No abstract

This study presents the resistance of sodium meta-silicate activated ground granulated blast furnace slag (GGBFS) to acidic and basic mediums. Geopolymer mortars were prepared with GGBFS activated by sodium meta-silicate activator having 4, 8, and 12% sodium concentrations by mass of slag. These mortars were exposed to two types of acid solutions, H2SO4 and HCl with a 5% concentration of acid-water solution. Similarly, some specimens were exposed to a basic medium composed of 25% NaOH solution with water. Exposure time for the acidic and basic mediums was set to one year. Comparison of results obtained from slag based geopolymer mortar was made with normal Portland cement control mortar. Normal control samples lost compressive strength significantly after exposure to acidic and basic medium in comparison to alkali activated slag mortar. Particularly, after exposure to H2SO4, the compressive strength of the normal control samples decreased by about 40%. Contrary to this, the slag based geopolymer mortar gained compressive strength after exposure to the acidic or basic mediums. An up to 21% strength increase was observed from the alkali activated slag mixtures made with 4% and 8% Na content.

The concrete is the most widely used building material in Turkey. Especially reinforced concrete dominates at building sector. Because of concrete is an non-homogeneous and non-isotropic material, the strength of concrete cannot be accurately achieved at the site. To control the mechanical properties of concrete in the site, non--destructive test methods can be used. They are useful for having no damage on concrete, however these test results sometimes gives deceptive results. In this study, two of non-destructive test methods, Schmidt hammer testing and ultrasonic pulse velocity methods were used for determining concrete compressive strength. 101 samples were poured concrete cube dimensions 150×150×150 mm 3 . On 28th days, rstly, the samples were applied Schmidt hammer test and ultrasonic pulse velocity test and then the compressive strength of these samples was measured by breaking in the press, destructive method. Thus, the new formulations are obtained for Schmidt hammer test and ultrasonic pulse velocity test.

Çalışma kapsamında iki atık malzeme olan Yüksek fırın cürufu (YFC) ve Çelikhane cürufu (ÇC) kullanılarak çimento yerine alternatif bağlayıcı elde edilmeye çalışılmaktadır. Bu amaçla, YFC ve ÇC farklı oranlarda kullanılarak geopolimer harçlar üretilmiştir. Cüruflar, %80 YFC+ %20 ÇC ve %60 YFC+ %40 ÇC olacak şekilde çimento yerine ikame edilerek kullanılmıştır. Cüruflu harçların aktivasyonu için %3, %5, %7.5 ve %9 oranında Na2SiO3 kullanılmıştır. Cüruflu geopolimer harçların 28 günlük basınç dayanımı sonuçları; %80 YFC+ %20 ÇC için sırasıyla; 40.14, 47.28, 59.87 ve 76.25 MPa olarak belirlenmiştir. %60 YFC+%40 ÇC içeren geopolimer harçların basınç dayanımları; 25.57, 44.92, 54.23 ve 66.65 MPa olarak belirlenmiştir. Dayanım sonuçları, geopolimer harçların %7.5 ve %9 Na2SiO3 oranlarında Portland çimentosuna kıyasla daha iyi dayanım verdiğini göstermektedir. Dayanım sonuçlarına bakıldığında, cüruflu geopolimer harçların çimento yerine bağlayıcı bir malzeme olabileceği anlaşılmaktadır.

Concrete is the most widely used construction material in contemporary construction technology.In particular, it holds an important place in the building industry in the World. Since concrete is an un-homogeneous material, determining the strength of concrete accurately is quite difficult. In this respect, to check the mechanical properties of concrete in-situ, non-destructive test methods can be used. They are useful as they do not damage concrete, however, these test results are sometimes deceptive. To reduce these deceptive results, destructive test methods were proposed to increase the accuracy of non-destructive methods (NDT).The objective of this study is to determine the strength of concrete with different characteristic strengths using destructive and non-destructive testing methods, and to establish new relationships between the compressive strength of concrete and Schmidt rebound values, and ultrasonic wave velocities. For this purpose, 101 concrete cube samples were prepared. After 7 Downloaded by [University of Sussex Library] at 00:11 28 June 2016A c c e p t e d M a n u s c r i p t 2 and 28 days of curing, Schmidt rebound and ultrasonic wave velocity tests were applied as nondestructive testing methods. New formulations and graphs were established by carrying out a multiple regression analysis between the ultrasonic wave velocities, Schmidt rebound values and compressive strengths. Thus, a new combined NDT method was developed with a nomogram. Furthermore, the applicability and accuracy of the formula and graph obtained were investigated by comparing the results of core samples from existing structures.The most important findings obtained from the study are summarized below. The concrete strength can be determined with non-destructive formulas obtained with an accuracy of 85%.High strength concrete cube samples in-house are obtained with 1.6% deviation and core samples in-situ can be obtained with 7.3% deviation with the newly developed NDT nomogram.These test results show that the newly developed NDT formulas in this study are a very good alternative for determining concrete strength in-situ.