Effect of characteristics of natural zeolites on their geopolymerization

The properties of clinoptilolite-based geopolymers are investigated with a focus on the parameters affecting the reactivity of clinoptilolite in a geopolymer binder. A complete characterization of raw materials was carried out as well as a determination of the mineralogical composition, microstructure and mechanical properties of geopolymers. The results of the investigation show that of the investigated materials, geopolymer made with clinoptilolite-bearing tuff from Bayburt has the highest compressive strength. The chemical and mineralogical characteristics of a raw material are important parameters that potentially control the geopolymeric reaction, whereas physical properties (particle size and BET specific surface area) are mainly influential at early stages of geopolymerization. Geopolymeric gel was found to be the main reaction product through characterization by XRD and SEM analysis. The geopolymer produced with the raw material from Bayburt had a narrow range of Si/Al ratios and possessed a geopolymer binder structure with an advanced nature. Lastly, in addition to clinoptilolite, feldspar has an additional effect on the geopolymeric reaction and enhances the process, especially at later ages

Role of inclusion size distribution of titanium dioxide on the nitrogen oxides reduction capability and microstructural characteristics of cementitious systems

This paper explores the effect of the inclusion size of titanium dioxide (TiO2) particles on a variety of performance properties of cementitious systems via experimental studies. In addition to comprehensive microstructural analysis including pore size distribution and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analyses, particular consideration was given to the effect of particle size distribution (PSD) of TiO2 particles on mechanical and photocatalytic properties and hydration kinetics of cementitious systems. Nano-sized, submicron-sized and micron-sized anatase-phase TiO2 powders were utilized as photocatalysts at a dosage of 5% by total weight of powder material. In addition to the single use of TiO2 particles with three different size ranges (nano, submicron and micron), they were also used in combination by adjusting their PSDs with three different PSD moduli (q): 0.1, 0.5, and 0.9. Test results show that techniques for achieving optimal microstructural characteristics of cementitious systems also help design and improve their performance in favor of multifunctionality. As a result of PSD optimization of TiO2 particles with three different size ranges, which was significantly influential on the microstructure of the cementitious systems, superior photocatalytic degradation results were obtained from mixtures containing lower amounts of nano-sized TiO2 particles. Cementitious composites with denser microstructure showed lower performance in terms of being able to maintain photocatalytic degradation capability for a prolonged period, whereas the opposite was the case for compressive strength. © 2021 Elsevier Lt

