• 한국농공학회지
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• 제41권1호
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• pp.97-105
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• 1999

Recently , polymer concrete has been widely used in the construction industry because of its quick setting, high strength, excellect adhesion, watertightness and chemical resistance compared to ordinary cement concrete. Its application is also increased. In this paper, lightweight polymer mortars using unsaturated polyester resin and lightweight aggregate are prepared with various mix proportations, and tested for slump working life, apparent specific gravity , flexural and compressive strengths. As a result, the slump and working life can be controlled and thier flexural and compressive strengths are 9.7 to 22.0 MPa , and 23.0 to 100.8 MPa respectively at apparent specific gravities of 0.86 to 1.73.

• 한국건설순환자원학회논문집
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• 제11권4호
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• pp.560-567
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• 2023

본 연구에서는 달라지는 화재 성상에 대비하기 위한 내화재료 연구의 일환으로 천연 탄산칼슘 재료인 굴 패각과 난각을 각각 잔골재로 치환하여 치환율에 따른 강도 및 내화성능을 평가하여 내화 재료로 사용하기 위한 자료를 제공하고자 하였다. 굴 패각과 난각은 각각 잔골재 대비 10~50 %를 치환하였고, KS 시험방법에 준하여 강도측정 및 간이가열 실험을 진행하였다. OS를 치환한 경우는 ES를 치환한 경우보다 강도가 높게 측정되었지만 이면온도 또한 높게 측정되었다. 이를 통해 폭발성 화재같이 강도성능이 요구되는 곳은 OS를 혼합한 내화보드를 사용하고, 1000 ℃이상의 고온화재 같이 높은 내화성능이 요구되는 곳은 ES를 혼합한 내화보드를 사용하는 등 용도에 맞게 선택할 수 있을 것으로 사료된다.

• 콘크리트학회논문집
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• 제13권1호
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• pp.16-22
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• 2001

PHC 파일은 높은 재하능력과 충격저항 그리고 경제성 및 내구성이 우수하지만 제품 제작시 프리스트레스 텐던이 적절한 콘크리트 덮개를 확보하여야 하며 엄격한 콘크리트 덮개를 확보하여야 하며 엄격한 품질관리가 요구된다. 원심 성형시 파일단면이 시멘트풀, 모르타르 층으로 분리되면 프리스트레스 텐던의 덮개를 충분히 확보하기 어려워 파일의 운반, 야적 및 항타시 발생하는 하중효과에 의해 균열이 발생할 수 있으며, 텐던의 부식을 유발할 수 있다. 본 연구에서는 프르텐션방식 원심력 고강도콘크리트 파일 생산시 원심력콘크리트의 원심조건이 파일의 재료분리층과 압축강도에 미치는 영향을 연구하기 위해 실험을 수행하였다. 실험결과에 의하면, 재료분리는 파일의 강도에 큰 영향을 주지는 않으나 원심력 크기 및 원심시간에 따라 재료분리층의 두께 변화가 심하여, 특히 고속의 원심 성형이 파일의 강도를 크게 하는 반면 재료분리도 크게 발생함을 알 수 있다. PHC 파일의 경우 재료분리가 크면 프리스트레싱 텐던의 피복두께 감소로 인해 부착력 감소, 텐던 주변의 종균열 발생, 내구성저하를 가져오고 또한, 텐던의 처짐, 비대칭 배치에 의해 불필요한 응력발생시 횡균열 발생이 가능하므로 재료분리가 적은 최적의 원심력, 원심시간결정은 중요한 것으로 보인다.

• Computers and Concrete
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• 제31권4호
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• pp.327-335
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• 2023

The most popular building material, concrete, is intrinsically linked to the advancement of humanity. Due to the ever-increasing complexity of cementitious systems, concrete formulation for desired qualities remains a difficult undertaking despite conceptual and methodological advancement in the field of concrete science. Recognising the significant pollution caused by the traditional cement industry, construction of civil engineering structures has been carried out successfully using Geopolymer Concrete (GPC), also known as High Performance Concrete (HPC). These are concretes formed by the reaction of inorganic materials with a high content of Silicon and Aluminium (Pozzolans) with alkalis to achieve cementitious properties. These supplementary cementitious materials include Ground Granulated Blast Furnace Slag (GGBFS), a waste material generated in the steel manufacturing industry; Fly Ash, which is a fine waste product produced by coal-fired power stations and Silica Fume, a by-product of producing silicon metal or ferrosilicon alloys. This result demonstrated that GPC/HPC can be utilised as a substitute for traditional Portland cement-based concrete, resulting in improvements in concrete properties in addition to environmental and economic benefits. This study explores utilising experimental data to train artificial neural networks, which are then used to determine the effect of supplementary cementitious material replacement, namely fly ash, Ground Granulated Blast Furnace Slag (GGBFS) and silica fume, on the compressive strength, tensile strength, and modulus of elasticity of concrete and to predict these values accordingly.

