• Journal of the Korea Concrete Institute
• /
• v.24 no.6
• /
• pp.745-752
• /
• 2012

This paper studies the effect of the compressive strength for combined alkali-activated slag mortars. The effect of activators such as alkali type and dosage factor on the strength was investigated. The alkalis combinations made using five caustic alkalis (sodium hydroxide (NaOH, A series), calcium hydroxide ($Ca(OH)_2$, B series), magnesium hydroxide ($Mg(OH)_2$, C series), aluminum hydroxide ($Al(OH)_3$, D series), and potassium hydroxide (KOH, E series)) with sodium carbonate ($Na_2CO_3$) were evaluated. The mixtures were combined in different dosage at 1M, 2M, and 3M. The study results showed that the compressive strength of combined alkali-activated slag mortars tended to increase with increasing sodium carbonate. The strength of combined alkali-activated slag mortars was better than that of control cases (without sodium carbonate). The result from scanning electron microscopy (SEM) analysis confirmed that there were reaction products of calcium silicate hydrate (C-S-H) and alumina-silicate gels from combined alkali-activated slag specimens.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.2
• /
• pp.130-137
• /
• 2018

In the construction industry, research on alkali activated cement using fly ash or blast furnace slag fine powder has been published in Korea and abroad as a way to reuse industrial byproducts without using cement at all and to obtain economical effects at the same time. the purpose of this paper is to evaluate the effect of the ratio and coefficient of hydration ratio and lime saturation degree on the strength of alkali activated slag cement by chemical quantitative analysis of alkali activated slag cement used in the management of existing portland cement. as a result, it was confirmed that the ratio and coefficient of hydration ratio and lime saturation are all within a certain range.

• Journal of Urban Science
• /
• v.9 no.1
• /
• pp.1-6
• /
• 2020

The thermoelectric characteristics of alkali activated slag composites containing multi-walled carbon nanotubes (MWCNT) was investigated in the present study. Three different MWCNT contents and exposed temperatures were considered, and their thermoelectric-related properties and internal structures were analyzed. It was found that the alkali activated slag composite with MWCNT 2.0 wt.% and the exposed temperature of 150℃ were the optimal condition to obtain the highest Seebeck coefficient and power factor. Based on the feasibility study, the extended size thermoelectric module with 130 elements was fabricated, and tested the electricity production capacity. Consequently, the present thermoelectric module produced 30.83 ㎼ of electricity at ∆T=178.4℃.

• International Journal of Concrete Structures and Materials
• /
• v.8 no.4
• /
• pp.289-299
• /
• 2014

Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-a'-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution ($SiO_2$-to-$Na_2O$ ratio or $M_s$ of 1-2) to provide a total alkalinity of 0.05 ($Na_2O$-to-binder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on $M_s$, (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.7
• /
• pp.810-819
• /
• 2007

Investigation of alkali activation of fly ash and blast furnace slag was carried out using waterglass and sodium hydroxide. XRD, FTIR, $^{29}Si$ and $^{27}Al$ NMR, TGA and SEM were used to observed the reaction products and microstructure of the fly ash/slag cement (FSC) pastes. The reaction products were amorphous or low-ordered calcium silicate hydrate and aluminosilicate gel produced from alkali activation of blast furnace slag and fly ash, respectively. On the basis of this investigation, waterglass solution with a modulus(Ms) of 1.0 and 1.2 is recommended for alkali activation of fly ash and blast furnace slag. Morphology of FSC pastes alkali-activated with Ms of 1.0 and 1.2 shows a more solid and continuous matrix due to restructuring of gel-like reaction products from alkali-activated fly ash and blast furnace slag together with another hydrolysis product(i.e., silica gel) from water glass.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2016.05a
• /
• pp.130-131
• /
• 2016

In this study, moisture absorption coefficient and efflorescence properties of Ordinary Portland cement and alkali-activated slag cement mortar were assessed according to their red mud substitution ratio. Tests were conducted to determine the cause of efflorescence, which is a significant obstacle to the recycling of red mud as a sodium activator in alkali-activated slag cement, and to find a method to control efflorescence.

