Showing papers by "Cengiz Duran Atiş published in 2016"

Strength Properties of Slag/Fly Ash Blends Activated with Sodium Metasilicate and Sodium Hydroxide+Silica Fume

Abstract: This study presents the strength properties of alkali activated Ground Granulated Blast Furnace Slag (GGBFS) /Fly Ash (FA) blend mortars prepared with sodium meta-silicate and, sodium hydroxide-silica fume combination mixture. The GGBFS/FA ratios were arranged at (100/0, 80/20, 60/40, 40/60, 20/80, 0/100). Water to “GGBFS+FA” ratio was kept constant at 0.5. Na concentration ratio to “GGBFS+FA” was kept constant at 6%. These ratios were in mass basis. Three different mixture parameters were used. In the first series of mixture, only sodium meta-silicate was used as activator. In second and third series, sodium hydroxide and silica fume combination was used as activator. Sodium hydroxide and silica fume was mixed with water and used directly in preparation of second series of mortar mixtures. For preparation of third series of mortar mixture, sodium hydroxide and silica fume were mixed continuously with water for three days to allow dissolution of silica fume in sodium hydroxide solution. At first, 3-days compressive strengths of all alkali activated mortar mixture were measured. After that due to the very low compressive strength of mortars made with high volume fly ash content, only 100/0 and 80/20 slag/fly ash ratios were investigated for 7, 14 and 28 days compressive and 28 days flexural strength. The results of the 3 days tests show that decreasing the slag/fly ash ratio decreases distinguishably the compressive strength of the mortars. The mortars produced with the mixture of sodium hydroxide and silica fume combination as activator showed satisfactory results when compared with those activated with sodium meta-silicate.

Effects of milled cut steel fibers on the properties of concrete

Abstract: This study presents the mechanical and transport properties of milled cut steel fiber reinforced concretes (MCSFRC). Properties studied include unit weight, workability, compressive strength, flexural strength, splitting tensile strength, bond strength, water absorption, water porosity, water sorptivity, rapid chloride ion permeability and drying shrinkage of concrete. Mixtures with a waterbinder ratio of 0.40, total binder content of 500 kg/m3 and milled cut steel fiber content of 0, 0.25, 0.50 and 1.00% by concrete volume were produced and tested. The laboratory results showed a slight reduction in compressive strength with the use of milled cut steel fiber. On the other hand milled cut steel fibers significantly improved the tensile strength and decreased the drying shrinkage. Although no significant increase was observed in the absorption, porosity and sorptivity, chloride ion permeability increased drastically with the increase of milled cut steel fiber content.

Comparison of Unit Price Method and Unit Area Cost Method for Construction Cost Estimation

Abstract: In the construction industry, increasing competition environment has led to decrease in the profit share of the projects. Accordingly, importance of construction cost estimation works has been increased for both the employer and the contractor. The purpose of this study has been to determine and compare the construction cost estimations obtained by widely used databases, “unit price method” (UPM) and “unit area cost method” (UACM) in Turkey. For this purpose, construction data from 420 projects, which were procured in accordance with the Public Tender Law no 4734 by the Turkish Ministry of Environment and Urbanism and completed between 2003 and 2011, were reviewed. Root mean square error (RMSE), mean absolute percentage error (MAPE) and coefficient of determination (R) were calculated for the comparison of actual and estimated cost values. Consequently, RMSE and MAPE values from UPM were underestimated with the ratio of 13.57% and 1.73% than UACM. Although UPM showed better performance than the UACM, it is not at a satisfactory level.

Sodyum sülfat i̇le akti̇fleşti̇ri̇len uçucu kül katkili harçlarin özelli̇kleri̇

Abstract: Portland cimentosunun icadindan once mineral katkilar sonmus kirecle karistirilarak harc imalinde baglayici olarak kullanilmistir. Gunumuzde de mineral katkilar, ekonomik olduklarindan ve ozellikle taze ve sertlesmis beton ile harcin bazi ozelliklerinde faydali degisiklikler sagladiklarindan, cimentoyla birlikte kullanilmaktadir. Calismada, Portland cimentosuna yuksek oranda kalsiyum iceren ucucu kul ve aktiflestirici susuz sodyum sulfat (Na 2 SO 4 ) ilaveleriyle uretilmis harc numunelerinin dayanimlari incelenmistir. Ucucu kul, cimento ile agirlikca % 10, % 20, % 30 ve % 40 oranlarinda ikame edilerek kullanilirken, sodyum sulfat ise toplam baglayici miktarinin % 0, % 2 ve % 4 oranlarinda kullanilarak kum/cimento orani 2,75 ve su/cimento orani ise 0,485 olan harc numuneleri uretilmistir. Ucucu kul katkili harc numunelerine susuz sodyum sulfatin aktivator olarak ilavesinin, harc numunelerinin bosluk oranlarina ve basinc ile egilmede cekme dayanimlarina etkileri 3, 7, 28 ve 90 gunluk kur sureleri sonunda tespit edilmistir. Bulgular, ucucu kulun % 20 ikame oranina kadar kullanilabilecegini, erken yas dayanim kayiplarinin ise baglayici miktarinin en fazla % 2’si kadar Na 2 SO 4 kullanilarak telafi edilebilecegini gostermistir. Anahtar Kelimeler: Ucucu kul, harc, basinc dayanimi, egilme dayanimi