Environmental investigation on the use of a phosphogypsum-based road material: Radiological and leaching assessment.

The transformation of phosphate ore into phosphoric acid results in the generation of high volumes of phosphogypsum (PG), an industrial by-product largely stockpiled worldwide. This solution, considered as the least damaging to the environment, constitutes a risk for the receiving environment due to the presence of harmful impurities such as heavy metals and radionuclides which hinder its large-scale valorization. This paper presents an environmental characterization of Moroccan phosphogypsum and an investigation on the environmental performance of a new lime (L) - fly ash (FA) treated phosphogypsum based road material.

Effect of phosphogypsum adding on setting kinetics and mechanical strength of geopolymers based on metakaolin or fly ash matrices.

Our study aims to highlight the effects of the addition of phosphogypsum on certain fresh and hardened characteristics of geopolymer matrices based on metakaolin or fly ash. In the fresh state, workability and setting were studied by rheology and by the electrical conductivity measurement. The hardened state was characterized by XRD, DTA, SEM, and compressive strength measurement.

Influence of the Integration of Geopolymer Wastes on the Characteristics of Binding Matrices Subjected to the Action of Temperature and Acid Environments.

Recycling geopolymer waste, by reusing it as a raw material for manufacturing new geopolymer binding matrices, is an interesting asset that can add to the many technical, technological and environmental advantages of this family of materials in the construction field. This can promote them as promising alternatives to traditional materials, such as Portland cements, which are not so environmentally friendly. Recent studies have shown that the partial replacement of reactive aluminosilicates (metakaolin and fly ash) up to a mass rate of 50% by geopolymer waste does not significantly affect the compressive strength of the new product.

Preparation of Cement Clinker from Geopolymer-Based Wastes.

In order to avoid potential environmental pollution from geopolymer-based material wastes, this work investigated the feasibility of using these materials as alternative raw materials in the preparation of cement clinker. The geopolymer binders and mortars were used as substitutes for natural mineral clays since they are rich in silica and alumina. Simulated geopolymer wastes were prepared by the activation of metakaolin or fly ash by an alkaline silicate solution.