Per §7.2 ('Maturity'), the standard maturity of concrete cured at 18°C…

Question

Per §7.2 ('Maturity'), the standard maturity of concrete cured at 18°C for 28 days is approximately:

Accepted Answer

A. {'text': 'About 19,400 °C-hr (degree centigrade hours)', 'label': 'A'}

1. §7.2 computes M = 28 × 24 × [18 - (-11)] = 19,488 °C-hr, taken as about 19,400 °C-hr standard.
2. This value anchors Plowman's relation A + B log10(maturity × 10⁻³) for the relative strength at any maturity.
_Source: IGNOU ET-522 Block-2 Unit-7 Strength of Concrete, §7.2 (Maturity), p. 51_

Answer

{'text': 'About 8,000 °C-hr (degree centigrade hours)', 'label': 'B'}

Answer

{'text': 'About 2,500 °C-hr (degree centigrade hours)', 'label': 'C'}

Answer

{'text': 'About 50,000 °C-hr (degree centigrade hours)', 'label': 'D'}