혼화재 종류 및 양생조건에 따른 속경성 SBR 시멘트 모르타르의 강도

조영국,정선호,장덕배 한국건축시공학회 2011 한국건축시공학회지 Vol.11 No.6

Ultra rapid-hardening cement is widely used for latex-modified mortar and concrete as repair and finishing material during urgent work. The purpose of this study is to evaluate the improvements in strength made to SBR cement mortars by the adding of various admixtures and by the use of different curing methods. SBR cement mortar was prepared with various polymer-cement ratios, curing conditions and admixture contents, and tested for flow, flexural and compressive strengths. From the test results, it was determined that the flow of SBR cement mortar increased with an increase in the polymer-cement ratio, and the water reducing ratio also increased. The strength of cement mortar is improved by using SBR emulsion, and is strengthened by adding metakaoline. The strength of SBR cement mortar cured in standard conditions was increased with an increase in the polymer-cement ratio, and attained the maximum strengths at polymer-cement ratios of 15 % and 10 %, respectively. The maximum strengths of SBR cement mortar are about 1.8 and 1.3 times the strengths of plain mortar, respectively. In this study, it is confirmed that the polymer-cement ratio and curing method are important factors for improving the strengths of rapid-hardening SBR cement mortar. 폴리머 시멘트 모르타르를 긴급공사의 보수․보강 재료로사용할 때, 초속경시멘트와 혼입하여 사용함으로써 시멘트의 빠른 응결과 시멘트 매트릭스 내부에서 형성된 폴리머필름의 작용이 물리적 성질과 내구성을 개선시킬 수 있다. 또한 각종 혼화재료를 혼입함으로써 매트릭스 내부 공극을충전하여 성질을 개선시킬 수 있는데, 양생방법이 큰 영향을 미칠 수 있다. 본 연구에서는 속경성 SBR 시멘트 모르타르의 압축강도와 휨강도에 영향을 미칠 수 있는 혼화재료와양생조건에 관하여 실험을 실시하여 그 영향성을 평가하고자 하였다. 본 연구결과, 초속경시멘트 모르타르에 SBR을혼입함으로써 휨강도와 압축강도가 크게 개선되었으며, 여기에 메타카올린을 혼입함으로써 보다 더 강도를 증진시킬수 있었다. 또한 양생방법에 있어서도 SBR을 사용한 경우에는 표준양생에서, SBR을 사용하지 않은 경우에는 수중양생에서 강도발현이 크게 나타났다.

Mechanical Properties of Cement Mortar

Tewodros Tekeste Ghebrab,Parviz Soroushian 한국콘크리트학회 2011 International Journal of Concrete Structures and M Vol.5 No.1

Theoretical models for prediction of the mechanical properties of cement mortar are developed based on the morphology and interactions of cement hydration products, capillary pores and microcracks. The models account for intermolecular interactions involving the nano-scale calcium silicate hydrate (C-S-H) constituents of hydration products, and consider the effects of capillary pores as well as the microcracks within the hydrated cement paste and at the interfacial transition zone (ITZ). Cement mortar was modeled as a three-phase material composed of hydrated cement paste, fine aggregates and ITZ. The Hashin’s bound model was used to predict the elastic modulus of mortar as a three-phase composite. Theoretical evaluation of fracture toughness indicated that the frictional pullout of fine aggregates makes major contribution to the fracture energy of cement mortar. Linear fracture mechanics principles were used to model the tensile strength of mortar. The predictions of theoretical models compared reasonably with empirical values.

Evaluation of Basic Properties of Cement Asphalt Mortar Depending on Sand Gradation and Cement Fineness

강일환,박태순 한국철도학회 2020 한국철도학회논문집 Vol.23 No.8

This study was conducted to investigate the effects of the sand gradation and cement fineness on cement asphalt mortar (CA mortar) for application to CA mortar in Korea. The CA mortar was prepared using three combined gradations of sand (CG1, CG2, and CG3) and three types of cement (C1, C2, and C3). The following basic properties of the CA mortar were analyzed: temperature of the mortar, flow value, air content, separation ratio, compressive strength, and expansion ratio. The test results showed that the separation ratio of the CA mortar increased and the flowability and compressive strength of the CA mortar decreased when the maximum sand size and gradation increased. The compressive strength of the CA mortar prepared with early hardening cement was higher than that of the CA mortar prepared with normal Portland cement. The temperature and expansion ratio of the CA mortar showed no significant relationship with the sand gradation or cement type.

