Mechanisms of k-struvite formation in magnesium phosphate cements

The formation of magnesium phosphate cements is based on an acid-base reaction between potassium dihydrogen phosphate and magnesium oxide. The reaction leads to the formation of k-struvite as main product. These cements, due to their specific properties, represent an interesting alternative solution for niche applications, such as cold weather repair materials or waste treatment materials. However, scarce information is found in the literature when it comes to certain aspects linked to the consolidation of the material. The main purpose of this study is thus to better understand the influence of both the pH and the species that are present in solution on the precipitation of the k-struvite. The present study highlights the fact that the consolidation of the material involves the formation of an initial transition phase. Indeed throughout the reaction, newberyite is first formed. With the pH increase, newberyite is dissolved, and these conditions enhance the crystallization of k-struvite. (C) 2016 Elsevier Ltd. All rights reserved.