Influence of perlite addition on the strength development and thermal stability of calcium aluminate cement mortars

Download

index.pdf

Date

2018

Author

Şengül, Kemal

Metadata

Show full item record

Item Usage Stats

236
views

160
downloads

Calcium aluminate cement is a special cement that reaches high strength in a short time but suffers a considerable loss of strength due to moisture and temperature-related conversion of metastable calcium aluminum hydrates. The study aimed to produce stratlingite as a stable hydration product to completely stop or reduce this chemical conversion using an inexpensive and abundant silica source. Ground perlite was chosen as the source of silica. Perlite was mixed with calcium aluminate cement in different proportions and two different water-to-binder ratios. The paste and mortar samples obtained were cured under different temperature and humidity conditions. Na2SO4 and Ca(OH)2 were also added in small quantities to these mixtures to investigate their influence on strength development and hydrated phases at early ages. A strength loss is observed in the pure cement samples due to conversion, after 20-30d for the dry-cured samples but after only 2-3d for the wet-cured samples. The loss is small and slow (<10-20 %) for the dry-cured samples, but quite significant (up to ~ 80 %) and rapid in wet-cured cases. As the amount of ground perlite that replaces the cement increases strength decreases. However, the early strength gained is maintained more for the perlite-incorporated mixtures. Stratlingite formation is confirmed by X-ray diffraction analysis in several of the perlite-containing mixtures. Loss of strength was completely prevented by the addition of 1-2 % Na2SO4 to mixtures containing more than 50 % perlite. Addition of Ca(OH)2 was not very effective against conversion, however, it greatly reduced setting time. Addition of perlite also decreased setting time. In contrast, Na2SO4 addition delayed setting. The heat of hydration decreased with increasing perlite content. Although the addition of perlite or chemicals proved beneficial, none of the mixtures were able to maintain a significant portion of their original strengths or masses after exposure to 600 ℃ or 1100 ℃.

Subject Keywords

Cement., Perlite., Calcium aluminate., Cement

URI

http://etd.lib.metu.edu.tr/upload/12621802/index.pdf
https://hdl.handle.net/11511/27057

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Influence of ground perlite on the hydration and strength development of calcium aluminate cement mortars Şengül, Kemal; Erdoğan, Sinan Turhan (Elsevier BV, 2021-01-10) © 2020 Elsevier LtdCalcium aluminate cement (CAC) concretes are desirable owing to their rapid strength development and resistance to high temperatures, sulfates and acids. They suffer two drawbacks, however, high cost and strength loss due to conversion of water-rich hydration products to more stable structures, resulting in a drop in strength. Although its rate is dependent on temperature and moisture, the conversion process is thermodynamically inevitable but can be prevented by adding sufficient quantit...
Effect of trass, granulated blast furnace slag and fly ash on delayed ettringite formation Topbaş, Selim; Tokyay, Mustafa; Hoşten, Çetin; Department of Cement Engineering (2010) Properly proportioned, placed and cured concrete can be durable under most conditions. However, deterioration of concrete does occur under certain environments. One of the problems that affect the durability of hardened concrete is delayed ettringite formation (DEF) which is an important problem encountered in precast concrete industry where high temperature curing is applied. Although there had been many researches on DEF, there are still many uncertainties about its chemistry and mechanism. In this study,...
Chemical preparation of carbonated calcium hydroxyapatite powders at 37 degrees C in urea-containing synthetic body fluids Bayraktar, D; Tas, AC (1999-01-01) An important inorganic phase of synthetic bone applications, calcium hydroxyapatite (HA, Ca-10(PO4)(6)(OH)(2)), was prepared as a single-phase ceramic powder. Carbonated HA powders were formed from calcium nitrate tetrahydrate and diammonium hydrogen phosphate salts dissolved in aqueous 'synthetic body fluid' (SBF) solutions, containing urea (H2NCONH2), at 37 degrees C and pH of 7.4, by using a novel chemical precipitation technique. These powders were also found to contain trace amounts of Na and Mg impuri...
Compressive strength development of calcium aluminate cement-GGBFS blends Kirca, Onder; Yaman, İsmail Özgür; Tokyay, Mustafa (2013-01-01) The compressive strength development of calcium aluminate cement (CAC) and ground granulated blast furnace slag (GGBFS) blends that were subjected to different curing regimes are investigated. The blends had GGBFS/CAC ratios between 0% and 80%, by mass. Mortar specimens, prepared with a water:binder:sand ratio of 1:2:6, were subjected to seven different curing regimes and the compressive strengths were monitored up to 210 days. In order to understand the effect of temperature on compressive strength develop...
Effect of mixture proportioning on the strength and mineralogy of magnesium phosphate cements Bilginer, Baki Aykut; Erdoğan, Sinan Turhan (Elsevier BV, 2021-3) Magnesium potassium phosphate cement (MKPC) has properties advantageous over ordinary portland cement such as quick setting and rapid strength gain. Although the effect of mixture proportioning on MKPC pastes has been studied, there are conflicting reports on how calcination of magnesia, parameters like magnesium-to-phosphate ratio (M/P) and water-to-binder ratio (W/B), added materials like borax and fly ash, or the addition of sand influence mineralogy and properties like setting and strength. These factor...

Citation Formats

K. Şengül, “Influence of perlite addition on the strength development and thermal stability of calcium aluminate cement mortars,” M.S. - Master of Science, Middle East Technical University, 2018.