• Journal of Environmental Science International
• /
• v.17 no.1
• /
• pp.107-112
• /
• 2008

A study on the enhancement of environmental durability of EPDM rubber materials for the aerator membrane was performed using a butyl rubber as a modifier. A conventional EPDM rubber formulation was evaluated as having about 26.0 wt% or more oil content from the chloroform immersion test. These oils would be gradually and continuously deleted from the aerator membrane when directly exposed to a waste-water or chemically corrosive fluids, making the membrane less flexible and the performance worse. To improve this, a butyl rubber (IIR) was utilized as the modifier for a low-ENB type of EPDM rubber formulation with low-oil content. The environmental durability of the IIR-modified EPDM rubber material was expected to be greatly enhanced compared to the conventional one. However, the mechanical and performance properties such as elongation, tensile strength, and air bubble size, etc. were still maintained as good as in the conventional one. Furthermore, TGA analysis of the IIR-modified EPDM material showed that there would be partially compatible between IIR and EPDM. It also showed that the initial degradation temperature of the IIR-modified EPDM could be somewhat increased, exhibiting the enhanced compatibility among the components and, thereby, more enhanced environmental durability.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.8
• /
• pp.4796-4801
• /
• 2014

To increase the riding comfort and running stability of articulated type high speed railway vehicles(HSRV), it is important that the gangway connections for the passenger car satisfied fire safety, sound proof and durability under triaxial angular displacement (rolling/yawing/pitching) modes. On the other hand, a domestic test standard on the durability of the rubber components has not been determined. In this study, the fatigue life was predicted using the results of the nonlinear finite element analysis and the fatigue properties. Moreover, a fatigue rig test of the component was constructed to examine the durability.

• Journal of the Korean Ceramic Society
• /
• v.47 no.5
• /
• pp.373-380
• /
• 2010

In this study, we studied on the durability of restorative cement mortar for deteriorated concrete at complex deteriorated conditions as variation of temperature and of humidities. We made a comparison between restorative materials with insulation function and restorative materials without insulation function in items of compressive and bending strength and permeability of water, durability for carbonation, salt damage, diffusion coefficient of salt at complex deterioration conditions like change of temperature, change of humidity, For insulation, we used close-pore type Alumino-Silicate lightweight aggregate and substituted 12 wt% and 15 wt% out of original restorative cement mortar without insulation function. As a result, it was found that original restorative cement mortar without insulation function fail to meet Korean Standard on polymer modified cement mortar for maintenance in concrete structure, but restorative cement mortar with insulation function is in contentment Korean Standard to meet excellent than restorative materials without insulation function for durability at complex deteriorated conditions.

• Advances in concrete construction
• /
• v.8 no.2
• /
• pp.119-126
• /
• 2019

This paper reports an experimental investigation conducted to evaluate the durability performance of concrete mixtures prepared utilizing blends of Type I Portland cement (OPC) and natural pozzolans (NPs) obtained from three different sources in Saudi Arabia. The control concrete mixture containing OPC alone as the binder and three concrete mixtures incorporating NPs were prepared keeping water/binder ratio of 0.4 (by weight), binder content of $370kg/m^3$, and fine/total aggregate ratio of 0.38 (by weight) invariant. The compressive strength and durability properties that included depth of water penetration, depth of carbonation, chloride diffusion coefficient, and resistance to reinforcement corrosion and sulfate attack were determined. Results of this study indicate that at all ages, the compressive strength of NP-admixed concrete mixtures was slightly less than that of the concrete containing OPC alone. However, the concrete mixtures containing NP exhibited lower depth of water penetration and chloride diffusion coefficient and more resistance to reinforcement corrosion and sulfate attack as compared to OPC. NP-admixed concrete showed relatively more depth of carbonation than OPC when subjected to accelerated carbonation. The results of this investigation indicates the viability of utilizing of Saudi natural pozzolans for improving the durability characteristics of concrete subjected to chloride and sulfate exposures.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.10 no.1
• /
• pp.157-164
• /
• 2006

This paper presents the durability characteristics of commercially available CFRP rebars under various environmental conditions. Two types of GFRP rebars were tested by using an accelerated aging method. A total of 264 rebar specimens were conditioned up to 132 days in the moisture, chloride. alkaline, and freeze-thaw environmental conditions. The durability characteristics of conditioned rebars were obtained by comparing the tensile strength, horizontal shear strength, and elastic modulus between the unconditioned and conditioned GFRP rebars. The test results indicated that the mechanical properties of GFRP were significantly reduced after conditioning. Long-term degradation of GFRP rebars was also estimated using the results of a short-term durability test.

