Finding things in ACI 318-14
The exam is open book, so the skill is knowing where to look. Chapter 25 of ACI 318-14 (Reinforcement Details) is laid out as:
- 25.2 minimum bar spacing
- 25.3 standard hooks and minimum inside bend diameters
- 25.4 development length, with deformed bars in tension at 25.4.2
- 25.5.2 tension lap splice lengths of deformed bars and wires
The trap is 25.4.2. Development length in tension is a related quantity, but a lap splice length is in 25.5.2. Look for the word "splice" in the heading.
Chapter 19 (Concrete: Design and Durability) holds specified compressive strength f'c at 19.2.1 and exposure categories and classes at 19.3.1.
ASTM tests on the job
Chapter 2 of the ACI Contractor's Guide (3rd ed.) lists the ASTM standards for field and lab testing:
- C172 sampling fresh concrete
- C143 slump
- C231 air content, pressure method
- C173 air content, volumetric method
- C138 density (unit weight) and yield
- C31 making and curing compressive strength specimens
- C39 compressive strength test of the cylinders
The two pairs people confuse
C31 versus C39. C31 is the field step: a technician molds and cures the cylinders. C39 is the laboratory step: the cylinders are broken in compression. Same cylinder, two standards. If the question says "molding and curing," the answer is C31, not C39. Sampling the fresh concrete is C172, which comes before either.
C231 versus C173. Both measure air content of fresh concrete. C231 is the pressure meter; C173 is the volumetric method. When the question says "pressure-type meter," it is C231. C138 measures density and yield, not air, and C39 has nothing to do with fresh concrete at all.
A way to hold them: the tests on fresh concrete (C172, C143, C231, C173, C138) happen at the truck; C31 happens in the field right after sampling; C39 happens later in the lab.