• Computers and Concrete
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• v.33 no.1
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• pp.41-53
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• 2024

Under constant and cyclic axial compression, square composite short columns reinforced with Self Compacting Concrete (SCC) added with scrap rubber infilled inside steel tubes and with different types of concrete were cast and tested. The test is carried out to find the effectiveness of utilizing an aggregate manufactured from industrial waste and to address the problems associated with the need for alternative reinforcements along with waste management. The main testing parameters are the type of concrete, the effect of fiber inclusion, and the significance of rubber-infilled steel tubes. The failure modes of the columns and axial load-displacement curves of the steel tube-reinforced columns were all thoroughly investigated. According to the test results, all specimens failed due to compression failure with a longitudinal crack along the loading axis. The fiber-reinforced column specimens demonstrated improved ductility and energy absorption. In comparison to the normal-weight concrete columns, the lightweight concrete columns significantly improved the axial load-carrying capacity. The addition of basalt fiber to the columns significantly increased the yield stress and ultimate stress to 9.21%. The corresponding displacement at yield load and ultimate load was reduced to 10.36% and 28.79%, respectively. The precision of volumetric information regarding the obtained crack quantification, aggregates, and the fiber in concrete is studied in detail through image processing using MATLAB environment.

• Korean Chemical Engineering Research
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• v.48 no.3
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• pp.391-396
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• 2010

In this research the characteristics of ammonia removal from malodorous waste-air were investigated under various operating condition of biofiilter packed with equal volume of rubber media and compost for the efficient removal of ammonia, representative source of malodor frequently generated at compost manufacturing factory and publicly owned facilities. Then the optimum conditions were constructed to treat waste-air containing ammonia with biofilter. Biofilter was run for 30 days(experimental frequency of 2 times/day makes 60 experimental times.) with the ammonia loading from $2.18g-N/m^3/h$ to $70g-N/m^3/h$ at $30^{\circ}C$. The ammonia removal efficiency reached almost 100% for I through IV stage of run to degrade up to the ammonia loading of $17g-N/m^3/h$. However the removal efficiency dropped to 80% when ammonia loading increased to $35g-N/m^3/h$, which makes the elimination capacity of ammonia $28g-N/m^3/h$ for V stage of run. However, the removal efficiency remained 80% and the maximum elimination capacity reached $55g-N/m^3/h$ when ammonia loading was doubled $70g-N/m^3/h$ for VI stage of run. Thus the maximum elimination capacity exceeded $1,200g-N/m^3/day$(i.e., $50g-N/m^3/h$) of the experiment of biofilter packed with rock wool inoculated with night soil sludge by Kim et al.. However, the critical loading did not exceed $810g-N/m^3/day$ (i.e., $33.75g-N/m^3/h$) of the biofilter experiment by Kim et al.. The reason to exceed the maximum elimination capacity of Kim et al. may be attributed to that the rubber media used as biofilter packing material provide the better environment for the fixation of nitrifying and denitrification bacteria to its surface coated with coconut based-activated carbon powder and well-developed inner-pores, respectively.

• Elastomers and Composites
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• v.46 no.2
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• pp.138-143
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• 2011

EPDM compounds and vulcanizates containing inorganic filler such as talc, calcium carbonate, or clay as well as carbon black were prepared, and the influence of inorganic filler on properties of the EPDM compounds and vulcanizates were investigated. The bound rubber contents did not significantly increase even though the inorganic filler was added. There were big aggregates in the EPDM samples with high loading inorganic filler. By adding the inorganic filler, the cure times tended to increase and the delta torque decreased. The modulus were on the whole decreased, whereas the elongation at break, tensile strength, and tear strength were increased by adding the inorganic filler. The decreased modulus and increased elongation at break can be explained with the decreased delta torque, the increases of tensile strength and tear strength can be explained with the increased elongation at break. By adding the inorganic filler, level of reinforcing in the EPDM compounds did not increase and the crosslink density decreased.

