• Journal of the Korea Concrete Institute
• /
• v.13 no.2
• /
• pp.114-122
• /
• 2001

The purpose of this study was to manufacture sintered lightweight aggregate using paper sludge ash and to evaluate the qualities of the aggregate according to various mix proportions, conditions of pelletization and sintering. The paper sludge ash alone, due to its mineral and chemical compositions could not gain suitable expansion and strength. Hence, it was essential to add mineral additives such as clay, fly ash etc. The optimum muting ratio range determined in this study is as follows , paper sludge ash 30∼50 %, clay 30∼50 %, fay ash 0∼40 %, Paper sludge 0∼10% and hematite 2∼3 %(for manufacturing lightweight aggregate both for non-structural and structural concrete). It was possible to manufacture various lightweight aggregate whose dry specific gravity ranged about from 0.6 to 1.4 by using this optimum mixing ratio. From the test results of the qualities of aggregate, it showed that the 10% granules crushing value test and water absorption percentage ranged about 5∼10 ton and 10∼20%. Thus, it was favorably comparable to those of the imported aggregate. The manufactured lightweight aggregate could be used for structural concrete and non-structural concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.05a
• /
• pp.114-115
• /
• 2019

When concrete is exposed to fire, the decomposition of Portland cement paste results in critical damage to the concrete structure of a building. Although the behavior of cement pastes after heating provides crucial information with respect to the reuse of the building exposed to fire, the recovery process of the damaged concrete structure has not yet been fully elucidated. In addition, research on appropriate additives such as carbon nanotube (CNT) has been increasing recently, however, investigation of CNT incorporated cement paste after decomposition of CNT by high temperature is not fully investigated. In this study, we investigated the physicochemical properties of CNT incorporated cement paste under different temperatures (200℃, 500℃ and 800℃). Also, the effects of different rehydration conditions (20℃ 60% RH and in water for different curing times) on the recovery of the paste were studied. The changes in tensile and compressive strength, surface observation of the specimens were characterized. In addition, the decomposition and formation of hydrates in the paste due to the heating process were studied using X-ray diffraction.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2019.11a
• /
• pp.149-150
• /
• 2019

When concrete is exposed to fire, the decomposition of Portland cement paste results in critical damage to the concrete structure of a building. However the recovery process of the damaged concrete structure has not yet been fully elucidated. In addition, research on appropriate additives such as carbon nanotube (CNT) and nanosilica has been increasing recently, however, investigation of CNT and nanosilica incorporated cement paste after decomposition of CNT by high temperature is not fully investigated. In this study, we investigated the physicochemical properties of CNT incorporated cement paste under different temperatures ($200^{\circ}C$, $500^{\circ}C$ and $800^{\circ}C$). Also, the effects of different rehydration conditions ($20^{\circ}C$ 60% RH and in water for different curing times) on the recovery of the paste were studied. The changes in tensile strength, surface observation of the specimens were characterized. In addition, the decomposition and formation of hydrates in the paste due to the heating process were studied using X-ray diffraction. The results showed that incorporation of nanosilica enhanced tensile strength after heating to each target temperatures.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.21 no.3
• /
• pp.411-417
• /
• 2023

During the operation of a nuclear power plant (NPP), the generation of radioactive waste, including dry active waste (DAW), concentrates, spent resin, and filters, mandates the implementation of appropriate disposal methods to adhere to Korea's waste acceptance criteria (WAC). In this context, this study investigates the potential use of polymer concrete (PC) as a high-integrity container (HIC) material for solidifying and packaging these waste materials. PC is a versatile composite material comprising binding polymers, aggregates, and additives, known for its exceptional strength and chemical stability. A comprehensive analysis of PC's long-term integrity was conducted in this study. First, its compressive strength, which is crucial for ensuring the structural stability of HICs over extended periods, was evaluated. Subsequently, the resilience of PC was tested under various stress conditions, including biological, radiological, thermal, and chemical stressors. The findings of this study indicate that PC exhibits remarkable long-term properties, demonstrating exceptional stability even when subjected to diverse stressors. The results therefore underscore the potential viability of PC as a reliable material for constructing high-integrity containers, thus contributing to the safe and sustainable management of radioactive waste in NPPs.

