Ahmet Tuncan

Re-usage of waste foundry sand in high-strength concrete.

In this study, the potential re-use of waste foundry sand in high-strength concrete production was investigated. The natural fine sand is replaced with waste foundry sand (0%, 5%, 10%, and 15%). The findings from a series of test program has shown reduction in compressive and tensile strengths, and the elasticity modulus which is directly related to waste foundry inclusion in concrete. Nevertheless the concrete with 10% waste foundry sand exhibits almost similar results to that of the control one. The slump and the workability of the fresh concrete decreases with the increase of the waste foundry sand ratio. Although the freezing and thawing significantly reduces the mechanical and physical properties of the concrete. The obtained results satisfies the acceptable limits set by the American Concrete Institute (ACI).

The use of waste materials in asphalt concrete mixtures

The purpose of this study was to investigate (a) the effects of rubber and plastic concentrations and rubber particle sizes on properties of asphalt cement, (b) on properties of asphalt concrete specimens and (c) the effects of fly ash, marble powder, rubber powder and petroleum contaminated soil as filler materials instead of stone powder in the asphalt concrete specimens. One type of limestone aggregate and one penetration-graded asphalt cement (75-100) were used. Three concentrations of rubber and plastic (i.e. 5%, 10% and 20% of the total weight of asphalt cement), three rubber particle sizes (i.e. No. 4 [4.75mm] - 20 [0.85 mm], No. 20 [0.85mm] - 200 [0.075mm] and No. 4 [4.75mm] - 200 [0.075mm]) and one plastic particle size (i.e. No. 4 [4.75mm] - 10 [2.00mm]) were also used. It was found that while the addition of plastic significantly increased the strength of specimens, the addition of rubber decreased it. No. 4 [4.75mm] - 200 [0.075mm] rubber particles showed the best results with respect to the indirect tensile test. The Marshall stability and indirect tensile strength properties of plastic modified specimens increased. Marble powder and fly ash could be used as filler materials instead of stone powder in the asphalt concrete pavement specimens.

Use of natural zeolites as a landfill liner

The purpose of this study is to investigate certain features of a novel material proposed to serve as an impervious liner in landfills. Various ratios of bentonites and zeolites (B/Z) compacted at optimum water content were tested to determine the strength parameters, permeability, pH, heavy metals and other properties. A B/Z ratio of 0.10 was found to be an ideal landfill liner material regarding its low hydraulic conductivity and high cation exchange capacity. The use of B/Z mixtures as an alternative to clay liners would provide potential to significantly reduce the thickness of base liner for landfills.

Physical, Mechanical and Micro-Structural Properties of F Type Fly-Ash Based Geopolymeric Bricks Produced by Pressure Forming Process

Geopolymer is a new class of three-dimensionally networked amorphous to semi-crystalline alumino-silicate materials, and first developed by Professor Joseph Davidovits in 1978. Geopolymers can be synthesized by mixing alumino–silicate reactive materials such as kaolin, metakaolin or pozzolans in strong alkaline solutions such as NaOH and KOH and then cured at room temperature. Heat treatment applied at higher temperatures may give better results. Depending on the mixture, the optimum temperature and duration vary 40-100 °C and 2-72 hours, respectively. The properties of geopolymeric paste depend on type of source material (fly ash, metakaolin, kaolin), type of activator (sodium silicate-sodium hydroxide, sodium silicate-potassium hydroxide), amount of activator, heat treatment temperature, and heat treatment duration. In this experimental investigation, geopolymeric bricks were produced by using F-type fly ash, sodium silicate, and sodium hydroxide solution. The bricks were treated at various temperatures for different hours. The compressive strength and density of F-type fly ash based geopolymeric bricks were determined at the ages of 7, 28 and 90 days. Test results have revealed that the compressive strength values of F-type fly ash based geobricks ranged between 5 and 60 MPa. It has been found that the effect of heat treatment temperature and heat treatment duration on the density of F-type fly ash based geobricks was not significant. It should be noted that the spherical particle size increased as the heat treatment temperature increased in the microstructure of F-type fly ash based geobricks treated in oven at the temperature of 60 °C for 24 hours.

