GB/T 16780-1997

📋 Scope / 适用范围 ai_extracted

This appendix is applicable to the calculation of the actual average strength grade of cement clinker. A2 Principle of Method The calculation is based on the strength indicators of Portland cement. According to the flexural and compressive strength values of clinker at various ages obtained from GB/T 177, the average strength grade of clinker is calculated in accordance with the strength indicators of Portland cement specified in GB/T 175. Among the average strength grades at each age, the lowest grade shall be taken as the actual average strength grade of the clinker. A3 Calculation A3.1 Clinker strength between grade 525 and grade 625 When the clinker strength falls between grade 525 and grade 625 according to the strength indicators in Table A1, the actual average strength grade of the clinker shall be calculated using Formula (A1). Table A1 MPa | Portland Cement Strength Grade | Compressive Strength | Flexural Strength | |-------------------------------|----------------------|-------------------| | | 3d | 28d | 3d | 28d | | 525 | 23.0 | 52.5 | 4.0 | 7.0 | | 625 | 28.0 | 62.5 | 5.0 | 8.0 | The average strength grade corresponding to the clinker strength at a certain age shall be calculated using Formula (A1): \( R_p = \frac{P_s - P_d}{P_g - P_d} \times 100 + R_d \) (A1) Where: \( R_p \) — Average strength grade corresponding to the clinker strength at a certain age; \( R_d \) — Lower strength grade when the clinker strength lies between two grades; \( P_s \) — Measured clinker strength at a certain age; \( P_d \) — Strength at a certain age for the lower grade, as determined from Table A1, which is lower than the measured clinker strength; \( P_g \) — Strength at a certain age for the higher grade, as determined from Table A1, which is higher than the measured clinker strength. A3.2 Clinker strength lower than grade 525 When the clinker strength is lower than grade 525, the actual average strength grade of the clinker shall be calculated using the strength indicators of ordinary Portland cement, as specified in Table A2, still applying Formula (A1). Table A2 MPa | Ordinary Portland Cement Strength Grade | Compressive Strength | Flexural Strength | |----------------------------------------|----------------------|-------------------| | | 3d | 28d | 3d | 28d | | 325 | 13.0 | 32.5 | 2.5 | 5.5 | | 425 | 17.0 | 42.5 | 3.5 | 6.5 | A3.3 Clinker strength higher than Portland cement grade 625 When the clinker strength is higher than Portland cement grade 625, the actual average strength grade of the clinker shall be calculated using Formula (A2): GB/T 16780—1997 \( R_p = \frac{P_s - P_B}{P_B} \times 100 + 625 \) (A2)

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