• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.161-168
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• 2012

The purpose of this study was to investigate the influence of recycled aggregates powder (RP) contents on recycled aggregates (RA) using fly-ash (FA) mortar in a condition of zero cement targeting earth filling materials, and the results can be summarized as follows. First, there was a tendency that as RP contents increased, W/B and air contents increased also. In the case of compressive strength, the strength was hardly developed at the early age, which was prior to 14 days; however, with the starting point of 14 days of age, strength of around 1.5~2.0 MPa was developed when it arrived at 28 days. At a curing temperature of $20^{\circ}C$, the more RP contents increased, the more the compressive strength increased in comparison with FA 100% at all levels except RP 100 %, showing the highest compressive strength at RP 25 %. At a curing temperature of $35^{\circ}C$, the temperature-dependence appeared to be large, as the RP contents were decreased compared to the curing temperature of $20^{\circ}C$. In addition, based on SEM analysis, this study was able to confirm that a pozzolanic reaction formed by an alkali stimulus of RA with the lapse of certain days even in 100 percent FA, causing the densification of tissues, and with RP 25%, hydrate was created the most densely by the hydration of unhydrated cement particles and pozzolanic reaction of FA.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.452-458
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• 2011

Bamboo is representing environmentally friendly building finishing materials as proven in the former researches. The purpose of this study is to evaluate the application properties of cementitious materials modified with bamboo charcoal as building finish materials. Flow test in fresh condition was conducted to assess the workability. Compressive and bending strength were measured after harding. As the thermal properties, thermal conductivity and density were measured. The properties were surpassing over them in case of using the pine charcoal in every tests. The thermal conductivity of them increased with the modified ratio. After the modified ratio 50%, the thermal conductivity decreased. Insolation and absorption performance is due to the lower density by modification of bamboo charcoal.

• Journal of the Korean Geosynthetics Society
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• v.14 no.2
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• pp.1-9
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• 2015

In this study, the objective of the study is to evaluate the effect of calcium carbonate powder, produced by the microbial reactions, on the strength of soft ground (sand). To analyze the cementation effects of calcium carbonate powder produced by microbial reactions on the strength of the sand, six different types of specimens (untreated, calcium carbonate, cement, carbonate+cement (1:9, 3:7, 5:5)) were made. The specimen were tested after curing (7 and 28 days). Uniaxial compressive strengths were measured on $D5cm{\times}H10cm$ specimens. Based on the test results, as both the weight ratio and the curing period increase, calcium carbonate, cement, and calcium carbonate+cement specimens showed an increase in the strength. In addition, compared with the strength of the specimen with cement, the strengths of the specimens with mixing ratios of 1:9, 3:7, and 5:5 (carbonate : cement) were found to be 93.5~95.8%, 825.%, 65.2~70.6%.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.85-92
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• 2021

The purpose of this study is to investigate the properties of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS) and alkali activators. The hardener-free EMMs with a GGBFS content of 20% using 4 types of alkali activators were prepared with various polymer-binder ratios, and tested for strengths, water absorption, carbonation depth, chloride ion and H2SO4 penetration depth. The conclusions obtained from the test results are summarized as follows: The compressive strength of the EMMs with a GGBFS content of 20% attains a maximum at a polymer-binder ratio of 10%. The flexural strength of the hardener-free EMMs using Ca(OH)2 as a alkali activator is improved with increasing polymer-binder ratios. However, the flexural strength of the EMMs using NaCO3, Na2SO4 and Li2CO3 is gradually decreased with increasing polymer-binder ratios. Regardless of the type of alkali activator, the water absorption, chloride ion penetration and carbonation depth are remarkably decreased with increasing polymer-binder ratios due to the epoxy film formed in the EMMs. The H2SO4 penetration depth of the hardener-free EMMs with a GGBFS content of 20% is gradually increased with increasing polymer-binder ratio. In this study, the properties of hardener-free EMMs using Ca(OH)2 as a alkali activator are more excellent than those of other alkali activators.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.242-243
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• 2014

In this study, industrial by-products including blast furnace slag, incineration ash and waste gypsum were used with recycled fine aggregates to manufacture the zero-cement mortar. The replacement ratio of anhydrite gypsum was fixed as 0, 10%, 20% the replacement ratio fo WA1 was fixed as 0.5% and 1.0%, respectively. It could be identified that when the replacement of gypsum was 20% and WA1 of 1.0%, the strength could be in the range of normal strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4C
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• pp.213-220
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• 2008

