Register now or log in to join your professional community.
reinforced steel bars without any coated is enoughif you used epoxy you should be very careful because this coating may reduced the bonding between concrete and steel bars, this will be happen if the epoxy became solid before you start concreting.
I have seen other comments from the specialist and found it useful. But, practically, following last research we found that uncoated rebars is the best choice for foundations as a result of the following:
Coated rebars are protected from corrosions. It is realistic fact, but, nobody can be sure that rebars will be safe from any scratch within the installation or as a result of stresses.
And no doubt, if this happens, the ions will attack the weakest point of steel (which is the new scratched point).So, all ions will attack one point and will cause severe corrosion in one place rather than distributed along rebar and mitigate the impact.
Non coated bar are good for foundation purpose, becose it will give much bond strength between concrete and steel. we are using coated steel bars when the project site is a salty atmosphere or errectio will be occur in much delay. as per standerds we have to use the bar before it's10% corrotion.
and it is very rare to have a localozed corrotion at scratched point as commented earlier. Since most of the cases the concretewill give a dry atmosphere for the bars.
I agree with Eng. Alaa Jawad , that is the main reason to use bars without coated scratchs in bars.
second reason is bond between steel bars and concrete is better in bars without coated.
Tanks for all engineers who answered this question.
rebar works perfect with concrete, if you coats the surface it depends completely on the interaction between1: concrete and coating
2: coating and rebar.
So: No , it isn't better
Alternative is galvanized steel, but it costs more.
Better is to make the concrete mixture resistant, put in additives to make the mixture close up better, and let all the cement develop. tehse additives cost, but you need only2% in a mixture.
for durability it is better to use epoxy coated bars in foundition in addition to a good qaulity (dense)concrete. it effects to resisit corrosion due to carbonation or cloride.
because it prevent any chemical reaction between bars and area sourounding bars in case of destroy the passivity of steel.
Hi,
epoxy For the purpose of corrosion protection, yes it is good, but for bonding issue between bar and concrete may create problem, best choice in my view use cementitious anti corrosive coating which will work like a primer and protective coating.
it will bound equally good with bar and concrete, and protect bar from corrosion as for a life time solution.
.
It's Not allowed to make a coating with epoxy paint for the R.bars in the foundation ,, for extra protection for the R.bars you can
1-use Anti -corrossion habitat mixed with ready mixed concrete with a ratio related to the approved mix design
2- Use water proof layers using membrane with adhesive agent OR coating the poured foundation with approved epoxy coating with two or three layers,the typeof epoxy coating should be applied with according to the circumstances around the foundation...i.e...if the water table pulluted with oil >>(
Epoxy coated bars are good
numerous problems related to foundations causing severe damage, and often, compromising the bearing capacity of structures and the durability. The reasons for this is its interaction with soil, incorrect assessment of moisture and water effects on:
ô¸ Foundations soil and
ô¸ Concrete of the foundations.
Foundations are exposed to following aggressive environmental effects :
ô¸ Physical -The most drastic form of the physical impact leading to concrete degradation is frost action. Namely, water which is retained in pores and cracks freezes in low temperatures and exposes concrete to often very high pressures (up to 220 MPa).
ô¸ Biological -The biological effects comprise the impact of vegetation, which causes the existing cracks to widen as the root systems of trees expand Particularly detrimental in these terms are fig, willow and liquidambar (it is common in warm climates, grown locally as decorative tree whose leaves and fruit resemble those of a chestnut tree)
ô¸ Chemical effects.-
- Aggregate expansion,
- Salt weathering,
- Carbonation,
- Leaching.
Since the foundations, after the construction has been completed, are usually hardly accessible, it is necessary to pay attention to prevention of the adverse impacts of potentially aggressive actions, than to repair the damage.
As FBEC are inert to alkaline as well as acidic media and have very low diffusion rate for corrosive elements like chlorides, water, oxygen etc it is best corrosion protection strategy for foundations
There were tests of steel reinforcement extracted from concrete after 15 years spent in real conditions, in the concrete with high concentration of chlorine. The best results were achieved by some types of stainless steels and the reinforcement impregnated by epoxy, while galvanized reinforcement, low-carbon chrome-steel bars and 3CR12 stainless steel bars had a weaker performance.[ International Scientific Conference Urban Civil Engineering and Municipal Facilities, SPbUCEMF-2015, zoran boric et al]
