When placing concrete in hot weather conditions in California, the CBC requires that the concrete temperature at the time of placement not exceed what maximum temperature?
Correct Answer
A) 90°F
CBC Section 1905.12 limits concrete temperature to a maximum of 90°F at placement in hot weather conditions. This requirement prevents rapid moisture loss, thermal cracking, and ensures proper hydration. Higher temperatures can lead to reduced workability and strength development issues.
Why This Is the Correct Answer
CBC Section 1905.12 limits concrete temperature to 90°F at the time of placement during hot weather. Above this threshold, the rapid evaporation of mix water accelerates setting time, reduces workability, increases shrinkage cracking risk, and can compromise long-term strength development. The 90°F limit is the standard referenced in this CBC section.
Why the Other Options Are Wrong
Option B: 100°F
100°F is too high and is not the limit set in CBC Section 1905.12. Placing concrete at 100°F would risk flash setting, surface cracking, and significantly reduced ultimate compressive strength. Some specifications may permit up to 95°F in certain contexts, but 100°F exceeds acceptable limits under this code section.
Option C: 95°F
95°F is the limit referenced in a different CBC section (1906.12), not Section 1905.12. This question cites Section 1905.12, where the limit is 90°F. The 5-degree difference between the two sections can trip up candidates who know the topic but misidentify which code section applies.
Option D: 85°F
85°F is more conservative than the code requires under Section 1905.12. While lower temperatures are generally better for concrete quality, the CBC does not mandate an 85°F limit for this section. This option might seem plausible as a conservative measure but is not the correct regulatory answer.
Memory Technique
For Section 1905.12: think '1905 = earlier section = lower temperature = 90°F.' The earlier the section number, the lower the temperature limit. This paired association helps distinguish the two sections.
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