High-early strength controlled low-strength material mixture designs containing no portland cement were developed using three different fine aggregates (natural sand, manufactured sand, and limestone screenings) for “green” rapid subgrade repair applications under the direction of the Federal Highway Administration (FHWA). An attempt was made to determine if fifty percent by volume replacement of the fine aggregate with ASTM No.67 stone would allow the modified mixtures to function as emergency “green” base repair materials. The substitution of coarse aggregate increased the static modulus of elasticity by an average of 69 and 78 percent at 24 hours and 28 days, respectively. The mixtures achieved a high level of stiffness, with a minimum of 7.9-GPa (1150-ksi) at one day. Further, the mixtures with coarse aggregate substitution had average California Bearing Ratios (CBR) of 83 and 605 percent at 6.5 and 24 hours, respectively. No mixture with coarse aggregate substitution had a CBR less than 55 at 6.5 hours and the mixture with limestone screenings as fine aggregate had a base quality CBR of 129 percent. At 24 hours, the CBRs of the mixtures with coarse aggregate substitution were above 300, far above the typically specified 100 for agood base. Coarse aggregate substitution increased CBR by 324 and 244 percent on average at 6.5 and 24 hours. Finally, average compressive strengths of the mixtures with coarse aggregate substitution were 0.3 and 3.5-MPa (43 and 507-psi) at 4 and 24 hours, respectively.
Abstract