Concrete Maturity and Equivalent Age (ASTM C1074)

The Arrhenius equivalent age at a 68 F reference, and the hours remaining to the mix's lab-calibrated TTF target. A 50 F week accrues 1,680 C-hr and reads as only 3.8 equivalent days - the cold slab is not '7 days old' - while three days at 90 F carry nearly six days of equivalent age. Datum 0 C and Q = 5000 K for Type I without admixtures, both editable. The strength a TTF represents comes only from the C1074 lab calibration of the actual mix; supplements, not replaces, acceptance cylinders.

M = (Ta - T0) x hours in deg C-hr (Nurse-Saul, one constant-temperature interval); te = exp(-Q x (1/(Ta+273.15) - 1/(Tr+273.15))) x hours (Arrhenius equivalent age, kelvin); target_hours = target_TTF / (Ta - T0) when a calibrated target is given.

ASTM C1074 (Standard Practice for Estimating Concrete Strength by the Maturity Method), by name; both maturity functions with their recommended Type I no-admixture constants.

The Nurse-Saul and Arrhenius maturity functions and the recommended constants are stated in ASTM C1074 and reproduced across the public maturity literature (NRMCA CIP 39); the arithmetic is public.

Estimate. AHJ and licensed professional govern.

Field names used by the API: concrete_temp_f, hours, datum_f, q_kelvin, ref_temp_f, target_ttf_c, M_c, M_f, te_hours, te_days, target_hours

• Datum and Q T0 = 0 C and Q = 5000 K are the C1074 recommendations for Type I cement without admixtures; other mixes calibrate their ownASTM C1074
• Single interval one average temperature over the period; a logged history sums interval by intervalASTM C1074
• Calibration governs TTF maps to strength only through the lab curve for the actual mix; acceptance cylinders are not replacedNRMCA CIP 39