Which of the following is NOT listed as a critical visual sign of potential contamination when delivering concrete?

• A. Color differences
• B. Lumps
• C. Temperature
• D. Strong odors

Answer: (C)

Visually assessing concrete for potential contamination relies on cues you can observe in real time. Color differences can reveal impurities or admixtures that don’t belong, giving you a flag that something isn’t right. Lumps indicate segregation or the presence of foreign material that shouldn’t be in the mix. Strong odors can signal contamination from organic matter or other substances. Temperature, however, isn’t something you can judge by sight; it requires a thermometer or other measuring device and is a measured parameter rather than a visual cue. While temperature control is important for quality, it isn’t listed as a visual sign of contamination.