In construction, Could aluminum be in direct contact with concrete? Is this allowed?
342328
Embedded aluminum roof flashing, aluminum water stops, aluminum electrical conduit, introduced aluminum powder (sometimes used to foam concrete), or embedded structural aluminum shapes may all corrode in concrete or mortar. In all cases, a reaction that forms aluminum hydroxide and hydrogen gas occurs, and may cause expansion and cracking of the concrete or mortar. The common use of calcium chloride (or other alkali compounds), and dampness of the concrete increases the reaction rate. Usually, coating the aluminum with bituminous paint, impregnated paper or felt, plastic, or an alkali-resistant coating will prevent or sharply reduce the corrosion.
588486
If you mill Aluminum plates to a very fine precision, and then stack the plates together they will become difficult to dislodge from each other.  The reason is not due to suction.  It is due to covalent bonds forming between the two slabs of metal!  Hard to believe isn't it!  I thought so too, even when I got a chance to see it first hand.
662022
No, most of it is chemically incorporated into the crystalline structure the cement forms.  Of course, some does evaporate, but this is undesirable.  This is why concrete is often covered until it cures.
307244
I think you need to use a special cnc machine\n any way herein below some under considration useful sites\n\n•http://www.8bestsites.com/aluminum-extrusion/6/\n\n•http://www.maytecinc.com/\n\n•http://www.extrusions.com/005issue/htmls/ExtrusionAdvantages.htm\n\n•http://unisource-tech.com/Products_-_Unisource_Technolog/Aluminum_Extrusion_front_panel/aluminum_extrusion_front_panel.html\n\n•http://www.aeroext.com/\n\n•http://www.pennaluminum.com/extproc.asp\n\n•http://www.sati.com.tw/
410825
Others have had similar problems and solved them.  See the link.  In general, metals (especially iron and its alloys) rust when exposed to moisture in the presence of oxygen.  The rust is a loose collection of molecules that allow more moisture and oxygen to reach the base metal.  For example, you can shine aluminum but it will quickly dull with oxidation.  The aluminum corrosion however forms a tenacious film that protect the metal from additional corrosion.  I heard that copper (flashing?) on a rooftop can cause aluminum gutters to corode.  Various alloys of iron (steel) including heat treatments may impart various corrosion properties, however, chrome is usually added to form stainless steels that best resists rusting.  Silicon steel may have to be protected.  Good luck.
1131804
You have the potential for galvanic corrosion.  Essentially, two metals at different potentials share electrons and one metal (the one with the higher potential) will start to erode and "plate" the other metal.\n\nTypically, using some sort of material that is a non-conductor (ceramics, rubber, etc) between the two or passivating the metal surfaces or coating the metal surfaces (prime and paint per ANSI standards) are your best options to prevent this.
634505
Check with OSHA about this.
553992
here is something:\nwww.mmsconferencing.com/nanoc/\npdf/finalcircular.pdf\nand here is something else:\nNano-concrete is an example of a non-exotic material made better through nanotechnology and coming to market.  The ability to see and analyze material at the nano-scale means that concrete can now be  manufactured in such a way as to enable 3-inch thick highway bridge decks.  There are 150,000 obsolete bridges in the U.S. alone.  Nano-concrete can enable them to be rebuilt more cheaply and faster, and to be stronger and longer lasting.  The key impediment will be standard aversion to new ideas in the construction industry.\nanyway, google it for more info
124635
Matt slabs or Mass Concrete
974254
Construction & Use Regulations.
