Author, Institution: Ignacio Villalón Fornés, Kaunas University of Technology
Science area, field of science: Technological Sciences, Civil Engineering , T002
Scientific Supervisor: Prof. dr. Danutė Vaičiukynienė (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002)
Dissertation Defence Board of Civil Engineering Science Field:
Prof. Dr. Žymantas Rudžionis (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002) – chairperson
Prof. Dr. Mindaugas Daukšys (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002)
Prof. Dr. Rimvydas Kaminskas (Kaunas University of Technology, Technological Sciences, Civil Engineering, T002)
Prof. Dr. Pavel Krivenko (Kyiv National University of Construction and Architecture, Ukraine, Technological Sciences, Materials Engineering, T008)
Dr. Ina Pundienė (Vilnius Gediminas Technical University, Technological Sciences, Materials Engineering, T008)
The doctoral dissertation is available at the library of Kaunas University of Technology (K. Donelaičio g. 20, Kaunas).
The dissertation defence was held remotely.
Annotation:
Phosphogypsum (PG) is the main by-product of the phosphate fertilisers´ production process. Since there are no substitutes for phosphorus in agriculture, PG is manufactured in humungous amounts all over the planet, but only 15 % of it is recycled. The rest part is stored in big and useless stockpiles, which, on the other hand, damage the environment. The only solution to this problem seems to lay on utilising this material in useful ways; for instance, as the binding material of building products.
In this context, the main goal of the current work involves improving the main properties of PG to make it a suitable binding material for building products by processing the specimens through the casting and the press-forming methods and through the addition of various industrial waste modifiers. The aptness of the PG to be used in building materials has been assessed by thoroughly investigating its main properties, such as the level of radioactivity, the toxicity, the mechanical strength, the water resistance, and the thermal and acoustic insulation.
These properties have been improved by modifying the processing method (either casting or press-forming, with or without immersion, various initial water content in the paste), by comparing various types of PG and by including several additives in various amounts (such as metallurgical sludge, waste zeolite, wood fibre and hydrated lime). During the research, a wide range of analysis methods have been employed: microstructural and composition analyses (XRD, XRF, SEM-EDS and particle size analysis), acidic impurity content (fluoride and phosphate colorimetry, pH), radionuclide activity concentration (gamma spectroscopy), mechanical strength standard tests (compressive and bending strengths), level of hydration (loss on ignition and hydration temperature analyses), thermal conductivity and sound pressure level analyses.
In brief, the results of the investigation show that the good properties of PG specimens offer new possibilities to the utilisation of PG as the binding material for structural building products, such as load-bearing bricks or blocks.
