Nuclear magnetic resonance analysis of freeze-thaw damage in natural pumice concrete

Abstract

This paper presents an analysis of the damage propagation features of the pore structure of natural pumice lightweight aggregate concrete (LWC) under freeze-thaw cyclic action. After freeze-thaw cycling, we conducted nuclear magnetic resonance (NMR) tests on the concrete and acquired the porosity, distribution of transverse relaxation time T2, and magnetic resonance imaging (MRI) results. The results showed the following. The T2 distribution of the LWC prior to freeze-thaw cycling presented four peaks representative of a preponderance of small pores. After 50, 100, 150, and 200 freeze-thaw cycles, the total area of the T2 spectrum and the porosity increased significantly. The MRI presented the changing spatial distribution of pores within the LWC during freeze-thaw cycling. Ultrasonic testing technology was applied simultaneously to analyze the NMR results, which verified that the new NMR technology demonstrated high accuracy and practicability for research regarding freeze-thaw concrete damage.

Keywords

• natural pumice concrete
• damage extension
• nuclear magnetic resonance (nmr)
• porosity
• relaxation time