• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.63-71
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• 2011

Portland cement production is under critical review due to high amount of $CO_2$ gas released to the atmosphere. Attempts to increase the utilization of a by-products such as fly ash and ground granulated blast-furnace slag to partially replace the cement in concrete are gathering momentum. But most of by-products is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. In this study, we investigated the influence of alkali activator and superplasticizer on the flowability and compressive strength of the alkali-activated mortar in oder to develop cementless alkali-activated concrete using blast furnace slag. In view of the results, we found out that the type and mixture ratio of alkali activator, the type and adding order of superplasticizer results to be significant factors. When cementless alkali-activated mortar using blast furnace slag manufactured with 1:1 the mass ratio of 9M NaOH and sodium silicate, and added superplasticizer before alkali activator in the mixer, we can be secured workability with 180 mm of flow during 1 hours and compressive strength of about 50 MPa under $20^{\circ}C$ curing condition at age of 28days.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.261-268
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• 2017

Red mud is an inorganic by-product obtained from the mineral processing of alumina from Bauxite ores. A highly alkali inorganic waste product with a pH level over 11, red mud in its original state negatively impacts the ecosystem, so appropriate treatment is necessary. The development of alkali activated slag-red mud cement can be a representative study aimed at recycling the strong alkali of the red mud as a construction material. However, Alkali-activated binders that use sodium activators have been reported to be more vulnerable to efflorescence. Therefore, in this study, the compressive strength, pore characteristics, water absorption, elution characteristics, and efflorescence properties of alkali-activated slag cement mortar were assessed according to their red mud substitution ratio.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.237-243
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• 2015

In this research, isothermal conduction calorimetry analysis has been conducted to investigate the reactivity of alkali activated slag binders. In order to secure the reactivity and workability of alkali activated slag binders, experiences with various types and concentrations of alkali activators were performed. Isothermal conduction calorimetry were measured with different alkali activators and mass ratio of $SO_3$ to binders as variables, and sodium tripolyphosphate ($Na_2P_3O_{10}$) and hydrated sodium borate ($Na_2B_4O_710H_2O$) were used to control setting time. As a results, alkali activated slag binders required alkali activators with 4 to 5 percent of concentration to accelerate the formation of calcium silicate hydrate(C-S-H) by alkali-activation, and overall heat generation rate delayed as accumulated heat decreased due to the high $SO_3$ contents. Moreover, the use of hydrated sodium borate as setting retarder causes elongated setting time due to delaying heat generation, so it can be considered that setting retarder played an important role in delaying total heat generation rate.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.240-241
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• 2018

In this paper, we tried to find the proper ratio of industrial byproducts which can express mechanical characteristics similar to ordinary portland cement by varying the ratio of industrial byproducts. as a result, the activated slag binder produced by the industrial byproduct in this study increased in compressive strength as the ratio of blast furnace slag increased and the fly ash ratio decreased.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.27-32
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• 2002

In this research influences of type and concentration of alkali activator and curing condition on the hydration, and properties of alkali activated blast furnace slag(AAS) concrete were investigated. Sodium carbonate and sulfate were used as alkali activators and their concentration were 4~10 weight percent with Na$_2$O equivalent to binder. The curing conditions were standard curing using 23$^{\circ}C$ water and activated curing chamber at $65^{\circ}C$. Results show that in case of sodium carbonate addition high early strengths were gained by activation of early hydration, but later strength gained was slight. On the other side sodium sulfate strengths were continuously increased with adding amount and ages. Steam curing activated early hydration so that early strengths were improved but later strengths were similar to standard curing. The strength reduction of AAS mortar with sodium sulfate was less than OPC mortar in 5% sulfuric acid solution so that AAS concrete can be useful for acid-resistance concrete.

• International Journal of Concrete Structures and Materials
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• v.8 no.3
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• pp.213-228
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• 2014

