Properties and hydration of cementitious systems containing low, moderate and high amounts of natural zeolites

Download
index.pdf
2007
Uzal, Burak
Show full item record
240
views
81
downloads
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.
Concrete.
http://etd.lib.metu.edu.tr/upload/12608974/index.pdf
https://hdl.handle.net/11511/17153
Graduate School of Natural and Applied Sciences, Thesis

Suggestions

Production of aerated alkali-activated slag pastes and mortars using hydrogen peroxide
Şahin, Murat; Erdoğan, Sinan Turhan; Bayer, Özgür; Department of Civil Engineering (2017)
Utilization of ground granulated blast furnace slag (GGBFS) through alkali activation for the production of construction materials can provide economic and environmental advantages. In this study, cement-free lightweight composites based on the alkali activation of GGBFS were produced with the incorporation of hydrogen peroxide, and their physical, thermal, and mechanical properties were investigated, under different curing conditions. Various water-to-slag ratios (W/S), hydrogen peroxide contents, and sand...
Effect of Synthetic Fibers on Energy Absorption Capacity of Normal and High Performance Concrete
Şengün, Emin; Alam, Burhan; Yaman, İsmail Özgür (null; 2016-06-08)
With the increasing aim of incorporating concrete in different applications and infrastructure elements, the use of macro synthetic fiber incorporated concretes has become real popular thanks to their high energy absorption capacity, toughness and impact resistance. The aim of this study is to investigate the effects of synthetic fibers on toughness and energy absorption of normal and high performance concretes. For this experimental study, eight concrete groups were designed using synthetic fibers of vario...
Use of dynamic modulus of elasticity to assess the durability of self consolidating concrete
Özerkan, N.G.; Yaman, İsmail Özgür (2012-12-01)
This paper presents the effect of freezing-thawing on self consolidating concrete (SCC) that contains different percentages of fly ash (FA) and air entraining agents (AEA). The effect of freezing-thawing on concrete is assessed on the basis of the change in the dynamic modulus of elasticity. The dynamic modulus of elasticity is determined from both ultrasonic pulse velocity and resonant frequency tests. An in-house resonant frequency test apparatus was developed using an accelerometer and a data acquisition...
Effect of synthetic fibers on flexural performance of normal and high performance concrete
Şengün, Emin; Alam, Burhan; Yaman, İsmail Özgür (null; 2016-09-19)
Macro synthetic fiber incorporated concretes are increasingly used for concrete applications owing to their high energy absorption capacity, toughness and impact resistance. The aim of this study is twofold; first to investigate the effects of synthetic fibers on the flexural performance and thus the energy absorption characteristics of normal and high performance concrete (HPC), and secondly to investigate the effects of specimen size. For this experimental study, eight concrete groups were designed using ...
Effectiveness of R&D tax incentives in Turkey
Taş, Ekin; Erdil, Erkan; Department of Economics (2021-7)
The aim of this study is to investigate the effectiveness of research and development (R&D) tax incentives in generating additional business R&D expenditures in Turkey by applying propensity score matching (PSM) to correct any selection bias and to estimate the average treatment effect on the treated (ATT). For this purpose, the hypothesis that “R&D tax incentives increase business sector R&D intensity (the ratio of firm’s net R&D expenditures to total turnover)” is tested and the effectiveness of R&D tax i...
Citation Formats
B. Uzal, “Properties and hydration of cementitious systems containing low, moderate and high amounts of natural zeolites,” Ph.D. - Doctoral Program, Middle East Technical University, 2007.
METU IIS - Integrated Information Service open@metu.edu.tr