Density Of Concrete

Bibliographic Entry	Result (w/surrounding text)	Standardized Result
Dorf, Richard. Engineering Handbook. New York: CRC Press, 1996.	"The density of normal concrete is 2400 kg/m3 and the density of lightweight concrete is 1750 kg/m3	1750–2400 kg/m3
Brooklyn Public Library Files; 1999	"Typical density of concrete (2.3 g/cm3)"	2300 kg/m3
McGraw-Hill Encyclopedia of Science and Technology.	"Volume generally assumed for the density of hardened concrete is 150 lb./ft3. (2400 kg/m3)"	2400 kg/m3

Concrete is an artificial material similar to stone that is used for many different structural purposes. It is made by mixing several different coarse aggregates such as sand and pebbles with water and cement and then allowing it to harden by hydration. Hydration causes crystals to form that interlock and bind together. According to the Brooklyn Public Library, concrete was first made in 500 BC and can last up to 50,000 years. Concrete is one of the most important building materials. From sidewalks to skyscrapers, we see concrete everyday everywhere. There are many different kinds of concrete. Reinforced concrete is strengthened by steel. This is done by casting concrete around steel rods or bars and most large structures such as bridges need this extra strong concrete. Prestressed concrete is made by casting concrete around steel cables stretched by hydraulic jacks. After the concrete hardens the jacks are released and the cables compress the concrete. Concrete when compressed is the strongest. This type of concrete is used for floors and roofs as well as other things. Precast concrete is cast and hardened before being used for construction. Precasting makes it possible to produce a mass number of concrete building materials. Nearly all of pre stressed concrete is precast as are concrete blocks. Concrete blocks are made in various weights and sizes and they are used to make about two-thirds of masonry walls in the US. Engineers have designed kinds of concrete for certain uses. Air-entrained concrete is good in harsh weather and is used for roads and airport runways. High-early-strength Concrete is used in hurried jobs and cold weather because it hardens quicker than ordinary concrete. Lightweight concrete weighs less than any other concrete because it is made from pumice: a naturally light mineral.

Bibliographic Entry	Result (w/surrounding text)	Standardized Result
Concrete Basics. Portland Cement Association.	"Density in Place: Density of normal CLSM in place typically ranges from 90 to 125 pounds per cubic foot (1840 to 2320 kg/cubic m)."	2320 kg/m3 (conventional)
Conversion Factors, Material Properties and Constants, Edward Boyden, MIT.	"Density Concrete 2242 kg/m^3"	2242 kg/m3 (conventional)
Material Notes. Faculty of the Built Environment, University of New South Wales.	"While conventional concrete has a density of about 2300 kg/m3, lightweight concrete has a density between 160 and 1920 kg/m3."	2300 kg/m3 (conventional) 160–1920 kg/m3 (lightweight)
Cube Competition. Concrete Society of Southern Africa.	"The concrete must be of a lightweight nature, with a mass of not greater than 1.5 kg/100 mm cube or a density of 1500 kg/m3"	< 1500 kg/m3 (lightweight)
Baldwin, Kelly. "Electrically Conductive Concrete: Properties and Potential."Construction Canada. Vol. 98, No. 1 (January/February 1998): 28-29.	"Density (kg/m3) 1450–1850"	1450–1850 kg/m3 (conducting)
Concrete Admixture 453. Pt. Union Ajidharma.	Density (kg/m3) Without 453 2320 With 453 2320	2320 kg/m3 (conventional)
Transit Mix Perlite Concrete. Schundler Company.	Wet Density Range in kg/m3 808.0 +/- 48.0 728.0 +/- 48.0 648.0 +/- 48.0 584.0 +/- 48.0	648–808 kg/m3 (lightweight)
Aerated Concrete, Lightweight Concrete, Cellular Concrete and Foamed Concrete. Pan Pacific Management Resources.	Density 300-600 kg/m3 (19-38 lbs/ft3) Made with Cement & Foam Only Density 600-900 kg/m3 (38-56 lbs/ft3) Made with Sand, Cement & Foam Density 900-1200 kg/m3 (56-75 lbs/ft3) Made with Sand, Cement & Foam Density 1200-1600 kg/m3 (75-100 lbs/ft3) Made with Sand, Cement & Foam	300–1600 kg/m3 (lightweight)
Is anyone buried in Hoover Dam? Bureau of Reclamation, US Department of the Interior.	"Typically, concrete has a density of 150 pounds per cubic foot, which means that a block of concrete that is one foot wide, one foot long, and one foot high would weigh 150 pounds. Water has the density of only 62.4 pounds per cubic foot."	2400 kg/m3
Pavement Conversion Factors. Washington State Department of Transportation.	pcf kg/m 2 PCCP 150 2403 ACP 137/0.10' 2439	2403–2439 kg/m3

