A contractor is building near an active lava flow zone. The foundation design must account for potential ground temperature increases. What additional consideration is required?
Correct Answer
B) Heat-resistant concrete admixtures and thermal barriers
Construction near lava zones requires heat-resistant concrete admixtures and thermal barriers to protect the foundation from elevated ground temperatures.
Why This Is the Correct Answer
Near active lava zones, ground temperatures can rise dramatically. Heat-resistant concrete admixtures maintain the concrete's structural integrity at elevated temperatures, while thermal barriers isolate the foundation from direct heat transfer. This combined approach addresses both the chemical and thermal degradation risks unique to volcanic environments.
Why the Other Options Are Wrong
Option A: Increased foundation depth only
Increased foundation depth alone does not address the thermal risk. While deeper foundations may reach more stable ground, they would still be exposed to elevated temperatures without heat-resistant materials or thermal isolation, making depth modification an incomplete solution.
Option C: Reduced reinforcement spacing only
Reduced reinforcement spacing alone increases the structural density of the rebar cage but does not address the primary hazard — heat degradation of the concrete and corrosion acceleration of the steel. Spacing adjustments without material modifications are insufficient near lava zones.
Option D: Standard concrete mix with no modifications
Standard concrete mix degrades significantly above 300°F (150°C). Near lava zones where ground temperatures can exceed these thresholds, using an unmodified standard mix would result in loss of compressive strength, spalling, and premature structural failure.
Memory Technique
Near lava = heat problem = need heat ARMOR. The two-part armor is: (1) heat-resistant admixtures for the concrete itself, and (2) thermal barriers between the hot ground and the foundation. Both layers of armor are required — admixtures alone or barriers alone are incomplete.
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