ConcreteP1D

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Concrete is a construction material composed of cement as well as other cementitious materials such as fly ash and slag cement, aggregate generally a coarse aggregate such as gravel, limestone, or granite, plus a fine aggregate such as sand, water, and chemical admixtures. Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar, and plaster. Combining water with a cementitious material forms a cement paste by the process of hydration. Sand, natural gravel and crushed stone are mainly used for this purpose.


 * 1) Accelerators speed up the hydration (hardening) of the concrete. Typical materials used are CaCl2 and NaCl.However use of Chlorides may cause corrosion in steel reinforcing and is prohibited in some countries.


 * 1) Retarders slow the hydration of concrete, and are used in large or difficult pours where partial setting before the pour is complete is undesirable. Typical polyol retarder is sugar,sucrose,sodium gluconate,glucose,citric acid,tartaric acid and etc.

Air entrainments add and entrain tiny air bubbles in the concrete, which will reduce damage during freeze-thaw cycles thereby increasing the concrete's durability. However, entrained air is a trade-off with strength, as each 1% of air may result in 5% decrease in compressive strength.


 * 1) Plasticizers/superplasticizers (water-reducing admixtures) increase the workability of plastic or "fresh" concrete, allowing it be placed more easily, with less consolidating effort. Typical plasticizers are liginsulfate,polyol type. Alternatively, plasticizers can be used to reduce the water content of a concrete (and have been called water reducers due to this application) while maintaining workability. This improves its strength and durability characteristics. Superplasticizers (high-range water-reducing admixtures) are a class of plasticizers which have fewer deleterious effects when used to significantly increase workability, representive superplasticizers are sulfonated naphthalene formaldehyde condensate,sulfonated melamine formaldehy condensate and acetone formaldehyde condensate, etc.,more advanced superplasticizer is polycarboxylate type.

Fly ash: A by product of coal fired electric generating plants, it is used to partially replace Portland cement (by up to 60% by mass). The properties of fly ash depend on the type of coal burnt. In general, silicious fly ash is pozzolanic, while calcareous fly ash has latent hydraulic properties.

Ground granulated blast furnace slag (GGBFS or GGBS): A by product of steel production, is used to partially replace Portland cement (by up to 80% by mass). It has latent hydraulic properties.

Silica fume: A by-product of the production of silicon and ferrosilicon alloys. Silica fume is similar to fly ash, but has a particle size 100 times smaller. This results in a higher surface to volume ratio and a much faster pozzolanic reaction. Silica fume is used to increase strength and durability of concrete, but generally requires the use of superplasticizers for workability.

High Reactivity Metakaolin (HRM): Metakaolin produces concrete with strength and durability similar to concrete made with silica fume. While silica fume is usually dark gray or black in color, high reactivity metakaolin is usually bright white in color, making it the preferred choice for architectural concrete where appearance is important.

Wire mesh, plastic mesh, and steel re-bar are all commonly used materials that cost about 10 cents per square foot.

Read more: http://www.servicemagic.com/article.show.Concrete-Cost-A-Primer.14119.html#ixzz0fEunSAqe

Expect gravel to run about $12 per cubic yard delivered to the work site.

Read more: http://www.servicemagic.com/article.show.Concrete-Cost-A-Primer.14119.html#ixzz0fEugLC1F

Concrete prices is $70 per cubic yard of concrete.

In summary:

Lastly, the slab is placed.
 * T-shaped foundations are used in areas where the ground freezes.
 * First, the footing is placed.
 * Second, the walls are constructed and poured.

Slab-on-grade foundation

In summary:

The slab-on-grade is monolithic (poured all at one time).
 * Slab on grade used in areas where ground does not freeze.
 * The edges of the slab-on-grade are thicker than the interior of the slab.

Frost Protected

Site Foundation - Frost Protected ConcreteNetwork.com

In summary:


 * Only works with a heated structure.
 * Has the benefits of a the slab-on-grade method (concrete poured monolithically) in areas subject to frost.
 * Concrete is poured in one operation, versus 3 pours required for T-shaped foundations.

