• Journal of the Korea Concrete Institute
• /
• v.24 no.2
• /
• pp.121-127
• /
• 2012

Cement has been traditionally used as a main binding material of high ductile fiber reinforced cementitious composites. The purpose of this paper is to investigate the feasibility of using alkali-activated slag and polyvinyl alcohol (PVA) fibers for manufacturing high ductile fiber reinforced cementless composites. Two mixture proportions with proper flowability and mortar viscosity for easy fiber mixing and uniform fiber dispersion were selected based on alkali activators. Then, the slump flow, compression, uniaxial tension and bending tests were performed on the mixes to evaluate the basic properties of the composites. The cementless composites showed an average slump flow of 465 mm and tensile strain capacity of approximately 2% of due to formation of multiple micro-cracks. Test results demonstrated a feasibility of manufacturing high ductile fiber reinforced composites without using cement.

• Journal of the Korea Concrete Institute
• /
• v.24 no.2
• /
• pp.137-145
• /
• 2012

Strength model for blasted furnace slag mortar blended with sodium was investigated in this study. The main parameters of AAS (alkali activated slag) mortar were dosage of alkali activator, water to binder ratio (W/B), and aggregate to binder ratio (A/B). For evaluating the property related to the dosage of alkali activator, sodium carbonate ($Na_2CO_3$) of 4~8% was added to 4% dosage of sodium hydroxide (NaOH). W/B and A/B was varied 0.45~0.60 and 2.05~2.85, respectively. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide ($Na_2O$) in sodium hydroxide and sodium carbonate is proposed to assess the compressive strength of alkali activated mortars. Test results clearly showed that the compressive strength development of alkali-activated mortars were significantly dependent on the proposed alkali quality coefficient. Compressive strength development of AAS mortars were also estimated using the formula specified in the previous study, which was calibrated using the collected database. Predictions from the simplified equations showed good agreements with the test results.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.2
• /
• pp.190-197
• /
• 2020

This paper evaluates the mechanical properties and durability of cement matrix blended with mineral admixtures and ferronickel slag(FNS) powder which is an industrial b y-product during ferronickel smelting process. The hydration heat, pore structure, compressive strength, length change, rapid chloride penetration test(RCPT), and freezing and thawing resistance of ternary blended cement matrix were investigated and compared with ordinary portland cement matrix. The result showed that the compressive strength of ternary blended cement matrix using ferronickel slag powder and mineral mixture was low in strength compared to the reference concrete, but recovered to a certain extent by using alkali activator. Length change of cement mortar using FNS powder have shown less shrinkage occurs than the reference specimen. In addition, irrespective of using the alkali-activators, all ternary mix are indicative of the 'very low' range for chloride ion penetrability according to the ASTM C 1202, and the freeze-thaw resistance also showed excellent results.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.1
• /
• pp.1-7
• /
• 2019

Recently, studies on alkali activated slag(AAS) binders that do not use cement have been actively conducted. It is known that AAS concrete is highly resistant to chloride damage based on the test method used for ordinary concrete. However, it is fully not understood whether the test method used for concrete can be applied to AAS mixtures. Therefore, in this study, we verified the consistency of NT Build 492 and ASTM C 1202 test methods by applying various experimental variables. According to the experimental results, the two tests yielded opposite results. Therefore, the chloride durability of AAS mortar can be different depending on the evaluation method.

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

• Journal of the Korea Institute of Building Construction
• /
• v.15 no.2
• /
• pp.161-167
• /
• 2015

Nowadays, all the world face to the global warming problems due to the emission of $CO_2$. From the previous studies, recycled aggregates were used as an alkali activator in blast furnace slag to achieve zero-cement concrete, and favorable results of obtaining strength were achieved. In this study, gypsum and incineration waste ash were used as the additional alkali activation and effects of the gypsum and incineration waste ash to enhance the performance of the mortar were tested. Results showed that although the replacement ratio of 0.5% of incineration waste ash and 20% of anhydrous gypsum resulted in the low of mortar at the early age, while it improved the later strength and achieved the similar strength to that of conventional mortar (at 91 days).

• Journal of the Korea Concrete Institute
• /
• v.26 no.2
• /
• pp.117-124
• /
• 2014

Globally, there are environmental problems due to greenhouse gas emissions. $CO_2$ emissions rate of the cement industry is very high, but the continued demand of cement is needed in the future. In this study, in order to reduce the environmental impact of $CO_2$ emissions from cement production. The experiments were carried out for the development of non-sintered cement (have not undergone firing burning) by granulated ground blast furnace slag. In order to compare the characteristics by curing, an experiment was conducted by changing the curing conditions such as atmospheric steam curing, observe the mechanical properties for the measurement of flexural compressive strength by mortar, observe the chemical properties such as acid resistance, $Cl^-$ penetrate resistance and analyzed the mechanism of hydration by XRD, SEM experiments. From the experimental results, as compared with portland cement usually confirm the mechanical and chemical properties excellent, it is expected be possible to apply to the undersea, underwater and underground structures that require superior durability. In addition, based on the excellent compressive strength by steam curing, it is expected to be possible to utilize as a cement replacement material in the secondary product of concrete. In the future, to solve the problem through continued research, it will be expected to reduce the effect of environmental load and to be excellent economics.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.363-364
• /
• 2010

Recently, various researchers have studied alkali-activated concrete that do cementless as the binder. This study analyzed the effect on cementless mortar by flay ash and blast furnace slag of blast slag as the binder with no use of cement, by observing compressive strength and micro-structure.

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

• Journal of the Korea Concrete Institute
• /
• v.24 no.3
• /
• pp.315-322
• /
• 2012

Alkali-activated slag (AAS) is the most obvious alternative materials that can replace OPC. But, AAS industrial usage as a structural material should be evaluated for its durability. Carbonation resistance is one of the most important factors in durability evaluation. Test results for 18 slag-based mortars activated by sodium silicate and 6 OPC mortars were obtained in this study to verify the carbonation property. Main variables considered in the study were flow, compressive strength before and after carbonation, and carbonation depth. Mineralogical and micro-structural analysis of OPC and AAS specimens prior to and after carbonation was conducted using XRD, TGA, FTIR FE-SEM. Test results showed that CHS was major hydration products of AAS and, unlike OPC, no other hydration products were found. After carbonation, CSH of hydration product in AAS turned into an amorphous silica gel, and alumina compounds was not detected. From the analysis of the results, it was estimated that the micro-structures of CSH in AAS easily collapsed during carbonation. Also, the results showed that this collapse of chemical chain of CSH lowered the compressive strength of concrete after carbonation. By increasing the dosage of activators, carbonation resistance and compressive strength were effectively improved.