• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.65-73
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• 2015

This study discussed the pozzolanic properties of calcined sewage sludge (CSS) according to calcination and fineness conditions. The chemical and mineralogical analysis of CSS according to calcination temperature and time were carried out and compared with that of the existing pozzolanic materials such as fly-ash, blast furnance slag and meta-kaolin. Various mortars were made by mixing those CSS and $Ca(OH)_2$ (1:1 wt. %), and their compressive strength and hydrates according to experimental factors such as fineness of CSS and curing age were also investigated in detail. The results show clearly the potentiality of calcined sewage sludge (CSS) as an admixture materials in concrete, but the CSS should be controlled by calcination temperature and time, and fineness etc. In this experimental condition, the calcination temperature of $800^{\circ}C$, calcination time of 2 hours and fineness of $5,000cm^2/g$ were optimum conditions in consideration of the mechanical properties and economic efficiency of CSS. The compressive strength of CSS mortars was higher than that of fly-ash mortars and blast furnace slag mortars, especially at the early ages. Then, the utilization of CSS in construction fields was greatly expected.

• Journal of the Korea Institute of Building Construction
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• v.19 no.6
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• pp.485-494
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• 2019

This study is to evaluate the effect of admixtures such as blast-furnace slag and fly ash on adhesion in flexure and tension of polymer cement mortar(PCM) using SAE emulsion. The test specimens are prepared with five polymer-cement ratios and five admixture contents, and tested for flexural strength, adhesion in flexure, tensile strength and adhesion in tension. Based on the test results, no improvement of flexural strength and adhesion in flexure caused by admixtures in PCM can be indicated, but the tensile strength and adhesion in tension is improved due to mixing of the admixtures. In particular, the maximum of adhesion in tension of PCM with P/C 20% and BF content of 10% is 3.35MPa which is about 2.36 times higher than that of ordinary cement mortar, and 1.32 times that of PCM that does not contain any admixture. The average ratio of adhesion in tension to tensile strength of PCM was 48.7%. It is apparent that admixture contents of 5% or 10% could be proposed for improvement of tensile strength and adhesion in tension of PCM.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.124-132
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• 2018

This research presents the results of an investigation on the characteristic of multi-component blended high fluidity mortars. The binder was blended ordinary Portland cement(OPC), ground granulated blast furnace slag(GGBFS), calcium sulfoaluminate(CSA) and ultra rapid setting cement(URSC). The GGBFS was replaced by OPC from 30%(P7 series), 50%(P5 series) and 70%(P3 series), CSA and URSC was 10% or 20% mass. The superplasticizer of polycarboxylate type were used. A constant water-to-binder ratio(w/b)=0.35 was used for all mixtures. Test were conducted for mini slump, setting time, V-funnel, compressive strength and drying shrinkage. According to the experimental results, the contents of superplasticizer, V-funnel and compressive strength increases with an increase in CSA or URSC contents for all mixtures. Moreover, the setting time and drying shrinkage ratio decrease with and increase in CSA or URSC. CSA decreased dry shrinkage but URSC had less effect. However, the mixed binders of CSA and URSC had a large effect of reducing drying shrinkage by complementary effect. This is effective for improving the initial strength of URSC, and CSA is effective for the expansion and improvement of long-term strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.457-464
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• 2022

In this study, XRF, Loss on ignition, SEM, and PSA analysis were performed on four types of fly ash in Vietnam and compared with fly ash in Korea. As a result, PC boiler fly ash in Vietnam has a similar chemical composition to that of PC boiler fly ash in Korea, where the content of SiO₂, Al₂O₃, and Fe₂O₃ accounts for about 70%. In addition, the result showed that blast furnace slags in Vietnam and Korea have similar quality criteria and performance. A binder material mixing test using four types of fly ash supplied from Vietnam was conducted, and the compressive strength ranged from 7.60 to 13.25 MPa after 28 days of curing. Vinh Tan fly ash showing the highest compressive strength was selected as the soil injection material for the chemical grouting method. For the formulation of the chemical grouting method, sodium silicate No.3 and silica-sol were used as liquid-A. As a result of measuring the gel time and the compressive strength of the homogel, they showed good performance satisfying the quality criteria applied in Korean construction fields. Therefore, Vinh Tan fly ash can be used as a soil injection material for the chemical grouting method.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.405-412
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• 2008

