• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.3
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• pp.108-117
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• 2013

Among the byproducts from thermal power plant using coal combustion, fly ash as mineral admixture is widely utilized in concrete manufacturing for its engineering merits. However residuals including bottom ash are usually reclaimed. This study presents an evaluation of engineering properties in cement mortar with pond ash (PA). For this work, two types of pond ash (anthracite and bituminous coal) are selected from two reclamation sites. Cement mortar specimens considering two w/c (0.385 and 0.485) ratios and three replacement ratio of sand (0%, 30%, and 60%) are prepared and their workability, mechanical, and durability performance are evaluated. Anthracite pond ash has high absorption and smooth surface so that it shows reasonable workability, strength development, and durability performance since it has dense pore structure due to smooth surface and sufficient mixing water inside. Reuse of PA is expected to be feasible since PA cement mortar has reasonable engineering performance compared with normal cement mortar.

• Resources Recycling
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• v.20 no.3
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• pp.40-47
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• 2011

In this study, we investigated the strength, shrinkage and durability of alkali-activated mortar using blast furnace slag only, and admixed with blast-furnace slag and fly ash as cementious materials in oder to develop cementless alkali-activated concrete. In order to compare with the alkali-activated mortar, the normal mortar using ordinary portland cement was also test. In view of the results, we found out that strength development, the resistance to shrinkage and freezing-thawing of the cementless alkali-activated mortar have better than the mortar using ordinary portland cement. Especially, using the combined with blast furnace slag and fly ash develop high strength of above 60 MPa, reduce shrinkage of about 40% and improve freezing-thawing durability of approximately 20%, but promote the velocity of carbonation of 2~3 times.

• International Journal of Highway Engineering
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• v.15 no.3
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• pp.1-8
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• 2013

PURPOSES : This study is to evaluate the feasibility of using the alkali activated cement concrete for application of partial-depth repair in pavement. METHODS : This study analyzes the compressive strength of alkali activated cement mortar based on the changes in the amount/type/composition of binder(portland cement, fly ash, slag) and activator(NaOH, $Na_2SiO_3$, $Na_2CO_3$, $Na_2SO_4$). The mixture design is divided in case I of adding one kind-activator and case II of adding two kind-activators. RESULTS : The results of case I show that $Na_2SO_4$ based mixture has superior the long-term strength when compared to other mixtures, and that $Na_2CO_3$ based mixture has superior the early strength when compared to other mixtures. But the mixtures of case I is difficult to apply in the material for early-opening-to-traffic, because the strength of all mixtures isn't meet the criterion of traffic-opening. The results of case II show that NaOH-$Na_2SiO_3$ based mixtures has superior the early/long-term strength when compared to NaOH-$Na_2SiO_3$ based mixtures. In particular, the NaOH-$Na_2SiO_3$ based some mixtures turned out to pass the reference strength(1-day) of 21MPa as required for traffic-opening. CONCLUSIONS : With these results, it could be concluded that NaOH-$Na_2SiO_3$ based mixtures can be used as the material of pavement repair.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.3
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• pp.204-210
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• 2013

This study has focused on the possibility for recycling tailings from the Sangdong tungsten mine (TA) as admixture for concrete. TA has been accumulating for several decades in Sangdong, a region in Korea, and there is a growing demand for alternative uses for this hazardous substance. In particular, the use must be in accordance with the hazardous materials stipulations under the Korean waste control act. This study showed that TA presented pH of 8.0-9.3, 18.7-22.0% of water content, 2.7% of maximum ignition loss. The chemical composition of TA showed minute differences from each depth of sampling that represented approximately 50% of $SiO_2$ and 13% of both $Al_2O_3$ and $Fe_2O_3$. The chemical composition of Cd, Cu, Zn and Pb from mortar incorporating TA showed lower levels of hazardous materials which met the specifications of the waste control act in Korea. The TA mortar also appeared very effective for stabilizing/solidifying heavy metals particularly when used in conjunction with SG.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.427-435
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• 2012

In order to evaluate the effects of exposure conditions on the resistance to sulfate attack of normal and blended cement mortars, several mechanical characteristics of the mortars such as expansion, strength and bulk density were regularly monitored for 52 cycles under sodium sulfate attack. The mortar specimens were exposed to 3 different types of exposure conditions; 1) continuous full immersion(Exposure A), continuous half-immersion(Exposure B) and cyclic wetting-drying(Exposure C). Experimental results indicated that the maximum deterioration was noted in OPC mortar specimens subjected to Exposure B, showing the wide cracks in the portions where attacking solution is adjacent to air. Additionally, the beneficial effect of ground granulated blast-furnace slag and silica fume was clearly observed showing a superior resistance against sodium sulfate attack, because of its lower permeability and densified structure. Thus, it is suggested that when concrete made with normal cement is exposed to sulfate environment, proper considerations on the exposure conditions should be taken.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.167-173
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• 2018

