Experimental study on recycled steel fiber concrete
Some basic properties of recycled steel fiber aggregate were tested, such as surface features, water absorption, apparent ensity, crushing index, cube compressive strength and so on. Recycled steel fiber aggregate were used to replace the natural aggregate by 0%, 25%, 50% and 100% proportion to make concrete. Afterward, compressive strength, splitting tensile strength and flexural strength were investigated at ages 3, 7 and 28 days. The results showed that thorn appearance of recycled steel fiber aggregate makes packing density decrease, crushing value and absorption increase. The compressive strength, splitting tensile strength and flexural strength of the recycled concrete depend on the mix proportions. Generally, the strength of recycled concrete can be 15–25% lower than that of concrete made with virgin aggregate.
Compressive Strength of Steel Fiber Reinforced Polymer Modified Recycled Aggregate Concrete
Demolish existing structures for better economic gains, functional and structural performance, and non-availability of land or disposal sites in nearby areas of all major cities worldwide turned as a significant reason for the crushing demolished concrete instead of using it as landfill. Research work aimed at arriving Recycled Concrete (RC) with the help of two materials, i.e. Steel Fibers (SF) and Styrene-Butadiene Rubber (SBR) latex, as additives to improve strength parameters of it. SF and SBR added in RC to examine & strengthen and termed as Steel Fiber Reinforced Polymer Modified Recycled Aggregate Concrete (SFRPMRAC). For this purpose, 198 cubes each of M20 (trial-1) and M25 (trial-2) cast separately to check compressive strength and its stress-strain behaviour for Natural Concrete (NC), RC & SFRPMRAC. The volume fractions of SF added 0.5%, 1% & 1.5% m3 of concrete and dosages of SBR latex varied from 2.5%, 5% and 7.5% by cement weight for preparation of cubes made of RC. From experimental results, SFRPMRAC with SF volume fraction of 1% m3 of concrete and 5% by cement weight provides an improvement in compressive strength by 8.62 % & 10.73 % for trial -1 and 11.51 % & 12.57 % for trial - 2 at 28 & 90 days when compared with NC. Compression stress-strain behaviour for SFRPMRAC with SF 1% m3 of concrete and 5% by weight of cement shows higher strain values at the peak stress. SFRPMRAC arrests the sudden drop of load due to co-matrix bond formation between SF and SBR in a linear direction compared to a similar NC & RC mix for both trials. It reflects significant improvement and approval of compressive strength for the desired purpose.
Predictors of health-promoting behaviors among freshman dental students at Istanbul University.
The aim of this cross-sectional study was to determine the predictors of health-promoting behaviors among freshman dental students at Istanbul University. Data were collected from a convenience sample of 111 students using questionnaires including a sociodemographic section, the Health-Promoting Lifestyle Profile II, the Health Value Scale, the Generalized Self-Efficacy Scale, the Perceived Stress Scale, and the Multidimensional Scale of Perceived Social Support. Data were analyzed using descriptive statistics, t-test, Pearson's correlation, and stepwise multiple linear regression. The overall health-promoting lifestyle behaviors among these students were at a moderate level, indicating that they engaged in health-promoting behaviors sometimes to often. They scored highest on the spiritual growth but lower on the health responsibility subscales. Females reported having engaged more in health responsibility behaviors and lower in physical activity than did males. Students from high-income families reported more physical activity. Significant correlations were found between overall health-promoting lifestyle behaviors, self-efficacy, health value, stress, and social support. Among all the related factors, self-efficacy was the most strongly predictive factor: it explained 61 percent of the variance in overall health-promoting behaviors. Thus, self-efficacy as a cognitive-perceptual factor should be considered by dental educators when planning educational interventions to promote students' healthy lifestyle.