Rheological properties and mechanical durability of 3D-printed concrete based on low-field NMR

Abstract

3D-printed concrete has been widely used in building structures. It is essential to study the influence reasons of rheological properties during stirring process and mechanical durability for 3D printed concrete during salt-frozen environments. The rheological properties, mechanical durability and porosity properties of basalt fiber-reinforced 3D-printed materials under salt freeze-thaw cycles are analyzed in this work. The moisture changes during the process of stirring and microscopic porosity characteristics inside structure were investigated by using low-field nuclear magnetic test technology. Pore distribution characteristics are studied based on fractal theory, and the prediction model of rheological properties, mechanical properties were both prosed based on T2 spectrum signal. Results show moisture change reflect the rheological properties of cement paste during stirring, the pore distribution presents a process of increasing dimension inside structure under salt freeze-thaw, and a 0.1 %—0.3 % volume content of basalt fiber can be helpful to improve the mechanical durability. The developed strength prediction model based on the fractal dimension coefficients and pore proportion weights of different pore components exhibit high fitting accuracy and strong interpretability, which can effectively predict the compressive and flexural strengths of 3D-printed concrete under salt–frozen conditions. This study will promote the 3D printed concrete applied in salt freezing-thawing environment.