For concrete placed in California during hot weather conditions, what is the maximum allowable concrete temperature at the time of placement according to the CBC?
Correct Answer
C) 90°F
CBC Section 1909.5.3 limits concrete temperature to a maximum of 90°F at the time of placement. This requirement is particularly important in California's hot climate regions to prevent rapid moisture loss, plastic shrinkage cracking, and reduced concrete strength. Higher temperatures can also cause difficulties with workability and finishing.
Why This Is the Correct Answer
CBC Section 1909.5.3 sets the maximum concrete temperature at placement at 90°F. Above this temperature, hydration accelerates, workability decreases, plastic shrinkage cracking risk increases, and long-term strength is reduced. The 90°F limit is specifically calibrated to maintain adequate quality in California's hot-weather environments.
Why the Other Options Are Wrong
Option A: 95°F
95°F exceeds the CBC limit by 5°F. At this temperature, the risks of rapid moisture loss, accelerated set time, and reduced compressive strength are significant. Choosing 95°F indicates an off-by-increment error — a common trap when answer choices are closely spaced.
Option B: 100°F
100°F is well above the code maximum. While some might associate round numbers with standards, 100°F concrete would experience severely compromised workability and strength development. This option is a high-end distractor designed to catch candidates who guess rather than recall the specific code value.
Option D: 85°F
85°F is actually cooler than the maximum allowed — meaning it would be acceptable, not a limit. This distractor tests whether candidates understand the word 'maximum.' Concrete at 85°F is fine; the code only prohibits placement above 90°F.
Memory Technique
Remember '90 is the Go/No-Go line for hot concrete.' If the thermometer reads 90°F or below, you're still legal. Picture a digital thermometer flashing red at 91°F with a 'STOP' symbol — the concrete truck must turn around.
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