• Advances in concrete construction
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• 제5권1호
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• pp.75-86
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• 2017

An experimental work was carried out to study the effect of hybrid fiber on the tension stiffening and cracking characteristics of geopolymer concrete (GPC). A total of 24 concentrically reinforced concrete specimens were cast and tested under uniaxial tension. The grade of concrete considered was M40. The variables mainly consist of the volume fraction of crimped steel fibers (0.5 and 1.0%) and basalt fibers (0.1, 0.2 and 0.3%). The load deformation response was recorded using LVDT's. At all the stages of loading after the first cracking, crack width and crack spacing were measured. The addition of fibers in hybrid form significantly improved the tension stiffening effect. In this study, the combination of 0.5% steel fiber and 0.2% basalt fiber gave a better comparison than the other combinations.

• Advances in concrete construction
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• 제8권1호
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• pp.33-37
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• 2019

The present investigation is mainly focused on studying the flexural behavior of reinforced geopolymer concrete (RGPC) beams under pure bending. In this study, copper slag (CS) was used as a partial replacement of fine aggregate. Sand and CS were blended in different proportions (100:0, 80:20, 60:40 and 40:60) (sand:CS) by weight. Fly ash and ground granulated blast furnace slag (GGBS) were used as binders and combination of sodium hydroxide (8M) and sodium silicate solution were used for activating the binders. The reinforcement of RGPC beam was designed as per guidelines given in the IS 456-2000 and tested under pure bending (two-point loading) after 28 days of ambient curing. After conducting two point load test the flexural parameters viz., moment carrying capacity, ultimate load, service load, cracking moment, cracking load, crack pattern and ultimate deflection were studied. From the results, it is concluded that RGPC beams have shown better performance up to 60% of CS replacement.

• Steel and Composite Structures
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• 제45권6호
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• pp.877-894
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• 2022

Geopolymer concrete (GPC) has emerged as a feasible choice for construction materials as a result of the environmental issues associated with the production of cement. The findings of this study contribute to the development of machine learning methods for estimating the properties of eco-friendly concrete to help reduce CO₂ emissions in the construction industry. The compressive strength (f_c) of GPC is predicted using artificial intelligence approaches in the present study when ground granulated blast-furnace slag (GGBS) is substituted with natural zeolite (NZ), silica fume (SF), and varying NaOH concentrations. For this purpose, two machine learning methods multi-layer perceptron (MLP) and radial basis function (RBF) were considered and hybridized with arithmetic optimization algorithm (AOA), and grey wolf optimization algorithm (GWO). According to the results, all methods performed very well in predicting the f_c of GPC. The proposed AOA - MLP might be identified as the outperformed framework, although other methodologies (AOA - RBF, GWO - RBF, and GWO - MLP) were also reliable in the fc of GPC forecasting process.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.21-22
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• 2020

In this study, the pile filling materials of the pile in drilled piling was studied. cement milk is mostly used as the filling materials of bored pile. The use of filling material based on cement milk is inefficient at field construction because it needs a lot of the charging mass. thickening agent was added to the cement milk to perform settlement estimation experiment on a circular cylinder, and as a result of examining the compressive strength of the day, it was found that the settlement estimation was significantly reduced. However, the strength was relatively low, it was confirmed that there was no problem with the regulation because the main surface fixative required relatively low strength.

• 콘크리트학회논문집
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• 제21권6호
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• pp.689-696
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• 2009

최근 들어 균열 치유 향상도의 가속화 방안으로서 전기 화학적 전착 기법을 활용한 인공 균열 치유방법에 관한 실험연구가 수행되고 있다. 이 연구에서는 고내구성 콘크리트의 설계 및 유지관리를 위한 방안으로서 혼합콘크리트의 사용에 따른 인공 균열 치유방법상의 부식방식 모니터링의 비교 및 균열 치유향상도의 분석을 수행하였다. 이를 위해 철근콘크리트내로의 가압전류의 특성분석, 가용 전해질의 특성분석, 갈바닉 전류 모니터링, 선형분극저항측정 비교, 균열 치유 전/후의 치유향상도의 사진화상분석등을 통해 혼합 콘크리트의 인공 균열 치유기법 적용에 따른 치유 향상도를 실험적 연구로서 수행하였다. 실험결과로부터, 인공균열치유에 의한 가압전류 측면에서 20,000 min의 통전시간에 따라 점차적으로 가압전압값이 증가하면서 2.9 V로 물/시멘트비에 관계없이 수렴하고 있음을 알수 있었고, 갈바닉전류 모니터링에 따른 부식지연성은 W/C의 경우에 0.4 $>$ 0.5 $>$ 0.6의 순서로, 결합재별 비교에 있어서는 OPC $>$ 60%GGBS $>$ 10%SF $>$ 30% PFA의 순서로 나타남을 알 수 있었다. 한편 전기화학적 전착기법에 의한 치유후 기존 균열면적의 76.47%가 치유됨을 확인하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권1호
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• pp.111-118
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• 2014

본 연구는 시멘트 경화체로부터의 알칼리 침출에 의한 pH 증가와 알칼리 침출속도에 관하여 수행되었다. 배합, 물-시멘트 비, 결합재에 따른 영향을 평가하기 위해 각각을 변수로 하여 시험체를 제작하였다. 시험체는 정사각형 수조형태로 내부에 물을 저장하여 이온이 해리되어 침출될 수 있도록 하였다. 또한 시험체 내부 용액의 대기접촉으로 인한 예기치 못한 화학적 반응을 방지하기 위해 폴리에틸렌 수지로 포장했다. 침투능과 침투속도를 결정하기 위해 용액의 pH는 더 이상 변화가 없을 때까지 시간 경과에 따라 측정하였다. 알칼리 침출에 의한 용액의 pH 변화에 있어서 물-시멘트 비의 영향은 거의 없는 것으로 나타났으며, 반면에 결합재에 따른 영향은 큰 것으로 나타났다. 결합재로 OPC 만을 사용한 경우에 알칼리 침출이 높았으며, 30% PFA와 60% GGBS의 경우에 알칼리 침출이 낮았다. pH 측정이 종료된 후, 시험체 내부 표면으로부터 깊이 1.0 mm 간격으로 채취한 시료를 증류수로 현탁시켜 현탁액의 pH를 측정하였다. OPC의 경우에는 약 7-8 mm 깊이까지 침출의 영향을 받고, 30% PFA와 60% GGBS의 경우에는 침출 영향을 받는 깊이가 더 깊어짐을 알 수 있었다.

