Portland Cement Based Immobilization/Destruction of Chemical Weapon Agent Degradation Products

Abstract

The direct immobilization and destruction of two compounds relevant to chemical warfare agents, ethyl methylphosphonic acid (EMPA) and thiodiglycol (TDG), within a freshly mixed Portland cement paste was studied. Cement hydration and phase formation were analyzed to determine the upper limits on the loading of these chemicals achievable in an immobilization setting. EMPA, a degradation product of the nerve agent VX, alters the phase formation within the cements, allowing calcium aluminate dissolution while retarding hydration of calcium silicate clinker phases. This yielded ettringite, and sufficient calcium silicate hydrate for setting at 10 wt % loading, but the cohesive calcium silicate binding phase was lacking when EMPA was added at 25 wt %. The addition of TDG, a degradation product of sulfur mustard, uniformly retards the entire range of cement hydration mechanisms. Heat output was lowered and extended over a longer time frame, and less strength forming phases were produced. Up to 10% wt. TDG could be accommodated by the cement, but higher loadings caused severe disruption to the cement setting. This work demonstrates the ability of Portland cement to directly incorporate up to 10% wt. of these contaminants, and still form a stable set cement with conventional hydration phases.

Developing Innovative Cement Composites Containing Vine Shoot Waste and Superplasticizers

“…The amount of oxygen vacancies in NMR is very small; the peak at about 35 ppm, corresponding to the Al(V), is present in all the samples [48]. In the case of CPW and CPWSR41 present in the Al(IV) region, a small and very broad peak at 70 ppm corresponding to impurities in the C-S-H gel is observed [56]. The Al(VI) region is characterized by three spectral lines: at 13 ppm corresponding to the AFt phase, which is present only in spectra of CP, CPSR3, and CPSR41 and absent in spectra of CPW, CPWSR3, and CPWSR41; at 10 ppm corresponding to AFm phase, which is present in all spectra; and at 5 ppm corresponding to third aluminate hydrate (T) phase, which is also present in all spectra [57,58].…”

“…27 Al MAS NMR spectra are presented in Figure 7 with a clear separation between the Al(IV) and Al(VI) regions. The Al(IV) region presents two small and very broad peaks: at 80.5 ppm corresponding to unreacted clinker phases and 70 ppm corresponding to impurities in the C-S-H gel [56] in the CP, CPSR3, CPSR41, and CPWSR3. The amount of oxygen vacancies in NMR is very small; the peak at about 35 ppm, corresponding to the Al(V), is present in all the samples [48].…”

Hydrogen Impact on Cement Integrity during Underground Hydrogen Storage: A Minireview and Future Outlook

“…During UHS, the usage of chemical-based additives can be one of the practical approaches to improving the integrity of the cement seal and its properties. These additives include retarders, accelerators, extenders, fluid loss control additives, dispersants, gas migration prevention additives, expansion additives, and chemical degradation products. , The selection of the additive type primarily depends upon the well profile, type of fluid, temperature, and pressure. However, during gas storage application, evaluating the interactions between the injected gas and additives is crucial to avoid any possible cement degradation and to ensure the integrity of the cement sheath .…”

Multimodal Characterization of Materials and Decontamination Processes for Chemical Warfare Protection

“…In the field of CWA decontamination, PXRD is used primarily for the initial sample characterization prior to the uptake/decomposition studies. Because each crystalline solid produces a distinct diffraction pattern, in mixtures those patterns are superimposed allowing one to analyze sample purity or phase composition. − Further, the nature of the PXRD method requires crystalline materials with an extensive long-range order. On the basis of the quality of the diffractogram, we can extract information, such as crystallinity of the sample, defined as size of coherently diffracting domains, or the possible presence of defects, stacking faults or partial framework collapse.…”