• Smart Structures and Systems
• /
• v.29 no.2
• /
• pp.337-350
• /
• 2022

This paper focuses on predicting the post-heating mechanical properties of cementitious composites reinforced with multi-scale additives using the Artificial Neural Network (ANN) approach. A total of four different feed-forward ANN models are developed using 261 data sets collected from 18 published sources. The models are optimized using 12 input parameters selected based on a comprehensive literature review to predict the residual compressive strength, the residual flexural strengths, elastic modulus, and fracture energy of heat-damaged cementitious specimens. Furthermore, the ANN is employed to predict the impact of several variables including; the content of polypropylene (PP) microfibers and carbon nanotubes (CNTs) used in the concrete, mortar, or paste mix design, length of PP fibers, the average diameter of CNTs, and the average length of CNTs. The influence of the studied parameters is investigated at different heating levels ranged from 25℃ to 800℃. The results demonstrate that the developed ANN models have a strong potential for predicting the mechanical properties of the heated cementitious composites based on the mixing ingredients in addition to the heating conditions.

• Journal of the Korea Concrete Institute
• /
• v.27 no.1
• /
• pp.3-9
• /
• 2015

In this study, hydration properties of ordinary Portland cement were examined, shown from a limestone and blast furnace slag alone or their mixture up to 10% as a minor mineral additives. As of setting time, it was identified that final setting became faster as the amount of limestone mixture increased, which showed limestone accelerated early hydration faster than blast furnace slag. This is because limestone did accelerate the hydration of alite. At the age of 3 days, limestone 5%-blast furnace slag 5% mixture had the highest compressive strength of mortar. It is because hydration acceleration of alite by limestone, and $Ca(OH)_2$ that was additionally formed by hydration acceleration of alite reacted with blast furnace slag, and as a result, additionally created C-S-H hydrate. Regarding the hydration properties by the age of 7 and 28 days, limestone 3%-blast furnace slag 7% of composited mixture showed the largest compressive strength, and in comparison with the 3 days in curing age. This period is when hydration reaction of blast furnace slag is active and the amount of hydrate depends on the amount of blast furnace slag mixture more than that of the limestone mixture. And in order to vitalize hydration reaction of blast furnace slag the amount of $Ca(OH)_2$ created has to increase, and thus, a small amount of limestone is necessary that can accelerate the hydration of alite. Therefore, after the age of 7 days, the fact that there were a large amount of blast furnace slag mixture and small amount of limestone mixture was effective to the strength development of ordinary Portland cement.

• International Journal of Highway Engineering
• /
• v.18 no.6
• /
• pp.25-34
• /
• 2016

OBJECTIVES : This is a basic research for the domestic production of airport-airside deicers. This research selected basic materials for deicers appropriate for the pavement of domestic airports by evaluating the deicing performances of basic materials used in international-standard airport deicers and their impacts on pavements. METHODS : Laboratory investigation was conducted to evaluate the asphalt surface tensile strength, concrete scaling impact, ASR impact, and deicing performances of sodium formate (NaFm), potassium formate (KFm), sodium acetate (NaAc), and potassium acetate (KAc), which are the basic de-icing materials commonly used at international airports, approved by the FAA. In addition, the analyses were also performed on the airside deicer urea, which is currently used in domestic airports. RESULTS : Laboratory investigation confirmed that sodium formate, potassium formate, sodium acetate, and potassium acetate had superior surface tensile strength, concrete scaling impact, and deicing performance compared to airside urea, but they also had greater impacts on concrete ASR. Among these materials, sodium formate had the best asphalt surface tensile strength, concrete scaling impact, and deicing performance, while also having the greatest impact on ASR; hence, mitigation plans for ASR were needed, if it were to be used as airport-airside deicer. CONCLUSIONS : It is necessary to consider additional additives to prevent ASR of concrete pavements when developing airport-airside deicers using sodium formate, potassium formate, sodium acetate, and potassium acetate.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.1
• /
• pp.69-75
• /
• 2012