Precast Concrete Products

Agricultural Products

Precast concrete products can withstand the most extreme weather conditions and will hold up for many decades of constant usage. Products include bunker silos, cattle feed bunks, cattle grid, agricultural fencing, H-bunks, J-bunks, livestock slats, livestock watering trough, feed troughs, concrete panels, slurry channels, and more. Prestressed concrete panels are widely used in the UK for a variety of applications including agricultural buildings, grain stores, silage clamps, slurry stores, livestock walling, and general retaining walls. Panels can either be used horizontally and placed either inside the webbings of RSJs (I-beam) or in front of them. Alternatively panels can be cast into a concrete foundation and used as a cantilever retaining wall.

Building and Site Amenities

Precast concrete building components and site amenities are used architecturally as fireplace mantels, cladding, trim products, accessories, and curtain walls. Structural applications of precast concrete include foundations, beams, floors, walls, and other structural components. It is essential that each structural component be designed and tested to withstand both the tensile and compressive loads that the member will be subjected to over its lifespan.

Retaining Walls

Precast concrete provides the manufacturers with the ability to produce a wide range of engineered earth retaining systems. Products include: commercial retaining wall, residential retaining walls, sea walls, mechanically stabilized earth (MSE) panels, modular block systems, segmental retaining walls, etc. Retaining walls have 5 different types which include: gravity retaining wall, semigravity retaining wall, cantilever retaining wall, counterfort retaining wall, and buttress retaining wall.

Sanitary and Stormwater

Sanitary and Stormwater management products are structures designed for underground installation that have been specifically engineered for the treatment and removal of pollutants from sanitary and stormwater run-off. These precast concrete products include stormwater detention vaults, catch basins, andmanholes.

Transportation and Traffic Related Products

Precast concrete transportation products are used in the construction, safety and site protection of road, airport and railroad transportation systems. Products include: box culverts, 3-sided culverts, bridge systems, railroad crossings, railroad ties, sound walls/barriers, Jersey barriers, tunnel segments, precast concrete barriers, TVCBs, central reservation barriers and other transportation products. Used to make underpasses, surface-passes and pedestrian subways, so that traffic in cities is disturbed for less amount of time.

Utility Structures

For communications, electrical, gas or steam systems, precast concrete utility structures protect the vital connections and controls for utility distribution. Precast concrete is nontoxic and environmentally safe. Products include: hand holes,hollowcore products, light pole bases, meter boxes, panel vaults, pull boxes, telecommunications structures, transformer pads, transformer vaults, trenches, utility buildings, utility vaults, utility poles, controlled environment vaults (CEVs,) and other utility structures.

Water and Wastewater Products

Precast water and wastewater products hold or contain water, oil or other liquids for the purpose of further processing into non-contaminating liquids and soil products. Products include: aeration systems, distribution boxes, dosing tanks, dry wells, grease interceptors, leaching pits, sand-oil/oil-water interceptors, septic tanks, water/sewage storage tanks, wetwells, fire cisterns and other water & wastewater products.

Precast Concrete

Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and lifted into place. In contrast, standard concrete is poured into site-specific forms and cured on site. Precast stone is distinguished from precast concrete by using a fine aggregate in the mixture, so the final product approaches the appearance of naturally occurring rock or stone.

