Material Properties Flashcards
7 cards from real ASCE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Material Properties flashcards as text
Under ACI 318, at what age is the specified compressive strength of concrete (f'c) normally defined?
Answer: 28 days
f'c is normally based on standard cylinders tested at 28 days unless the specification gives a different age.
For normal-weight concrete, which ACI expression approximates the modulus of elasticity Ec in psi?
Answer: Ec = 57,000√f'c
ACI 318 permits Ec = 57,000√f'c psi for normal-weight concrete.
What is the ACI 318 expression for the modulus of rupture of normal-weight concrete in psi?
Answer: fr = 7.5λ√f'c
ACI 318 gives the modulus of rupture as fr = 7.5λ√f'c, where λ = 1.0 for normal-weight concrete.
If all other factors stay the same, what happens when the water-cement ratio of a concrete mix goes up?
Answer: Compressive strength goes down and permeability goes up
More water leaves more capillary pores, which lowers strength and durability.
What is the time-dependent increase in strain of concrete under a sustained constant stress called?
Answer: Creep
Creep is strain that keeps growing under a sustained load, which is why long-term deflections exceed immediate ones.
Which ASTM C150 portland cement type is used when high early strength is needed, such as for fast form removal?
Answer: Type III
Type III cement is ground finer and hydrates faster, so it gains strength early.
Which is a typical effect of replacing part of the portland cement with Class F fly ash?
Answer: Less heat of hydration and better long-term strength and durability
Fly ash is a pozzolan that reacts slowly with calcium hydroxide, which lowers heat and refines pore structure over time.