Standard Test Average Test Average ASTM C 97 Absorption (3) 0.08 % Bulk Specific Gravity (3) 2 634 ASTM C 99 Modulus of Rupture Day (3) 2 300 psi ASTM C 170 Compressive Strength Day (5) 21 700 psi ASTM C 241 Abrasion Resistance Day (3) 43.5 Ha ASTM C 880 Flexural Strength Day (5) 2 100 psi