By producing precast concrete in a controlled environment (typically referred to as a precast plant), the precast concrete is afforded the opportunity to properly cure and be closely monitored by plant employees. Utilizing a Precast Concrete system offers many potential advantages over site casting of concrete. The production process for Precast Concrete is performed on ground level, which helps with safety throughout a project. There is a greater control of the quality of materials and workmanship in a precast plant rather than on a construction site. Financially, the forms used in a precast plant may be reused hundreds to thousands of times before they have to be replaced, which allows cost of formwork per unit to be lower than for site-cast production.

Total precast concrete building systems are becoming a popular choice for many construction projects. Architectural and structural precast, prestressed concrete components can be combined to create the entire building.

Precast products range from small mass produced items like the concrete hollow masonry blocks below to the cast on site tilt up wall panels above.
precast concrete products have certain advantages over cast in situ work.
In the case of the wall panels above they are an excellent method of quickly building odd shaped and repetitive wall panes.

The Manufacturing Process Of Concrete

The manufacture of concrete is fairly simple. First, the cement (usually Portland cement) is prepared. Next, the other ingredients—aggregates (such as sand or gravel), admixtures (chemical additives), any necessary fibers, and water—are mixed together with the cement to form concrete. The concrete is then shipped to the work site and placed, compacted, and cured.

Preparing Portland cement

• 1 The limestone, silica, and alumina that make up Portland cement are dry ground into a very fine powder, mixed together in predetermined proportions, preheated, and calcined (heated to a high temperature that will burn off impurities without fusing the ingredients). Next the material is burned in a large rotary kiln at 2,550 degrees Fahrenheit (1,400 degrees Celsius). At this temperature, the material partially fuses into a substance known as clinker. A modern kiln can produce as much as 6,200 tons of clinker a day.
• 2 The clinker is then cooled and ground to a fine powder in a tube or ball mill. A ball mill is a rotating drum filled with steel balls of different sizes (depending on the desired fineness of the cement) that crush and grind the clinker. Gypsum is added during the grinding process. The final composition consists of several compounds: tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite.

Mixing

• 3 The cement is then mixed with the other ingredients: aggregates (sand, gravel, or crushed stone), admixtures, fibers, and water. Aggregates are pre-blended or added at the ready-mix concrete plant under normal operating conditions. The mixing operation uses rotation or stirring to coat the surface of the aggregate with cement paste and to blend the other ingredients uniformly. A variety of batch or continuous mixers are used.
• 4 Fibers, if desired, can be added by a variety of methods including direct spraying, premixing, impregnating, or hand laying-up. Silica fume is often used as a dispersing or densifying agent.

Transport to work site

• 5 Once the concrete mixture is ready, it is transported to the work site. There are many methods of transporting concrete, including wheelbarrows, buckets, belt conveyors,
  
  

  The first step in making concrete is to prepare the cement. One type of cement, Pordand cement, is considered superior to natural cement because it is stronger, more durable, and of a more consistent quality.
  To make it, the raw materials are crushed and ground into a fine powder and mixed together. Next, the material undergoes two heating steps—calcining and burning. In calcining, the materials are heated to a high temperature but do not fuse together. In burning, however, the materials partially fuse together, forming a substance known as "clinker." The clinker is then ground in a ball mill—a rotating steel drum filled with steel balls that pulverize the material.
  
  

  After the Portland cement is prepared, it is mixed with aggregates such as sand or gravel, admixtures, fibers, and water. Next, it is transfered to the work site and placed. During placing, segregation of the various ingredients must be avoided so that full compaction—elimination of air bubbles—can be achieved.
  special trucks, and pumping. Pumping transports large quantities of concrete over large distances through pipelines using a system consisting of a hopper, a pump, and the pipes. Pumps come in several types—the horizontal piston pump with semi-rotary valves and small portable pumps called squeeze pumps. A vacuum provides a continuous flow of concrete, with two rotating rollers squeezing a flexible pipe to move the concrete into the delivery pipe.