• Journal of the Korea Institute of Building Construction
• /
• v.8 no.1
• /
• pp.57-62
• /
• 2008

Twelve mortars were mixed and tested to explore the effect of gypsum on the compressive strength development and shrinkage strain of alkali-activated mortars. Powder typed sodium silicate and ground granulated blast-furnace slag were employed as alkaline activator and source material, respectively, to produce cementless mortar. The main variables investigated were alkali quality coefficient combining the concentration of activator and main compositions in source material, and the adding amount of gypsum ranged between 1 and 5% with respect to the weight of binder. Initial flow, compressive strength development, modulus of rupture, and shrinkage strain behavior of mortar specimens were measured. In addition, the hydration production of alkali-activated pastes with gypsum was traced using X-ray diffraction and energy-dispersive X-ray analysis combined with scanning electron microscope image. Test results showed that the initial flow of slag-based alkali-activated mortar was little influenced by the adding amount of gypsum. On the other hand, the effect of gypsum on the compressive strength of mortar specimens was dependent on the alkali quality coefficient, indicating that the compressive strength increased with the increase of the adding amount of gypsum until a certain limit, beyond which the strength decreased slowly. Shrinkage strain of mortar tested was little influenced by the adding amount of gypsum because no ettringite as hydration product was generated. However, the adding of gypsum had a beneficial effect on reducing the microcrack in the alkali-activated mortar.

• Journal of the Korean Society of Safety
• /
• v.30 no.4
• /
• pp.120-127
• /
• 2015

The aim of the present study is to investigate some characteristics of concrete according to addition of blast furnace slag and alkali-activator dosages. Blast furnace slag was used at 30%, 50% replacement by weight of cement, and liquid sulfur having NaOH additives was chosen as the alkaline activator. In order to evaluate characteristics of blast furnace slag concrete with sulfur alkali activators, compressive strength test, total porosity, chloride ions diffusion coefficient test were performed. The early-compressive strength characteristics of blast furnace slag concrete using a sulufr-alkali activators was compared with those of reference concrete and added 30, 50% blast furnace slag concrete. Also, Blast furnace slag concrete using sulfur-alkali activators enhanced the total porosity, chloride ions diffusion coefficient than two standard concrete. Alkali-activated blast furnace slag concrete was related to total porosity, compressive strength and chloride ions diffusion coefficient each others. As a result, it should be noted that the sulfur-alkali activators can not only solve the demerit of blast furnace slag concrete but also offer the chloride resistance of blast furnace slag concrete using sulfur alkali activators to normal concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.2
• /
• pp.170-178
• /
• 2015

In this study, it was developed eco-friendly alkali-activated slag fiber reinforced concrete using ground granulated blast furnace slag, alkali activator (water glass, sodium hydroxides), and steel fiber. Eight reinforced concrete beam using alkali-activated slag concrete were constructed and tested under monotonic loading. The major variables were mixture ratio of alkali activator, mixed/without of steel fiber. Experimental programs were carried out to improve and evaluate the flexural performance of such test specimens, such as the load-displacement, the failure mode, the maximum load carrying capacity, and ductility capacity. All the specimens were modeled in scale-down size. The reinforced concrete beams using the eco-friendly alkali-activated slag fiber reinforced concrete was failed by the flexure or flexure-shear in general. In addition, the maximum strength increased with the adding the mol of sodium hydroxide, and the specimen reinforced the steel fiber showed the value of maximum strength which is increased by 15.8% through 25.9%. It is thought that eco-friendly alkali-activated slag fiber reinforced concrete can be used with construction material and product to replace normal concrete. If there is applied to structures such as precast concrete member and production of 2nd concrete product, it could be improved the productivity and reduction of construction duration etc.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2018.05a
• /
• pp.134-135
• /
• 2018

In this paper, we investigate the characteristic of ASRC concrete with the addition of liquefaction red mud using red ud which can be used as an alkali activator of alkali-activated slag cement. as a result, the compressive strength and the efflorescence area increased, and as the amount of liquid red mud increased, the compressive strength decreased and the efflorescence area increased.