Distributions of Compressive Strength Obtained from Various Diameter Cores

Test results from cores with diameters smaller than the standard sizes and with length-to-diameter (l/d) ratios less than 1 are considered to be unreliable due to higher variability in concrete strength. There is, however, still a lack of evidence in the literature regarding the unreliability of the compressive strength data for these lower-volume cores. Significantly important is the missing verification of such statements concerning the random variations of concrete strength, supported with statistical approaches. Statistically significant data sets under such conditions are very rare. In this study, the issue was addressed by exploring the features of the compressive strength obtained from different diameter cores using probabilistic concepts—in particular, when the l/d is less than 1— and shed light on the uncertainty regarding the reliability of the data taken under these conditions. The major outcome of this study is that concrete cores with diameters less than the standard-size cores and larger than microcores could be effectively used in practice to represent the variations in concrete strength, provided that the number of core samples and l/d are sufficiently high.

Some Factors Influencing Effect of Core Diameter on Measured Concrete Compressive Strength

Various concrete mixtures were produced using crushed limestone and river gravels with four different maximum sizes of 10, 15, 22, and 30 mm (0.39, 0.59, 0.87, and 1.18 in.). The 28-day cube strength of concrete mixtures ranged between 28 and 43 MPa (4061 and 6236.6 psi). Beam specimens were cast by these concrete mixtures and cores were drilled from the beams. Compressive strength tests were performed at the ages of 7, 28, and 90 days on a total of 2268 core and cube specimens and the effect of core diameter on concrete core strength was examined. The strength correction factors were determined to convert the strength of a core with a diameter of 144, 69, or 46 mm (5.67, 2.72, or 1.81 in.) to that of a core having a diameter of 94 mm (3.70 in.). As the maximum aggregate size increased, the strength of the core decreased and, consequently, the correction factors increased. The effect was more pronounced for smaller diameter cores. The correction factors were somewhat higher for cores drilled from river gravel concrete. The age of the concrete was found to be an important factor in the strength correction of different diameter cores, that is, the older the concrete, the lower the correction factor. It should be noted, however, that it is very difficult to use age-versus-correction factor relation in practical terms. Additionally, test results showed that the length-to-diameter ratio of the specimen is more significant for small-diameter cores.

Effect of Length-to-Diameter Ratio of Core Sample on Concrete Core Strength—Another Look

Cores with diameters of 144, 94, 69, and 46 mm and length-to-diameter (l/d) ratios of 0.75, 1, 1.25, 1.5, 1.75, and 2, were removed from beam specimens produced from eight different concrete mixtures. Compressive strength tests were conducted on a total of 1876 core specimens. Strength correction factors were determined for converting the strength of the cores with l/d ratios ranging from 1.75 to 0.75 to the strength of an equivalent standard specimen with a l/d ratio of 2. The effects of type and maximum size of aggregate and core diameter on these correction factors were examined. As it was expected, the correction factors gradually decreased with the decrease in l/d. The effect was found to be more pronounced for cores with a smaller diameter. The results also revealed that the effects of type and maximum size of the aggregate on correction factors were not significant. The proposed strength correction factors differ only slightly from those currently recommended in ASTM C 42/C 42M-04 [1] and they are very close to those proposed by Bartlett and MacGregor cited by Arioglu [2–4].

