Construction Dive Seattle's Rainier Square Tower Proving Ground for Reinforced Concrete Core Alternative All the foundation specs we build on require rebar to be free of rust and mill scale.
A. Tim Fisher responds: Fortunately, there are a couple of standards you can cite in your defense. The ATM standard for deformed steel reinforcement (A706) and the Concrete Reinforcement Steel Institute (CSI) Manual of Standard Practice both give the same recommendation: Reinforcing bar with rust, mill scale, or a combination of both is satisfactory, provided the minimum dimensions, weight, and height of the deformations (the formed protrusions on the bar) of a hand-wire-brushed test sample are not less than the values specified in the standard.
In fact, studies have shown that mill scale and light rust enhance the bond between concrete and steel. Tim Fisher is the field engineering editor for Aberdeen’s Concrete Construction magazine.
Question: The project inspector is requiring us to wire-brush mill scale and rust off all our rebar. Although the rebar has been at the site for a couple of weeks, we don't think the rust is that heavy or will interfere with the bond between the concrete and steel.
The ATM standard specification for deformed steel reinforcement and the Concrete Reinforcing Steel Institute (CSI) Manual of Standard Practice both give the same information: Reinforcing bars with rust, mill scale, or a combination of both should be considered as satisfactory, provided the minimum dimensions, weight, and height of deformation of a hand-wire-brushed test specimen are not less than the applicable ATM specification requirements. This inspection criteria recognizes studies that have shown mill scale and rust enhance the bond between concrete and steel.
Construction Dive Seattle's Rainier Square Tower Proving Ground for Reinforced Concrete Core Alternative The process of inspecting a house required knowledge of local construction methods along with understanding the causes of deterioration or failure of the building components.
Any plumbing or electrical requires a channel cut into the brick and across the concrete posts and beams to properly bury the conduits and pipes in the finish plaster. I soon learned that most laborers demolish old walls, or old houses, with 12-pound sledgehammers while wearing huaraches that most people would have discarded years ago.
It is not uncommon to find everyone on a construction site wading through rubble, bricks and tangled pieces of rebar because no one feels responsible for any meaningful clean-up on a regular basis. As the new construction moves forward, piles of sand, gravel, bricks and bags of cement sprout on the sidewalk or street in front of the project.
When the time comes to form up the roof or second floor, a crew arrives with a large truckload of wooden pallets and small-diameter, tree trunk poles. Since none of the poles are the same length, small scraps of wood, or bricks, or rocks, are used as shims in an attempt to level the elevated forms.
I am sure I could ramble on for several more paragraphs, getting into more construction detail; however, I refrain from such discourse to prevent my readers’ eyes from rolling back as they slip into a state of bored torpidity. After getting the general gist of the construction procedure I spent time talking with people who had purchased homes and had dealt with a variety of problems.
When I examined walls and ceilings where the plaster had failed and sloughed off in large chunks, the exposed rebar was incredibly rusty and flaking. While he was in the States for a few weeks, his bedroom ceiling experienced an instantaneous, catastrophic failure, which relocated 1,000 pounds of plaster to the floor in less than a second.
While viewing the wreckage with the stunned owner upon his return to his beloved home, I noticed a number of orange spots around the rusty ceiling rebar, now exposed by the collapse. Apparently, when this ceiling had failed the first time, someone had painted the rustyrebar with rust inhibiting primer thinking it would halt the oxidation process.
A couple of years ago a gringo friend rose from her chair under the concrete awning of an old property now hosting a popular restaurant along the Macon. Recently, a friend showed me the remains of her cat’s food bowl after a large piece of ceiling lost its battle with gravity.
As a consequence I highly recommend that anyone live in an older Mexican home in areas where building practices resemble those used here undertake the yearly exercise of using a broomstick or pole to tap as much of the ceiling as possible to find the hollow spots that could foretell future problems. Bodies Kellogg describes himself as a very middle-aged man who lives full-time in Mazatlán with a captured tourist woman and the ghost of a half wild dog.