Placing and compacting

• 6 Once at the site, the concrete must be placed and compacted. These two operations are performed almost simultaneously. Placing must be done so that segregation of the various ingredients is avoided and full compaction—with all air bubbles eliminated—can be achieved. Whether chutes or buggies are used, position is important in achieving these goals. The rates of placing and of compaction should be equal; the latter is usually accomplished using internal or external vibrators. An internal vibrator uses a poker housing a motor-driven shaft. When the poker is inserted into the concrete, controlled vibration occurs to compact the concrete. External vibrators are used for precast or thin in situ sections having a shape or thickness unsuitable for internal vibrators. These type of vibrators are rigidly clamped to the formwork, which rests on an elastic support. Both the form and the concrete are vibrated. Vibrating tables are also used, where a table produces vertical vibration by using two shafts rotating in opposite directions.

Curing

• 7 Once it is placed and compacted, the concrete must cured before it is finished to make sure that it doesn't dry too quickly. Concrete's strength is influenced by its moisture level during the hardening process: as the cement solidifies, the concrete shrinks. If site constraints prevent the concrete from contracting, tensile stresses will develop, weakening the concrete. To minimize this problem, concrete must be kept damp during the several days it requires to set and harden.

Production of concrete

 Raw Material

Structural concrete normally contains one part cement to two parts fine mineral aggregate to four parts coarse mineral aggregate, though these proportions are often varied to achieve the strength and flexibility required in a particular setting. In addition, concrete contains a wide range of chemicals that imbue it with the characteristics desired for specific applications. Portland cement, the kind most often used in concrete, is made from a combination of a calcareous material (usually limestone) and of silica and alumina found as clay or shale. In lesser amounts, it can also contain iron oxide and magnesia. Aggregates, which comprise 75 percent of concrete by volume, improve the formation and flow of cement paste and enhance the structural performance of concrete. Fine grade comprises particles up to. 20 of an inch (five millimeters) in size, while coarse grade includes particles from. 20 to. 79 of an inch (20 millimeters). For massive construction, aggregate particle size can exceed 1.50 inches (38 millimeters).
Aggregates can also be classified according to the type of rock they consist of: basalt, flint, and granite, among others. Another type of aggregate is pozzolana, a siliceous and aluminous material often derived from volcanic ash. Reacting chemically with limestone and moisture, it forms the calcium silicate hydrates that are the basis of cement. Pozzolana is commonly added to Portland cement paste to enhance its densification. One type of volcanic mineral, an aluminum silicate, has been combined with siliceous minerals to form a composite that reduces weight and improves bonding between concrete and steel surfaces. Its applications have included precast concrete shapes and asphalt/concrete pavement for highways. Fly ash, a coal-burning power plant byproduct that contains an aluminosilicate and small amounts of lime, is also being tested as a possible pozzolanic material for cement. Combining fly ash with lime (CaO) in a hydrothermal process (one that uses hot water under pressure) also produces cement.
A wide range of chemicals are added to cement to act as plasticizers, superplasticizers, accelerators, dispersants, and water-reducing agents. Called admixtures, these additives can be used to increase the workability of a cement mixture still in the nonset state, the strength of cement after application, and the material's water tightness. Further, they can decrease the amount of water necessary to obtain workability and the amount of cement needed to create strong concrete. Accelerators, which reduce setting time, include calcium chloride or aluminum sulfate and other acidic materials. Plasticizing or superplasticizing agents increase the fluidity of the fresh cement mix with the same water/cement ratio, thereby improving the workability of the mix as well as its ease of placement. Typical plasticizers include polycarboxylic acid materials; superplasticizers are sulphanated melamine formaldehyde or sulphanated naphthalene formaldehyde condensates. Setretarders, another type of admixture, are used to delay the setting of concrete. These include soluble zinc salts, soluble borates, and carbohydrate-based materials. Gas forming admixtures, powdered zinc or aluminum in combination with calcium hydroxide or hydrogen peroxide, are used to form aerated concrete by generating hydrogen or oxygen bubbles that become entrapped in the cement mix.
Cement is considered a brittle material; in other words, it fractures easily. Thus, many additives have been developed to increase the tensile strength of concrete. One way is to combine polymeric materials such as polyvinyl alcohol, polyacrylamide, or hydroxypropyl methyl cellulose with the cement, producing what is sometimes known as macro-defect-free cement. Another method entails adding fibers made of stainless steel, glass, or carbon. These fibers can be short, in a strand, sheet, non-woven fabric or woven fabric form. Typically, such fiber represents only about one percent of the volume of fiber-reinforced concrete.