Concrete makes up the majority of the cost of a concrete project. To get a more accurate estimate contact your local [|Ready-Mix] supplier. || **$75 per cubic yard** Cost will vary depending on the amount of dirt you need to move. Hourly rates apply for a tractor and operator. || **$50 per hour** || Cost for gravel or sand delivered to the job site. Read about [|subgrades and subbases] here. || **$12 per cubic yard** || Labor is the biggest cost for concrete forms. Setting up concrete forms and finishing concrete is backbreaking work. [|More about concrete forming supplies.] || **$1 - $1.50 per square foot** || Reinforcement is required because all concrete cracks, so if you want your cracks to remain small, you'll need reinforcement. Wire mesh, re-bar, plastic mesh, and fiber in the mix are all commonly used materials. || **.10 cents per square foot** || http://www.concretenetwork.com/
 * **Concrete**
 * National Average in 2008 ||
 * [[image:http://www.concretenetwork.com/photo-gallery/images/180x130Exact/site_26/concretenetwork-com_19524.jpg width="180" height="130" caption="ConcreteNetwork.com" link="http://www.concretenetwork.com/photo-gallery/site_26/concretenetwork-com_19524/"]] || **Grading**
 * [[image:http://www.concretenetwork.com/photo-gallery/images/180x130Exact/site_26/free-reformed-church-of-southern-river_10492.jpg width="180" height="130" caption="Free Reformed Church of Southern River" link="http://www.concretenetwork.com/photo-gallery/site_26/free-reformed-church-of-southern-river_10492/"]] || **Subbase**
 * [[image:http://www.concretenetwork.com/photo-gallery/images/180x130Exact/site_26/free-reformed-church-of-southern-river_19525.jpg width="180" height="130" caption="Free Reformed Church of Southern River" link="http://www.concretenetwork.com/photo-gallery/site_26/free-reformed-church-of-southern-river_19525/"]] || **Concrete Forms and Finishing**
 * [[image:http://www.concretenetwork.com/photo-gallery/images/180x130Exact/site_26/free-reformed-church-of-southern-river_19526.jpg width="180" height="130" caption="Free Reformed Church of Southern River" link="http://www.concretenetwork.com/photo-gallery/site_26/free-reformed-church-of-southern-river_19526/"]] || **Reinforcement**

www.**concrete**.com =The Basic Mix:=

A general teacher's guide for concrete preparation
The physical properties of density and strength of concrete are determined, in part, by the proportions of the three key ingredients, water, cement, and aggregate. You have your choice of proportioning ingredients by volume or by weight. Proportioning by volume is less accurate, however due to the time constraints of a class time period this may be the preferred method. A basic mixture of mortar can be made using the volume proportions of 1 water : 2 cement : 3 sand. Most of the student activities can be conducted using this basic mixture. Another "old rule of thumb" for mixing concrete is 1 cement : 2 sand : 3 gravel by volume. Mix the dry ingredients and slowly add water until the concrete is workable. This mixture may need to be modified depending on the aggregate used to provide a concrete of the right workability. The mix should not be too stiff or too sloppy. It is difficult to form good test specimens if it is too stiff. If it is too sloppy, water may separate (bleed) from the mixture. Remember that __water is the key ingredient.__ Too much water results in weak concrete. Too little water results in a concrete that is unworkable. >
 * Suggestions:**
 * 1) If predetermined quantities are used, the method used to make concrete is to dry blend solids and then slowly add water (with admixtures, if used).
 * 2) It is usual to dissolve admixtures in the mix water before adding it to the concrete. Superplasticizer is an exception.
 * 3) Forms can be made from many materials. Cylindrical forms can be plastic or paper tubes, pipe insulation, cups, etc. The concrete needs to be easily removed from the forms. Pipe insulation from a hardware store was used for lab trials. This foam-like material was easy to work with and is reusable with the addition of tape. The bottom of the forms can be taped, corked, set on glass plates, etc. Small plastic weighing trays or Dairy Queen banana split dishes can be used as forms for boats or canoes.
 * 4) If compression tests are done, it may be of interest to spread universal indicator over the broken face and note any color changes from inside to outside. You may see a yellowish surface due to carbonation from CO2 in the atmosphere. The inside may be blue due to calcium hydroxide.
 * 5) To answer the proverbial question, "Is this right?" a [|slump test] may be performed. A slump test involves filling an inverted, bottomless cone with the concrete mixture. A Styrofoam or paper cup with the bottom removed makes a good bottomless cone. Make sure to pack the concrete several times while filling the cone. Carefully remove the cone by lifting it straight upward. Place the cone beside the pile of concrete. The pile should be about 1/2 to 3/4 the height of the cone for a concrete mixture with good workability. (SEE DIAGRAM)
 * 1) To strengthen samples and to promote hydration, soak concrete in water (after it is set).
 * 2) Wet sand may carry considerable water, so the amount of mix water should be reduced to compensate.
 * 3) Air bubbles in the molds will become weak points during strength tests. They can be eliminated by:
 * i. packing the concrete.
 * ii. Tapping the sides of the mold while filling the mold.
 * iii. "rodding" the concrete inside the mold with a thin spatula.
 * 1) Special chemicals called "water reducing agents" are used to improve workability at low water to cement ratios and thus produce higher strengths. Most ready-mix companies use these chemicals, which are known commercially as superplasticizers. They will probably be willing to give you some at no charge.
 * 2) You can buy a bag of cement from your local hardware store. A bag contains 94 lb. (40kg) of cement. Once the bag has been opened, place it inside a garbage bag (or two) that is well sealed from air. This will keep the cement fresh during the semester. An open bag will pick up moisture and the resulting concrete may be weaker. Once ce

