huangyhg

in situ concrete testing
i have asked a contractor to core sample a concrete slab that was rain effected. i am concerned about porosity adn would like to test for density. if there is anyone with guidance or suggestions i would appreciate the input
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was the slab affected by rain during placement of the concrete or after completion of the work?
if during placement i expect your concern is that the concrete crew did not work well during the rain and that the concrete was not properly compacted, therefore reducing the density.
if the rain was after the work was complete i doubt that it has affected the density of the concrete and it is more likely that you have a surface finish problem.
it was rain effected during placement. the superintedent instructed them to cease work but they did not. there is now a dispute adn i would like a rational and justifiable basis for the next part of the "discussion".
i have a couple of questions.
1. is this a suspended structural slab or sog?
2. how thick is the slab?
3. how old was the slab before cores were taken?
4. have you noticed any drying shrinkage cracking in area placed prior to commencement of rain and also the area placed during rain?
5. was the area that was placed prior to commencement of rain protected while it was raining?
6. were cores also taken from the area which had been placed prior to rain?
7. in addition to the tests you have in mind, will any of the cores be tested for strength and subjected to some limited petrographic analysis?
some astm standards to consider are:
astm c42-standard test method for obtaining and testing drilled cores and sawed beams of concrete---note 5 in this standard recommends that the concrete be at least 14 days old prior to coring. astm c642-standard test method for density, absorption, and voids in hardened concrete, and some of the test methods in astm c856-standard practice for petrographic examination of hardened concrete to evaluate the microstructure of the sample.
for some more ideas, check this thread which was started by ron
suspended slab
all poured same day
top surface of 5mm has been water blasted off
am conerned about what is underneath
cores not taken yet
trying to resolve methodolgy
thanks for the thread link
so you have a justifiable concern and you expect the contractor to prove to you that the slab has been constructed within the requirements of the specification.
there are 2 sides to this, technical and cotractual. fistly you should check the specification to see which standards or codes of practice are relevant. are you in usa or uk? you can then either propose a testing regime, or check the contractors proposal.
contractually you need to look in the contract to read the clauses referring to tests and opening up the works.
finally for now the contractor should not receive full payment for this work until it is proved to have been carried out according to the specification.

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