A building project in Honolulu requires a concrete slab exposed to severe saltwater conditions. The structural engineer specifies a water-cement ratio not to exceed 0.40. If 600 pounds of cement are used, what is the maximum water content allowed?
Correct Answer
C) 240 pounds
Maximum water = 600 lbs cement × 0.40 w/c ratio = 240 pounds of water. Lower w/c ratios reduce permeability and improve resistance to chloride penetration.
Why This Is the Correct Answer
The correct answer is 240 pounds. The water-cement (w/c) ratio is defined as the weight of water divided by the weight of cement. Rearranging: Maximum water = w/c ratio × cement weight = 0.40 × 600 lbs = 240 lbs. This low w/c ratio is specified for severe saltwater exposure because less mixing water means fewer and smaller pores in the hardened concrete, reducing permeability and slowing chloride ion penetration.
Why the Other Options Are Wrong
Option A: 200 pounds
200 pounds corresponds to a w/c ratio of 200/600 = 0.333, which is lower than the specified maximum of 0.40. While 200 lbs of water would produce even lower permeability concrete, it does not represent the maximum allowed by the 0.40 specification — it is more restrictive than required and could make the concrete difficult to place and consolidate.
Option B: 280 pounds
280 pounds would give a w/c ratio of 280/600 = 0.467, which exceeds the specified maximum of 0.40. Using 280 lbs of water violates the engineer's specification and would produce more permeable concrete, increasing vulnerability to chloride penetration in the severe saltwater environment.
Option D: 320 pounds
320 pounds yields a w/c ratio of 320/600 = 0.533, well above the 0.40 maximum. This significantly exceeds the specification, producing highly permeable concrete that would rapidly admit chloride ions, accelerating reinforcement corrosion. This is a clear code and specification violation.
Memory Technique
W/C ratio is always Water over Cement — like a fraction with water on top. To find maximum water: flip the formula to Water = Ratio × Cement. For 0.40 × 600: think 40% of 600 = 240. Quick check: 10% of 600 = 60, so 40% = 4 × 60 = 240.
More Hawaii Questions
A concrete mix design for coastal construction specifies a water-cement ratio of 0.40. If 650 lbs of cement is used per cubic yard, how many gallons of water should be added?
A contractor is installing hurricane straps rated at 1,500 pounds each. If the calculated uplift force on a rafter is 3,200 pounds, how many straps are required with a 2.0 safety factor?
Hawaii Building Code requires special inspection for concrete placement in seismic design categories. What is the minimum frequency for concrete strength testing?
What is the maximum allowable deflection for roof rafters under design wind loads in Hawaii's hurricane zones?
Which roofing attachment method is specifically required in Hawaii's hurricane zones for asphalt shingles on residential construction?
A building in Maui requires hurricane straps rated for 175 mph winds. If each strap must resist 1,200 lbs of uplift force and you have 48 roof-to-wall connections, what is the total uplift resistance provided?
During construction of a beachfront property, you notice white crystalline deposits forming on the concrete surface. This indicates:
You discover expansive clay soil conditions during excavation for a residential foundation in Kona. The plasticity index is 28. What foundation system is most appropriate?
According to Hawaii building requirements, hurricane straps connecting roof trusses to wall plates must be rated for what minimum uplift force in high wind zones?
A concrete slab foundation in Hawaii requires a vapor barrier. Due to high humidity and frequent rainfall, what type of vapor barrier is most appropriate?
People Also Study
Business & Financial Management
120 questions · 70% to pass
Contract Administration
60 questions · 70% to pass
Project Management
60 questions · 70% to pass
Related Study Resources
Previous Question
In Hawaii's tropical climate, what is the most effective method for preventing subterranean termite infestation in new construction?
Next Question
During a building inspection in Hawaii, you notice termite damage to floor joists. According to Hawaii regulations, what immediate action is required?