Funct. Mater. 2021; 28 (4): 737-742

doi:https://doi.org/10.15407/fm28.04.737

Influence of nano-C-S-H on the mechanical properties of recycled concrete

Wei He1,2, Gang Liao1,2

1Department of Traffic and Municipal Engineering, Sichuan College of Architectural Technology, 610399 Sichuan Chengdu, China
2Deyang Key Laboratory of Building and Bridge Structure Engineering, Sichuan College of Architectural Technology, 618000 Sichuan Defang, China

Abstract: 

In this paper, in order to improve the mechanical property of recycled concrete, nano-C-S-H was added to modify recycled concrete, and the mechanism of the improvement was also discussed. The methods of X-ray diffraction (XRD), Scanning electronic microscope (SEM), and Mercury intrusion porosimetry (MIP) were applied to characterize the microstructure of nano-C-S-H modified recycled concrete. The results showed that the effect of nano-C-S-H was remarkable, namely, the 7-day compressive strength increased from 22.5 MPa to 33.5 MPa and flexural strength from 1.74 MPa to 2.25 MPa. SEM images showed that the matrix of recycled concrete became denser after adding nano-C-S-H. XRD confirmed that the hydration product increased with the addition of nano-C-S-H. MIP results demonstrated that the pore structure was refined by nano-C-S-H and porosity of recycled concrete was reduced noticeably. All measurements proved that the hydration process of cement was accelerated by nano-C-S-H and more hydration products had been produced, which contributed to densify the microstructure of recycled mortar and was the main reason for improving the mechanical properties of recycled mortar.

Keywords: 
recycled concrete, recycled cement powder, nano-C-S-H, improved mechanical properties.

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