Concrete Prices: The Basics
How much does concrete cost? There are many different concrete products out on the market that can make this a difficult question to answer. In addition, there are a number of different instances that the material could be used for plus money to pay the contractor for his time. Ready mix concrete is what is used for most home remodeling jobs and is usually preferred over mixtures made on site due to time and labor. Therefore, if you’ve contracting a job, ready mix concrete is likely what you’ll get and be paying for. There are a variety of costs that factor into the price of poured concrete depending on the size of the area that needs to be filled. If the project is small expect there to be a minimum contractor’s fee associated with the job. Overall, anything between $3 and $10 per square foot is generally a reasonable base cost (Note: larger sites will have the cheaper square footage). In addition to pouring, getting stamped or tiled cement is also an option if you’re looking to add a decorative touch to the finished product. Stamping is a special finish that is done while the material is still modifiable and is done after pouring. This can increase the based cost by 50% or 100%. Making a vertical structure out of concrete, such as a retaining wall, can be a different picture. Due to things such as gravity and other considerations it takes different materials and tactics to use the concrete. Because of this your base costs could triple. Of course, concrete has a number of uses outside of foundations and driveways. Using it in a more finesse way, as in roofing or counter tops, is an interesting prospect. Getting concrete tiles for say a kitchen or bathroom counter top can be quite expensive running $65 to $150. While it’s more expensive than some other materials it can be quite long lasting, giving it the added value needed to justify the price. Concrete roofing tiles are a different ball game and run more inline with the costs of pouring the material. For these you’ll be looking to pay about $5 per square foot for budget tiles and as high as $11 for more elaborately designed tiles. Those are some of the base costs for some simple concrete uses. As time goes on we’ll look at other potential jobs and look at other possibilities. In between now and then, have a look at some of our other articles which can be accessed on the side bar to shed more light on [|concrete prices].

**Ingredients**
maximum strength and durability will still not be attained unless the sand and coarse aggregate you use consist of well-graded, clean, hard, and durable particles free of undesirable substances (figure 6-1). WATERTIGHTNESS OF CONCRETE The ideal concrete mix is one with just enough water required for complete hydration of the cement. However, this results in a mix too stiff to pour in forms. A mix fluid enough to be poured in forms always contains a certain amount of water over and above that which will combine with the cement. This water eventually evaporates, leaving voids, or pores, in the concrete. Penetration of the concrete by water is still impossible if these voids are not inter- connected. They may be interconnected, however, as a result of slight sinking of solid particles in the mix during the hardening period. As these particles sink, they leave water-tilled channels that become voids when the water evaporates. The larger and more numerous these voids are, the more the watertightness of the concrete is impaired. The size and number of the voids vary directly with the amount of water used in excess of the amount required to hydrate the cement. To keep the concrete as watertight as possible, you must not use more water than the minimum amount required to attain the necessary degree of workability. GENERAL REQUIREMENTS FOR GOOD  CONCRETE  The first requirement for good concrete is to use a cement type suitable for the work at hand and have a satisfactory supply of sand, coarse aggregate, and water. Everything else being equal, the mix with the best graded, strongest, best shaped, and cleanest aggregate makes the strongest and most durable concrete. Second, the amount of cement, sand, coarse aggregate, and water required for each batch must be carefully weighed or measured according to project specifications. Third, even the best designed, best graded, and highest quality mix does not make good concrete if it is not workable enough to fill the form spaces thoroughly. On the other hand, too much fluidity also results in defects. Also, improper handling during the overall concrete making process, from the initial aggregate handling to the final placement of the mix, causes segregation of aggregate particles by sizes, resulting in nonuniform, poor-quality concrete. Finally, the best designed, best graded, highest quality, and best placed mix does not produce good concrete if it is not proper] y cured, that is, properly protected against loss of moisture during the earlier stages of setting. CONCRETE INGREDIENTS  LEARNING OBJECTIVE: Upon completing   this section, you should be able to identify the   ingredients essential for good concrete. The essential ingredients of concrete are cement, aggregate, and water. A mixture of only cement and water is called cement paste. In large quantities, however, cement paste is prohibitively expensive for most construction purposes. PORTLAND CEMENT Most cement used today is portland cement. This is a carefully proportioned and specially processed combination of lime, silica, iron oxide, and alumina. It is usually manufactured from limestone mixed with shale, clay, or marl. Properly proportioned raw materials are pulverized and fed into kilns where they are heated to a temperature of 2,700°F and maintained at that temperature for a specific time. The heat produces chemical changes in the mixture and transforms it into clinker—a hard mass of fused clay and limestone. The clinker is then ground to a fineness that will pass through a sieve containing 40,000 openings per square inch. Types of Cement There are five types of Portland cement covered under “Standard Specifications for Portland Cement.” These specifications are governed by the American Society for Testing and Material (ASTM) types. Separate specifications, such as those required for air-entraining portland cements, are found under a separate ASTM. The type of construction, chemical composition of the soil, economy, and requirements for use of the finished concrete are factors that influence the selection of the kind of cement to be used. TYPE I.— Type I cement is a general-purpose  cement for concrete that does not require any of the special properties of the other types. In general, type I cement is intended for concrete that is not subjected

