• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.66-74
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• 2021

The objective of this study is to evaluate the practical application potential and limitations of the modified fly ash(MFA) by vibration grinding as a partial replacement of ordinary portland cement(OPC). The test parameters investigated were the replacement level of fly ash(FA) and FA for OPC, varying from 10% to 40%, and curing temperatures of 5, 20, and 40℃. The various characteristics(including slump, air content, bleeding, setting time, compressive strength development, and hydration products) of MFA concrete were measured and then compared with those of the concrete with conventional FA. Test resul ts showed that the MFA prefers to FA in reducing the bl eeding of fresh concrete and enhancing the compressive strength gain at an early age. The compressive strength ratios between MFA and FA concrete specimens at an age of 1 day were 135%, 146%, and 111% at the curing temperatures of 5, 20, and 40℃, respectively. The corresponding ratios at an age of 28 days were approximately 110%, regardless of the curing temperatures. The X-ray diffraction analysis also revealed less calcium hydroxide products in MFA pastes than in FA pastes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.4
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• pp.52-59
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• 2018

To control chloride attacks which is a representative deterioration in RC(Reinforced Concrete) structures, many studies have been conducted. Above all, a method using mineral admixture was known to be effective for corrosion protection. In this study, durability test about chloride attacks was carried out for concrete specimens containing FA(Fly Ash)-representative concrete mineral admixture and OPC concrete specimens considering 3 different levels of W/B(Water to Binder). Accelerated chloride diffusion coefficient tests referred to Tang's method, total passed charge tests referred to ASTM C 1202, and compressive strength tests based on KS F 2405 were performed at each target age day. Also, based on previous studies of 28 days, time-parameter which is a key parameter for diffusion behavior is evaluated and its relations with compressive strength at the age of 365 days is evaluated. After the age of 49 days, chloride resistance of FA concrete is much improved than that of OPC concrete, which arose out of stable hydrates due to pozzolan reaction of fly ash. Time-parameter of FA concrete is evaluated to be about 1.5 times larger than that of OPC concrete. Also, time-parameter of FA concrete has a linearly decreasing relation while that of OPC concrete has a linearly increasing relation with compressive strength development.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.687-693
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• 2015

The present study proposed a k-value to determine the water-to-binder ratio of concrete using fly ash (FA) or ground granulated blast-furnace slag (GGBS) as a partial replacement of ordinary portland cement (OPC) with regard to an equivalent strength of OPC concrete. From the regression analysis using an extensive database including 7076 concrete mixes, k-values were determined for various water-to-binder ratios when the replacement ratio of OPC by the addition of FA or GGBS were below 50%. For deriving an equation to identify k-value, the relationship of concrete compressive strength and water-to-binder ratio was generalized by an exponential function. In general, k-values decreased with the increases in the addition of FA or GGBS for replacement of OPC and water-to-binder ratio. The rate in decreasing k-value against water-to-binder ratio was marginally affected by the addition of FA or GGBS, although a higher k-value was commonly obtained for GGBS concrete than for FA concrete at the same water-to-binder ratio. Consequently, the determined k-values were simplified as a function of water-to-binder ratio and the addition ratio of FA or GGBS as replacement of OPC.

• Korean Journal of Environmental Agriculture
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• v.17 no.3
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• pp.189-194
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• 1998

In order to evaluate the residual effects of bituminous coal fly ash, gypsum, oyster shell as soil amendments, Chinese cabbage was cultivated on acidic sandy loam soils with low boron content. The soils were amended in the upper 15cm with amendments in previous year and the growth and qualities of plants were analyzed. Amendments treated one year before were, in metric tons per hectare, i) none(Check) ; ii) 80 fly ash(FA) ; iii) 4 shell(SH) ; iv) 56 fly ash + 24 gypsum (FG) ; v) 40 fly ash + 24 gypsum + 0.8 shell(FGS). Yield response in fresh weight of Chinese cabbage was in order of 834% for FGS > 780% for FG > 755% FA > 193% for SH plants. Reducing sugar, vitamin-C, and total nitrogen contents of leaves depending on treatments showed the same tendencies as that in yields, whereas crude fibre opposite to them. In particular, FA, FG, and FGS plants showed normal growth without both boron deficiency symptoms which appeared in Check and SH plants and possibilities of accumulation of heavy metals. In any soils treated with the above amendments, however, magnesium was insufficient.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.2
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• pp.97-104
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• 2010

In this study, the effect of blast furnace slag and gypsum addition on strength development of fly ash substituted concrete is investigated experimentally. As a result, the fluidity represented a similar or larger level than that of OPC but showed a tendency to decrease the fluidity according to the increase in the replacement level of BS and GS for the FA replacement concrete. In the case of the air content, although it showed a larger decrease compared to that of OPC, it also represented that BS and GS did not affect the air content significantly. Regarding the compressive strength in the case of the replacement of BS and GS for the FA 10% replacement concrete, it showed a higher early strength than OPC. Whereas, in the case of the BS 5% replacement and GS 1% incorporation for the FA 10% replacement concrete showed the most excellent performance due to its high strength. In the correlation of the compressive strength according to the kinds of admixtures, it was evident that the GS incorporation played an important role in high strength gain.

