• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.113-119
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• 2019

Many researches on alternative materials as construction materials is continuing by recycling industrial byproducts due to shortage of sitereclamation and natural aggregates. In this paper, engineering properties in early-aged OPC (Ordinary Portland Cement) and GGBFS (Ground Granulated Blast Furnace Slag) concrete are evaluated with EOS aggregate replacement. The related experiments were carried out with 0.6 of water to binder ratio, three levels of EOS replacement ratios (0%, 30% and 50%) for fine aggregate, and two levels of cement replacement with GGBFS (0% and 40%). Several tests such as slump air content, and unit mass measurement are performed for fresh concrete, and compressive strength and diffusion coefficient referred to NT BUILD 492 method are measured for hardened concrete. Through the tests, it was evaluated that the compressive strength in concrete with EOS aggregate increased to 3 days and 7 days but slightly decreased at the age of 28 days. In the accelerated chloride penetration test, GGBFS concrete showed reduced diffusion coefficients by 60 - 67% compared with OPC concrete. The lowest chloride diffusion coefficient was evaluated in the 50% replacement with EOS aggregate, which showed an applicability of EOS aggregate to concrete production.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.2
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• pp.191-199
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• 2021

In this study, the correlation between the influencing factors on corrosion and Half Cell Potential(HCP) measurement was analyzed considering the three levels of W/C ratio, cover depth, and chloride concentration. The HCP increased with enlarged cover depth, so it was confirmed that the increment of cover depth was effective for control of corrosion. Based on the criteria, the case of 60mm cover depth showed excellent corrosion control with under -200mV, indicating increase of cover depth is an effective method for reducing intrusion of external deterioration factors. When fresh water was injected to the upper part of specimens, very low level of HCP was monitored, but in the case that concentrations of chloride were 3.5% and 7.0%, HCP dropped under -200mV. In addition, the case with high volume of unit binder showed lower HCP measurement like increasing cover depth. Multiple regression analysis was performed to evaluate the correlation between the corrosive influence factors and HCP results, showing high coefficient of determination of 0.97. However, there were limitations such as limited number of samples and measuring period. Through the additional corrosion monitoring and chloride content evaluation after dismantling the specimen, more reasonable prediction can be achieved for correlation analysis with relevant data.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.192-201
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• 2023

In this paper, the strength properties of porous concrete containing natural fine aggregates and bottom ash aggregates were investigated, The material properties of natural fine aggregates and bottom ash were identified then used as aggregates for porous concrete. The water-binder ratio was constant at 0.25, and the com paction level of 0.5, 1.5, and 2.5 MPa was applied to produce a porous concrete specimen. Test of unit weight, ultrasonic velocity, compressive strength, and flexural tensile strength were perform ed and analyzed. The unit weight, ultrasonic velocity, com pressive strength, and flexural tensile strength increased as the compaction level increased and also the replacement rate of bottom ash with sand(fine aggregate) increased. In addition, through regression analysis, the correlation between the unit weight, compressive strength, and flexural tensile strength of bottom ash porous concrete was presented. Unit weight and strength properties are proportional to each other and showed an increasing correlation. In addition, the correlation coefficient (R²) value of regression analysis was calculated based on the experimental results of this study and those of other research papers.

• Applied Chemistry for Engineering
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• v.26 no.1
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• pp.104-110
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• 2015

It is known that polymer concretes are 8~10 times more expensive than ordinary Portland cement concretes; therefore, in the production of polymer concrete products, it is very important to reduce the amount of polymer binders used because this occupies the most of the production cost of polymer concretes. In order to develop a technology for the reduction of polymer binders, smooth and spherical aggregates were prepared by the atomizing technology using the oxidation process steel slag (electric arc furnace slag, EAFS) and the reduction process steel slag (ladle furnace slag, LFS) generated by steel industries. A reduction in the amount of polymer binders used was expected because of an improvement in the workability of polymer concretes as a result of the ball-bearing effect and maximum filling effect in case the polymer concrete was prepared using the smooth and spherical atomized steel slag instead of the calcium carbonate (filler) and river sand (fine aggregate) that were generally used in polymer concretes. To investigate physical properties of the polymer concrete, specimens of the polymer concrete were prepared with various proportions of polymer binder and replacement ratios of the atomized reduction process steel slag. The results showed that the compressive strengths of the specimens increased gradually along with the higher replacement ratios of the atomized steel slag, but the flexural strength showed a different maximum strength depending on the addition ratio of polymer binders. In the hot water resistance test, the compressive strength, flexural strength, bulk density, and average pore diameter decreased; but the total pore volume and porosity increased. It was found that the polymer concrete developed in this study was able to have a 19% reduction in the amount of polymer binders compared with that of the conventional product because of the remarkable improvement in the workability of polymer concretes using the spherical atomized oxidation steel slag and atomized reduction steel slag instead of the calcium carbonate and river sand.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.104-111
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• 2015

This study shows the mechanical properties of alkali-activated slag cement (AASC) synthesized using sulfate with NaOH solution. The used sulfates were calcium sulfate ($CaSO_4$, denoted CS) and sodium sulfate ($Na_2SO_4$, denoted SS). The replacement ratio of sulfates was 2.5, 5.0, 7.5 and 10.0% by weight of slag. NaOH solution of 2M and 4M concentration was used. A sample was activated with sulfate and activated with blended activator (blending NaOH solution with sulfate) respectively. 24 mix ratios were used and the water-binder weight ratio for the test was set 0.5. This research carried out the compressive strength, flexural strength, ultrasonic pulse velocity (UPV), absorption and X-ray diffraction (XRD). In the case of samples with CS, sample with 7.5% CS, sample with 2M NaOH+5.0% CS and sample with 4M NaOH+5.0% CS showed the good performance in the strength development. In the case of samples with SS, sample with 10.0% SS, sample with 2M NaOH+7.5% SS and sample with 4M NaOH+2.5% SS obtained good performance in strength. The results of UPV and water absorption showed a similar tendency to the strength properties. The XRD analysis of samples indicated that the hydration products formed in samples were ettringite, CSH and silicate phases. In this study, it is indicated that when compared to the use of sulfate only, the use of both sulfate and NaOH solution makes mechanical properties of AASC better.