Differences in salient beliefs associated with voluntary exercise training among South Korean firefighters before and after COVID-19

Background : Participating in voluntary exercise training is important to meet occupational requirements as well as firefighters’ health and safety. The purpose of this study is to identify salient beliefs associated with voluntary exercise training among firefighters in the pandemic era by comparing outcomes with those from a previous elicitation study, which was carried out before the COVID-19 outbreak. Methods : A total of 57 firefighters are recruited to participate in an elicitation study. Participants are requested to respond to six open-ended questions related to voluntary exercise training. Content analysis is used to create categories that combine similar factors in each belief. Beliefs mentioned by more than 30% of participants are used for comparison with the results of the previous research. Results : “Improves my physical ability” (n = 44) and “cause injury” (n = 17) are identified as behavioral beliefs in the present study, whereas “makes me tired” and “takes too much time” were also elicited in Lee’s study. Normative beliefs are “family members” (n = 45) and “colleagues” (n = 27) and these results are consistent with those in Lee’s study. “Lack of time” (n = 28), “exercise facilities” (n = 19), and “COVID-19” (n = 19) are elicited as control beliefs in the present study, whereas “physical condition” (n = 21) and “exercise partners” (n = 14) were elicited as other control beliefs, and “COVID-19” was not mentioned in Lee’s study. Conclusion : This study can contribute valuable information about salient beliefs associated with exercise training behavior among firefighters, particularly under pandemic conditions. Future researchers should develop tailored exercise training programs for firefighters based on current elicited beliefs.This research was supported by the Emergency Response to Disaster sites Research and Development Program funded by National Fire Agency(20013968)

Enhancement of Material Properties of Lime-Activated Slag Mortar from Intensified Pozzolanic Reaction and Pore Filling Effect

To utilize alkali-activated materials widely, this study investigates the effects of an intensified pozzolanic reaction and pore filling by silica fume on various material properties of lime-activated slag mortar. Although ground-granulated blast-furnace slag is classified as a cementitious material, it commonly requires an activator to enhance the performance of structural materials. In the first step of the improvement strategy, slag reaction is activated by hydrated lime. Next, silica fume is added to densify the microstructure by the physical pore filling effect and/or the pozzolanic reaction that additionally forms hydration products. This increased the compressive strength by 18% at 28 days and by 25% at 91 days under ambient curing condition, mainly due to the physical effect. Moreover, elevated temperature curing for three days was highly effective to further improve the strength, and to accelerate strength development. This is because both the physical effect and the chemical reaction are effective at the high temperature curing condition. The conducted microstructural investigation provided the evidence for the intensified pozzolanic reaction and pore filling effect, both of which are closely related to the mechanical properties. It is also found that the use of silica fume positively contributes to the dimensional stability. Since the developed material exhibits high strength (>40 MPa after 14 days) without Portland cement or highly toxic chemicals, it can be practically used as an eco-friendly structural mortar

Development of cementless ultra-high performance fly ash composite (UHPFC) using nucleated pozzolanic reaction of low Ca fly ash

© 2022 Elsevier LtdThis study developed ultra-high performance fly ash composite (UHPFC) by enhancing the pozzolanic reactivity of low-calcium fly ash (FA). Although it did not include Portland cement, the composite exhibited outstanding performance in workability, mechanical properties, and strength development. At room temperature (20 °C), the hydrated lime-activated FA containing silica fume showed a distinct acceleration period. Moreover, 3 days of steam curing at 60 °C guaranteed its final strength (∼110 MPa) before 7 days because of the synergistic effect between the ultrafine filler and steam curing. At 60 °C, the reactivity of FA was dramatically improved only when nucleation sites were provided by silica fume. Furthermore, increasing the curing temperature reciprocally affected FA and silica fume in the reaction; while FA was a leading participant in the pozzolanic reaction, silica fume mostly played a role as a physical filler, providing the nucleation site for reaction products.N