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 40mm × 40mm × 40mm 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.
Highlights
According to a United Nations Environment Programme survey, 1.4 billion tons of waste glass is discarded each year, including flat glass, daily glassware, and glass packaging containers, accounting for more than 80% of glass products [1]
The results indicate that the alkali component of glass powder (GP) is involved in the magnesium ammonia phosphate cement (MAPC) reaction
Glass powder was added to the system as a replacement for MgO, because of its non-absorbent surface and acid resistance [2], and it did not participate in the hydration of MKPC paste in the early reaction
Summary
According to a United Nations Environment Programme survey, 1.4 billion tons of waste glass is discarded each year, including flat glass, daily glassware, and glass packaging containers, accounting for more than 80% of glass products [1]. Most of these waste glasses consist of broken glass and substandard glass in production, and the random disposal of these glasses can cause great harm to the environment [2]. The studies of some scholars show that polypropylene fiber and silica fume [7,8], untreated coal and recycled aggregate [9], and untreated coal gangue [10] can improve the performance of concrete. For the application and development of waste glass, as early as the 1960s, attempts were made to apply waste glass in concrete [11,12], replacing fine aggregates
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