Six alkali-activated (AA) concrete mixes were tested to explore the significance and limitations of developing an environmental friendly concrete. Ground granulated blast-furnace slag and powder typed sodium silicate were selected as source material and an alkaline activator, respectively. The main parameter investigated was the replacement level of lightweight fine aggregate to the natural sand. Workability and mechanical properties of lightweight AA concrete were measured: the variation of slump with time, the rate of compressive strength development, the splitting tensile strength, the moduli of rupture and elasticity, the stress-strain relationship, the bond resistance and shrinkage strain. Test results showed that the compressive strength of lightweight AA concrete sharply decreased when the replacement level of lightweight fine aggregate exceeded 30%. In particular, the increase in the discontinuous grading of lightweight aggregate resulted in the deterioration of the mechanical properties of concrete tested. The measured properties of lightweight AA concrete were also compared, wherever possible, with the results obtained from the design equations specified in ACI 318-05 or EC 2, depending on the relevance, and the results predicted from the empirical equations proposed by Slate et al. for lightweight ordinary Portland cement concrete. The stress-strain curves of different concrete were compared with predictions obtained from the mathematical model proposed by Tasnimi. The measured mechanical properties of lightweight AA concrete generally showed little agreement with the predictions obtained from these equations.

• Corrosion Science and Technology
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• v.8 no.5
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• pp.171-176
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• 2009

The chloride threshold level (CTL) in mixed concrete containing, ordinary Portland cement (OPC), pulverized fuel ash (PFA) ground granulated blast furnace slag (GGBS), and silica fume (SF) is important for study on corrosion of reinforced concrete structures. The CTL is defined as a critical content of chloride at the steel depth of the steel which causes the breakdown of the passive film. The criterion of the CTL represented by total chloride content has been used due to convenience and practicality. In order to demonstrate a relationship between the CTL by total chloride content and the CTL by free chloride content, corrosion test and chloride binding capacity test were carried out. In corrosion test, Mortar specimens were cast using OPC, PFA, GGBS and SF, chlorides were admixed ranging 0.0, 0.2, 0.4, 0.8, 1.0, 1.5, 2.0, 2.5 and 3.0% by weight of binder. All specimens were cured 28 days, and then the corrosion rate was measured by the Tafel's extrapolation method. In chloride binding capacity, paste specimens were casting using OPC, PFA, GGBS and SF, chlorides were admixed ranging 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0% by weight of binders. At 28days, solution mixed with the powder of ground specimens was used to measure binding capacity. All specimens of both experiments were wrapped in polythene film to avoid leaching out of chloride and hydroxyl ions. As a result, the CTL by total chloride content ranged from 0.36-1.44% by weight of binders and the CTL by free chloride content ranged from 0.14-0.96%. Accordingly, the difference was ranging, from 0.22 to 0.48% by weight of binder. The order of difference for binder is OPC > 10% SF > 30% PFA > 60% GGBS.

• Corrosion Science and Technology
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• v.8 no.2
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• pp.74-80
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• 2009

The high alkaline property in the concrete pore solution protects the embedded steel in concrete from corrosion due to aggressive ions attack. However, a continuous supply of those ions, in particular, chlorides altogether with a pH fall in electrochemical reaction on the steel surface eventually depassivate the steel to corrode. To mitigate chloride-induced corrosion in concrete structures, finely grained mineral admixtures, for example, pulverized fuel ash (PFA), ground granulated blast furnace slag (GGBS) and silica fume (SF) have been often advised to replace ordinary Portland cement (OPC) partially as binder. A consistent assessment of those partial replacements has been rarely performed with respect to the resistance of each binder to corrosion, although the studies for each binder were extensively looked into in a way of measuring the corrosion rate, influence of microstructure or chemistry of chlorides ions with cement hydrations. The paper studies the behavior of steel corrosion, chloride transport, pore structure and buffering capacity of those cementitious binders. The corrosion rate of steel in mortars of OPC, 30% PFA, 60% GGBS and 10% SF respectively, with chloride in cast ranging from 0.0 to 3.0% by weight of binder was measured at 7, 28 and 150 days to determine the chloride threshold level and the rate of corrosion propagation, using the anodic polarization technique. Mercury intrusion porosimetry was also applied to cement pastes of each binder at 7 and 28 days to ensure the development of pore structure. Finally, the release rate of bound chlorides (i.e. buffering capacity) was measured at 150 days. The chloride threshold level was determined assuming that the corrosion rate is beyond 1-2 mA/$m^3$ at corrosion and the order of the level was OPC > 10% SF > 60% GGBS > 30% PFA. Mercury intrusion porosimetry showed that 10% SF paste produced the most dense pore structure, followed by 60% GGBS, 30% PFA and OPC pastes, respectively. It was found that OPC itself is beneficial in resisting to corrosion initiation, but use of pozzolanic materials as binders shows more resistance to chloride transport into concrete, thus delay the onset of corrosion.

