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Concrete Technology - Theory & Concepts

Properties of fresh and hardened concrete, mix design, and testing methods.

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ACI Strength Gain Profile

Adjust curing age and target 28-day strength to observe concrete compressive strength gain over time.

Curing Time (t)7 days
Day 1Day 90
Target 28-Day Strength (f'c,28)30 MPa
Low Strength (20)High Strength (60)
Note: Standard concrete specifications use the 28-day compressive strength (fc,28f'_{c,28}) as the design basis, at which hydration is assumed to be mostly stable.
ACI 209 Curve: Strength (MPa) vs Time (Days)
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ACI 209 empirical model

fc(t)=fc,28(t4+0.85t)f_c(t) = f'_{c,28} \left( \frac{t}{4 + 0.85t} \right)
fc(7)=30(74+0.85(7))f_c(7) = 30 \left( \frac{7}{4 + 0.85(7)} \right)
fc(7)21.1 MPaf_c(7) \approx 21.1 \text{ MPa}