A study on cemented sand reinforced with short fibers was carried out to improve its unconfined compressive strength and brittle behavior. Nak-dong River sand was mixed with Portland cement and polyvinyl alcohol (PVA) fibers. A PVA fiber widely used for concrete reinforcement is randomly distributed into cemented sand. Nak-dong River sand, cement and fibers with optimum water content were compacted in 5 layers and then cured for 7 days. The effect of fiber reinforcement rather than cementation was emphasized by using a small amount of cement. Weakly cemented sand with a cement/sand ratio less than 8% was fiber-reinforced with different fiber ratios and tested for unconfined compression tests. The effect of fiber ratio and cement ratio on unconfined compressive strength was investigated. Fiber-reinforced cemented sand with 2% cement ratio showed up to six times strength to non-reinforced cemented sand. Because of ductile behavior of fiber-reinforced specimens, an axial strain at peak stress of specimens with 2% cement ratio increases up to 7% as a fiber ratio increases. The effect of 1% fiber addition into 2% cemented sand on friction angle and cohesion was analyzed separately. When the fiber reinforcement is related to friction angle increase, the 8% of applied stress transferred to 1% fibers within specimens.

• Clean Technology
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• v.19 no.4
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• pp.423-429
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• 2013

This study aimed to develop flowable backfill material using oyster shell, coal ash, and surplus soil. The high temperature (> $800^{\circ}C$) reaction was required to convert $CaCO_3$ to CaO. The solid specimens formed by pozzlanic reaction between CaO and coal ash showed low unconfined compressive strength. The effect of kaolin and blast furnace slag was also examined. It was found that CaO and coal ash could not be utilized due to high cost and low performance. The use of oyster shell without calcination ($CaCO_3$) was evaluated. The specimens composing of oyster shell and cement showed the higher unconfined compressive strength than that composing of coal ash and cement. However, use of oyster shell is limited in mortar due to the presence of salt. Addition of soil into oyster shell-coal ash-cement mixture satisfied the specification of flowable backfill material by optimizing their ratio.

• Journal of Korean Society of Environmental Engineers
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• v.37 no.3
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• pp.159-164
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• 2015

This study investigated the environmental risk for up-cycling of air-cooled ladle furnace slag (LFS) and evaluated the mortar compressive strength of binary and ternary blended cements using LFS of 3, 5, 10 wt%. Based on the Soil Environment Conservation Act standard, there was no environmental risk of the up-cycling of LFS. Results of mortar compressive strength assesment showed that the compressive strength of two blended cements using LFS of lower than 5 wt% was about 1.1 times superior to that of un-substituted cement (ordinary portland cement, OPC); however the compressive strength of those with LFS of 10 wt% decreased with 10% compared with that of OPC.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.17-23
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• 2015

In this research, the $CO_2$ absorption performance of mortar was investigated. The level of $CO_2$ absorption in mortar with various binders including cement and nonsintered cement was examined. As a result for the mortar with photosynthetic bacteria, the compressive strength was similar to the one without the bacteria at early age but decreased at the age of 28 days. However, for the $CO_2$ absorption, with photosynthetic, the performance of the mortar with OPC, and nonsintered cement deceased to 21%(234 ppm) and 19.7%(243 ppm) respectively after 12 hours age.

• Resources Recycling
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• v.20 no.3
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• pp.40-47
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• 2011

In this study, we investigated the strength, shrinkage and durability of alkali-activated mortar using blast furnace slag only, and admixed with blast-furnace slag and fly ash as cementious materials in oder to develop cementless alkali-activated concrete. In order to compare with the alkali-activated mortar, the normal mortar using ordinary portland cement was also test. In view of the results, we found out that strength development, the resistance to shrinkage and freezing-thawing of the cementless alkali-activated mortar have better than the mortar using ordinary portland cement. Especially, using the combined with blast furnace slag and fly ash develop high strength of above 60 MPa, reduce shrinkage of about 40% and improve freezing-thawing durability of approximately 20%, but promote the velocity of carbonation of 2~3 times.