Here is some guidance on **how to make concrete**. There are four basic ingredients in varying proportions that are required for mixing concrete; Portland cement, sand, aggregate and water. The combined mix is measured in cubic feet; 27 cubic feet is equal to one cubic yard of concrete. Mixing can be done manually in a large plastic tub or wheelbarrow, or in a rotating portable cement mixer. Portland cement is a fine, white powder consisting of lime, iron, silica and alumina and is available as Types I through V. Type I cement is appropriate for most construction applications and can be purchased in standard bags containing one cubic foot of volume and weighing approximately 95 lbs. The ratio of sand to cement is an important factor in determining the concrete’s compressive strength. A ratio of Portland cement to sand at 1:3 will yield a concrete mix with a PSI (pounds per square inch) greater than 3000, sufficient for most minor jobs. Water combined with the cementitious material will form the paste or binder that holds the aggregate in place. Aggregate, or crushed rock, is classified as course, medium and fine, can be used in combination, and typically makes up ¾ of the volume of the concrete. Course aggregate will reduce the volume of cement needed and will not significantly affect the strength of the concrete, but will result in a rough surface finish. The strength properties of the concrete are inversely proportional to the water/cement ratio (by weight) which should be kept below .60. This means the weight of the water should not be more than 60% that of the cement. A higher ratio will produce a more plastic or fluid mix, but one that is likely to be deficient in strength and surface qualities. Adding water to the mix will initiate the hydration process, a chemical reaction that causes the concrete to harden or “cure”. Once poured, compacting is done to eliminate trapped air and vibrating can also be done to ensure uniformity within the mix. Excessive vibration however, will cause segregation, where the heavier aggregates settle near the bottom and the fluid paste rises to the top. Concrete is typically designed to be used at the strength it reaches after 28 days, but the hydration process continues for years. During the first two weeks of hydration, it is imperative that the concrete be kept wet or moist, particularly when pouring slabs, sidewalks or foundations. There are several methods for finishing concrete including “floating”, troweling, brooming and brushing. Also, ingredients known as admixtures are available and often used in larger commercial projects to alter or enhance various properties, such as air-entrained additives (insulation), accelerants and retardants (to change the rate of hydration), plasticizers (workability) and coloring agents.
 * How to Make Concrete**

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Rubberized Concrete

25 pounds of crumb rubber per cubic yard
 * 1) Quantities of crumb rubber from 20 pounds to 400 pounds have been added to portland cement **concrete** replacing from 1 percent to 25 percent of the aggregate.
 * 2) To maintain strength of 4,000 psi for highway applications up to 50 pounds per cubic yard or 3-percent replacement of aggregate is the maximum.
 * 3) Production of crumb rubber **concrete** is similar to working with fiber-reinforced **concrete**.
 * 4) Hanson Aggregates achieved higher compressive strength in crumb rubber **concrete** by reducing entrapped air in the mix.
 * 5) Small crumb rubber in the 30 mesh range seems to work better but does require the use of de-airing agents.

There is less cracking because the rubber reduces the expanding and shrinkage and eliminates 45 degree cracks, it can hold up to weather wear.
 * Crumb rubber** is a term usually applied to recycled rubber from [|automotive] and [|truck] scrap [|tires].

Quikrete® Portland Cement (1124-47)
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