Strength – Formulation Correlations in Magnesium Phosphate Cements for Nuclear Waste Encapsulation

The Influence of the Magnesium-to-Phosphate Molar Ratio on Magnesium Potassium Phosphate Cement Properties Using Either Wollastonite or Volcanic Ash as Fillers

“…Several authors related the strengthening to the formation of K-struvite, which occurs during the first days of the acid-base chemical reaction [7,43] and develops, thereafter, slowly with the associated consumption of remaining MgO. No other crystalline mineral phases other than K-struvite were observed, neither in the present study nor in previous works [7,28].…”

“…Several authors related the strengthening to the formation of K-struvite, which occurs during the first days of the acid-base chemical reaction [7,43] and develops, thereafter, The MKPC formulations including volcanic ash presented K-struvite crystals with irregular tabular morphologies at the three Mg/P molar ratios, although the crystal sizes were not much larger at higher Mg/P ratios (Figure 7a-c). The colour maps also confirmed that K-struvite was the predominant phase formed in the formulations with volcanic ash, although coexisting with accessory minerals initially present in the filler, mostly silicates and silicoaluminates (identified by the orange colour in Figure 7d).…”

Response to the discussion by Hongyan Ma and Ying Li of the paper “Characterization of magnesium potassium phosphate cement blended with fly ash and ground granulated blast furnace slag”

“…The motivation for our investigation of MPKCs is primarily directed toward application in the encapsulation of radioactive wastes. The mix proportions and water-to-solids ratio used in our study are common for MKPCs developed for such applications [3][4][5][6][7], in which high flow and controlled heat release are essential characteristics of the mix design. Our contribution [1], was therefore intended to establish the properties of a tightly controlled MKPC formulation envelope suitable for UK nuclear waste streams, rather than for civil engineering applications.…”