Alkali-activated binder (AAB) is recently being considered as a sustainable alternative to portland cement (PC) due to its low carbon dioxide emission and diversion of industrial wastes and by-products such as fly ash and slag from landfills. In order to comprehend the behavior of AAB, detailed knowledge on relations between microstructure and mechanical properties are important. To address the issue, a new approach to characterize hardened pastes of AAB containing fly ash as well as those containing fly ash and slag was adopted using scanning electron microscopy (SEM) and energy dispersive X-ray spectra microanalyses. The volume stoichiometries of the alkali activation reactions were used to estimate the quantities of the sodium aluminosilicate (N-A-S-H) and calcium silicate hydrate (CSH) produced by these reactions. The 3D plots of Si/Al, Na/Al and Ca/Si atom ratios given by the microanalyses were compared with the estimated quantities of CSH(S) to successfully determine the unique chemical compositions of the N-A-S-H and CSH(S) for ten different AAB at three different curing temperatures using a constrained nonlinear least squares optimization formulation by general algebraic modeling system. The results show that the theoretical and experimental quantities of N-A-S-H and CSH(S) were in close agreement with each other. The $R^2$ values were 0.99 for both alkali-activated fly ash and alkali-activated slag binders.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.114-121
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• 2010

Portland cement production is under critical review due to high amount of CO2 gas released to the atmosphere. Attempts to increase the utilization of a by-products such as fly ash and ground granulated blast-furnace slag to partially replace the cement in concrete are gathering momentum. But most of by-products is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. However, most study deal only with alkali-activated ground granulated blast furnace slag or fly ash, as for the combined use of the both, little information is reported. In this study, we investigated the influence of mixture ratio of fly ash/ blast furnace slag tand curing condition on the flowability and compressive strength of mortar in oder to develop cementless alkali-activated concrete. In view of the results, we found out that the mixture ratio of fly ash/blast furnace slag always results to be significant factors. But the influence of curing temperature in the strength development of mortar is lower than the contribution due to other factors. At the age of 28days, the mixture 50% fly ash and 50% ground granulated blast furnace slag activated with 1:1 the mass ratio of 9M NaOH and sodium silicate, develop compressive strength of about 65 MPa under $20^{\circ}C$ curing.

• Resources Recycling
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• v.19 no.4
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• pp.19-28
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• 2010

Attempts to increase the utilization of a by-products such as fly ash and blast furnace slag to partially replace the cement in concrete are gathering momentum. But most of by-products is currently dumped in landfills, thus creating a threat to the environment. Many researches on alkali-activated concrete that does not need the presence of cement as a binder have been carried out recently. However, most study deal only with alkali-activated blast furnace slag or fly ash, as for the combined use of the both, little information is reported. In this study, we investigated the influence of mixture ratio of fly ash/slag, type of alkaline activator and curing condition on the workability and compressive strength of mortar in oder to develop cementless alkali-activated concrete. In view of the results, we found out that the mixture ratio of fly ash/slag and the type of alkaline activator always results to be significant factors. But the influence of curing temperature in the strength development of mortar is lower than the contribution due to other factors. At the age of 28days, the mixture 50% fly ash and 50% slag activated with 1:1 the mass ratio of 9M NaOH and sodium silicate, develop compressive strength of about 65 MPa under $20^{\circ}C$ curing.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.37-44
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• 2017

Red mud is an inorganic by-product produced from the mineral processing of alumina from Bauxite ores. The development of alkali-activated slag-red mud cement can be a representative study aimed at recycling the strong alkali of the red mud as a construction material. This study is to investigate the optimum water content, compressive strength, water absorption and efflorescence of alkali-activated slag-red mud soil pavement according to binder type. The results showed that the optimum water content, moisture absorption coefficient and efflorescence area of alkali-activated slag-red mud soil pavement increased but the compressive strength of that decreased as the redmud content increased.

• Journal of the Korea Concrete Institute
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• v.25 no.3
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• pp.305-312
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• 2013

This paper reports the results of an investigation into the effects of silica fume on strength properties of alkali-activated slag cement (AASC) with water-binder (W/B) ratio and replacement ratio of silica fume content. The W/B ratio varied between 0.50 and 0.60 at a constant increment of 0.05. The silica fume content varied from 0% to 50% by weight of slag. The activators was used sodium hydroxide (NaOH) and the dosage of activator was 3M. The strength development with W/B ratio has been studied at different ages of 1, 3, 7 and 28 days. For mixes of AASC mortars with varying silica fume content, the flow values were lower than the control mixes (without silica fume). The flow value was decrease as the content of silica fume increase. This is because the higher surface areas of silica fume particles increase the water requirement. The analysis of these results indicates that, increasing the silica fume content in AASC mortar also increased the compressive strength. Moreover, the strength decreases with the W/B ratios increases. This is because the particle sizes of silica fume are smaller than slag. The high compressive strength of blended slag-silica fume mortars was due to both the filler effect and the activated reaction of silica fume evidently giving the mortar matrix a denser microstructure, thereby resulting in a significant gain in strength.