• Computers and Concrete
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• 제14권2호
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• pp.175-191
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• 2014

In recent years, the emergence of nanotechnology and nanomaterial has created hopes to improve various properties of concrete. Nano silica as one of these materials has been introduced as a cement replacement material for concrete mixture in construction applications. It can modify the properties of concrete, due to high pozzolanic reactions and also making a denser microstructure. On the other hand, it is well recognized that the use of mineral admixtures such as silica fume affects the mechanical properties and durability of cementitious materials. In addition, the superior performance of self-consolidating concrete (SCC) and self-consolidating mortars (SCM) over conventional concrete is generally related to their ingredients. This study investigates the effect of nano silica and silica fume on the compressive strength and chloride permeability of self-consolidating mortars. Tests include compressive strength, rapid chloride permeability test, water permeability, capillary water absorption, and surface electrical resistance, which carried out on twenty mortar mixtures containing zero to 6 percent of nano silica and silica fume. Results show that SCMs incorporating nano silica had higher compressive strength at various ages. In addition, results show that nano silica has enhanced the durability SCMs and reduced the chloride permeability.

• Computers and Concrete
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• 제15권2호
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• pp.167-181
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• 2015

"Mortar or concrete pneumatically projected at high velocity onto a surface" is called Shotcrete. Models that predict shotcrete design parameters (e.g. compressive strength, slump etc) from any mixing proportions of admixtures could save considerable experimentation time consumed during trial and error based procedures. Artificial Neural Network (ANN) has been widely used for similar purposes; however, such models have been rarely applied on shotcrete design. In this study 19 samples of shotcrete test panels with varying quantities of water, steel fibers and silica fume were used to determine their slump, cost and compressive strength at different ages. A number of 3-layer Back propagation Neural Network (BPNN) models of different network architectures were used to train the network using 15 samples, while 4 samples were randomly chosen to validate the model. The predicted compressive strength from linear regression lacked accuracy with $R^2$ value of 0.36. Whereas, outputs from 3-5-3 ANN architecture gave higher correlations of $R^2$ = 0.99, 0.95 and 0.98 for compressive strength, cost and slump parameters of the training data and corresponding $R^2$ values of 0.99, 0.99 and 0.90 for the validation dataset. Sensitivity analysis of output variables using ANN can unfold the nonlinear cause and effect relationship for otherwise obscure ANN model.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 가을 학술논문 발표대회
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• pp.127-128
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• 2022

In order to realize carbon neutrality in the international society, research on supplementary cementitious materials(SCMs) has been actively conducted as a way to reduce carbon dioxide emissions in the cement industry. However, the use of SCMs causes problems of initial hydration delay and strength reduction due to the reduction of tricalcium silicate(C3S) in the cement clinker. Therefore, in this study, the initial hydration and basic characteristics of cement mortar were confirmed by adding a C-S-H based hardening acceleration to blended cement mixed with Portland cement, blast furnace slag, fly ash, and limestone power. As a result of the heat of hydration and compressive strength test, it was confirmed that when hardening acceleration was added, the initial reactivity was high, so the heat of hydration was promoted, and the initial strength was increased. It is considered to be due to C-S-H seeding effect. Therefore, it is judged that the use of C-S-H based hardening acceleration can supplement the problem of initial hydration delay of blended cement in Korea.

• 한국구조물진단유지관리공학회 논문집
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• 제27권5호
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• pp.139-146
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• 2023

In this study, compressive strength and adhesion strength were measured as repair materials to evaluate the mechanical and electrical properties of compression and shear specimens with self-sensing repair materials. As a result of the experiment, the strength improvement rate of the compression test specimen was higher than the section enlargement area ratio, but the shear test specimen did not show an improvement in strength as much as the section enlargement area ratio. Compression experiments under load showed high correlation between FCR-Strain and FCR-Stress, confirming self-sensing performance. However, the shear test did not show as much correlation as the compression test. Accordingly, it is judged that the self-sensing repair material is suitable for the compression member on which the compression load acts in the building.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.11-12
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• 2015

This study analyzed sulfate resistance of strongly acid-resistant inorganic binder based on industrial byproducts. According to the study experiment, compared to OPC mixture, the mixture of high acid-resistant inorganic binder had excellent chemical resistance against 10% H₂SO₄ solution. In the case of ordinary portland cement, its sample with 28 days of immersion had severe corrosion on its mortar erosion part, and thus external appearance was damaged greatly, and compression strength decreased by around 57% and more.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.321-326
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• 1997

Recently, High Range Water Reducing Admixture be used increasingly in other to improve the demanded properties (fluidity, strength, durability etc.) and workability in concrete. These kinds of agent govern quality characteristics (air content, setting time, slump, bleeding etc) by the difference of its dispersing mechanism and performance in manufacture of flowed concrete. Accordingly, in this study, for the purpose of high quality construction in site, the comparative experiment of dispersing ability due to commercially available three types of agent were carried out in paste, mortar and concrete using tow types of cement (I, V). In conclusion, the bleeding reduction by the dispersing ability of agents was verified in the fresh properties of flowed concrete with sea water resistance.