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

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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.
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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.
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Burak Uzal
Properties and hydration of cementitious systems containing low, moderate and high amounts of natural zeolites · 2007 · 194 sayfa.
Danışman: Doç. Dr. Lutfullah Turanlı ; Prof. Dr. Hayrettin Yücel
Bu araştırmanı devamına: http://tez2.yok.gov.tr/tez.htm adresinden ulaşabilirsiniz.