122620
This is what I found:\n\nCALCIUM CHLORIDE\n\nCalcium Chloride can be used for and in the following:\n\nIce and Snow Melters. Production of Calcium Salts. Cold-weather concrete additive - Soil solidification - Tractor Tire weighting. Direct drying compound. Shoulder and base stabilization. Dustproofing and freeze-resisting ore and coal. Increases web strength of corrugating media.  Improves dye retention. An additive to oil well completion fluids. Cementing finished oil wells. Drilling mud additive and drying petroleum fractions.\n\nDust Control - Concrete Accelerator:\n\nCalcium Chloride has unique properties that make it ideal for maintaining unpaved roads and fortifying road bases for new construction. It is calcium chloride's ability to regulate moisture on road surfaces that is the key to building roads that last.\n\nCalcium Chloride keeps roads moist, day-in and day out, keeping nuisance dust down. Reduced pot-holing and rutting made possible by calcium chloride surface stabilization makes roads safer year round.\n\nStabilized calcium chloride roads can reduce aggregate loss by up to 75%. In addition, they significantly reduce the frequency and costs associated with periodic grading.\n\nUniform compaction and residual calcium chloride helps protect road bases from winter freezing and related frost heaving. Long known as an effective ice melter, calcium chloride lowers the freezing point of moisture in road bases to nearly 60 degrees below zero.\n\nCalcium Chloride protection of unpaved roads and road  bases is cumulative and long-tasting. The migration of calcium Chloride from road bases is minimal. Studies have shown that calcium chloride is still present and providing stabilization in road sub-bases nearly 30 years after initial construction.\n\nCalcium Chloride maintains workability in concrete with reduced water usage. In addition, faster setting means that manpower and labor hours can be reduced. And the number of forms required for a project can be minimized, since they can be re-used faster at the job-site.\n\nCalcium chloride is commonly used in industry as an accelerator.  Accelerated rates of strength development allow for earlier removal of forms, earlier finishing operations and availability for use.  This also allows for shorter curing and protection periods which can be advantageous, especially in cold weather conditions.  Briefly, calcium chloride reduces initial and final setting, resistance to sulfate attack and bleeding.  Tensile and flexural strength are slightly decreased.  However, compressive strength, water tightness and modulus of elasticity are increased.  Resistance to damage by freezing and thawing is improved early but may be less resistant at later ages.\n\nOne of the major problems encountered with the use of calcium chloride as an admixture is the effect that the chlorides have on reinforced concrete.  Prestressed concrete can contain no significant amount of calcium chloride.  The effect of corrosion hat the presence of chlorides may produce can be controlled if appropriate measures are taken.\n\nIce Melters\n\nCalcium Chloride Liquid: a liquid brine in its natural state and is converted into a dry material by removing the water. It quickly absorbs water from the atmosphere. When calcium chloride is converted into a liquid, it gives off heat. Calcium chloride will melt ice at temperatures of-25° F.\n\nThe growing need for corrosion-inhibited deicers has prompted manufacturers to explore their production.  One example of this is a new corrosion-inhibited grade of liquid calcium chloride designed to meet or exceed deicers standards in all respects.  In addition to providing low corrosion versus salt, it has calcium chloride's operational benefits in that it continues to melt snow and ice at 20 degrees F, the temperature at which salt becomes an inefficient deicer.\n\nThose using corrosion-inhibited calcium chloride for deicing and anti-icing, report that it aggressively melts snow an
973045
Concrete, as it cures, forms a complex and insoluble "crystalline" structure.  Crystalline materials such as this have atoms that are more or less "locked" in place by the kinds of chemical bonds that formed during the curing process.  Since the atoms are more or less fixed in space relative to one another, they can't slip and slide to dissipate stresses.  So, when a large enough force is applied, the strong chemical bonds finally break and a "brittle fracture" occurs.  One observes concrete shatter, creating splinters and dust, and the material is described as brittle.
75835
Surfactants are used to prevent the surface tension forming the bubbles.  However, carefull experimentation must be done to make sure they do not have a negative effect on the strength of the concrete.
714809
The previous answer is almost correct, except that concrete actually set under water.  So they just have to make a form, put reinforcing steel in it, and pour concrete in the form in a way that displaces the water out of the form.  In time, concrete will harden even under water.\n\nFor you information, after concrete is poured, it is important to keep the concrete moist in the first 24 hours when it cures.
744760
I use water at work that is so pure it is at 10 MegaOhms of resistance (this is extremely pure). It falls on the bare concrete all the time. Nothing has ever happened, be it stains, etching, or pitting. I've seen it eat right through the rough spots on metal when it is heated to steam, but never concrete. Of course, I do realize that the concrete has been sealed with a polymer of some sort. But there are places where we've dropped things that have chipped the concrete. The water was fallen in those specific places, and even flooded across them. Nothing.\n\nNow water that pure CAN be erosive and it is an extreme solvent. You wouldn't believe how fast things dissolve in water that pure. It will rust metal faster than you've ever seen and it will break welds and springs in a steam system. This I've personally witnessesd.
519144
drop a concrete block on it
665018
According to BS 8110:Part 1, the structural use of concrete, precast concrete beam and cast in-situ beam can be designed using same design approaches and design criteria. But additional design criteria must be consider for precast concrete beam in resisting stresses caused by\n\nHANDLING\nSTORING\nTRANSPORTING\nERECTING\n\nBecause precast concrete beam is fabricated in factory, finished beam must be transported, stroed and erected. During these processes, different type of stresses will be exerted. This condition is absent in cast in-situ concrete.\n\nSecondly, design of connection for precast concrete beam is also very important to maintain its compatibility to the structure.\n\nThirdly precast concrete beam is also more affected by shrinkage and thermal expansion of concrete, thus movement joints must be design and adequtely supplied.\n\nFor more information about precast concrete design, please refer to BS 8110:Part 1 Section 5.