Healing of Micro-Cracks in Fly Ash Cement Composite using NaOH and Na2SiO3 Solution

Volume 6 Issue 3 September - November 2017

Research Paper

Healing of Micro-Cracks in Fly Ash Cement Composite using NaOH and Na2SiO3 Solution

Shaswata Mukherjee*, Saroj Mandal**, U. B. Adhikari***

* Research Scholar, Department of Civil Engineering, Jadavpur University, Kolkata, India.

** Professor, Department of Civil Engineering, Jadavpur University, Kolkata, India.

*** Retd. Scientific Officer, Central Glass and Ceramic Research Institute, Kolkata, India.

Mukherjee, S., Mandal, S., and Adhikari, U.B. (2017). Healing of Micro-Cracks in Fly Ash Cement Composite using NaOH and Na2SiO3 Solution. i-manager’s Journal on Structural Engineering, 6(3), 37-45. https://doi.org/10.26634/jste.6.3.13733

Abstract

Microstructural properties of autonomically healed 0, 20, 40, and 60% OPC replaced by fly ash in cementitious composites are reported in this paper. Artificial micro-cracks were generated on cementitious cube specimens by the applications of compressive loads. NaOH (10-M) and Na SiO solution were used as healing agent. The cracked 2 3 O specimens were either injected or submerged in the chemical solution, followed by heat curing at 60 C for 48 hours. Self-healing in terms of recovery of properties were observed in UPV measurement and compressive strength study. Specimens containing 40% fly ash content mortar specimens showed better recovery of UPV and compressive strength. For limitation and better control of some analytical testing like TGA (Thermogravimetric Analysis), FTIR (Fourier-Transform Infrared Spectroscopy), XRD (X-ray Diffraction), SEM-EDAX (Scanning Electron Microscope with Energy Dispersive X-ray Analysis) were done in paste mixes rather than mortar mixes. Sodium calcite and sodium aluminate phases were found at the crack zone after submerging and injection of the NaOH (10 M) and Na SiO solution in 40% fly ash content paste 2 3 mix. FTIR analysis shows higher degree of geo-polymerization after submerging. TGA confirms higher mass loss for mix without any fly ash for both submerged and injected specimens. SEM reveals that the microstructure is more homogeneous in submerged specimens.