알카리활성 무시멘트 경량모르타르의 유동성, 압축강도 및 내화특성

양근혁(Yang Keun-Hyeok),심재일(Sim Jea-Il),이설(Lee Seol),황혜주(Hwang Hey-Zoo) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.8

Sixteen cementless mortars using alkali-activated (AA) hwangtoh (HT) binder or AA ground granulated blast-furnace slag (GGBS) binder were mixed and tested. The main variables investigated were water-binder ratio, lightweight fine aggregate-to-binder ratio, and maximum size of lightweight aggregate. Initial flow and air content were measured in the fresh mortars, and compressive strength development was recoreded in the hardened mortars. In addition, fire resistance of the AA lightweight mortars was evaluated against the variation of water-binder ratio. Test results showed that the workability of AA GGBS lightweight mortars was commonly lower than that of AA HT lightweight mortars. On the other hand, compressive strength of AA GGBS lightweight mortars was greatly higher than that of the company AA HT lightweight mortars. The compressive strength of AA mortars tested increased with the increase of their oven-dry density, showing that higher increasing rate was developed in AA GGBS lightweight mortars than in AA HT lightweight mortars. In addition, higher residual compressive strength ratio under high temperature was observed in AA GGBS lightweight mortars than in the company AA HT lightweight mortars. In particular, the thermal conductivity of AA lightweight mortars was highly lower than that of oridinary portland cement pastes with the same oven-dry density. This indicates that AA GGBS lightweight mortar has the advantage over the fire resistance.

콘크리트 도로시설물 적용을 위한 유무기계 하이브리드 모르타르 보수재의 성능평가

황재남,이승태,박광필,하상욱 한국도로학회 2018 한국도로학회논문집 Vol.20 No.6

PURPOSES : The objective of this study is to evaluate the performance of combined organic and inorganic hybrid mortar used as repair materials (UM mortar) for concrete road facilities by comparison with cement repair materials (RM mortar). METHODS: In order to produce UM mortar, four different levels of inorganic materials were adopted and the ratio of main resin to hardener was fixed at 1:2. For comparison, RM mortar made with cement repair materials was also produced. Fluidity, strength characteristics, length change, and freezing-thawing resistance of the mortars were measured at the predetermined periods. In addition, the microstructures of the mortars was performed on the 28-day mortar samples to examine the properties of the interfacial transition zone (ITZ). RESULTS : It was observed that the mechanical properties, except for compressive strength, and freezing-thawing resistance of UM mortars were much better than those of RM mortar. Furthermore, showing a densified ITZ properties on the UM mortars from the microstructural observation, the usage of UM mortars exhibited a beneficial effect on the enhancement of mortar properties. CONCLUSIONS: It is concluded that the application of combined organic and inorganic hybrid mortars is a possible option for the repair of deteriorated concrete road facilities.

Effect of Viscoelastic Deformation for CA Mortar on Mechanical Responses of Track Structures

Juanjuan Ren,Wei Du,Shijie Deng,Yuanjie Xiao,Haolan Li,Genyuan Tian 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.7

The viscoelastic deformation of cement emulsified asphalt mortar (CA mortar) can lead to gaps between the mortar and track slab, thereby adversely affecting the mechanical capability and deformation behavior of the track structures. According to the time hardening rate method, a solid model of the China Railway Track System I (CRTS-I) slab track was established to study the viscoelastic characteristics of mortar. What's more, this paper also analyzed the influence of viscoelastic deformation of mortar on the mechanical responses of track structures. The results obtained indicate that the viscoelastic deformation of CA mortar under train loading occurs mainly in the area from the track slab end to the third fastener, which is about 1.5 m long. Its viscoelastic deformation can reach nearly 0.6 mm. The maximum mortar stresses under passenger train and freight train loads with considering the viscoelastic deformation of mortar 0.6 mm, are 0.382 MPa and 0.566 MPa, respectively, which are both 2 to 3 times greater than those under normal conditions (without CA mortar failure, namely none vertical deformation of mortar). Besides, the vertical accelerations of rail and track slab are also significantly larger than those under normal conditions when the viscoelastic deformation of CA mortar is taken into account. And these values under the freight train load are greater than those under the passenger train load. Therefore, we suggest that future research should take the adverse impact of viscoelastic deformation of CA mortar into account when studying the mechanical responses of track structures. Furthermore, for the shared passenger and freight railway lines, the passage of freight trains should be strictly controlled.

