• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.1
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• pp.74-80
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• 2009

This study analysis the fundamental properties of temperature-dependence corresponding the change of curing temperature classified by the replacement ratio of BS, and the results are summarized as following. As the properties of flow, plain satisfied with the target slump, and as the replacement ratio of BS increased, the flow increased, but the air content slightly decreased. The time of set delayed as the replacement ratio of BS increased, but the curing temperature $35^{\circ}C$, even with 80% BS replaced concrete, the time of set was faster than $5^{\circ}C$, $20^{\circ}C$ plain, so the temperature-dependence was much greater. The compressive strength was decreased as the replacement ratio of BS increased, especially as the curing temperature lower, the compressive strength was lower comparatively. Also as the age increased, the plain developed more strength, therefore it show the temperature-dependence is much larger.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.363-370
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• 2016

Lightweight geopolymers are more readily produced and give higher fire resistant performance than foam cement concrete. Lowering the density of solid geopolymers can be achieved by inducing chemical reactions that entrain gases to foam the geopolymer structure. This paper reports on the effects of adding different concentrations of aluminum powder on the properties of cellular structured geopolymers. The apparent density of lightweight geopolymers has a range from 0.7 to $1.2g/m^3$ with 0.025, 0.05 and 0.10 wt% of a foaming agent concentration, which corresponds to about 37~60 % of the apparent density, $1.96g/cm^3$, of solid geopolymers. The compressive strength of cellular structured geopolymers decreased to 6~18 % of the compressive strength, 45 MPa of solid geopolymers. The microstructure of geopolymers gel was equivalent for both solid and cellular structured geopolymers. The workability of geopolymers with polyprophylene fibers needs to be improved as in fiber-reinforced cement concrete. The lightweight geopolymers could be used as indoor wall tile or board due to fire resistance and incombustibility of geopolymers.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.207-213
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• 2018

Nowadays, circulating fluidized bed combustor(CFBC) boilers system that can reduce environmental pollution particles are widely used in electric power plants. But the fly ash generated from CFBC boilers has lower $SiO_2$ and higher MgO and $SO_3$ contents and also has free CaO inducing expansion and abrupt initial setting of concrete. Therefore, revised KSL5405 for CFBC fly-ash as well as pulverized coal combustion(PCC) is introduced in the concrete field. In this study, the chemical properties and mechanical properties of blended cements with PCC and CFBC fly-ash produced in Korea are analyzed. The blended cement with only CFBC fly ash shows a lower length change than OPC but a higher flow change ratio. The compressive strength of blended cement paste with PCC and CFBC fly ash is slightly greater than that of cement paste with only PCC fly-ash. Based on the results, CFBC flyash blended cement products should be used with PCC flyash to ensure the material stability and material properties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.90-96
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• 2009

The high rising building construction makes increasing the requirement of high strength concrete. Especially, the workability analysis is related with dispersion of admixture such as SF for improving strength and FA, BS for reducing construction cost and improving durability of Ultra High Strength Concrete which has over 100 MPa of compressive strength is very important. Precisely, decreases dispersion because of lumping situation of each admixture and it causes the workability of admixture is decreased. Therefore, the workability of cement paste is tested for analyze effects of pre-mixed cement for solving those problems with it to this research. The summary of the results are like below. First of all, OBS is increasing workability more than OFS. This result causes that the glassy surface of BS in the OBS is increasing workability and the absorption of admixture of FA in the OFS is decreasing workability. In the case of mixing methods, pre-mixing method is increasing workability more than normal one. This result shows that the normal mixing method is bad dispersion of binders. The other side, the pre-mixing method is good. Furthermore, depending on the mixing time, according to the increasing mixing time such as 30, 60, and 120 seconds, the dispersion of binders and workability turns better.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.235-244
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• 2020

This study conducted a series of studies to offer a novel method of using CBS-dust that produced as by-product in the manufacture of cement. Four different contents of BS and CBS-dust were adopted for test parameters of this study. Mortar with 50% of W/B was fabricated. First, in the case of the fresh mortar, the flow decreased as the CBS-dust replacement rate increased, but the binder composition ratio BS 45% and 65% showed higher fl ow than Pl ain when repl acing CBS-dust 5%. In the case of air content, overall, the tendency was proportional to the CBS-dust replacement rate, and chloride tended to exceed the reference value at all replacement rates except for the CBS-dust 0% replacement. The compressive strength of the hardened mortar shows the resul t that the strength is improved when the CBS-dust is repl aced by 5% to 10%, and the CSH gel and structure formation is confirmed by microstructure analysis through the hydration reaction when the CBS-dust is replaced. Therefore, for a given condition CBS-dust is used as a early-strength admixture in a concrete secondary product that uses a large amount of admixture without reinforcing bars it can be an effective method for enhancing the strength of concrete as an alkali activator.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.236-245
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• 2021

It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

• Journal of the Korean Geosynthetics Society
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• v.18 no.1
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• pp.79-89
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• 2019