• 한국건축시공학회지
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• 제13권4호
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• pp.391-399
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• 2013

본 연구에서는 40 MPa 및 60 MPa급의 고강도 콘크리트를 제조함에 있어서, 보통 포틀랜드 시멘트에 대해 60~80%를 고로슬래그 미분말로 대체하고, 알카리 설페이트계(Modified Alkali Sulfate type) 자극제(Activator)를 활용하여 조기강도 개선효과 및 콘크리트의 길이변화 특성을 고찰하였다. 이에 따라 알카리 자극제를 결합재 대비 1%를 사용한 결과, 미소수화열은 72시간의 누적 발열량이 약 45%가 향상되어 초기의 강도 성능 향상에 기여하는 것으로 판단되며, 콘크리트의 유동성은 다소 감소하였으나, 3일과 7일 강도는 8~12% 향상되어 고로슬래그 미분말을 60% 수준으로 대체하여 고강도 콘크리트를 제조할 때 초기재령의 강도 확보에 알카리 설페이트계 자극제의 활용이 효과적인 것으로 나타났다. 또한 길이변화 시험 결과는, 40 MPa와 60 MPa 시험체 모두 BS40 > BS60 > BS60A > BS80A의 순으로 길이변화가 큰 것으로 나타났고, 알카리 자극제의 사용에 따라 길이변화가 다소 개선되는 것으로 나타났다.

• Advances in concrete construction
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• 제9권2호
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• pp.139-147
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• 2020

This paper reports the effect of Rice Husk Ash (RHA) in geopolymer concrete on strength, durability and microstructural properties under ambient curing at a room temperature of 25℃ and 65±5% relative humidity. Rice husk was incinerated at 800℃ in a hot air oven. and ground in a ball mill to achieve the required fineness. RHA was partially added in 10, 15, 20, 25, 30 and 35 percentages to fly ash with 10% of GGBS to produce geopolymer concrete. Test results exhibit that the substitution of RHA in geopolymer concrete resulted in reduced strength properties during initial curing. In the initial stage, workability of GPC mixes was affected by RHA particles due to the presence of dormant particles in it. It is evident from the microstructural study that the presence of RHA particles densifies the matrix reducing porosity in concrete. This is due to the presence of RHA in geopolymer concrete, which affects the ratio of silica and alumina, resulting in polycondensation reactions products. This study suggests that incorporation of rice husk ash in geopolymer concrete is the solution for effective utilization of waste materials and prevention of environmental pollution due to the dumping of industrial waste and to produce eco-friendly concrete.

• Advances in concrete construction
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• 제8권4호
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• pp.305-309
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• 2019

Pervious concrete pavements are the need of the day to avoid urban flooding and to facilitate ground water recharge. However, the strength of pervious or porous concrete is considerably less compared to conventional concrete. In this experimental investigation, an effort is made to improve the strength of pervious concrete by adopting fibres and a small amount of fine aggregate. A porous concrete with cement to aggregate ratio of 1:5 and a water-powder ratio of 0.4 is adopted. 30% of the cement is replaced by cementitious material ground granulated blast furnace slag (GGBS) for better strength and workability. Recron fibres at a dosage of 0.5, 1.0 and 1.5% by weight of cement were included to improve the impact strength. Since concrete pavements are subjected to impact loads, the impact strength was also calculated by "Drop ball method" in addition to compressive strength. The effect of fine aggregate and recron fibres on workability, porosity, compressive and impact strength was studied. The investigations have shown that 20% inclusion of fine aggregate and 1.5% recron fibres by weight of cement give better strength with an acceptable range of porosity.

• Computers and Concrete
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• 제22권2호
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• pp.183-196
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• 2018

The rheological behaviour of high strength self compacting concrete (HS-SCC) studied through an experimental investigation is presented in this paper. The effect of variation in supplementary cementitious materials (SCM) $vis-{\grave{a}}-vis$ four different types of processed crushed sand as fine aggregates is studied. Apart from the ordinary Portland cement (OPC), the SCMs such as fly ash (FA), ground granulated blast furnace slag (GGBS) ultrafine slag (UFS) and micro-silica (MS) are used in different percentages keeping the mix -paste volume and flow of concrete, constant. The combinations of rheology, strength and durability are equally important for selection of mixes in respect of high-rise building constructions. These combinations are referred to as the rheo-strength and rheo-durability which is scientifically linked to performance based rating. The findings show that the fineness of the sands and types of SCM affects the rheo-strength and rheo-durability performance of HS-SCC. The high amount of fines often seen in fine aggregates contributes to the higher yield stress. Further, the mixes with processed sand is found to offer better rheology as compared to that of mixes made using unwashed crushed sand, washed plaster sand, washed fine natural sand. The micro silica and ultra-fine slag conjunction with washed crushed sand can be a good solution for high rise construction in terms of rheo-strength and rheo-durability performance.