• Earthquakes and Structures
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• v.7 no.6
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• pp.1001-1024
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• 2014

The size of spread footings was found to be unnecessarily large from some actual engineering practices constructed in Taiwan, due to the strict design provisions related to footing uplift. According to the earlier design code in Taiwan, the footing uplift involving separation of footing from subsoil was permitted to be only up to one-half of the foundation base area, as the applied moment reaches the value of plastic moment capacity of the column. The reason for this provision was that rocking of spread footings was not a favorable mechanism. However, recent research has indicated that rocking itself may not be detrimental to seismic performance and, in fact, may act as a form of seismic isolation mechanism. In order to clarify the effects of the relative strength between column and foundation on the rocking behavior of a column, six circular reinforced concrete (RC) columns were designed and constructed and a series of rocking experiments were performed. During the tests, columns rested on a rubber pad to allow rocking to take place. Experimental variables included the dimensions of the footings, the strength and ductility capacity of the columns and the intensity of the applied earthquake. Experimental data for the six circular RC columns subjected to quasi-static and pseudo-dynamic loading are presented. Results of each cyclic loading test are compared against the benchmark test with fixed-base conditions. By comparing the experimental responses of the specimens with different design details, a key parameter of rocking behavior related to footing size and column strength is identified. For a properly designed column with the parameter higher than 1, the beneficial effects of rocking in reducing ductility and the strength demand of columns is verified.

• Elastomers and Composites
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• v.56 no.3
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• pp.179-186
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• 2021

Carbon-based nanofillers, including nanodiamond (ND) and carbon nanotubes (CNTs), have been employed in epoxy matrixes for improving the toughness, using the tow prepreg method, of epoxy compounds for high pressure tanks. The reinforcing performance was compared with those of commercially available toughening fillers, including carboxyl-terminated butadiene acrylonitrile (CTBN) and block copolymers, such as poly(methyl methacrylate)-b-poly(butyl acrylate)-b-poly(methyl methacrylate) (BA-b-MMA). CTNB improved the mechanical performance at a relatively high filler loading of ~5 phr. Nanosized BA-b-MMA showed improved performance at a lower filler loading of ~2 phr. However, the mechanical properties deteriorated at a higher loading of ~5 phr because of the formation of larger aggregates. ND showed no significant improvement in mechanical properties because of aggregate formation. In contrast, surface-treated ND with epoxidized hydroxyl-terminated polybutadiene considerably improved the mechanical properties, notably the impact strength, because of more uniform dispersion of particles in the epoxy matrix. CNTs noticeably improved the flexural strength and impact strength at a filler loading of 0.5 phr. However, the improvements were lost with further addition of fillers because of CNT aggregation.

• Elastomers and Composites
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• v.49 no.1
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• pp.43-52
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• 2014

The effect of nanoclay (Cloisite 20A) on the self-adhesion behavior of uncured brominated-isobutylene-isoprene rubber (BIIR) has been studied. The dispersion state of nanoclay into the rubber matrix was examined by SEM, TEM and XRD analysis. The thermal degradation behavior of the filled and unfilled samples was examined by TGA and improvement in the thermal stability of the nanocomposites occurred based on the weight loss (%) measurements. Also, addition of nanoclay enhanced the cohesive strength of the material by reinforcement action thereby reducing the degree of molecular diffusion across the interface of butyl rubber. However, the average depth of penetration of the inter-diffused chains was still adequate to form entanglement on either side of the interface, and thus offered greater resistance to peeling, resulting in high tack strength measurements. The improvement in tack strength was only achieved at critical nanoclay loading above 8 phr. Contact angle measurement was also made to examine the surface characteristics. There was no significant interfacial property change by employing the nanoclay.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.226-234
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• 2021

The objective of this study is to establish the fundamental design data for axial load-displacement relationship under axial monotonic or cyclic responses of seismic damping·isolation (SDI) units developed for ceiling structures. The main parameters include the installation of a spring, the number of rubber layer, prestress stress of bolts for connector between the spring and rubbers, and loading type. Test results showed that SDI units with a spring in the core and higher prestress stress of bolts tended to be higher stiffness at the ascending branch and more ductile behavior at the descending branch. This trends more notable for the specimens under monotonic load rather than cyclic loads. Consequently, the energy dissipation of SDI unit can be optimally designed with the following conditions: installation of a spring within 3-layer rubbers and prestress applied to the bolts at 10% of their yielding strength . When compared with the experimental tension capacity of the developed SDI units, the predictions by JIS B 2704-1 and KDS 31 00 are conservative under monotonic loading but higher by approximately 10% under cyclic loading.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.05a
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• pp.255-258
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• 2002