Doğal zeolitlerin inşaat endüstrisinde kullanımı

TÜBİTAK MAG01.07.2007İnşaat sektöründe önceleri boyutlandırılmış yapı taşı olarak kullanılan doğal zeolitlerin , son yıllarda çimento/betonda ilave bağlayıcı katkı malzemesi olarak ve bunun yanı sıra hafif agrega olarak kullanımı daha yaygın hale gelmeye başlamıştır. Öte yandan doğal zeolit içeren çimento ve beton sistemlerinin hidratastonu ve özellikleri konusunda literatürde kısıtlı bilgi bulunmaktadır. Özellikle Türkiye’deki başlıca doğal zeolit rezervlerine ait malzemeleri içeren çimento ve beton sistemleri konusunda sistematik bilgi bulunmamaktadır. Bu projede, Türkiye’deki doğal zeolitlerin inşaat endüstrisinde kullanımının yaygınlaştırılması amacıyla, Türkiye doğal zeolitlerinin puzolanik katkı maddesi olarak çimento-beton endüstrisinde ve hafif yapı malzemeleri üretiminde hafif agrega olarak kullanılabilirliğinin araştırılarak bu konuda uygulama için gerekli bilimsel verilerin elde edilmesi amaçlanmıştır. Bu amaçla; öncelikle Türkiye’deki başlıca iki doğal zeolit rezervinden (Manisa/Gördes, Balıkesir/Bigadiç) temin edilen doğal zeolitlerin karakterizasyonu yapılmış ardından bu malzemelerin puzolanik aktiviteleri, değişik (düşük, orta, ve yüksek) miktarlarda doğal zeolit içeren katkılı çimentoların ve beton karışımlarının özellikleri tespit edilerek değerlendirilmiştir. Ayrıca bu malzemelerin hafif agrega olarak kullanımlarına yönelik özellikleri de tespit edilerek değerlendirilmiştir. Deneysel çalışmalar sonucunda; çalışmalarda kullanılan Gördes ve Bigadiç doğal zeolitlerinin önemli düzeyde puzolanik aktivite gösterdikleri ve bu durumun muhtemelen onların reaktif SiO2 içerikleriyle ve yüksek BET yüzey alanlarıyla ilişkili olduğu; doğal zeolit katkılı portland çimentolarının normal portland çimentosuna kıyasla daha hızlı ilk ve son priz süreleri gösterdikleri ve bu durumun doğal zeolitlerin yüksek BET yüzey alanlarının bir sonucu olarak ortaya çıktığı; doğal zeolit ikamesinin çimento hamurlarının gözenek boyut dağılımını küçülttüğü ve bunun sonucunda çimento hamurlarının basınç dayanımı ve geçirimsizliğini artırdığı; doğal zeolitler sayesinde sadece 180 kg/m3 portland çimentosu iii dozajı kullanılarak 7 günlük basınç dayanımı 25 MPa, 28 günlük basınç dayanımı ise 45-50 MPa düzeyinde olan beton karışımları hazırlanabildiği ve bu beton karışımlarının klor-iyonu geçirgenliklerinin çok düşük olduğu tespit edilmiştir. Ayrıca Gördes doğal zeolitinin temel fiziksel özellikleri açısından hafif agrega olarak kullanılabileceği ancak alkali-silika reaktivitesi açısından, hızlandırılmış metot ile test edildiğinde güvenli görünmesine rağmen bu konuda tedbirli olunması gerektiği tespit edilmiştir.Use of natural zeolites as supplementary cementing material and lightweight aggregate in building industry has become popular in recent years, which are previously utilized as only dimension stone. On the other hand, there are limited information on properties and hydration of cement and concrete systems containing natural zeolites in published literature. Specifically, there are no systematical information on cementitious systems containing natural zeolites from major zeolite deposits in Turkey. In this project, in order to promote the widespread use of Turkish natural zeolites in building industry, it was aimed to investigate the potential use of Turkish natural zeolites as pozzolanic admixture in cement/concrete industry and as a lightweight aggregate in production of lightweight materials of construction. For these purposes, a detailed characterization of natural zeolites obtained from two major deposits (Manisa/Gördes, Balıkesir/Bigadiç) in Turkey was made and then their pozzolanic activity as well as the properties of blended cements and concretes containing various amounts of zeolites were determined. In addition, the properties of the natural zeolites as lightweight aggregate were also determined. Experimental studies indicated that the following conclusions; Gördes and Bigadiç zeolites used in the study exhibited considerable pozzolanic activity probably as a result of their reactive SiO2 contents and relatively high BET surface area; natural zeolite blended cements showed faster initial and final setting time when compared to ordinary portland cement, which is associated with high BET surface area of natural zeolites; natural zeolite replacement refined the pore size distribution of cement pastes and therefore improves their strength and impermeability; use of natural zeolites provided a concrete mixture, made with only 180 kg/m3 portland cement dosage, having 7-day compressive strength of 25 MPa, 28-day compressive strength of 45-50 MPa, very low chloride-ion permeability. In addition, it was v also determined that Gördes zeolite is proper to use as lightweight aggregate in terms of physical properties, however, it should be taken preventive precautions against alkali-silica reaction in spite of the fact that it appears safe when tested with the accelerated method

Düşük, orta ve yüksek miktarlarda doğal zeolit içeren bağlayıcı sistemlerin özellikleri ve hidratasyonu.

