Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement

Abstract

Waste glass is a bulk solid waste, and its utilization is of great consequence for environmental protection; the application of waste glass to magnesium phosphate cement can also play a prominent role in its recycling. The purpose of this study is to evaluate the effect of glass powder (GP) on the mechanical and working properties of magnesium potassium phosphate cement (MKPC). Moreover, a 40 mm × 40 mm × 40 mm mold was used in this experiment, the workability, setting time, strength, hydration heat release, porosity, and microstructure of the specimens were evaluated. The results indicated that the addition of glass powder prolonged the setting time of MKPC, reduced the workability of the matrix, and effectively lowered the hydration heat of the MKPC. Compared to an M/P ratio (MgO/KH2PO4 mass ratio) of 1:1, the workability of the MKPC with M/P ratios of 2:1 and 3:1 was reduced by 1% and 2.1%, respectively, and the peak hydration temperatures were reduced by 0.5% and 14.6%, respectively. The compressive strength of MKPC increased with an increase in the glass powder content at the M/P ratio of 1:1, and the addition of glass powder reduced the porosity of the matrix, effectively increased the yield of struvite-K, and affected the morphology of the hydration products. With an increase in the M/P ratio, the struvite-K content decreased, many tiny pores were more prevalent on the surface of the matrix, and the bonding integrity between the MKPC was weakened, thereby reducing the compressive strength of the matrix. At less than 40 wt.% glass powder content, the performance of MKPC improved at an M/P ratio of 1:1. In general, the addition of glass powders improved the mechanical properties of MKPC and reduced the heat of hydration.

High-Temperature Resistance of Modified Potassium Magnesium Phosphate Cement

“…The greater the MgO content, the shorter the setting time of MKPC, which indicates that the setting time is related to the concentration of Mg 2+ in the cementitious material. The greater the MgO content, the faster its dissolution rate, the more favorable the hydration reaction, the more Mg 2+ enters the cementitious, and the shorter the setting time [24,25].…”

“…the cementitious material. The greater the MgO content, the faster its dissolution rate, the more favorable the hydration reaction, the more Mg 2+ enters the cementitious, and the shorter the setting time [24,25].…”

“…When the silica fume admixture is less than 10%, the flexural strength of the specimens basically no longer increases compared with the MKPC net paste. This is because when M:P is small, MgO reacts with KH 2 PO 4 to generate more products, which is the main provider of the strength of MKPC [24], and the admixture of silica fume plays the role of filling the pores of the matrix. When M:P is greater than 2:1, the products generated by the reaction between MgO and KH 2 PO 4 are reduced and more unreacted MgO remains [25,33], which leads to a decrease in the strength of MKPC.…”

Processing of End-of-Life Materials and Industrial Wastes

“…Deng et al [ 7 ] contributed with an article, entitled “Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement”. Huge amounts of waste glass, including, especially, flat glass, daily glassware and glass packaging containers, are discarded in the world.…”

Hydration Behavior of Magnesium Potassium Phosphate Cement: Experimental Study and Thermodynamic Modeling

“…Compared with ordinary Portland cement, MPC has numerous outstanding properties, e.g. high strength at an early age [ 4 , 5 , 6 ], rapid setting [ 7 ], strong bonding to concrete substrates [ 8 , 9 , 10 ], and excellent durability [ 11 ]. Therefore, it is widely used in various fields, including the repair of civil structures [ 7 ], the stabilization/solidification (S/S) of low-level nuclear wastes and heavy metal wastes [ 12 , 13 , 14 ], treatment of waste water [ 15 ] and restorations of teeth and bones [ 16 , 17 , 18 ].…”