Experimental study on the influence of ultrasonic surface treatment on freeze-thaw and carbonation resistance properties of concrete

• Ultrasonic surface treatment is an effective method for improving the freeze-thaw and carbonation resistance of concrete with a high content of supplementary cementitious materials (SCM). • The dense microstructure of the ultrasonic hardening layer reduces water and CO 2 penetration. • The reduction in mass loss ratio of concrete during freeze-thaw cycles is attributed to fewer interfacial defects at the matrix-aggregate interface. Cement concrete, the predominant modern construction material, exhibits poor durability owing to its porous microstructure. Surface treatment has emerged as an effective method to enhance concrete's durability. While surface coating or modification techniques are commonly employed, they necessitate additional materials, thereby increasing engineering costs. In contrast, ultrasonic surface treatment(UST) of concrete offers a novel physical approach that requires no supplementary materials, rendering it a cost-effective and promising alternative. However, the frost resistance of ultrasonically treated concrete, particularly in the context of extensive use of supplementary cementitious materials, has not been extensively investigated in prior research. This study investigates the use of UST to enhance the frost and carbonation resistance of concrete. Results show that UST significantly improves both properties. Specifically, the relative dynamic elastic modulus of treated concrete increased by 11.37%-19.31%, mass loss rate decreased by 32.25%-52.86%, carbonation depth reduced by 24.22%-26.16%, and the carbonation coefficient dropped from 3.302–3.463 to 2.357–2.441. These enhancements are attributed to the refinement of the concrete surface microstructure and the improvement of defects at the matrix-aggregate interface due to UST. Consequently, UST represents a beneficial complement to conventional air entrainment and coating methods for enhancing the frost and carbonation resistance of concrete.