Development of water-repellent cement mortar using silane enriched with nanomaterials

Karthick, Subbiah,Park, Dong-Jin,Lee, Yun Su,Saraswathy, Velu,Lee, Han-Seung,Jang, Hyun-O,Choi, Hyun-Jun Elsevier 2018 Progress in organic coatings Vol.125 No.-

<P><B>Abstract</B></P> <P>The exposure of reinforced concrete structures to freezing temperatures during winters can create internal stresses and surface microcracks in concrete owing to tiny ice crystal formations in the pores of concrete structures. Thus, in the present study, superhydrophobic surfaces were created on concrete by spraying and admixing superhydrophobic materials, comprising 1H,1H,1H,2H-perfluorodecyltriethoxysilane (PFDTS) with nano TiO<SUB>2</SUB> and SiO<SUB>2</SUB> inclusions, with cement mortar. TiO<SUB>2</SUB> nanomaterials were synthesized using ginger (<I>Zingiber officinale</I>) as a bio-template. The PFDTS enriched with nanomaterials (PFDTS-NM) was admixed with cement mortar during casting and was spray-coated on the cement mortar surface after casting. The spray-coated and admixed cement mortar sample surfaces were characterized by XRD, SEM/EDAX, and UV–vis spectroscopy, and their water-repellent properties were evaluated by measuring the contact angles (CA) and conducting water absorption and freeze-thawing tests. The pore size distributions of the samples before and after freeze-thawing were evaluated by mercury intrusion porosimetry (MIP). The results confirm the presence of PFDTS with inclusions of rod-shaped TiO<SUB>2</SUB> nanoparticles on the concrete surface. Further, the CAs of normal, coated, and admixed cement mortar surfaces were found to be 45.5°, 162.3°, and 162.0°, respectively. The spray-coated and admixed concrete can be used to form superhydrophobic surfaces on concrete structures to reduce water absorption and increase the durability of cement mortar.</P> <P><B>Highlights</B></P> <P> <UL> <LI> TiO<SUB>2</SUB> was successfully synthesized by bio-template synthesis method. </LI> <LI> PFDTS-enriched with nanomaterials (TiO<SUB>2</SUB> and SiO<SUB>2</SUB>) was developed as a superhydrophobic surface on cement mortar. </LI> <LI> PFDTS-enriched-nanomaterial exhibit superhydrophobic surface with UV-shielding ability. </LI> <LI> The water-contact angles of coated and admixed cement mortar were 162.3° and 162.0° respectively. </LI> <LI> The PFDTS-enriched-nanomaterial has better freeze-thawing barrier performance than normal cement mortar. </LI> </UL> </P>

타일 떠붙임 시멘트 모르타르의 배합비 변화에 따른 품질 특성 및 시공성에 대한 관능 평가

황인성 ( Hwang Yin-seong ),기태경 ( Ki Tae-kyoung ),한동엽 ( Han Dong-yeop ),노상균 ( Noh Sang-kyun ) 한국건축시공학회 2021 한국건축시공학회지 Vol.21 No.1

The aim of the research is providing a fundamental data on quality and constructability of direct tile setting method depending on various cement to sand ratio for tiling dry cement mortar. A large number of tile setting failures reported is related with the cement mortar and its construction for tiling. Because of different materials of tiles, the properties of tiling dry cement mortar, an adhesive for tiling, can influence on quality and constructability of tiling differently. Practically, the easiest way of controlling the properties of the tiling dry cement mortar is to control the proportion of cement and sand. Hence, in this research, sand to cement ratio (S/C) was controlled. Since there is no standarized method on evaluating performance of dry cement mortar for tiling, a several sensory evaluation methods were suggested and executed. According to the experiments conducted in this research, the adhesive performance of cement mortar for tiles can be different depending on the sides such as tile and substrate. Additionally, depending on S/C, finishability, initial adhesive performance, and tile shifting resistance can be changed for ceramic tile. Therefore, under the conditions of this research, about 5 of S/C can be recommended for appropriate performace of tiling dry cement mortar.

Hybrid-ANFIS approaches for compressive strength prediction of cementitious mortar and paste employing magnetic water

Mosbeh R. Kaloop,Omar M.M. Yousry,Pijush Samui,Mohamed M.Y. Elshikh,Jong Wan Hu 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.4