• Advances in concrete construction
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• v.6 no.1
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• pp.47-68
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• 2018

This article reports the utilization of fly ash (FA) waste product from industry and silpozz which is an agro-waste from agriculture as an environmental friendly material in construction industry. The evaluation of strength and durability study was observed using FA and silpozz as a partial replacement of Ordinary Portland Cement (OPC). The studied parameters are compressive strength, flexural strength, split tensile strength and bond strength as well as the durability study involves the acid soluble chloride (ASC), water soluble chloride (WSC), water absorption and sorptivity. Scanning electron microscopy (SEM) and XRD of selected samples are also done. It reveals from the test results that the deterioration factor (DF) in compressive strength is 4% at 365 days. The DF of split tensile strength and flexural strength is 0.96% and 0.6% at 90 days respectively. The minimum slip is 1mm and 1.1mm after 28 days of testing bond strength for NWC and SWC sample respectively. The percentage decrease in bond strength is 10.35% for 28 days SWC samples. The pre-cast blended concrete samples performed better to chloride diffusion. Modulus of elasticity of SWC samples are also studied.The water absorption and sorptivity tests are conducted after 28 days of curing.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.3
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• pp.129-140
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• 2013

Bottom Ash is industrial by-product from a thermoelectric power plant. An immense quantities of bottom ash have increased each year, but most of them is reclaimed in ash landfill. In this study, in order to raise recycling rate of Bottom Ash, it is suggested to cure Bottom Ash (BA) mixtures mixed with cement, lime, Fly Ash (FA), and oyster shell (OS). Mixtures of 5~20 % mixing ratio had been cured for 1, 3, 7, 14, and 28 days using sealed curing and air-dry curing method. Unconfined compressive strength test was conducted to determine strength and deformation modulus ($E_{50}$) change for mixtures as mixing ratio and curing day, water contents of mixtures were measured after test. As a result, strength and $E_{50}$ were increased as mixing ratio and curing days, but values and tendencies of them appeared in different as kind of mixture, mixing ratio, curing method, and curing days. The results showed the addition of cement, lime, Fly Ash, and oyster soil in Bottom Ash could improved strength and $E_{50}$ and enlarge its field of being used.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.69-74
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• 1995

The primary purpose of this study is to investigate reusal techniques of fly ash of combined heat power plant in the construction field, which may contribute to the saving of construction materials and conservating environment. Firstly chemical and physical characteristics of fly ash is analysed. And then, the usability of the concrete is tested by investigating the flowablility and stength development through parameters of various replacement ratios with respect to different mixing conditions. Finally, the durability and mechanical properties(elastic modulus) of the concrete is tested. As the result of the study, the following conclusions are derived : (1) the quantity of the CaO in the fly ash is relatively high based on the chemical analysis, (2)the compressive strength ratio of the mortar is satisfied with the specification, but the unit water ratio increased, (3)high strength concrete of more than 400kg/$\textrm{cm}^2$ can be developed in the ranges of FA 30%, W/B 40%, (5)the slump loss with the elapsed time due to the delivery is decreased as the replacement ratio of the fly ash is increased, (6)the modulus of the elasticity is matched withn the specification of the Architectural Institute of Korea.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.49-50
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• 2016

Recently in Korea, some studies on concrete that mass quantity of additives are substituted in order to respond to the government's Low Carbon Green Growth Policy are being conducted. As on of additives, FA as an industrial by-product is used in a large quantity. However, In some of the domestic FA refineries, since some quantity of concrete without passing through the refining process is released for sales for the reasons of the shortening of production time and the cost reduction, etc., it exerts a bad influence on the quality of concrete. Therefore, in this study, there was implemented an experiment on the effects of using an extreme quality of FA which is available for distributing domestically on the engineering characteristics of lean mortar. As a result, it was found that the quality of FA exerts its effect on the compression strength bigger than the flow property or the air volume.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.47-48
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• 2016

Recently over the world, many studies on the methods for using some binding materials which replace cement, such as FA, etc., for reducing CO₂. However, it has sometimes been reported that some cement products without passing through the refining process at some of FA refineries in Korea are released for sales for some reasons of shortening the production time and the cost reduction, etc., so it exerts a bad effect on the quality of many construction structures. Therefore, in this study, it was intended to conduct an experimental review on the effects of using an extreme quality of FA which is distributable domestically on the engineering characteristics of high-strength mortar. As a result, it was judged that it is beneficial for the engineering characteristics of concrete, such as, flow property, air volume and strength, etc, to use some refined FA.