Abstract Layered double hydroxide (LDH) phases that form during cement hydration can incorporate a variety of interlayer anions in their positions. Here, range general formula [M II (1− x ) M III ( (OH) 2 ][A n − ] / ·zH O were synthesized, where = Mg 2+ (hydrotalcite) or Ca (AFm), Al 3+ such /Al] (Ca and Mg, atomic units) 3 (Mg only), A Cl , Br I . All the synthesized characterized to assess composition, density, crystal structure. By approach from undersaturation, solubility data these...

Abstract Calcium nitrate (CN: Ca(NO 3 ) 2 has been shown to mitigate alkali–silica reaction (ASR) in concrete. Such ASR mitigation suggested be on account of precipitate (i.e., barrier or passivation layer) formation‐induced dissolution inhibition reactive/dissolving aggregate surfaces. Herein, we examine the ability CN across two cements (Type I/II and Portland Limestone Cement), for aggregates varying reactivity, different types dosages SCMs (supplementary cementitious materials, i.e.,...

Intermediate level waste produced in UK nuclear power generation is encapsulated or immobilised blended cements comprising blast furnace slag (BFS) and Portland cement (PC), to be emplaced a proposed geological disposal facility (GDF). The wasteforms are expected exposed temperatures from 35 80 °C during the initial 150 years of GDF operation. Thermodynamic modelling applied here describe phase assemblages hydrated 1:1, 3:1 9:1 BFS-PC blends, with participation hydrogarnet as an important...

Abstract Stable, durable immobilization of radioactive wastes requires robust understanding the sub-surface geochemical processes that occur in repository environments. For example, accelerated dissolution (corrosion) nuclear waste glasses (i.e., so-called “Stage III” corrosion) following precipitation zeolitic phases is a significant issue could result radionuclide release. However, current uncertainties establishing tendency for persistence zeolites results difficulties estimating chemical...

An updated calcium silicate hydrate (C–S–H) model incorporating aluminium-containing end-members was used for thermodynamic modelling of blended cements using blast-furnace slag and Portland cement (BFS:PC) with ratios 1:1, 3:1 9:1, GEMSelektor. Selective dissolution magic angle spinning nuclear magnetic resonance (MAS NMR) studies were performed to determine the degree hydration (DoH) anhydrous material as an input parameter work. Both techniques showed similar results determining DoH BFS...

Abstract Synthetic hydrotalcites were produced by a co‐precipitation method. The are represented the general formula [M II (1‐x) M III (x) (OH) 2 ][A n− ] x/n ·zH O, where is divalent cation (eg, Mg 2+ or Ca ), trivalent Al 3+ ) and A interlayer anion. Herein, = Mg, such that [Mg/Al] [2, 3] (atomic units) , represents intercalant species including: OH − SO 4 2− CO 3 anions. thermochemical data of each compound including their solubility constants (K so density molar volume quantified at T 25...

This study describes the relationship between physio-mechanical and chemical properties of sand-lime materials which have undergone hydrothermal treatment, were modified through introduction glass components (90% sand, GS). Process parameters such as temperature, pressure saturation vapor found to a significant impact on series reactions well formation transformation solid hydrates. During stirring process mass, temperature reaction lime water in presence quartz sand (QS) was determined be...

Abstract Accelerated concrete carbonation is an expanding option for decarbonizing construction. Factors such as mixture design and environment can influence the maximum CO 2 utilization that be achieved during a process. A process designed to utilize water‐saturated dilute source wherein < concentration (v/v%) 16, was modeled in AspenPlus©. regression model developed correlate uptake, relative humidity (11%–100%), ([CO ] = 2—16 v/v%), temperature ( T 11–74°C) conditions within reactor....

Optimizing the spatial distribution of contacting gas and processing conditions enhances CO₂ mineralization reactions material properties carbonate-cementitious monoliths.

Acoustic stimulation offers a green pathway for the extraction of valuable elements such as Si, Ca, and Mg via solubilization minerals industrial waste materials. Prior studies have focused on use ultrasonic frequencies (20–40 kHz) to stimulate dissolution, but megasonic (≥1 MHz) offer benefits matching resonance solute particles an increased frequency cavitation events. Here, based dissolution tests series minerals, it is found that under conditions produced enhancements between 4×-to-6× in...