The compressive strength is an important mechanical feature of concrete that is needed in construction design. Thus, a lot of investigations were carried out to predict the compressive strength of various concretes. However, the prediction models for the compressive strength of cement mortar or paste that include magnetic water (MW) and granulated blast-furnace slag (GBFS) are still limited. The current study has developed hybrid algorithms based on adaptive neuro-fuzzy inference system (ANFIS) for modeling the compressive strength of cement mortar and paste that made with MW and GBFS as a novel mixture content. A total of 144 experimental sets of concrete-compressive strength tests for each cement mortar and paste were collected to train and validate the proposed methods, in which the cycles number of water magnetization, cement, GBFS, superplasticizer contents and curing time are set as the input data while the compressive strength value is set as the output. The developed hybrid algorithms of ANFIS optimized by firefly algorithm (FA), Improved Particle Swarm Optimization (IPSO) and biogeographybased optimization (BBO) algorithms for predicting the compressive strength of the mortar and paste. The proposed models and relevance vector machine (RVM) approach were evaluated and compared. The results showed that the ANFIS-FA outperforms other models for modeling the compressive strength of cement mortar and paste. The adjusted-coefficient of determination and root mean square error values of cement mortar models (96.20%, 92.33%, 92.36% and 89.41%) and (2.17 MPa, 3.10 MPa, 3.18 MPa and 3.06 MPa) and of cement paste models (96.92%, 80.91%, 92.19% and 88.18%) and (2.45 MPa, 5.80 MPa, 4.39 MPa and 5.20 MPa) were determined for ANFIS-FA, ANFIS-IPSO, ANFIS-BBO and RVM models, respectively, which indicate that the ANFIS-FA is a suitable model for estimating the compressive strength of cement mortar and paste that include MW. Moreover, the sensitivity of MW and GBFS is shown high for modeling the compressive strength of cement mortar.

현무암 섬유의 나노실리카 입자 개질에 따른 시멘트 모르타르와 섬유 계면의 부착강도 특성

서동주,박종건,권호찬,송기창,허광희 한국콘크리트학회 2024 콘크리트학회논문집 Vol.36 No.2

현무암 섬유는 시멘트계 복합체와의 부착성능이 매우 낮아 건설 재료로서의 적용이 제한적이다. 본 연구에서는 시멘트 모르타르에서 현무암 섬유의 계면 부착특성을 향상시키기 위해, 알칼리성 환경하에서 실란커플링제인 GPTMS(glycidoxypropyl trimethoxysilane)와 TEOS(tetraethyl orthosilicate)의 화학적 결합에 의해 현무암 섬유의 표면을 나노실리카 입자로 개질하였다. 현무암 섬유의 조성과 미세구조를 SEM, EDS 및 FT-IR로 특성화하고 분석하였다. 나노실리카 입자는 현무암 섬유의 표면에 완전히 덮여 균일하게 분포되어, 결과적으로 나노실리카 입자의 얇은 층이 형성되는 것으로 나타났다. 아울러, 시멘트 모르타르 내에 매입된 현무암 섬유의 계면 부착강도에 대한 새로운 표면개질 방법의 효과를 검증하기 위해 단일섬유 인발시험도 수행하였다. 실험 결과, 나노실리카로 개질된 현무암 섬유 시멘트 모르타르(basalt fiber cement mortar, BFCM)의 계면 부착강도는 개질되지 않은 BFCM에 비해 상당히 향상된 것으로 나타났다. 단일섬유 인발시험 및 SEM 분석 결과는 현무암 섬유 표면의 나노실리카 입자가 섬유와 시멘트 매트릭스 사이의 계면 결합력을 증가시켜 시멘트 모르타르 내에 현무암 섬유의 가교 효과를 향상시키고, 최종적으로 시멘트 모르타르의 계면 부착강도가 향상된 것으로 나타났다. Basalt fiber exhibits notably low bonding performance with cement-based composites, limiting its application as a construction material. We aimed to enhance the interfacial bond properties of basalt fibers in cement mortar by modifying their surface with nano-silica particles through chemical bonding of GPTMS (glycidoxypropyl trimethoxysilane) and TEOS (tetraethyl orthosilicate), a silane coupling agent. The composition and microstructure of the basalt fiber were characterized and analyzed using SEM, EDS, and FT-IR imaging techniques. The resulting nano-silica particles were completely covered and uniformly distributed on the surface of the basalt fibers, forming a thin layer. In addition, a single fiber pull-out test was performed to verify the effect of the new surface modification method on the interfacial bond strength of basalt fibers embedded in cement mortar. The experimental results showed that the interfacial bond strength of basalt fiber cement mortar (BFCM) modified with nano-silica was significantly enhanced compared to unmodified BFCM. Single fiber pull-out experiments and SEM analysis revealed that nano-silica particles on the surface of basalt fibers increased the interfacial bond strength between the fibers and the cement matrix. This enhancement facilitated the bridging effect of basalt fibers in the cement mortar, ultimately improving the interfacial bond strength of the cement mortar.