In general, calcium is required for the reaction of blast furnace slag fine powder and fly ash. The by-products generated during the process of producing recycled aggregates have different calcium contents depending on the crushing stage and the possibility of using the process by-product as a concrete mixture is also different. In this study, the effect of the calcium content of the by-products on the compressive strength was investigated and the block was fabricated by using this. To utilize the by-products as an admixture, the calcium content was analyzed and the bending strength and surface temperature were measured according to the shape of the water storage block. As a result of this study, the possibility of making a block using recycled aggregate by-products was verified and arch type block was constructed to secure storage capacity and bending strength. Also, the surface temperature of the water storage block was reduced by $9^{\circ}C$ or more than that of the general permeable block.

• Resources Recycling
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• v.23 no.4
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• pp.37-46
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• 2014

Carbon dioxide generated from construction materials and construction material industry among the fields of construction is approximately 67 million tons. It is about 30% of the carbon dioxide generated in the fields of construction. In order to reduce carbon dioxide in the fields of construction, it is necessary to control the use of fossil fuel consumed and decrease carbon emission by reducing the secondary and tertiary curing generating carbon dioxide in construction material industry. Therefore, this study manufactured mortar by having cement as the Plain and substituting three binding materials up to 50% and then adopted different curing methods to analyze congelation and strength characteristics. Test results for strength property by changing binding materials showed that specimens with blast furnace slag, CSA 15% and CAMC 5% resulted in positive effect for strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.429-435
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• 2020

In this study, physical properties and EMP shielding performance evaluation of cement paste according to the amount of milled carbon fiber was conducted to develop EMP shielding cement using carbon fiber. The length of the milled carbon fiber used was 100㎛, and it was used as a cement admixture because it showed a powdery form to the naked eye. As a result of the experiment, when 5% of the amount of cement was used, the milled carbon fiber was effective in compressive strength and EMP shielding, and the shielding effect did not increase when used beyond that. As a result of examining the EMP shielding performance according to the thickness of the specimen, the plain without milled carbon fiber had no effect of increasing the shielding rate according to the thickness. The shielding performance of the specimens using the milled carbon fiber increased as the thickness increased. Therefore, in order to increase the EMP shielding rate when comparing and evaluating the performance according to the amount of milled carbon fiber used and the thickness of the specimen, 5% of the milled carbon fiber used is optimal. In addition, the method of increasing the thickness is considered to be effective.

• Resources Recycling
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• v.32 no.6
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• pp.18-24
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• 2023

This study undertook initial investigations into the carbonation of chlorine bypass dust, aiming to apply it as a raw material for cement and as an admixture for concrete. Various experimental methods, including XRD(X-ray diffraction), XRF(X-ray fluorescence), and particle size distribution analyses, were employed to verify the physical and chemical properties of chlorine bypass dust, with and without water washing. The mineral carbonation extent of chlorine bypass dust was examined by considering the dust type, stirring temperature, and experiment duration. Notably, a higher degree of mineral carbonation was observed in water-washed bypass dust than its non-water-washed counterpart, indicating an elevated calcium content in the former. Furthermore, an augmented stirring temperature positively impacted the initial stages of mineral carbonation. However, divergent outcomes were observed over time, contingent upon the specific characteristics of dust types under consideration.

• Journal of the Korea Institute of Building Construction
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• v.10 no.4
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• pp.11-20
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• 2010

This study carried out a Mock-up test to apply Low-heat Cement (CF) that is adjusted to a fineness of $3,000\;{\pm}\;200\;cm^2/g$ by substituting Coarse particle Cement (CC) and fly ash with ordinary Portland Cement (OPC), then applied it on-site. The result of the test is as follows. The Mock-up test showed that the amount of admixture in CF increased SP agent and AE agent slightly more compared to OPC, while temperature history showed that the highest temperature of CF was around $6{\sim}10^{\circ}C$ lower than that of OPC. Compressive strength in CF was low compared to that of OPC, but the strength width became narrow at the age of 28 days, which is not considered to be significant. In on-site application, slump, air content and chloride content all satisfied the target values, while the temperature history showed that the highest temperature in the center by each cast was about $34^{\circ}C$ in the first cast, $42^{\circ}C$ in the second cast, and $39^{\circ}C$ in the third cast. Compressive strength of specimen for strut management showed low value compared to standard curing, but its strength was reduced at the age of 28 days.