• Journal of the Korea Concrete Institute
• /
• v.23 no.3
• /
• pp.311-320
• /
• 2011

Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.

• Journal of the Korea Institute of Building Construction
• /
• v.5 no.1 s.15
• /
• pp.81-88
• /
• 2005

As a part of efforts for conformity of demand to high quality of concrete and for solution of economic problem, blast-furnace slag has been utilized by means of cement replacement. With utilization of blast-furnace slag, superior performance can be ensured, environmental pollution can be prevented and economical advantage can be obtained. But blast-furnace slag has a lot of disadvantages like retardation of strength manifestation etc. in field construction, so properties examination of concrete using blast-furnace slag instead of cement is necessary. For upper necessity, it is planed that basic data for utilization and performance management of blast-furnace slag by means of cement replacement is presented with experimental comparison and investigation of engineering properties of concrete according to the replacement ratio and fineness of blast-furnace slag.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.1
• /
• pp.72-79
• /
• 2007

This study investigates the engineering properties of concrete incorporating lime stone crushed fine aggregate(Ls), which has been abandoned about 20% of total production due to the low purity. Test results showed that increase of Ls had favorable fluidity and slightly decreased air content. Bleeding capacity of all specimens was not appeared as those were high strength mixture proportion, but the specimens using more Ls accelerated initial and final setting. For the mechanical properties, specimens incorporating higher ratio of Ls, overall, resulted in increase of compressive strength, and exhibited very small inclined tendency in a dynamic elasticity modulus test In addition, for the durability properties, specimens incorporating higher Ls dramatically decreased a drying shrinkage and showed similar tendency in a frost & thaw test, as well as showing no more change in an accelerated neutralization test from the beginning. In conclusion, as it was confirmed in the experimental test, the high strength concrete applying Ls did not showed any problems in the aspects of engineering properties and mostly exhibited even more excellent quality than the specimens using natural fine aggregate.

• Journal of the Korea Institute of Building Construction
• /
• v.13 no.3
• /
• pp.235-241
• /
• 2013

In this study, a mortar was produced using re-dispersible polymer powders that addresses the defects of aqueous polymer and improves the durability of cement mortar. Also, an attempt was made to examine the properties of polymer modified mortars using re-dispersible polymer powders by strength and durability tests between ordinary Portland cement mortars and polymer modified mortars mixed with aqueous dispersion. The test showed that strength and durability are improved considerably compared with ordinary Portland cement mortar, and the performance of aqueous polymer cement mortar was considerably improved. Accordingly, it is expected that high-quality prepackaged polymer modified mortars can be produced using re-dispersible polymer powders.

• International Journal of Concrete Structures and Materials
• /
• v.8 no.2
• /
• pp.157-164
• /
• 2014

Ground granulated blast-furnace slag (GGBS) is a green construction material used to produce durable concrete. The secondary pozzolanic reactions can result in reduced pore connectivity; therefore, replacing partial amount of Portland cement (PC) with GGBS can significantly reduce the risk of sulfate attack, alkali-silica reactions and chloride penetration. However, it may also reduce the concrete resistance against carbonation. Due to the time consuming process of concrete carbonation, many researchers have used accelerated carbonation test to shorten the experimental time. However, there are always some uncertainties in the accelerated carbonation test results. Most importantly, the moisture content and moisture profile of the concrete before the carbonation test can significantly affect the test results. In this work, more than 200 samples with various water-cementitious material ratios and various replacement percentages of GGBS were cast. The compressive strength, electrical resistivity, chloride permeability and carbonation tests were conducted. The moisture loss and microstructure of concrete were studied. The partial replacement of PC with GGBS produced considerable improvement on various properties of concrete.