주입재료에 따른 Anchor Bar의 인발저항 특성

여규권 ( Geu Guwen Yea ),송영석 ( Young Suk Song ) 대한지질공학회 2008 지질공학 Vol.18 No.2

본 연구에서는 급경사면에 설치되는 여수로를 지탱하기 위한 Anchor bar의 인발저항 특성을 현장실험을 통하여 조사하였다. Anchor bar의 주입재료로 시멘트 모르타르와 시멘트 밀크를 사용하였으며, 조건별 주입재료의 일축압축강도를 측정하였다. 측정결과 시멘트 모르타르와 시멘트 밀크는 물시멘트비가 증가함에 따라 일축압축강도가 감소하며, 재령일이 증가함에 따라 일축압축강도가 증가한다. 한편, 동일한 물시멘트비와 재령일을 가질 경우 시멘트 밀크의 일축압축강도가 시멘트 모르타르의 압축강도보다 더 큼을 알 수 있다. 현장에서 Anchor bar의 인발시험시 편심이 작용되지 않도록 하기 위하여 너트형태의 철근 고정커플링을 Anchor bar에 삽입하여 설치장비를 개선시켜 시험을 실시하였다. Anchor bar의 인발시험결과 시멘트 밀크의 경우 강도발현은 재령초기에 크게 발생되는 반면 시멘트 모르타르의 경우 재령일자가 지남에 따라 강도발현이 증가하였다. 따라서 Anchor bar의 신속한 시공을 위해서는 강도발현이 재령초기에 크게 발생되는 시멘트 밀크를 주입재료로 사용하는 것이 바람직하다. In this study, the pull out resistance characteristics of an anchor bar to support a spillway installed in a slope are investigated by field tests. The injection materials were a cement mortar and cement milk. Unconfined compression strengths of those materials under several conditions were measured. As the result of compression test, the unconfined compression strengths of the cement mortar and the cement milk have positive proportional relationship with the water-cement ratio. They also have negative proportional relationship with increasing the curing time. In the same condition of water-cement ratio and curing time, the unconfined compression strength of cement milk is larger than that of cement mortar. In order to reduce the eccentricity in anchor bar during pull-out test in the field, the installation apparatus was improved by inserting a nut type of steel fixing coupling into the anchor bar. As the result of the pull-out test, the strength modification of cement milk was increased steeply at the early curing time. However, that of cement mortar was increased gradually with passing the curing time. Therefore, the cement milk has to use as the injection material for a prompt construction of anchor bar because the strength modification of cement milk is occurred at the early curing time.

Influence of palm oil fuel ash on behaviour of green high-performance fine-grained cement mortar

Sagr, Salem Giuma Ibrahim,Johari, M.A. Megat,Mijarsh, M.J.A. Techno-Press 2022 Advances in materials research Vol.11 No.2

In the recent years, the use of agricultural waste in green cement mortar and concrete production has attracted considerable attention because of potential saving in the large areas of landfills and potential enhancement on the performance of mortar. In this research, microparticles of palm oil fuel ash (POFA) obtained from a multistage thermal and mechanical treatment processes of raw POFA originating from palm oil mill was utilized as a pozzolanic material to produce high-performance cement mortar (HPCM). POFA was used as a partial replacement material to ordinary Portland cement (OPC) at replacement levels of 0, 5, 10, 15, 20, 25, 30, 35, 40% by volume. Sand with particle size smaller than 300 ㎛ was used to enhance the performance of the HPCM. The HPCM mixes were tested for workability, compressive strength, ultrasonic pulse velocity (UPV), porosity and absorption. The results portray that the incorporation of micro POFA in HPCMs led to a slight reduction in the compressive strength. At 40% replacement level, the compressive strength was 87.4 MPa at 28 days which is suitable for many high strength applications. Although adding POFA to the cement mixtures harmed the absorption and porosity, those properties were very low at 3.4% and 11.5% respectively at a 40% POFA replacement ratio and after 28 days of curing. The HPCM mixtures containing POFA exhibited greater increase in strength and UPV as well as greater reduction in absorption and porosity than the control OPC mortar from 7 to 28 days of curing age, as a result of the pozzolanic reaction of POFA. Micro POFA with finely graded sand resulted in a dense and high strength cement mortar due to the pozzolanic reaction and increased packing effect. Therefore, it is demonstrated that the POFA could be used with high replacement ratios as a pozzolanic material to produce HPCM.

Development of Water-repellent Cement Mortar by using Silane Enriched with Nanomaterials

( Han Seung Lee ),( Dong-jin Park ),( Yunsu Lee ),( Subbiah Karthick ) 한국건축시공학회 2018 한국건축시공학회 학술발표대회 논문집 Vol.18 No.1

Tn this present study, the superhydrophobic surface was developed on the cement mortar surface by using water repellent materials. For better superhydropohicity, it was developed by using silane as binder and which was enriched with filler materials of SiO₂ and TiO₂ nanomaterials. Those nanomaterials enriched with silanes were admixed in cement mortar during casting time and another was coated on the cement mortar surface. The water repellent properties of spray coated and admixed cement mortars were evaluated by measuring the contact angle which was compared with normal cement mortar.