• Environmental Engineering Research
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• v.21 no.4
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• pp.341-349
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• 2016

To improve the utilization rate of construction waste as mine backfilling materials, this paper investigated the feasibility of using recycled powder as mine paste backfilling cementitious material, and studied the pozzolanic activity of recycled construction waste powder. In this study, alkali-calcium-sulfur served as the activation principle and an orthogonal test plan was performed to analyze the impact of the early strength agent, quick lime, and gypsum on the pozzolanic activity of the recycled powder. Our results indicated that in descending order, early strength agent > quick lime > gypsum affected the strength of the backfilling paste with recycled powder as a cementitious material during early phases. The strength during late phases was affected by, in descending order, quick lime > gypsum > early strength agent. Using setting time and early compressive strength as an analysis index as well as an extreme difference analysis, it was found that the optimal ratio of recycled powder cementitious material for mine paste backfilling was recycled powder:quick lime:gypsum:early strength agent at 78%:10%:8%:4%. X-ray diffraction analysis and scanning electron microscope were used to show that the hydration products of recycled powder cementitious material at the initial stages were mainly CH and ettringite. As hydration time increased, more and more recycled powder was activated. It mainly became calcium silicate hydrate, calcium aluminate hydrate, etc. In summary, recycled powder exhibited potential pozzolanic activities. When activated, it could replace cementitious materials to be used in mine backfill.

• Advances in concrete construction
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• v.10 no.4
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• pp.301-310
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• 2020

The following paper concentrates on the objective of studying the influences of extent of duration and temperature on the Pozzolanic properties as well as reactivity of locally existing natural clay of Nai Gaj, district Dadu, Sindh Pakistan. The activation of the clay only occurs through heating when temperature in a furnace chamber reaches 600, 700 and 800oC for 1, 2 and 3 hours and at 900 and 1000℃ for 1 and 2 hours. Furthermore, the strength activity index (SAI) of advanced pozzolanic material happens to be identified through 20% cement replacement for different samples of calcined clay as per ASTM C-618. The compressive strength test of samples had been operated for 7 and 28-days curing afterwards. The maximum compressive strength had been seen in mix E in which cement was replaced with clay calcined at 700℃ for 1 hour that is 27.05 MPa that is 24.31% more than that of control mix. The results gathered from the SAI verdicts the optimal activation temperature is 700℃ within a one-hour time period. The SAI at a temperature of 700℃ with a one-hour duration at 28 days is 124.31% which happens to satisfy the requirements of the new Pozzolanic material, in order to be applied in mortar/concrete (i.e., 75%). The Energy- dispersive spectrometry (EDS) along with the X-ray diffraction (XRD) have been carried out in means of verifying whether there is silica content or amorphous silica present in metakaolin that has been developed. The findings gathered from the SAI were validated, as the analysis of XRD verified that there is in fact Pozzolanic activity of developed metakaolin. Additionally, based on observation, the activated metakaolin holds a significant influence on the increase in mortar's compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.05a
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• pp.109-110
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• 2013

The purpose of this study was to investigate pozzolanic activity according to the firing temperature of the rice straw ash. In order to measure amount of SiO2 of rice straw ash, XRF(X-ray fluorescence) analysis was tested. Also to evaluate properties of mortars using rice straw ash, mortar flow, cement setting time, compressive strength was tested. As a results, as the mortar with a mixture ratio of rice straw ash up to 15% was found to have a compressive strength superior to that of plain mortar.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.259-268
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• 2014

This paper presents results of an experimental study which investigates the effect of industrial pozzolan made from calcined silt of dam at $750^{\circ}C$ for 5 h, on mechanical properties and durability of ordinary mortar, compared to the silica fume. Mortar specimens prepared with 5, 10 and 15 % of calcined silt to substitute cement were evaluated for their compressive and flexural strength, sulfate, acid and penetration of chloride ions resistance. The results were compared with ordinary mortar (without addition) and mortar containing 10 % of silica fume. The results obtained showed that the calcined silt of dam has a high potential to be used as a pozzolanic material, it improves the strength and the durability of mortar and compete the silica fume.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.211-216
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• 1994

This study dealt with the properties for fly ash of conbined heat power plant and application for concrete industry. For this purpose, fly ash sampled Ulsan conbined heat power plant and analyzed for physical and chemical properties. As analyzed results of fly ash, contents of $SiO_ and Al_O_ $in the fly ash of Ulsan were less than those of Thermo-electric power plant(Boryuing), but contents of CaO were tem times as much as those of Boryung, because of these differences, it is expected that pozzolanic activity of concrete using fly ash of Ulsan will be different from another fly ash. Concrete specimens were tested to evaluate concrete preformance when 10 to 50 percent of the portland cement by weight in the concrete mix was replaced with fly ash of conbined heat power plant. As test results, workability and consideration in the fresh concrete were increased and concrete strength was showed more than 400kg/$\textrm{cm}^2$ for the required age. This study would be provided valuable data for the practical utilization of fly ash(conbined heat power plant). In the future, properties of fly ash concrete including long term strength, elapsed time, pozzolanic activity, modulus of elasticity, sulfate resistance, shrinkage, freeze-thaw durability and so on will be studied.

• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.531-536
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• 2014

Recently, the amounts of dredge sea soil in south Korea have been increasing because of various maintenance works at harbors and rivers. Dredged sea soil contains various contaminants. Hence, prior to recycling the dredged sea soil, the various contaminants should be removed to prevent a secondary contamination due to the leaching of hazardous chemicals. Pretreated dredged sea soil can be buried under the ground or used for land reclamation. In this study, however, pretreated dredged sea soil was used to investigate the level of pozzolanic activity. The properties of pretreated dredged sea soil were investigated, the method for heat treatment was determined, and the compressive strength of mortar using dredged sea soil was examined. According to the XRF result, the main components of dredged sea soil were $SiO_2$ of over 55%, and $Al_2O_3$ and $SO_3$ of some amounts. Results from XRD and TG/DTA showed that pretreated dredged sea soil can be used as a pozzolanic material. When dredged sea soil was thermally treated for 90 min at $550^{\circ}C$, a compressive strength result was similar to that of control mortar.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.189-198
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• 2008

Generally, UFF A(Ultra Fine Fly Ash) has merit that advances a greater concrete workability and activates a greater pozzolanic reaction than common fly ash due to its ultra fine particle size. These properties enhance concrete durability by reducing permeability and increasing resistance of alkali silica reaction(ASR) and sulfate attack, etc. Due to these reasons, UFFA can be used in a rapid setting concrete. The purpose of this study is to develop and evaluate the rapid setting concrete with UFF A as a repair material for early-opening-to-traffic. In previous studies, if only UFFA is added to the rapid setting concrete mixture, pozzolanic reaction doesn't happen actively. Therefore, in this study, the chemical and physical tests were performed for rapid setting concrete with UFFA including calcium hydroxide and the activity of pozzolanic reaction was evaluated. Finally, the effectiveness of this mixture on enhancing concrete durability was investigated. As results, adding UFF A decreased the water/cement ratio of concrete, and compensated the reduced portion of the early strength of concrete. Also, rapid setting concrete with UFFA including calcium hydroxide activated a greater pozzolanic reaction than normal-UFF A concrete. As calcium hydroxide increases, electrical indication of concrete's ability to resist chloride ion penetration is promoted significantly.

• Advances in concrete construction
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• v.6 no.2
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• pp.159-175
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• 2018

The main aim of this study is to investigate the possible effects of metakaolin on strength and durability properties of concrete. For this purpose, concrete mixtures are produced by substituting cement with metakaolin 0, 5, 10 and 20% by weight. The amount of binder for the concrete mixtures are 300 and $400kg/m^3$ with a constant water to cement ratio of 0.6. Compressive and bending strengths, freeze-thaw and high-temperature resistances, capillary coefficients and rapid chloride permeability properties were determined and compared each other. Because of all the experiments conducted, it has been found that the use of metakaolin as a pozzolanic additive in concrete have positive effects especially on compressive and bending strengths, capillary, rapid chloride permeability, freeze-thaw resistance, and high temperatures, up to $800^{\circ}C$. The results indicated that the performance of concrete can be enhanced by metakaolin. Particularly, compressive strength and durability properties have found to be improved with increasing metakaolin content which is attributed to pozzolanic activity and filler effect. Furthermore, metakaolin has relatively positive impacts under elevated temperatures and freeze-thaw effects. However, almost all the strengths of entire concrete specimens are lost at $800^{\circ}C$. Consequently, the optimum metakaolin substitution ratio can be suggested to be 20% as per this study.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.66-71
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• 1995

This study reviews the internationally existing standards for fly ash and the other pozzolanic materials. The standards reviewed for this report covers the thirteen contries around the world including USA. It is found that the comparison of standards appeared to be different for technical test requirements from the country to country. This may be due to the different composition of fly ash produced in each different country as by-product. It is importantly shown that the four countries, including USA have standardized to compose the total 70% of $SiO_2+Al_2O_3+Fe_2O_3$. The other countries have required to have the individual chemical composition, such as 45% $SiO_2$ in Japan. The loss on ignition is generally in the range of 5-6%, but the maximum 12% was allowed in some countries. This depends on the quality of fly ash. The moisture content is generally less than 3% in all countries except India allows up to 12% The pozzolanic activity (as the compression) has been standardized that the 28 days curing in compression was subjected in all countries but 91 days curing in compression was tested in Japan. It is shown that KS L 5405 is almost identical to JIS A 6201.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.49-57
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• 2013

Recently, recycling of industrial by-products and CO2 reduction have been important issues in the world. In this reason, applications and reuse of Fly ash as a binder for concrete, which is generated in thermoelectric power plant, have been one of the effective recycle methods. In order for Fly ash to be applied to concrete, Korean Standard(KS) has selected and managed quality such as $SiO_2$, fineness, specific gravity, ignition loss and activity index. However, there is a limits for activity index, whose test period required is at least 28 days or 91 days. Activity index is the critical indication standard to determine mechanical strength of concrete that contained Fly ash. To complement the disadvantage of test method, this research provided "API test method", which quickly measure Pozzolanic reaction of Fly ash can be considered as a alternative of activity index. Then, the adaptable API test method need to be investigated through comparative analysis with the test result of API, activity index and K-value. The test method can make evaluation of Fly ash quality faster and more accurate. As a result, most Fly ash produced in Korea has not been satisfied in the KS quality standard except water content and specific gravity, and especially fluidized bed boiler ash has its characteristics. Also, API, activity index and K-value have superior interrelationship. The interrelationship between API and activity index and K-value gets increased as the material age gets higher, so API test can be considered as very useful test method for Pozzolanic reaction evaluation of Fly ash.