Location: Agroclimate and Hydraulics Research UnitTitle: Experimental determination of mode I traction-separation law parameters for cement to steel bonds
|AL DUSHAISHI, MOHAMMED - Oklahoma State University|
|BOCANEGRA-YANEZ, JOSE - Oklahoma State University|
|LEE, HUNJOO - Oklahoma State University|
Submitted to: Soil Science Research Network (SSRN)
Publication Type: Pre-print Publication
Publication Acceptance Date: 4/27/2022
Publication Date: 4/27/2022
Citation: Wise, J., Al Dushaishi, M., Bocanegra-Yanez, J., Lee, H.P., Hunt, S.L. 2022. Experimental determination of mode I traction-separation law parameters for cement to steel bonds. Soil Science Research Network (SSRN). Article id4095188. Available: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4095188.
Interpretive Summary: Cement is used in everything from general construction to fluid barriers. Debonding of cement to steel is not well understood, and previous research only focuses on measuring the bond strength. Theoretical models show that debonding is more complex and two other parameters (critical energy and contact stiffness) are critical in the analysis of bonds. A new experimental method was developed which measured all three parameters and tested different strain rates. The results showed that slow strain rates cause relaxation of the bond during failure compared to the faster strain rates. From testing over 120 samples, specific values for the bond strength, critical energy, and contact stiffness were determined. These results can be used in integrity models to more accurately predict the failure of cement to steel debonding.
Technical Abstract: Portland cement is commonly used in everything from general construction to fluid barriers in environmental and petroleum structures. Finite element models have shown that the bond strength between cement to steel is a weak point in integrity analyses, but the failure mechanism is not well understood. Bond strength of cement to steel has been modeled using traction separation law which includes the bond strength, critical energy, and contact stiffness associated with the bond. However, experimental measurements only focus on the bond strength resulting in an incomplete analysis of the failure. A novel experimental methodology was developed to measure the tensile bond strength, critical energy, and contact stiffness of neat cement to steel bonds cured at atmospheric conditions for two days. Strain rates of 0.1 mm/min, 1.0 mm/min, and 10 mm/min were tested. The results showed that the 0.1 mm/min strain rate is too slow for bond testing since two of the bonding parameters experience relaxation during testing and result in low values. The 1.0 and 10 mm/min strain rates do not have statistical significance with respect to the bonding parameters. From the direct tensile tests of neat cement to steel, the bond strength is 0.61 MPa, the critical energy is 204.2 J/m^2, and the contact stiffness is 1.00E+09 N/m^3.