Lime activated flyash-phosphogypsum blend as a low-cost alternative binder

Area of Science:

• Materials Science
• Civil Engineering
• Waste Management

Background:

• Industrial solid wastes like phosphogypsum and fly ash present disposal challenges.
• Developing sustainable binders from waste materials is crucial for the construction industry.
• Lime activation is a common method for utilizing industrial byproducts in binders.

Purpose of the Study:

• To investigate the feasibility of using a blended binder made from phosphogypsum and fly ash activated with lime.
• To determine the optimal mix proportions for maximizing the strength of the blended binder.
• To compare the performance of the blended binder with conventional materials.

Main Methods:

• Investigated three mix proportions of phosphogypsum and fly ash with varying lime content.
• Determined minimum lime content using the Eades and Grim pH test.
• Cast paste and mortar specimens, cured for seven days, and tested compressive strength.
• Evaluated masonry prism strength and performed X-ray diffraction analysis on the optimal blend.

Main Results:

• The optimal blend consisted of 5% lime with a 3:1 ratio of fly ash to phosphogypsum.
• This optimal blend exhibited higher compressive strength than conventional Portland cement and lime mortar.
• Masonry prisms made with the optimal blend showed strength comparable to Portland cement mortar masonry.

Conclusions:

• A sustainable and high-strength binder can be formulated from phosphogypsum and fly ash.
• The optimal blend's strength is attributed to the formation of calcium silicate hydrate, ettringite, and portlandite.
• This research offers a promising alternative for utilizing industrial solid wastes in construction applications.