The extent of the benefits provided by use of SCMs in cementitious systems increases as their percentage amounts in total binder increases. However, the proportion of SCMs in cementitious systems is limited, especially for natural pozzolans, by some factors such as increase in water requirement and decrease in rate of strength development. Therefore investigations are needed to increase the amount of natural pozzolans in blended cements or in concrete as much as possible without decreasing their performance. This aim requires studies on cementitious systems with more reactive natural pozzolans than widely-used ones. The objective of the study was to investigate the pozzolanic activity of natural zeolites (clinoptilolite) from two localities in Turkey, and properties of cementitious systems containing low (15%), moderate (35%) and high (55%) amount of them. The study covers characterization of the natural zeolites used, evaluation of their pozzolanic activity in comparison with some popular mineral admixtures, and properties of pastes, mortars, and concrete mixtures containing low, moderate, and high amounts of natural zeolites. Reactivity of the natural zeolites with Ca(OH)2 was found to be higher than those of the fly ash and the non-zeolitic pozzolan, but lower than that of the silica fume. Natural zeolite blended cements were characterized with the following highlighted properties; faster setting than portland cement, low amounts of Ca(OH)2 and capillary pores larger than 50 nm in hardened pastes, relatively dense microstructure of hardened paste than portland cement, more compatibility with melamine-based superplasticizer than being with naphthalene-based one, and excellent compressive strength performance. Concrete mixtures containing natural zeolites as partial replacement for portland cement were characterized with the following properties; 7-day compressive strength of ~25 MPa and 28-day strength of 45-50 MPa with only 180 kg/m3 portland cement and 220 kg/m3 zeolite dosages (55% replacement), comparable modulus of elasticity with plain portland cement concrete, “low” and “very low” chloride-ion penetrability for low and large levels of replacement, respectively.Ph.D. - Doctoral Progra

Effect of mineralogical composition of clinoptilolite-bearing tuffs on their performance as a natural pozzolan in cementitious systems

In this study, pozzolanic reactivity and strength activity of zeolitic tuffs containing similar amount of zeolitic phase (clinoptilolite) and different types and amounts of impurities were examined in order to understand the role of mineralogical composition in the efficiency of zeolitic natural pozzolans. Mineralogical and chemical compositions as well as the physical properties of the zeolitic tuffs were determined. Their pozzolanic reactivity were measured as depletion of calcium hydroxide in the pastes containing lime and zeolitic tuff, which is determined by thermogravimetric analysis. Furthermore, compressive strength of blended cement mortars prepared with 20% replacement of Portland cement by finely ground tuffs were determined at 7, 28 and 56 days of age. It was demonstrated that the type and amount of impurities in mineralogical composition of zeolitic tuffs are significantly effective on their early pozzolanic reactivity. Zeolite mineral content, however, is more determinative on long term reactivity. For a strength activity, mineralogical composition was clearly effective on the preparation of mortar samples, which depends on water requirement of zeolitic tuffs

Practical charts to identify the predominant clay mineral based on oxide composition of clayey soils

WOS: 000390621800059This study proposes some useful practical charts representing the relationships between oxide composition and the type of predominant clay mineral present in clay soils. In order to produce the charts, the data set are collected from published literature. Some useful classification schemes for predominant clay mineral type were obtained by using binary and ternary graphs of oxide composition data. The most successful relations indicating the type of clay mineral have been found on SiO2 versus Al2O3 + Fe2O3 + FeO, SiO2 versus MgO + CaO + Na2O + K2O binary plots, SiO2 Al2O3 Others and SiO2 - Al2O3 - K2O ternary plots. (C) 2016 Elsevier B.V. All rights reserved

High-volume natural pozzolan concrete for structural applications

This paper presents the results of preliminary studies on concrete mixtures containing high volumes of natural pozzolan-(50%- by mass of total cementitious materials) for- structural applications. Three different kinds, of natural pozzolans from. Turkish deposits were used to prepare the high-volume natural pozzolan (HVNP) concrete. mixtures. Two additional mixtures with a high-volume of low-calcium fly ash and granulated blast-furnace slag were also prepared for comparison purposes. In addition, a conventional portland cement concrete mixture was prepared as a reference. The dosage required for a high-range water-reducing admixture for a given slump, air content, setting time, compressive strength, splitting-tensile strength, and resistance to chloride-ion, penetration was determined for the mixtures. Preliminary results indicated that the high-volume natural pozzolan concrete mixtures studied are suitable for structural concrete applications with 1.74 to 2.03 ksi (12 to 14 MPa) and 4.21 to 5.51 ksi (29 to 38 MPa) compressive strengths at 3 and 28 days, respectively