Selection of cementitious mixes as a barrier for landfill leachate containment

Cementitious materials have traditionally not been economically viable for most landfill containment systems. Conventional liners have been made with clay and high-density polyethylene membranes, supporting packed aggregate layers. This paper describes an alternative technology in which low-cost concrete liners may be constructed, making use of materials, which are considered to be wastes by their primary producers. Many materials that have the potential for use either as binder or as aggregate materials for concrete currently form part of the United Kingdom landfill inventory. Although unattractive for use as structural concrete, they offer considerable utility for landfill liner applications. Recent increases in disposal costs including the introduction of the landfill tax have, however, made low cost low strength mixes a financially attractive option as a barrier for landfill leachate containment. In this paper the required properties of cementitious mixes for this purpose are discussed. The results of an extensive investigation into potential mixes using various mineral wastes are presented and the measured properties are compared with those, which are required. All of the mixes, which have been investigated, contain large amounts of secondary materials. If these materials were treated as wastes their disposal costs would be high, so the mixes may be designated “negative cost mixes.” The results indicate that some of these mixes are well suited to this application

Experimental investigation and simplistic geochemical modeling of CO2 mineral carbonation using the mount tawai peridotite

In this work, the potential of CO2 mineral carbonation of brucite (Mg(OH)2) derived from the Mount Tawai peridotite (forsterite based (Mg)2SiO4) to produce thermodynamically stable magnesium carbonate (MgCO3) was evaluated. The effect of three main factors (reaction temperature, particle size, and water vapor) were investigated in a sequence of experiments consisting of aqueous acid leaching, evaporation to dryness of the slurry mass, and then gas-solid carbonation under pressurized CO2. The maximum amount of Mg converted to MgCO3 is ∼99%, which occurred at temperatures between 150 and 175 °C. It was also found that the reduction of particle size range from >200 to <75 μm enhanced the leaching rate significantly. In addition, the results showed the essential role of water vapor in promoting effective carbonation. By increasing water vapor concentration from 5 to 10 vol %, the mineral carbonation rate increased by 30%. This work has also numerically modeled the process by which CO2 gas may be sequestered, by reaction with forsterite in the presence of moisture. In both experimental analysis and geochemical modeling, the results showed that the reaction is favored and of high yield; going almost to completion (within about one year) with the bulk of the carbon partitioning into magnesite and that very little remains in solution

The prevalence and incidence of mental ill-health in adults with autism and intellectual disabilities

The prevalence, and incidence, of mental ill-health in adults with intellectual disabilities and autism were compared with the whole population with intellectual disabilities, and with controls, matched individually for age, gender, ability-level, and Down syndrome. Although the adults with autism had a higher point prevalence of problem behaviours compared with the whole adult population with intellectual disabilities, compared with individually matched controls there was no difference in prevalence, or incidence of either problem behaviours or other mental ill-health. Adults with autism who had problem behaviours were less likely to recover over a two-year period than were their matched controls. Apparent differences in rates of mental ill-health are accounted for by factors other than autism, including Down syndrome and ability level

Potential for carbon dioxide reduction from cement industry through increased use of industrial pozzolans

Concrete is the most widely used material on earth, eclipsing the combined volumes of all other man made materials by a factor of ten. In terms of its embedded carbon, it is a benign product, being associated with relatively little CO2 per unit mass when compared with metals, glasses and polymers. Conversely, it is made in such vast quantities, that it is responsible for over five percent of anthropogenic CO2. Despite recent advances in kiln design and alternative, low energy clinkers, it seems likely that the greatest carbon savings from the industry are likely to be made by the inclusion of supplementary cementing materials. This article reviews some of the options currently under investigation, especially from the UK perspective, and highlights that some of the research needs to be satisfied before such materials are more widely adopted

Relationships between CYP2D6 phenotype, breast cancer and hot flushes in women at high risk of breast cancer receiving prophylactic tamoxifen: results from the IBIS-I trial

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