Innovative shielding solutions by geopolymer paste and fly ash as effective substitution of cement materials for sustainable protection

Abstract

This study aimed to evaluate gamma radiation shielding material based on fly ash (FA) type ASTM C 618 Class F with a sodium silicate solution with two molarity values. The composite geopolymer paste was synthesized by activating the alkaline solution and curing at 70 °C for 1 h. The sodium silicate solution was added to the FA matrix with two molarity values of SiO2/Na2O (2.2 and 3.3). The density of each sample GPp1 and GPp2 are 2.121 g/cm3 and 2.212 g/cm3, respectively. The XRD patterns revealed the successful preparation of the prepared samples. Scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) determined the samples' surface morphology and elemental composition. The compressive strength of GPp2 sample was higher than for the GPp1 sample at 7 and 28 days, respectively. The density and tensile strength of the GPp2 sample are high compared to GPp1. Also, the thermal expansion coefficients for GPp2 are 5.16 × 10-4 K-1 while the GPp1 equals 2.65 × 10-4 K-1. To evaluate the photon shielding competences of the geopolymer samples, the parameters such as half-value layer (HVL), mean free path (MFP), effective atomic number (Zeff), effective electron density (Neff), and exposure buildup factor (EBF) were calculated. The highest Zeff was obtained for the GPp2 sample, whereas the lowest values were obtained for MFP, HVL, and Neff. Additionally, μm values were compared to theoretical Phy-X/PSD. It can be concluded that the investigated fly ash-based geopolymer paste is a promising material for gamma radiation shielding.