The field measurement and laboratory experiment were conducted to investigate the effect of reducing the surface temperature of the functional aspect of the heat island phenomenon of the permeable block which is made the recycled synthetic resin rather than the existing concrete permeable block. Field measurement was taken for 3 days in consideration of dry condition and wet condition and laboratory experiment was divided into dry condition, rainfall simulating condition, and wetting condition. The variations of temperature and the evaporation rate of water moisture content after experiment were confirmed. As a result of field measurement, it is confirmed that the surface temperature decreases due to the difference in albedo of the pore block surface rather than the cooling effect due to the latent heat of vaporization. The evaporation of moisture in a dry state where drought persisted or a certain level of moisture was not maintained in the surface layer. As a result of laboratory experiment, resin permeable block gives higher surface temperature when it is dry condition than concrete permeable block, but the evaporation of water in the pore is kept constant by capillary force in rainfall simulation condition, and higher temperature reduction rate. As a result of measuring the evaporation rate after laboratory experiment, it is confirmed that the effect of reducing temperature is increased as the evaporation rate of water is higher. Based on these results, correlation formula for evaporation rate and temperature reduction rate is derived.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.1
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• pp.109-116
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• 2021

In order to replace mineral aggregate used as road pavement materials with steel slag aggregate, this present study evaluated mechanical properties of SMA Concrete mixtures using steel slag aggregate as oxidized slag from electric furnace in iron works. The variables of this experiment are the aggregate type of mineral and steel slag and the sieve sized of 10mm and 13mm. The physical properties inclu ding the specific gravity and absorption rate etc. of the slag aggregate mixtu res satisfied the KS standard as asphalt mixtu re. As a resu lt of evalu ating the mechanical properties of the asphalt mixtures, the optimum asphalt content of the slag aggregate mixtures were lower than that of the mineral aggregate mixtures, but other quality standards were all satisfied. In the deformation strength evaluation, the slag aggregate mixtures were measu red slightly higher than that of the mineral aggregate mixtu res, and the dynamic stability test satisfied the 2,000pass/mm standard value in all specimens. And, the moduli of resilient of the slag aggregate mixtures showed an improved value compared with the mineral aggregate mixtures. Therefore, as the resilient rate of the slag aggregate mixtures improved, it is speculated that there will be an effect of improving public performance according to the repeated traffic load of the vehicle.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.185-194
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• 2022

Coffee is one of the most consumed beverages in the world and is the second largest traded commodity after petroleum. Due to the great demand of this product, large amounts of waste is generated in the coffee industry, which are toxic and represent serious environmental problems. This study aims to study the possibility of recycling spent coffee grounds (SCG) as a mineral admixture by replacing the cement in the manufacturing of concrete. To recycle the coffee g rounds, the SCG was dried to remove moisture and fired in a kiln at 850 ℃ for 8 hours. Carbonized coffee grounds are produced as coffee grounds ash (CGA) through ball mill grinding. The chemical composition of the prepared coffee grounds ash was investigated using X-ray fluorescence (XFR). According to the chemical composition analysis, the major elements of coffee grounds ash are K₂O(51.74 %), CaO(15.92 %), P₂O₅(14.39 %), MgO(7.74 %) and SO₃(6.89 %), with small amounts of F₂O₃(0.66 %), SiO₂(0.59 %) and Al₂O₃(0.31 %) content. To evaluate quality and mechanical properties, substitutions of 5, 10, and 15 wt.% of coffee grounds ash (CGA) were tested. From the quality test results, the 28-day activity index of CGA5 reached 80 %, and the flow value ratio reached 96 %, which is comparable to the minimum requirement for second-grade FA. From the test results of the mortar, the optimal results have been found in specimens with 5 wt-% coffee grounds ash, showing good mechanical and physical properties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.450-456
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• 2022

In this study, as the preliminary research on the development of heating concrete members, compressive strength and accelerated chloride diffusion behavior in the mortar specimens containing C₁₂A₇ based binder and anhydrite was evaluated. Also, the effect of the mixing ratio of the citric acid based retarder was quantitatively evaluated by considering 4 levels of mixing cases. The compressive strength tests of the mortar specimen were performed referred to KS L ISO 679, and the accelerated chloride diffusion tests were performed according to NT BUILD 492 and ASTM C 1202. In the mortar with 0.3 % of retarder, the highest compressive strength was evaluated, which showed the strength development ratio of 127.6 % compared to the control case. It was considered that engineering performance was improved by effectively securing setting and curing time with 0.3 % of citric acid based retarder. As the result of the evaluation of the passed charge and the accelerated chloride diffusion coefficient, the evaluation results had similar behavior with the results of compressive strength. According to the previous study, the strength behavior and the chloride diffusion behavior had a linear relationship. The mixture showing the highest strength performance had the highest durability performance for chloride ingress, and the heating concrete development from this study will be performed in the future.