Experimental Study on Internal and External Salt Attack from Seawater and Sea-Sand to Mortars

Jikai Zhou,Xu He 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.8

Seawater and sea-sand are potential material for concrete in marine environment. This paper aimed to study the influence of internal and external salt attack from seawater and sea-sand on the performance of mortars. Six groups of mortars with different salt attack types were designed. The length, mass, dynamic elastic modulus and pH value of all mortars were measured in the test. The hydrate phase was obtained by thermodynamic simulation, and the phase after 322 days attacked was detected by X-ray diffraction (XRD). Internal seawater and sea-sand attack could improve the early length change of mortars before 28 days. And the early mass growth rate of mortars of seawater mixed mortars was slow. While the influence of seawater and sea-sand on the early dynamic elasticity modulus was limited. The external environment was the main factor affecting the length, mass and dynamic elasticity modulus of mortars after 28 days. Differences of hydrate phases in different mortars were ettringite (AFT), monosulfate, hemicarbonate, monocarbonate, Friedel's salt and Kuzel's salt. The more salt in mixing materials, the larger the volume of hydration solid phase. The salt attack from seawater and sea-sand could increase pH of the simulated solution in mortars. Ettringite and brucite could be clearly observed by XRD in mortars attacked by external seawater, and gypsum and Friedel's salt could be observed in all mortars. It was more reasonable to use mass to evaluate the deterioration degree of the mortars attacked by seawater or sea-sand.

Resistance of coal bottom ash mortar against the coupled deterioration of carbonation and chloride penetration

Jang, J.G.,Kim, H.J.,Kim, H.K.,Lee, H.K. Elsevier Ltd 2016 Materials & Design Vol.93 No.-

<P>This paper investigated the resistance of bottom ash mortar against the coupled deterioration of carbonation and chloride penetration. To evaluate the resistance of the mortar, a comparative study was conducted with variables of ordinary mortar, lightweight mortar using expanded shale, fly ash cement mortar, and slag cement mortar. Test results showed that a combination of carbonation and chloride penetration accelerated the rate of chloride penetration into the mortar regardless of the mortar type. The replacement of sand with bottom ash moderated the penetration depth of chloride under coupled-deterioration environments, while the overall penetrated-chloride contents showed no significant differences. It can be concluded in a coupled-deterioration environment that the chloride resistance of the bottom ash mortar was greater than that of both ordinary mortar and lightweight mortar. The type of cement paste on the surface of a carbonated mortar had a governing impact on the chloride penetration. (C) 2015 Elsevier Ltd. All rights reserved.</P>

콘크리트 도로시설물용 보수재료로서 유무기계 하이브리드 모르타르의 내화학성 평가

이승태 한국도로학회 2020 한국도로학회논문집 Vol.22 No.1

PURPOSES: This study aims to evaluate the resistance to chemical attack of combined organic and inorganic hybrid mortars as the repair materials (i.e., HRM mortar) used for concrete road facilities through a comparison with mortars made from cement repair materials (i.e., IRM mortar). METHODS: Inorganic materials used as a binder and two mineral fillers were adopted to produce HRM mortars. The ratio of the main resin versus the hardener was fixed at 2:1. For comparison, IRM mortars made of cement repair materials were also manufactured. The mortars were exposed to chemical solutions, such as NaCl, MgSO4, Na2SO4, and H2SO4, with the same concentration of 5% after 7 days of curing. The compressive strength, compressive strength loss, mass ratio, and relative bulk density of the mortar samples exposed to the chemical solutions were measured at predetermined periods. In addition, a scanning electron microscope observation was performed to evaluate the microstructures and the products formed by the chemical reaction of the mortar samples. RESULTS : As a result, the resistance to chemical attack of the HRM mortars was found to be much better than that of the IRM mortars, regardless of the types of attacking sources. This finding implies that HRM is a highly promising and versatile material because of its excellent resistance to chemical attack. CONCLUSIONS: The application of the combined organic and inorganic hybrid mortars is a possible option for repair of concrete road facilities exposed to aggressive environments.

