Refractory concretes of chemical bond with diverse aggregates

N. HIPEDINGER, A.N. SCIAN Y E.F. AGLIETTI.

Procedia Materials Science

Elsevier Ltd.

Lugar: Amsterdam; Año: 2012 vol. 1 p. 425 - 431

2211-8128

Abstract In this work three cold-setting refractory concretes using the chemical magnesia-phosphate bond were prepared. A mixture of calcined alumina, microsilica, magnesium oxide and phosphoric acid was designed to form cordierite during the heating. This cementitious paste acts like a matrix in which the aggregates are embedded. Three different aggregates were used: cordierite-mullite (C), mullite chamotte (M) and tabular alumina (T) with the objective to analyze its behaviour and the matrix-aggregate interaction. These concretes set at room temperature, being observed by XRD, in addition to the typical reflections of each aggregate, the presence of MgHPO4·3H2O (newberyite) in low proportion and predominantly amorphous phase. At 110 °C were not detected crystalline hydrated phosphates. At 1100 °C was formed aluminium orthophosphate, AlPO4 cristobalite type. At 1350 °C the matrix was transformed into cordierite-mullite, being also detected small amounts of Mg3(PO4)2. Although the phases developed in the matrix during heating were similar for three concretes, performance at elevated temperatures was different. The possible causes of unsatisfactory behaviour of concretes made with aggregates of mullite chamotte and tabular alumina were analyzed. The main properties of concrete made with cordierite-mullite aggregates were presented.