Wednesday, October 19, 2016

Does failure on concrete compressive strength of a sample taken from a structure conclude structural failure?

Question ( Reader from Contractor Blog)

if i get a core sample of concrete in a newly built existing structure and found out based on laboratory test that the compresive strength of the sample is below  3000psi, does it conclude that the structure is unsafe or structurally unsound.
Are there other factors needed to be considered in determining structural soundness of the structure?

Answer ( Eng. Yasela)

Well , whether structure is unsafe or not depends on several factors.
first issue to be resolved , what is the design strength of the concrete that used in  design of the structure. Presuming it is 3000 psi, as you have mentioned, below the par values of 3000 psi  required further inquire . Further it is important to evaluate by what margin it get failed.

innitially, you can carry out a non destructive  test such as hammer bound test though the particular tests are not widely accepted . then you can carry out core drilling and test the sample. by means of these tests, you can evaluate the actual strength of the concrete of the structure.

with this figure you can check the design calculations. many distinguish concrete practice worldwide use factor of safety for the material and strength. if the actual concrete strength figures are higher than these values which is after the  applying of factor of safety, the strength of the structure should not be in question

however durability aspects of the structure may compromised due to serviceability conditions such as width of the crack, fatigue etc. these  issues are to be examined by a experienced structural engineer.

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