RUST is caused by the reaction of air (O2) and moisture (H2O), and it is a common and natural phenomenon for most steel products. Corrosion occurs when steel reacts with chloride ions (Cl-), CO2 in presence of toxic environment.
Corrosion is uneven erosion/pitting of metal surface/ribs due to intense rusting and is harmful to the intended service performance of rebar.NEVER USE SEVERELY RUSTED OR PITTED REBARS. Never keep your rebar in direct contact with ground, and without any tarpaulin cover for longer period of exposure.
It is observed that the uncovered column rebars projected off above floor slab level is particularly loosely affected at the junction of slab top with the projected rebars. The reason for same is that during curing for 28 days (in general) or rainfall, the water accumulates at this junction.
Measures recommended for preventing Corrosion of embedded reinforcement in concrete The concrete should be properly compacted by tamping or vibration and adequately cured.
After the RCC structure is passed for quality and finish, it may be rendered with cement plaster of 1:2 or 1:3 proportion. Cement, sand, stone aggregates and water, should be tested for chloride and sulfate contents, as corrosion of the embedded reinforcement bar is likely to happen if the total water-soluble chloride and sulfate contents exceed the limits of 50 ppm and 500 ppm respectively in raw concrete mix.
Adequate nominal cover thickness should be provided to steel reinforcement satisfying durability requirements as per table 16 of BIS456-2000 (table 16A on fire resistance requirement also needs to be satisfied along with it). Existing RCC structures may be protected from reinforcement corrosion in aggressive atmospheres by applying protective surface coatings to the exposed surfaces of concrete.
Heavy rusting of reinforcement should be removed by wire brushing or application of commercially produced debuting and forfeiting jellies of approved quality. Since it may not be possible to restrict the chloride and sulfate content within the tolerable limits in marine atmospheres or in contact with seawater, the reinforcement bars should be coated with a protective coating of inhibited cement slurry (for guidance on application, please refer appendix-B of BIS9077).
It should be ensured that no oil or paint is applied as a protective coating to the reinforcement bar. 7, it is to be noted that protective coatings involve considerable cost involvement, stringent process control, and possibility of damage during handling or fabrication (cutting and bending) of rebar.
At this junction, to avoid such headache on coatings, Tata Tisconoffers you “CRS”: Corrosion resistance steel, which possess inbuilt corrosion resistance properties in rebar (due to inherent chemistry composition of the mother billets). It has been found that Corrosion resistance index (Cry) of Tuscon CRS is 1.30, i.e, Corrosion rate of Tuscon CRS is (1.3-1)/1.3 = about 23% lesser in comparison to ordinary Fe500D rebars.
Disclaimer: This document aims only at highlighting good construction practices and meaningful applications during/after construction, to overcome the challenge of rust / corrosion of reinforcement bar. We at engineeringcivil.com are thankful to Sir Sour av Outta for submitting this very useful information to us.
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-- It is available at automotive paint shops and neutralizes the rust. Reply... Nor's Forum Posts: 6Randomly Selected Image.
If you can wire brush off the rust, that should be ok and should still meet the standard steel requirements. However, if the rust is thick then the effective diameter of the rebar will be reduced and should be taken into consideration in the design requirements.
The important thing is that the rebar should be able to bond to the concrete. Therefore, remove any dirt, mud, oil or any coating that will prevent the bonding.
Senior Member Probably looks better than the stuff I had delivered to put in the floor of my bathroom. The only time it will pose a problem is if the next big thing is to polish your floor back to show your red off.
Landscaper As long as it is encased fully inside the concrete once poured. If any bits of steel are protruding the concrete, they will rust and it travels down into the rest of the sheet.
Once encased in concrete, the alkaline environment pretty much stops the rusting but the textured surface of light rust aids adhesion to the steel. Once encased in concrete, the alkaline environment pretty much stops the rusting but the textured surface of light rust aids adhesion to the steel.