• Journal of the Korea Concrete Institute
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• v.23 no.6
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• pp.765-772
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• 2011

The present study summarizes a series of compressive tests on concrete cylinder in order to examine the stressstrain relationship of alkali-activated (AA) slag concrete. The compressive strength and unit weight of concrete tested ranged from 8.6 MPa to 42.2 MPa and from $2,186kg/m^3$ to $2,343kg/m^3$, respectively. A mathematical equation representing the complete stress-strain curve was developed based on test results recorded from 34 concrete specimens. The modulus of elasticity, strain at peak stress, slopes of ascending and descending branches of stress-strain curves were generalized as a function of compressive strength and unit weight of concrete. The mean and standard deviation of the coefficient of variance between measured and predicted curves were 6.9% and 2.6%, respectively. This indicates that the stress-strain relationship of AA slag concrete is represented properly with more accuracy in the proposed model than in some other available models for ordinary portland cement (OPC) concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.21-22
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• 2021

This study incorporates fine waste glass (GS) as a replacement for natural sand (NS) in ground granulated blast furnace slag (GGBS) based alkali activated mortar (AAm). Tests were conducted on the AAm to determine the mechanical properties, apparent porosity and the durability based on its resistance to Na2SO4 5% and H2SO4 2% concentrated solutions. The study revealed that increasing GS up to 100 wt%, increased strength and decreased porosity. The lower porosity attained with the incorporation of GS, improved the resistance of mortar to Na2SO4 and thus increasing durability. However, the durability of mortar to H2SO4 solution was negatively impacted with the further reduction of porosity observed with increasing GS above 50 wt.% believed to be caused by the stress induced as a result of expansive reaction products created when the mortar reacted with acid.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1630-1636
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• 2009

Nine alkali-activated (AA) mortars were mixed and cured at water or air-dried conditions to explore the significance and limitation for the application of the combination of Ba and Ca ions as an alkali-activator. Ground granulated blast-furnace slag (GGBS) was used for source materials, and calcium hydroxide (Ca(OH)₂) and barium hydroxide (Ba(OH)₂) were employed as alkali activators. Test results clearly showed that the water curing condition was more effective than the air-dried curing condition for the formation of the denser calcium silicate hydrate (C-S-H) gels that had a higher molar Si/Ca ratio, resulting in a higher strength development. At the same time, the introduction of Ba(OH)₂ led to the formation of 2CaO·Al₂O₃·SiO₂·8H₂O (C₂ASH₈) hydrates with higher molar Si/Al and Ca/Al ratios. Based on the test results, it can be concluded that the developed cementless mortars have highly effective performance and high potential as an eco-friendly sustainable building material.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.205-212
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• 2016

This research investigates the influence of ground granulated blast furnace slag (GGBFS) composition on the alkali-activated slag cement (AASC). Aluminum oxide ($Al_2O_3$) was added to GGBFS binder between 2% and 16% by weight. The alkaline activators KOH (potassium hydroxide) was used and the water to binder ratio of 0.50. The strength development results indicate that increasing the amount of $Al_2O_3$ enhanced hydration. The 2M KOH + 16% $Al_2O_3$ and 4M KOH + 16% $Al_2O_3$ specimens had the highest strength, with an average of 30.8 MPa and 45.2 MPa, after curing for 28days. The strength at 28days of 2M KOH + 16% $Al_2O_3$ was 46% higher than that of 2M KOH (without $Al_2O_3$). Also, the strength at 28days of 4M KOH + 16% $Al_2O_3$ was 44% higher than that of 4M KOH (without $Al_2O_3$). Increase the $Al_2O_3$ contents of the binder results in the strength development at all curing ages. The incorporation of AASC tended to increases the ultrasonic pulse velocity (UPV) due to the similar effects of strength, but increasing the amount of $Al_2O_3$ adversely decreases the water absorption and porosity. Higher addition of $Al_2O_3$ in the specimens increases the Al/Ca and Al/Si in the hydrated products. SEM and EDX analyses show that the formation of much denser microstructures with $Al_2O_3$ addition.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.77-86
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• 2013

