Difficulty: Easy
Correct Answer: More than 5%
Explanation:
Introduction / Context:
Water absorption is a key durability indicator for building stones. Excessive absorption correlates with higher porosity, reduced strength, frost susceptibility, and accelerated weathering. The question seeks the commonly accepted rejection threshold for general works.
Given Data / Assumptions:
Concept / Approach:
Stones with absorption above about 5% by weight are typically considered poor for general construction due to increased susceptibility to dampness, salt crystallization, and frost damage. Premium stones often exhibit absorption well below this value, while more porous varieties may be restricted to non-critical uses after treatment.
Step-by-Step Solution:
Verification / Alternative check:
Traditional specifications and handbooks cite ≤5% as a desirable maximum for general construction stones, with lower values for severe exposure conditions.
Why Other Options Are Wrong:
Common Pitfalls:
Applying a single threshold to all environments (marine/freeze-thaw may demand stricter limits); ignoring sealing/finishing requirements that can mitigate but not fully offset high porosity.
Final Answer:
More than 5%
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