Development of Alkali-Activated Porous Concrete Composition from Slag Waste

HIGHLIGHTS: The precursor of alkali activated slag was made from slag and 0, 3, 5, 7 and 10% phosphogypsum. Phosphogypsum and H(2)O(2) led to positive changes of porous alkali-activated slag concrete. The recommended content of phosphogypsum is 3–5% in alkali-activated slag system. Porous concrete had a compressive strength of 2.12–7.95 MPa, a density of 830 kg/m(3)–1142 kg/m(3), and a thermal conductivity of 0.0985–0.2618 W/(m·K). This porous concrete is recommended for the production of low-strength insulation blocks. ABSTRACT: In this paper, a porous alkali-activated slag concrete was developed that can be used in the construction sector as a sustainable building material and potentially as an alternative to the aerated concrete products currently on the market. Ferrous slag from the metallurgical industry (Finland) and phosphogypsum from a fertilizer plant (Lithuania) were used as precursors in alkali-activated systems. The addition of hydrogen peroxide and phosphogypsum led to positive changes in the final properties of the test material. Porous concrete based on alkali-activated slag was analyzed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) methods. The compressive strength, density, thermal conductivity and porosity of the hardened specimens were evaluated as well. Research is being conducted with the material in question to create a cheap, particularly low-energy demanding building material. This material must have suitable mechanical properties for the structure and, at the same time, suitable thermal conductivity properties. It was determined that this porous concrete had compressive strength in the range of 2.12–7.95 MPa, density from 830 kg/m(3) to 1142 kg/m(3), and thermal conductivity in the range of 0.0985–0.2618 W/(m·K). The results indicate that the recommended content of phosphogypsum in alkali-activated material is 3–5% due to the optimal distribution of the mechanical and thermal properties and the conductivity. Alkali-activated slag and phosphogypsum material can be used in the manufacture of low-strength insulation blocks and to protect structures from the effects of high temperatures.