From discarded waste to valuable products: Barite combination with chrysotile mine waste to produce radiation-shielding concrete

Chrysotile, the most common serpentine polymorph, represents one of the most hazardous mine wastes known for its associated health risks. For the first time, chrysotile mine waste combined with barite was recycled to produce radiation shielding concrete (RSC) with promising mechanical and radiation attenuation properties. Chrysotile concrete (CC) was amended by 25% and 50% of mine waste of barite as a heavy-weight mineral to produce CB1 and CB2 concrete mixes, consecutively. Compared to CC, the physico-mechanical properties of CB1 and CB2 were evaluated. In all concrete mixes, XRD, FTIR, and TG/DTG analyses were employed to detect their different hydration phases and cement particles, while XRF was utilized to determine their chemical composition. Also, SEM analysis was necessary to characterize the microstructural features, particularly the interfacial transition zone (ITZ) between aggregates and cement matrix. Moreover, their radiation attenuation for all the prepared mixtures against gamma-rays, as well as thermal and fast neutrons was evaluated using 60Co and PuBe sources coupled with stilbene, BF3, and NaI detectors. Also, the experimental radiation attenuation results were validated through WinXCom and NXcom programs, as well as MCNP-5 simulation code. A higher barite ratio (50%) notably increased the compressive and splitting tensile strength (fc and ft, respectively) of CB2 by about 91% and 111%. Conversely, the lower ratio (25%) reduced fc and ft of CB1 by approximately 7.9% and 11% at 90 days, respectively. Furthermore, CB2 exhibited improved microstructure, mitigating the adverse effects of depleted hydration. Otherwise, the fast neutron and gamma-ray attenuations were enhanced with more superiority to the higher ratio of 50%. Ultimately, the theoretical and simulation investigations of radiation attenuation demonstrated acceptable agreement with experimental results across all concrete mixtures. Consequently, hazardous chrysotile can be valorized as aggregates enclosed or stabilized in RSC with adhering to risk management instructions.