The strength properties of alkali-activated silica fume mortars

Mustafa Sarıdemir,Serhat Çelikten 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.2

In this study, the strength properties of alkali-activated silica fume (SF) mortars were investigated. The crushed limestone sand with maximum size of 0-5 mm and the sodium meta silicate (Na2SiO3) used to activate the binders were kept constant in the mortar mixtures. The mortar specimens using the replacement ratios of 0, 25, 50, 75 and 100% SF by weight of cement together with Na2SiO3 at a constant rate were produced in addition to the control mortar produced by only cement. Moreover, the mortar specimens using the replacement ratio of 4% titanium dioxide (TiO2) by weight of cement in the same mixture proportions were produced. The prismatic specimens produced from eleven different mixtures were de-moulded after a day, and the wet or dry cure was applied on the produced specimens at laboratory condition until the specimens were used for flexural strength (ffs) and compressive strength (fc) measurement at the ages of 7, 28 and 56 days. The ffs and fc values of mortars applied the wet or dry cure were compared with the results of control mortar. The findings revealed that the fc results of the alkali activated 50% SF mortars were higher than that of mortar produced with Portland cement only. It was found that the ffs and fc of alkali-activated SF mortars cured in dry condition was averagely 4% lower than that of alkali-activated SF mortars cured in wet condition.

무기안료가 시멘트모르타르의 압축강도와 흡수율에 미치는 영향

송혁,이재용,고성석 한국안전학회 2004 한국안전학회지 Vol.19 No.2

The aim of this study was to investigate the influence of inorganic pigments on the physical properties of cement mortar. For this purpose, the compressive stieugth and absorption test were carried out on cement mortar mixed with inorganic pigments by changing the proportion of cement mortar, water-cement ratio, and ratio of pigment. The result of this study can be summarized as follows: The compressive strength of colored mortar rapidly increased in red and yellow mortar, as the mix ratio of pigment increased. In case of green and black mortar, however, the compressive strength decreased as the mix ratio increased. In case of red and yellow mortar, the absorption of colored mortar increased as the mixing ratio increased, if the mean particle diameter of the pigment is small. In case of green and black mortar, the absorption ratio decreased as the mix ratio increased. After investigating the overall physical properties of colored mortar, it was confirmed that the proper mix ratio of pigment securing the properties of colored mortar was below 6% of the weight of the cement to be used.

Influence of the Quality of Recycled Aggregates on Microstructures and Strength Development of Concrete

Moon Dae-Joong,Moon Han-Young,Kim Yang-Bae Korea Concrete Institute 2004 콘크리트학회논문집 Vol.16 No.6

The quality of recycled aggregate is affected by original concrete strength and the manufacturing process of recycled aggregates. In this study, the porosity of old and new mortar, and the compressive strength of concrete were investigated to examine the influence of recycled aggregate on the concrete. Six kinds of recycled coarse aggregates were produced from concrete blocks of differing strength levels (A:60. 1MPa, B:41.7MPa, C:25.5MPa). Original concrete strength and the bond mortar of recycled aggregate influences the pore structures of both old and new mortar. The pore size distribution of old mortar was found to be greatly affected by age, and the reduction of the porosity of bond mortar on low strength recycled aggregate increased at a greater rate than that of bond mortar on high strength recycled aggregate. The pore size distribution of new mortar in recycled aggregate concrete changed in comparison with that of new mortar in virgin aggregate concrete. The total porosity of new mortar using B level recycled aggregates was smaller than that of new mortar with A, and C level recycled aggregates. Moreover, the compressive strength of recycled aggregate concrete was found to have been affected by original concrete strength. The compressive strength of concrete only changed slightly in the porosity of new mortar over $15\%$, but increased rapidly in the porosity of new mortar fewer than $15\%$.

Influence of the Quality of Recycled Aggregates on Microstructures and Strength Development of Concrete

문대중,문한영,김양배 한국콘크리트학회 2004 콘크리트학회논문집 Vol.16 No.6

The quality of recycled aggregate is affected by original concrete strength and the manufacturing process of recycled aggregates. In this study, the porosity of old and new mortar, and the compressive strength of concrete were investigated to examine the influence of recycled aggregate on the concrete. Six kinds of recycled coarse aggregates were produced from concrete blocks of differing strength levels (A:60.1MPa, B:41.7MPa, C:25.5MPa).Original concrete strength and the bond mortar of recycled aggregate influences the pore structures of both old and new mortar. The pore size distribution of old mortar was found to be greatly affected by age, and the reduction of the porosity of bond mortar on low strength recycled aggregate increased at a greater rate than that of bond mortar on high strength recycled aggregate. The pore size distribution of new mortar in recycled aggregate concrete changed in comparison with that of new mortar in virgin aggregate concrete. The total porosity of new mortar using B level recycled aggregates was smaller than that of new mortar with A, and C level recycled aggregates. Moreover, the compressive strength of recycled aggregate concrete was found to have been affected by original concrete strength. The compressive strength of concrete only changed slightly in the porosity of new mortar over 15%, but increased rapidly in the porosity of new mortar fewer than 15%.