The Effects of Filler Glasses on Mechanical Properties of Concrete

According to the relevant literature, the utilisation of different kind of glasses in concrete introduces positive effect on the mechanical behaviour. The factor affecting physical and mechanical properties and chemical endurance of concrete is the amount of structural pores, which form within its structure. Suitable filler materials can be used in concrete to decrease them. Such a material possesses not only pore filling ability but also pozzolanic character. Therefore, employing glasses as an additive in concrete can improve the final mechanical properties. In the present study a filler glass with a chemical composition of 40 Si02, 14 Zr02, 15 SrO, 20 Mg0 and 11 Fe203 (in wt. %), was used as an additive in the preparation of concrete. Filler glass additive percentages by weight relative to cement were 0, 5, 10 and 15. The water: cement ratio was 0.45 and the type of cement employed was Portland 42.5. After the concrete specimens were cured for 7, 28 and 56 days the compressive strength, indirect tensile strength, 28 and 56 days water absorption and capillary permeability parameters were measured. Dynamic modulus of elasticity was also determined for the 28 days-cured specimens by ultrasound test. The results showed that the concrete specimens with 15 % glass gave better results than 10 % glass substitution in terms of compressive strength, indirect tensile strength, water absorption and capillary permeability. Consequently, it was observed that the relative properties were improved by adding the filler glass as 10 and 15 % unlike 5 % incorporation. Introduction The performance of concrete where glass filler is used as a partial replacement has seldom been reported. Improvement in concrete strength has generally meant the better mechanical properties of concrete. Concrete codes and standards specify the fine material requirements necessary to obtain adequate strength values on which pores have detrimental effects. It has been gathered that the improving effect of micro filler materials on mechanical properties of concrete was due to their ability to decrease pores [1].Some glasses of the SrO-MgO-ZrO2-SiO2 (SMZS) system are well characterised with their high endurance against alkali solutions [2-8]. Therefore, the use of their aggregates in combination with fly ash as an additive in concrete reinforcement was previously reported to be possible [9]. SrO content which slightly worsens durability was gradually replaced by Mn2O3 and/or Fe2O3 in the chemical compositions and new SrO-Mn203-Fe203-MgO-ZrO2-SiO2 (SMFMZS), SrO-Mn203-MgO-ZrO2-SiO2 (SMMZS) and SrO-Fe203-MgO-ZrO2-SiO2 (SFMZS) system glasses were produced, characterised and also examined to determine their alkali resistance. Then, it was found that some glasses of the SFMZS system exhibited very high endurance. The main objective of the study was to investigate the effect of the most resistant glass in this system as a filler material on the behaviour of concrete. Experimental Materials. The filler glass produced at the Department of Materials Science and Engineering of Anadolu University was used in the current study. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 2169-2172 doi:10.4028/www.scientific.net/KEM.264-268.2169

Geotekstil, Geogrid ve Çelik Şerit Donatılı Şevlerde Modelleme Çalışması

Zeminin dogal kosullarinin degismesi, yuksek miktarda hafriyat gerektiren otoyol ve demiryolu kenarlari veya destekli kazilardaki sev stabilitesi projelerinde beklenmedik gerilme artislarina neden olmaktadir. Bu islem sirasinda farkli yukleme durumlarinda bazi guvenlik sorunlari olusabilmektedir. Ek olarak, sev stabilitesi tasarimi ekonomik cozum gerektirmektedir. Şev destek yapilari icin bu onemli gereksinimler goz onunde bulundurularak en efektif tasarim yapilmalidir. Bu calismada; kapsamli bir literatur taramasinin ardindan, donatili zemin yapisinin on kisminda yer alan derin kazilar dikkate alinarak sev stabilitesi problemi tum yonleriyle incelenmistir. Geotekstil (GT), geogrid (GG) ve celik serit (SS) donatilar, hem deney surecinde hem de Plaxis yazilimi ile modelleme asamasinda sevin stabilite kosullarinin arttirilmasi isleminde kullanilmistir. Her donati tipi zemin tasima kapasitesi artisi saglamis ve kendine has yer degistirme davranisi gostermistir. Dolayisiyla, sunulan degerlere gore tasima kapasitesi ve yer degistirme gereklilikleri dogrultusunda, tasarim islemi ve sahadaki insa surecinde en efektif donati elemani secilebilecektir.

Use of Sepiolite and Zeolite Mixtures as a Landfill Liner

This study presents an investigation into the possibility of using sepiolite and zeolite mixtures to design a landfill liner. Leakage from the impervious layer into the environment is the main difficulty of storing hazardous waste. Therefore, determining the impermeable layer and in-situ application procedure is very important and needs laboratory experimentation. For this purpose, a series of experiments have been conducted on a mixture of zeolite+sepiolite. The geotechnical, physico-chemical and micro-structural properties of 30% sepiolite by weight of zeolite have been determined through laboratory testing. At the end of the research, the results show that zeolitesepiolite mixtures can be effectively used in bottom lining systems for hazardous, industrial and municipal waste.