Attached information shows construction details of a water tank. The slab was poured in one pour and the walls (incl. Baffles) were poured in two even sections. Forms were stripped 3 days after pouring walls. The weather on these pour days was not extreme. The difference between the minimum to maximum temperatures were only 5 or 6 degrees. The cracking was identified through most holes allowed for formwork ties perpendicular to the wall thickness.
The cracks were in vertical direction originating from the base to nearly half way of the height of the external walls. The cracks appear to be wider near the base and narrowing with the height. The cracks appeared within the first week after the concrete placement, first noticed as soon as the formwork was removed.
The following are events:
1. Tank Base poured (Temperature min 9.3, max 16.5°C)
2. North side of structure poured (including north wall, ½ east wall, ½ west wall & intermediate baffle) (Temperature min 17.4°C, max 30.6°C)
3. Formwork stripped (first sign of cracking through formwork tie bars)
4. South side of structure poured (including south wall, ½ east wall, ½ west wall, intermediate baffle & overflow weir) (Temperature min 14.1°C, max 22.5° C)
5. Formwork stripped (similar cracks to first pour noticed)
6. Water testing commenced and leakages detected.
Photograph of the cracks in concrete and water leakage are shown in pictures attached.
Drawings are also attached.
Your assignment is to identify the type of cracks and convince the reader of your report the conclusions that you have reached in your report.
(1) List all the possible type of reasons that may have caused these cracks
(2) Discuss the reasons for and against each type of cracks mentioned above;
(3) Arrive at a conclusion backed by logical arguments that the type of crack you consider is the most likely cause of the cracks found.
(4) Present calculations to back up your argument if possible.
(5) Having identified the type of cracks above, now discuss the how these types of cracks can be avoided in future in the same type of situations.