The study was conducted to determine the effects of adding pig blood as an admixture to both mortar and concrete. The mortar tests included the determination of its unit weight, flow and its compressive strength. Moreover, the concrete test includes the determination of air content, slump, bleeding, setting time compressive strength and freeze-thaw resistance of the material. As the test result, the utilization of pig blood, as an additive to both mortar and concrete mixtures causes air entrainment. The mortar flow increased and both the unit weight and the compressive strength of mortar decreased. As the blood replacement rate increases, the air content decreases over time, the setting and amount of bleeding showed a tendency to decline and reduced compressive strength, and the freeze-thaw resistance of the concrete increased.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.29 no.4
• /
• pp.132-141
• /
• 1987

The objective of the study was to obtain the compressive the tensile and the fleniril strengthes, thermal resistance, chemical resistance and fire resistance of the reclaimed plastic corcrete in order to investigate the feasibility as a new construction material This reclaimed plastic concrete is a compositive material which is composed of sand and blend of 50% of LDPE(Low density polyethylene) and 50% of HDPE (High density polyethylene) which are inexpensive and easy to reclaim. The results obtained in the study are summarized as follows: 1. As the binder content ranging from 20 to 40 % increase, the compresie, the splitting tensile and the flexural strengthes were increased. The compressive strenzth of the specimen tested was the highest and flexural strength the next and tensile strength the lowest 2. The compressive, the tensile and flexural strengthes of specimens made of fine sand were higher than those of coarse sand. The compressive, the tensile and the flexural strengthes of specimens made of high pressure molding were higher than those of low pressure molding. 3.In comparison with different additives, the specimens with carbon black was excellent and B. H. T. good and ferric oxide poor for thermal resistance. 4. In relationship between the flexural strength with varying temperature from -23$^{\circ}C$ to 80$^{\circ}C$. The flexural strengthes were decreared as temperature increased at 25 %, 30 % and 35 % of binder contents, respectively. Especially at 60$^{\circ}C$, the flexural strength was significantly decreased. 5. The decrement of flexural strengthes and the weight losses after 7 days immersion in acid or alkali solutions were not significant. 6. Fire resistance of the reclaimed plastic concrete was not significantly influenced by the contents of sand. However, the fire resistance of the reclaimed plastic concrete was depend upon melting and ignition properties of the binder itself. Therefore. a proper selection of the binder and the fire retardant are recommended in arder to improve fire resistance of the reclaimed plastic concrete.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.1
• /
• pp.26-32
• /
• 2020

Concrete recycling is becoming mandatory rather selective due to depletion of constructional materials and increase of concrete waste. Studies on recycling concrete are conducted in various point of view for long time. However, standard or guideline of many countries for the application of recycled aggregate concrete(RAC) has restrictions such as low replacement rate of coarse aggregate and no fine aggregate allowed due to inferior material properties of recycled aggregate. This study intends to figure out the feasibility of casting natural aggregate concrete(NAC) and RAC separately in a structural member. In making RAC, replacement rate of coarse aggregate was 50, 100% in RAC and treatment of interface of two concretes is introduced. RAC treatment of recycled aggregate or inclusion of additives was not done as it can increase embodied energy of concrete work. Double-shear test with uniformly distributed loading was adopted to evaluate shear strength at the interface of two concretes. After curing it was hard to distinguish interface of two concretes. Experimental result revealed that specimen with higher replacement rate showed higher shear-to-compressive strength ratio, which is possibly attributed to coarse aggregate size and roughness of sheared section. Further study on the effect of various parameters is required and subsequent research activity is on-going.