Effect of aggregates and water contents on the properties of magnesium phospho-silicate cement.pdf
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Cement Concrete Composites 27 (2005) 11–18
/locate/cemconcompEffect of aggregates and water contents on the properties
of magnesium phospho-silicate cement
Zhu Ding, Zongjin Li *
Department of Civil Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
Received 16 May 2003; accepted 2 March 2004Abstract
Properties of magnesium phospho-silicate cement (MPSC) mortars with different fine aggregates, and different water contents
were investigated in the present work. Three types of fine aggregates, natural sand, dead burnt magnesia and alumina particles were
used. Two types of hard burnt magnesia powder with MgO content 89.51 and 71.50 wt.% were used as binder. Compressive strength
of MPSC mortar with different water/binder ratios were determined at ages of 1, 3, 7, and 24 h. The 3, 7, and 28 day compressive
strength and modulus of elasticity were also tested. It was found that the compressive strength of MPSC mortar decreases with the
increase of sand content, regardless of sand type. However, the strength reduction of MPSC mortars formed with magnesia and
alumina sand was much smaller than that of mortars formed with natural sand. Moreover, in spite of the raw materials, compressive
strength and elastic modulus of MPSC decreased with the increase of water/binder ratio at all ages. The hydrate products were
analysed by XRD and TG-DTA, and the porosity of MPSC mortar was analysed by MIP. Results showed total porosity increased
with the increase of water content. The content of hydrate product of MPSC, phosphate hexahydrate, also increased with the
increase of water content. However, it seems that the change of mechanical properties of MPSC is mainly controlled by increase of
total porosity which was determined by water content.
2004 Elsevier Ltd. All rights reserved.
Keywords: Magnesium phosphate cement; Fly ash; Aggregate; Water content; Microstructure1. Introduction
Cements made from magnesia have been developed
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