PSI - Issue 64

Hamzeh Shdeifat et al. / Procedia Structural Integrity 64 (2024) 1360–1368 Shdeifat at al. / Structural Integrity Procedia 00 (2019) 000–000

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results in thermal instability that might have deleterious impacts on the bond strength. In Fig. 5 and Fig. 6, mix KC14R.6(TS), which have been quenched in water, exhibited a great thermal resilience by recording a slight reduction in compressive strength and slight increase in shrinkage when compared to mix KC14R.6, which have been left to cool down naturally. It's noteworthy to mention that none of the mixes exhibited visible surface cracking at both firing periods. Fig. 7a shows the surface conditions of samples for mix KC14R.6 which have been allowed to cool down naturally, while Fig. 7b depicts the surface conditions of mix KC14R.6(TS) which have been thermally shocked by water quenching.

Fig. 7. (a) naturally cooled down samples; and (b) water quenched samples.

Despite experiencing high shrinkage post firing and additional thermal shock impacts from water quenching, the synthesised geopolymer did not display any visible cracks. 4. Conclusions The study presented the thermomechanical performance of potassium-based FA geopolymer in correlation with its suitability for NSM CFRP application under elevated temperatures following fire heating rate. Based on the experimental findings the following conclusions can be drawn: • Changing the oxide ratio of the activator had a greater influence on the compressive strength at ambient temperature comparted to changing its total alkali content. • Mixes with increased total alkali content in the activator had greater impact on the residual compressive strength and expansive behaviour at the first hour of firing, but high shrinkage at the second hour of firing. • The introduced thermal shock impacts resulted in a slight additional reduction in strength and volume without resulting in any visible cracking. • Although volume stability at elevated temperatures is important for the adhesive in NSM CFRP application, expansion at elevated temperatures can be advantageous for the bond strength. References Abdulkareem, O. A., Mustafa Al Bakri, A. M., Kamarudin, H., Khairul Nizar, I. & Saif, A. e. A. 2014. 'Effects of elevated temperatures on the thermal behavior and mechanical performance of fly ash geopolymer paste, mortar and lightweight concrete'. Construction and Building Materials, 50 , 377-387. Al-Abdwais, A. H., Al-Mahaidi, R. & Al-Tamimi, A. K. 2017. 'Performance of NSM CFRP strengthened concrete using modified cement-based adhesive at elevated temperature'. Construction and Building Materials, 132 , 296-302. Al-Safy, R., Al-Mahaidi, R. & Simon, G. P. 2012. 'Investigation of thermo-mechanical properties of adhesive used for bonding CF fabrics to concrete members using post-curing techniques'. Composites Part B: Engineering, 43 , 2950-2959. Alarcon-Ruiz, L., Platret, G., Massieu, E. & Ehrlacher, A. 2005. 'The use of thermal analysis in assessing the effect of temperature on a cement paste'. Cement and Concrete Research, 35 , 609-613.