Standard Test Average Test Average ASTM C 97 Absorption (3) 0.87 % Bulk Specific Gravity (3) 2 590 ASTM C 99 Modulus of Rupture Day (3) 2 000 psi ASTM C 170 Compressive Strength Day (5) 21 300 psi ASTM C 241 Abrasion Resistance Day (3) 35.7 Ha ASTM C 880 Flexural Strength Day (5) 1 800 p