Effects of a Self-Developed Composite Modifier on the Compressive Strength, Shrinkage Behavior, and Microstructure of Cement-Stabilized Macadam

Abstract

Cement-stabilized macadam is widely used in pavement base layers but is susceptible to shrinkage-induced cracking. This study evaluated a self-developed composite modifier, designated DX-3, with the aim of improving volumetric stability while maintaining compressive strength. Mixtures with cement dosages of 4.0%, 4.5%, and 5.0% and DX-3 dosages of 0–2.0% were tested for unconfined compressive strength (UCS), drying shrinkage, temperature shrinkage, and microstructural characteristics using SEM and EDS. The UCS generally increased with DX-3 dosage up to 1.5% and then stabilized or slightly decreased. At 4.5% cement and 1.5% DX-3, the 7 d and 28 d UCS reached 5.67 and 7.43 MPa, respectively. Adding 1.5% DX-3 reduced the total drying shrinkage coefficient by 21.54–30.93%, the average temperature shrinkage coefficient by 2.71–3.72%, and the peak coefficient by 3.45–4.58%. The greatest temperature shrinkage sensitivity occurred at 0 to −10 °C. SEM observations indicated a more continuous cementitious matrix with more gel-like microstructural features after DX-3 modification. Overall, DX-3 improved shrinkage-related volumetric stability without compromising basic compressive strength.