Concrete Homes Design

How to use the concrete?
How using concrete and ICFs for concrete home construction can slash heating and cooling costs, improve your comfort and safety, and help preserve the environment?

Concrete Home Eddie Burks

Concrete homes are known for their durability and cost-saving features. With ICF construction, homeowners are finding that they can design a concrete home to look just like a wood-frame house, but they garner many other added benefits by choosing to build with concrete.In fact, more and more home-owners are doing just that, for reasons ranging from reducing escalating heating and cooling costs to allaying fears of being in the path of another hurricane on the magnitude of Katrina.

These savvy homeowners are saying "no" to wood framing and erecting their castles using concrete building systems for the exterior structural walls. In 2005, concrete homes accounted for nearly 18% of all new single-family detached homes, up from 16.3% in 2004, according to the National Association of Home Builders (NAHB) and the Portland Cement Association (PCA). Simply put, one out of every six new houses built in the U.S. are now made of concrete.

Tom Bonner

While some of these homes use traditional concrete wall systems, such as concrete masonry and concrete cast onsite in removable forms, the most explosive growth is in the use of insulating concrete forms, or ICFs, for building both foundation and above-grade walls. These easy-to-erect, stay-in-place forms are made of high-density plastic foam and filled with fresh concrete and steel reinforcement to create a super-insulated thermal sandwich that's airtight, quiet, and highly resistant to fire and strong winds. And ICF walls can be covered with most standard interior and exterior finishing materials, allowing your fortress to assume any architectural style, from Victorian to Colonial to ultra-contemporary.

Reward Wall Systems

Although it's almost impossible to spot a concrete home, since the walls are often hiding beneath a traditional façade of brick, stucco or lap siding, chances are good that at least one is located right in your own neighborhood. ICF homes are going up in all regions of the country, especially in areas vulnerable to devastating hurricanes and tornadoes and climate extremes. Many of these houses are custom built, but more builders are beginning to erect entire subdivisions of concrete homes.

Blocks with interlocking mortarless system?

The INCABLOCK concrete blocks can be used for conventional construction of walls and entire houses or buildings. It provides greater design flexibility while providing significantly greater structural strength and earthquake resistance compared to the standard concrete blocks.


Interlocking capabilities on all contact faces, with each block forms a dilatation joint in each contact face (top-bottom-left side-right side), increasing the flexibility to resist earthquakes and high winds.
 
Let's see what other special advantages about the INCABLOCK in detail! 

Self-alignment capabilities:
All blocks in the system are component to each other and can only be fit in one way.

Cost effective:
10 times faster than regular construction, 3 minutes compared to 39 minutes per conventional square meter. Easy assembly and construction, even if grout is needed.

Innovative design:
Hollow cells in the block interior allows the passage of re-bars, insulation materials, cables and pipes for utilities and grout when needed.


Unskilled labor rated:
After the first course is grouted to the flooring structure, the blocks are quickly assembled.

Fire resistant:
Since concrete blocks do not support combustion, their mass transfers heat slowly and their fire resistance is very high.

Sound control:
Especially important in multi unit housing, commercial and industrial applications, is excellent. It's also important in sound barriers for populated areas on highways.

Attractive finishes:
Perfectly aligned blocks with no mortar provide a better surface for applying decorative finishes by brush, towel or spray, in some areas may be left expose.