This study investigates the fundamental properties of the water-binder (W/B) ratio and fine aggregate-binder (F/B) ratio in the alkali-activated slag cement (AASC) mortar. The W/B ratios are 0.35, 0.40, 0.45, and 0.50, respectively. And then the F/B ratios varied between 1.00 and 3.00 at a constant increment of 0.25. The alkali activator was an 2M and 4M NaOH. The measured mechanical properties were compared, flow, compressive strength, absorption, ultra sonic velocity, and dry shrinkage. The flow, compressive strength, absorption, ultra sonic velocity and dry shrinkage decreased with increases W/B ratio. The compressive strength decreases with increase F/B ratio at same W/B ratio. Also, at certain value of F/B ratio significant increase in strength is observed. And S2 (river sand 2) had lower physical properties than S1 (river sand 1) due to the fineness modulus. The results of experiments indicated that the mechanical properties of AASC depended on the W/B ratio and F/B ratio. The optimum range for W/B ratios and F/B ratios of AASC is suggested that the F/B ratios by 1.75~2.50 at each W/B ratios. Moreover, the W/(B+F) ratios between 0.13 and 0.14 had a beneficial effect on the design of AASC mortar.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.299-300
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• 2010

Flow and compressive strength of slag mortars activated by $MgNO_3$ were measured to examine the significance and limitation for the use of Mg-ion as an alkali-activator. The compressive strength of mortars tested was significantly dependent on the addition amount of $MgNO_3$, showing that 30~60% higher strength was developed in water-cured mortars than in air-cured mortars.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.361-362
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• 2010

Six alkali-activated(AA) concrete mixes were tested to ascertain the effect of unit binder content on the slump and compressive strength of concrete. Test results showed that the compressive strength of AA-concrete increased with the increase of the unit binder content, while the increasing rate was lower that recorded in ordinary portland cement concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.107-108
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• 2017

In this search, by evaluating the field applicability of soil mixed pavement of Red mud is mixed into the soil mixed pavement field applicability, and tries to present the basic data about the site application of recycling of red mud and low carbon construction material to. As a result, the conventional soil concrete organization standards (SPS-KSCICO-001: 2003) meets the criteria for parking lot, making use of red mud, natural color as well as the natural loess is expressed.

• Advances in nano research
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• v.3 no.4
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• pp.225-242
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• 2015

The current investigation aims to study performance of geopolymer mortar reinforced with Multiwalled carbon nanotubes upon exposure to $200^{\circ}C$ to $1000^{\circ}C$ for 2 hrs. MWCNTs are doped into slag Geopolymer mortar matrices in the ratio of 0.0 to 0.4, % by weight of binder. Mortar composed of calcium aluminosilicate to sand (1:2), however, binder composed of 50% air cooled slag and 50% water cooled slag. Various water / binder ratios in the range of 0.114-0.129 used depending on the added MWCNT, while 6 wt., % sodium hydroxide used as an alkali activator. Results illustrate reduction in mechanical strength with temperature except specimens containing 0.1 and 0.2% MWCNT at $200^{\circ}C$, while further increase in temperature leads to decrease in strength values of the resulting geopolymer mortar. Also, decrease in firing shrinkage with MWCNT up to 0.1% at all firing temperatures up to $500^{\circ}C$ is observed, however the shrinkage values increase with temperature up to $500^{\circ}C$. Further increase on the firing temperature up to $1000^{\circ}C$ results in an increase in the volume due to expansion.

• Computers and Concrete
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• v.21 no.5
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• pp.559-567
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• 2018

In this study alkali activation of Electric Arc Furnace Slag (EAFS) is studied with a comprehensive test program. Three different silicate moduli (1-1,5-2), three different sodium concentrations (4%-6%-8%) for each silicate module, two different curing conditions (45%-98% relative humidity) for each sodium concentration, two different curing temperatures ($400^{\circ}C-800^{\circ}C$) for each relative humidity condition and two different curing time (6h-12h) for each curing temperature variables are selected and their effects on compressive strength was evaluated then regression equations using multiple linear regressions methods are fitted. And then to select the best regression models confirm with using the variables, the regression models compared between itself. An Artificial Neural Network (ANN) models that use silicate moduli, sodium concentration, relative humidity, curing temperature and curing time variables, are formed. After the investigation of these ANN models' results, ANN and multiple linear regressions based models are compared with each other. After that, an explicit formula is developed with values of the ANN model. As a result of this study, the fluctuations of data set of the compressive strength were very well reflected using both of the methods, multiple linear regression with quadratic terms and ANN.