Dental chewing masticator, which is an essential device for evaluating the wear of dental resin and the interfacial failure between the filling resin and enamel of tooth used in conservative dentistry, was developed. This dental chewing masticator mimics the chewing motion and loading by adapting DC motor and rotary cam system. Chewing loading of 49N was imposed by computer-displacement control, loadcell, LM guide, and spring system. Extracted tooth was fixed into a holding jig, and this jig was mounted with rubber pad on the $15^{\circ}$inclined surface to consider the lateral movement of periodontal ligament. A water bath was installed for providing the environment of inside mouth and for circulating the $5^{\circ}C-55^{\circ}C$ water to evaluate the effect of hydrothermal cycling on the damage of resin filled teeth during long-term chewing activity.

• Elastomers and Composites
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• v.20 no.3
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• pp.189-204
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• 1985

The purpose of this study is to examine the dynamic properties, especially the damping and fatigue properites, of NR vulcanizates and to find out the vulcanizate which can be used as damping materials in industry. The results of this study can be summarized as follows: 1. In the ODR test, the S-2 vulcanizate was the fastest one in terms of having reached to optimum cure times($t_{90}$) and, with the same formula, when 50phr of HAF carbon black loaded, the shortest optimum cure times has shown. 2. The S - 2 vulcanizate was the best than the others in the physical properties. In aging properties, however, the E - 1 vulcanizate appeared to be better than the other vulcanizates. 3. The results of the RDS test for the NR vulcanization system under the condition of 0.1% strain amplitude and 1 Hz frequency showed no connection between Tg and the the nature of the crosslinking system, but 50phr loading of HAF carbon black increased Tg. The damping values of vulcanizates in the elastic region showed a strong relations the damping values and the crosslinking system. The S - 2 vulcanizate with higher crosslink density had lower damping values than other vulcanizates, and furthermore, the SH - 2 vulcanizates with 50phr loading of HAF carbon black increased the damping values. 4. The Goodrich Flexometer test showed that the heat buildup for the gum NR vulcanizates was less than for those which contained 50phr of HAF carbon black. In particular, the fatigue life of the vulcanizate with lower damping values appeared to be longer than that of the vulcanizates with higher damping values. In the fatigue test, the increasment of the loading or the temperature, applied to the vulcanizates, appeared to be shorten their fatigue life.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.419-426
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• 1999

In this study, the reaction rate constant, activation energy, total crosslinking density, elastic constant, cure properties ($t_5,\;t_{90}$), modulus, and abrasion resistance of rubber compounds were investigated as a function of cure temperatures, cure systems and reinforcing filler loadings. Reaction rate constants showed strong dependence on thc carbon black loading, cure temperature and cure system, and increased sharply with increasing the reaction temperatures. The lowest activation energy was obtained in the efficient cure (EC) system which corresponds to the high level of sulfur to accelerator ratio, and the activation energy was decreased with decreasing the carbon black loadings. The change of carbon black loadings directly affects the modulus and abrasion resistance, but the change of cure system showed various effects on the rubber compounds. Increased carbon black loadings showed the high modulus, improved abrasion resistance and short scorch time but decrease in crosslinking density and elastic constant. Higher crosslinking density and elastic constant were shown in the EC cure system regardless of carbon black loadings, but scorch timc ($t_5$) was not affected by the change of the ratio of sulfur to accelerator. Rapid optimum cure time ($t_{90}$) were showen in the EC cure system. Also, the equivalent cure curve coefficient of rubber compound was 0.96 for conventional cure (CC) system, and 0.94 for semi-efficient cure (SEC) and EC system regardless carbon black loadings. As regarding the abrasion resistance, wear volume showed the logarithmic increase for the loaded weight.