Photon Shielding Quantities of Historical Lime Mortars from Spanish Colonial Structures in the Philippines

Ionizing radiation poses a major risk to industrial, medical, and radiological systems, as well as the nuclear power sector. Radiation must be contained to avoid harming radiation workers. The use of appropriate shielding material must be observed. In this study, various historical lime mortars from Spanish colonial structures in the Philippines are investigated for their unique radiation shielding characteristics. These include [i] mortar samples from the foundational ruins of the former San Francisco Church in Intramuros, Manila (INT); [ii] joint mortar from Fort Almonte in Bacolod, Lanao del Norte (LDN); [iii] mortar from the ruins of a 19^th century Roman Catholic Church in Manila (MNL); iv) wall plaster from a 19^th century Loboc Church convent in Bohol (LOB); and v) church debris mortar of Baclayon Church in Bohol (BAC). For reference, self-compacting concrete (SCC) was also analyzed. The best radiation shielding for X-ray, low, and high gamma-ray energies appears to be the BAC because it has the highest mass attenuation coefficient (MAC) from energies between 5–500 keV and above 3000 keV. The second-highest MAC is that of LOB, which is almost identical to the MAC of the SCC. The MNL has the lowest MAC, as it lacks a significant number of high atomic number elements, which is present in other historical lime mortars. The fact that BAC has the highest effective atomic number (Z_eff) for all photon energies from 1–10⁶ keV suggests that it is the best historical lime mortar for shielding against photon radiation. The BAC has the lowest energy absorption (EABF) and exposure (EBF) buildup factors for all photon energies, indicating that it is the best lime mortar for photon radiation shielding. EABF and EBF for historical lime mortars are as follows: BAC < SCC < LOB < LDN < INT < MNL.