The Environmental Protection Agency (EPA) provides access to information on a variety of topics related to the environment and strives to inform citizens of health risks. The EPA also has an extensive library network that consists of 26 libraries throughout the United States, which provide access to a plethora of information to EPA employees, scientists, and researchers. The EPA implemented a reorganization project to digitize their materials so they would be more accessible to a wider range of users, but this plan was drastically accelerated when the EPA was threatened with a budget cut. It chose to close and reduce the hours and services of some of their libraries. As a result, the agency was accused of denying users the “right to know” by making information unavailable, not providing an adequate strategic plan, and discarding vital materials. This case study explores the background of the digitization project, the practices implemented, and the critiques of the project.

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The Environmental Protection Agency

Recent advances in understanding the role of supplementary cementitious materials in concrete

Recycling and recovery routes for incinerated sewage sludge ash (ISSA): a review.

Metakaolin as cementitious material: History, scours, production and composition – A comprehensive overview

Thermoddem: A geochemical database focused on low temperature water/rock interactions and waste materials

Reaction kinetics of FEBEX bentonite in hyperalkaline conditions resembling the cement–bentonite interface

Reactivity of the cement-bentonite interface with alkaline solutions using transport cells

Compliance of concrete – bentonite barriers is a key issue in the performance assessment of long-term underground storage of radioactive waste. The reaction of synthetic alkaline solutions (K–Na–OH and Ca–(OH) 2 ) interacting by diffusion with a Mg-saturated compacted FEBEX-bentonite column of 2.1 cm thickness was investigated through closed-system experiments at 60 °C over 6 and 12 months. The first few millimeteres near the surface were grated to resolve mineralogical changes at sub-mm resolution determined by XRD, SEM, BET and the analysis of exchangeable cations. Alkaline cations diffused beyond the mineralogical alteration zone (2–2.5 mm), and were exchanged by Mg 2+ in the interlayer region of montmorillonite, but no K-silicates were formed. The presence of minor zeolites in the alteration assemblage was only detected by XRD on samples treated with ethylene-glycol. A cemented rim mixed with poorly ordered clay materials, mainly brucite, a chlorite-like phase and Mg-smectite was found at the interface. Montmorillonite was partially dissolved and a part of it remained shielded by the newly-formed cementation crusts. Cation diffusion through the interlayer of montmorillonite is inferred to be the dominant transport pathway in compacted bentonite equilibrated with external high pH solutions. The high pH front diffused at a much slower rate due to buffering of mineral reactions.

Alteration of compacted bentonite by diffusion of highly alkaline solutions

Concrete and bentonite are being considered as engineered barriers for the deep geological disposal of high-level radioactive waste in argillaceous rocks. Three hydrothermal laboratory experiments of different scalable complexity were performed to improve our knowledge of the formation of calcium aluminate silicate hydrates (C-A-S-H) at the interface between the two materials: concrete-bentonite transport columns, lime mortar-bentonite transport columns and a portlandite- (bentonite and montmorillonite) batch experiment. Precipitation of C-A-S-H was observed in all experiments. Acicular and fibrous morphologies with certain laminar characteristics were observed which had smaller Ca/Si and larger Al/Si ratios with increasing temperature and lack of accessory minerals. The compositional fields of these C-A-S-H phases formed in the experiments are consistent with Al/(Si+Al) ratios of 0.2–0.3 described in the literature. The most representative calcium silicate hydrate (C-S-H) phase from the montmorillonite–cement interface is Al-tobermorite. Structural analyses revealed a potential intercalation or association of montmorillonite and C-A-S-H phases at the pore scale.

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Formation of C-A-S-H phases from the interaction between concrete or cement and bentonite

Calcined residual paper sludge can be reused and valorized in a safe an environmental way by the construction industry. The highly reactive metakaolin produced by calcination of the paper sludge exhibits good pozzolanic properties and permits its incorporation in cement systems. The pozzolanic reaction of metakaolin in Ca(OH) 2 -saturated solution at 40 °C is reported in this study as a function of time, up to 1 year. The stability of hydrates phases has been evaluated according to the evolving aqueous conditions. Analytical determinations of the solid phase show early formation of C–S–H phases and a later precipitation of laminar minerals, hydrotalcite and stratlingite, at the expense of the C–S–H phases. The thermodynamic calculations confirm the experimental observations.

Raúl Fernández

Papers

Reaction kinetics of FEBEX bentonite in hyperalkaline conditions resembling the cement–bentonite interface

Reactivity of the cement-bentonite interface with alkaline solutions using transport cells

Alteration of compacted bentonite by diffusion of highly alkaline solutions

Formation of C-A-S-H phases from the interaction between concrete or cement and bentonite

Mineralogical and chemical evolution of hydrated phases in the pozzolanic reaction of calcined paper sludge