• Journal of the Korea Institute of Building Construction
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• v.6 no.3 s.21
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• pp.75-82
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• 2006

This study investigates the influence of various blending factors on cement paste fluidity and find out the most effective evaluation method of cement paste flow, comparing flow test apparatuses such as ring flow(R-F), flow cone(F-C) and mini slump(M-S). A viscometer also measures the rheology coefficients to secure faithful numerical data. Firstly, series I examines cement paste, affected by several cement products and mineral admixture types in the range of W/B 40%, ordinary fluidity, and W/B 30%, high fluidity. In this series, the three types of cement product depended on companies, are randomly used and the mineral admixture, such as fly ash, blast furnace slag and silica fume, are incorporated in the cement paste, in response to the ratio of 10, 20, to 30%, respectively. In addition, series II studies various chemical admixture types, affecting the cement paste. This series is carried out with manufacturing companies and component types in the range of W/C 30%, high fluidity. For the manufacturing companies, randomly four products are used and for the component types, polycaboxylate, melamine, naphthalene and lignosulfonate type are chosen. Test results showed that in the fluidity test of cement paste considering various types of blending factors, R-F exhibited similar tendency with F-C and M-S. In the analysis of consistency curves measured by viscometer, the fluidity evaluation method using flow test apparatuses was significantly effective, except for the some of the low fluidity specimens. In conclusion of this study, R-F was the most convenient, faithful and effective fluidity evaluation method of cement paste.

• Journal of the Korean Society of Safety
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• v.27 no.2
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• pp.49-56
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• 2012

If cement can be manufactured with industrial byproducts such as granulated blast furnace slag, phosphogypsum, and waste lime instead of clinker, there would be many advantages, including maximum use of these industrial byproducts for high value-added resources, conservation of natural resources and energy by omitting the use of clinker, minimized environmental pollution problems caused by CO2 discharge, and reduction of the production cost. By this reason, in this study, mechanical behavior tests of non-burnt cement concrete were performed, and elasticity modulus and stress-strain relationship of non-burnt cement concrete were proposed. 6 test members were manufactured and tested according to reinforcement ratio and concrete compressive strength. By the test results, there was no difference between ordinary concrete and non-burnt cement concrete of flexural behavior. In order to verify the proposed non-burnt cement concrete model, nonlinear analytical model was derived by using strain compatibility method. By the results of comparison between test results, ordinary concrete model and proposed model, The proposed model well predicted the flexural behavior of non-burnt cement concrete.

• Journal of Soil and Groundwater Environment
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• v.18 no.1
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• pp.102-111
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• 2013

A novel MgO-based binder was developed and applied to treat the anoxic sediment that was collected from Seonakdong river, Korea and was contaminated with heavy metals. The treated sediment was evaluated by measuring compressive strength, expansion, leaching of heavy metals and storage characteristics for $CO_2$. Initially, an optimal blending ratio of lime (L)/fly ash (FA)/blast furnace slag (BFS) that was to be mixed with MgO was screened to be $L_{0.3}-FA_{0.1}-BFS_{0.6}$. Long-term strengths of the sediments that were treated by various mixtures of MgO and $L_{0.3}-FA_{0.1}-BFS_{0.6}$ were then evaluated and the blending ratios between 4 : 6 and 6 : 4 were found optimal, which yielded a compressive strength of 4.09 MPa. On this basis, the optimal MgO-based binder was selected to be a 5 : 5 mixture of MgO and $L_{0.3}-FA_{0.1}-BFS_{0.6}$. The good performance of the MgO-based binder was believed to be due to the formation of Mg $(OH)_2$, which filled the micropores and also increased the density of the solidified matrices. The MgO-based binder exhibited an average stabilizing capacities for heavy metals of 92.9%, which was similar to or higher than that of Portland cement. It was found that 69.1 kg of carbon dioxide could be sequestrated after 365 days of curing when treating a ton of anoxic sediments.