggregates and fines mixture, Pour mixtures into two pre-constructed wooden molds. 2 rebars are pre-installed for each concrete sample located parallel at 2 inch up from the bottom of the concrete and 2 inches apart. Make 1 block of concrete (sample #3) with the following proportions. 45 lbs of aggregates and fines mixture, Pour mixtures into two pre-constructed wooden molds. 2 rebars are pre-installed for each concrete sample located parallel at 2 inch up from the bottom of the concrete and 2 inches apart. Curing period for all 3 concrete beams is 15 days. Curing samples are located at the green house open area. 1. Pour water and cement and mix it in the bucket using the shovel.
Then add aggregates and fines mixtures and continue stir until all materials are equally mixed. 2. Perform slump test using the slump test equipments and allow the testing concrete slump to have 4-inch separation between the top of the slump and the inspection scale. (if the slump test is failed, then add more aggregates and fines or add more water until the slump test is 4-inches apart) 3. Install the rebars to all three pre-constructed wooden molds. (Do this step prior to pour concrete into the molds) 4. Pour concrete into the first 2 molds. 5. Repeat step 1 through 4 for the last concrete sample with the indicated concrete mix proportion. 6. Place the samples in front of the Green House for cure. 7. Take the cured concrete beams out of the wooden molds and test the flexural strengths using the hydraulic concrete-beam machine. 8. Relate our results to the real situation in the formal report. Water/Cement/Aggregates Ratio 1:2:3 1:2:3 3:1:9 Flexural Strength (psi) 5,980 10,040 5,260 Since there was enough time for our experiment to cure the samples for 28 days, our samples were only cure for 14 days. As a result of this time period the result we got for the strength are 86% efficient since the concrete has full hardness after 28 days of curing.
(Attachment 6) Different results were obtained for each sample since water/cement/aggregate ratios and rebar sizes differed. Sample 1 and sample 2 had the same water/cement/aggregate ratio, which is 1:2:3 but they had different rebar sizes. Sample 1 had 3/8-inch diameter reinforcement where sample 2 had ?-inch diameter reinforcement. The compression failure for sample 1 occurred at 5,980 lbs where sample 2 failed at 10,040 lbs. The strength obtained from sample 2 was much higher than sample 1 since reinforcement keeps the concrete together and makes it harder to crack. This shows that the reinforcement size makes the strength of the concrete much higher. Sample 1 and sample 3 have same sizes of reinforcement bars (3/8-inch diameter) but their water/cement/aggregate ratio is different. Sample 1 has 1:2:3 w/c/a ratio and sample 3 has 3:1:9 w/c/a ratio. As a result of different water/cement ratio, where sample 1 has a less water/cement ratio, it has more strength. The strength for sample 1 is 5,980 lbs where sample 3 has strength of 5,260 lbs.
As a result of our experiment, the two important aspects in concrete design (durability and strength) are water/cement ratio and the size of the reinforcement bar that are used. It is seen that increasing the size of the reinforcement increases the strength of the concrete. That’s the reason why heavy reinforcement is used and building foundations and columns whereas small sizes of reinforcement are used in slab sections. In a building the most compressive forces are on the foundation and this is the reason why larger size of reinforcement bars are used. Comparing our sample 2 with the other samples, it can be seen that sample 2 is much more suitable to use in the foundation than the other 2 samples since it has almost twice the strength.
The results obtained from the experiment agree with the primary objective. It is seen that we cannot just mix cement, water, and aggregate in a random ratio and build a structure. There are many different mixes of concrete that serve different purposes. It is a wise idea to test the concrete when building a large structure so that unexpected failure doesn’t happen.
Studying and getting ready to become civil engineers, we learned a lot of information by doing the concrete research and also experienced this information practically during our experiment. This meets our secondary objective.
Bibliography:
References: Day, K. (1999).
Concrete Mix Design, Quality Control and Specification, 2nd edition; E & FN Spon. Neville, A. (1996).
Properties of Concrete, 4th Edition; John Wiley & Sons, Inc. Neville A., Brooks J. (1987).
Concrete Technology; Longman Scientific & Technical. Shah S., Ahmad S. (1994).
High Performance Concrete: Properties and Applications; Mc Graw-Hill, Inc. U.S. Department of the Interior. (1981).
Concrete Manual: A water resources technical publication, 8th edition; United States government printing office. Waddell, J. (1978).
Fundamentals of Quality Precast Concrete; National Precast Concrete Association.
