shakeelahsan
Civil/Environmental
We have to go about obtaining cores from RCC Slabs. I'd request to guide me for obtaining cores and interpreting compressive strength results.
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Guide for Obtaining Cores and Interpreting Compressive Strength Result 4
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SkiisAndBikes
Structural
I believe it is important to determine the cause of the deterioration before considering rehabilitation or replacement. The deterioration looks significant.
If chlorides are suspected, what would be their source, i.e. chloride laden water or calcium chloride in the original concrete mix, deicing salts used to melt snow and ice in winter climates or other? The photographs show deterioration on the underside ... what is the condition of the top surface? If the top surface of the concrete is not deteriorated than it is a possibility that chlorides in the original concrete mix combined with moisture has led to this deterioration on the underside. Chloride profiles over various slab depths would provide indicators.
Has carbonation of the structural slab been considered? I have encountered this type of deterioration a couple of times where machinery/furnace fumes were not exhausted properly. Carbonation typically occurs over long periods of time.
I have worked on several projects using hydrodemolition equipment and it works really well under the right circumstances. I have only worked on the top surface of slabs with hydrodemolition equipment although I understand there is equipment that will do vertical and soffit surfaces. The equipment is specialized and expensive.
Given the low compressive strength results for the concrete and the possibility the concrete is contaminated with chlorides, the choice of saving the slab would likely be a short term solution, deterioration will continue or even advance at a more rapid rate in the concrete you leave. Gather as much information as possible before considering the rehabilitation, total replacement or constructing a new slab below the existing slab options. The testing mentioned above will cost very little compared to the construction costs being contemplated. Concrete mix design, waterproofing, etc.. all need to be considered.
If chlorides are suspected, what would be their source, i.e. chloride laden water or calcium chloride in the original concrete mix, deicing salts used to melt snow and ice in winter climates or other? The photographs show deterioration on the underside ... what is the condition of the top surface? If the top surface of the concrete is not deteriorated than it is a possibility that chlorides in the original concrete mix combined with moisture has led to this deterioration on the underside. Chloride profiles over various slab depths would provide indicators.
Has carbonation of the structural slab been considered? I have encountered this type of deterioration a couple of times where machinery/furnace fumes were not exhausted properly. Carbonation typically occurs over long periods of time.
I have worked on several projects using hydrodemolition equipment and it works really well under the right circumstances. I have only worked on the top surface of slabs with hydrodemolition equipment although I understand there is equipment that will do vertical and soffit surfaces. The equipment is specialized and expensive.
Given the low compressive strength results for the concrete and the possibility the concrete is contaminated with chlorides, the choice of saving the slab would likely be a short term solution, deterioration will continue or even advance at a more rapid rate in the concrete you leave. Gather as much information as possible before considering the rehabilitation, total replacement or constructing a new slab below the existing slab options. The testing mentioned above will cost very little compared to the construction costs being contemplated. Concrete mix design, waterproofing, etc.. all need to be considered.
Snow is not a problem in that region (SE Asia?). Mix of high heat, salty air (if by the ocean), humidity is likely the culprit. You may nedd to take a few samples from different areas to evaluate the extent of deterioration to make the call - demo, or repair.
I agree that this concrete is not capable of structural rehabilitation.
SkiisAndBikes brings up a good point about calcium chloride in the mix; however, if this is in a temperate climate, that's not likely...in any case, the source of the chloride needs to be determined in order to accommodate a repair scheme.
At this point, the beams would be suspect as well, since they are likely of similar concrete.
It looks like reconstruction is in order.
SkiisAndBikes brings up a good point about calcium chloride in the mix; however, if this is in a temperate climate, that's not likely...in any case, the source of the chloride needs to be determined in order to accommodate a repair scheme.
At this point, the beams would be suspect as well, since they are likely of similar concrete.
It looks like reconstruction is in order.
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