The sequestration of CO2 within stable mineral carbonates (e.g., CaCO3) represents an attractive emissions-reduction strategy because it offers energy efficient, environmentally benign, and leakage-free alternative to geological storage. However, the pH levels aqueous streams equilibrated with CO2-containing gas (pH ∼ 4) are lower than required for carbonate precipitation > 8). Thus, use regenerable ion exchange materials is proposed induce alkalinity in achieve mineralization without...

Sequestration of CO 2 within stable mineral carbonates (e.g., CaCO 3 ) represents an attractive emission reduction strategy because it offers a leakage-free alternative to geological storage in environmentally benign form. However, the pH aqueous streams equilibrated with gaseous containing (pH < 4) are typically lower than that which is required for carbonate precipitation > 8). Traditionally, alkalinity provided by stoichiometric reagent NaOH) renders these processes...

By focusing the power of sound, acoustic stimulation (i.e., often referred to as sonication) enables numerous "green chemistry" pathways enhance chemical reaction rates, for instance, mineral dissolution in aqueous environments. However, a clear understanding atomistic mechanism(s) by which promotes remains unclear. Herein, combining nanoscale observations dissolving surface topographies using vertical scanning interferometry, quantifications rates via analysis solution compositions...

The stability and reactivity of SrCO3 within a blended Portland-slag cement at both 20 °C 60 (to simulate an indicative waste form for disposal) was determined via XRD, TG-MS, SEM-EDX thermodynamic modelling. Sr14CO3 is potential long-term sink trapping radioactive 14C, produced through the nuclear fuel cycle, therefore understanding its in cementitious forms interest importance. Incorporation 30 wt% caused minor reactions to occur, resulting increased formation carbonated AFm phases, along...

The disposal of highly concentrated brines from coal power generation can be effectively accomplished by physical solidification and chemical stabilization (S&S) processes that utilize fly ashes as a reactant. Herein, pozzolanic are typically combined with calcium-based additives to achieve S&S. While the reactions ash–(cement)–water systems have been extensively studied, reactivity in hypersaline (ionic strength, Im > 1 mol/L) is comparatively less understood. Therefore, interactions Class...

Metal cation identity determines the zeolite topology. Framework topology total cationic content. Potassium predominantly counterbalances Al anions; sodium and calcium are structure-directing agents.

Abstract The “U‐phase,” a sodium‐containing (alumino‐ferrite‐monosubstituent) AFm phase, has been observed to form in sodium‐enriched highly alkaline cementitious systems, for example, of relevance nuclear waste, and saline industrial brine management. But, minimal information is available the U‐phase's (e.g., solubility or thermodynamic properties) due its limited stability tendency transform into ettringite monosulfoaluminate. Herein, U‐phase was systematically synthesized at four...

In this study, the well-established service life design code defined in fib Bulletin 34 is adapted to predict time initiation of reinforcement corrosion alkali-activated concretes submerged marine conditions. The model approach based on probabilistic calculation needed for a critical concentration chloride ions, migrating from external environment towards rebar, accumulate at surface steel and initiate reaction. information required define parameters derived literature data, relating...

Abstract Hypersaline brines can be solidified and stabilized via the hydraulic pozzolanic reactions between fly ash(es) calcium-based additives. Although recent work has examined ash reactivity in single-salt (“simple”) hypersaline (ionic strength, Im > 1 mol/L), effects of mixed-salt solutions on remain unclear. Herein, a Class C (calcium oxide [CaO]-rich) or F (CaO-poor) mixture with calcium hydroxide is reacted bearing sodium chloride (NaCl), (CaCl2), magnesium (MgCl2), sulfate...

The pore structures of hardened Portland/slag cement pastes (>75 wt% slag content), and the initial capillary absorption moisture through these pores, were monitored using ex situ synchrotron X-ray computerised microtomography in quantitative neutron radiography. structure becomes more constricted as hydrates its microstructure develops. This mechanism was effective even at a content high 90 cementitious blend, where lowest total porosity significant refinement identified extended curing...