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Abstract
In order to increase the recycling of phosphogypsum waste, this study explored the feasibility of using phosphogypsum to replace some of the lime and aggregate in the lime‐fly ash‐crushed stone mixture which is a widely used road base material in China. For this purpose, compaction, compressive strength, composition structures, wetting‐drying cycle tests, and shrinkage tests were carried out on the lime‐fly ash‐phosphogypsum‐crushed stone composite to investigate its performance. The results indicate that lime‐fly ash‐crushed stone modified with phosphogypsum has the required strength of the road base material and favourable performances in environment (wetting‐drying cycle) stability. The image processing analysis and shrinkage tests demonstrated that phosphogypsum can significantly improve the compactness and shrinkage performance of lime‐fly ash‐crushed stone mixture. A suitable content of phosphogypsum and a reasonable content of fine aggregate are conducive to improving the roadway engineering properties (i.e., decreasing shrinkage cracks and increasing compressive strength) of lime‐fly ash‐phosphogypsum‐crushed stone composites.
Highlights
Phosphogypsum (PG) a by-product from the phosphoric acid industry is a remarkable solid waste, and about 4.5–5.0 tonnes of dry-based PG is outputted per ton of phosphoric acid recovered [1]
PG was used to replace some amount of the lime and aggregate in the typical lime-fly ash (FA)-CS mixture without changing the dense skeleton structure. e properties and performance of lime-FA-PG-CS composite used as road base material were investigated to prepare it for the wider application
Its mechanical property, composition structures, and volume stability are investigated comparing with the typical lime-FA-CS mixture
Summary
Phosphogypsum (PG) a by-product from the phosphoric acid industry is a remarkable solid waste, and about 4.5–5.0 tonnes of dry-based PG is outputted per ton of phosphoric acid (as P2O5) recovered [1]. Erefore, PG is usually used together with FA and lime to increase strength and reduce shrinkage cracks of road base (or subbase) materials. The content of PG should not be very high because of the expansivity of ettringite [8,9,10] Most of these studies focused on the modification of PG for lime-FA binder or lime-FAstabilized soils. Lime-FA-CS (or gravel) is a widely used road base material in China [11, 12], and it has many advantages such as steady strength development, simple construction, and the utilization of waste FA, but the shrinkage cracks often occur, and the early strength of it is very slow. PG was used to replace some amount of the lime and aggregate in the typical lime-FA-CS mixture without changing the dense skeleton structure. e properties and performance of lime-FA-PG-CS composite used as road base material were investigated to prepare it for the wider application
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