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Cement is one of the most consumed materials in the world. The cement industry is responsible for a large portion of global carbon dioxide emissions. Cement production and therefore carbon ...

This paper describes the development and validation of a one-dimensional, large-strain consolidation-coupled contaminant transport model. The RCM-XPORT2 model uses the CS2 large-strain consolidation approach coupled with reactive advective/dispersive solute transport through a deforming saturated porous media, capped with a reactive sequestering geomaterial known as a reactive core mat (RCM). Validation of the model is presented by simulating consolidation-coupled contaminant transport experiments performed on naphthalene-spiked sediment from the Neponset River in Milton, Massachusetts. Finally, the paper presents a hypothetical case study of pre- and post-RCM application polychlorinated biphenyl (PCB) fate and transport in the Lower Neponset River using RCM-XPORT2 and U.S. EPA Water Quality Analysis Simulation Program surface water quality model. The Neponset River case study evaluates the long-term effect of sediment RCM capping on reducing the water column PCB concentration.

Recently, hydrogels have been employed in a variety of engineering applications as promising materials, since their porous structure and hydrophilicity enables them to absorb a large amount of water. Atomistic simulations lead to a better understanding of their properties at nanoscale, especially mechanical properties. In this study, hydrogel is studied using a molecular dynamics (MD) framework, considering condensed-phased optimized molecular potential (COMPASS) as the force field. Polyethylene glycol diglycidyl ether (PEDGE) and poly-oxy-alkylene-amines (Jeffamine) are the epoxy and curing agent used for hydrogels, and a novel cross-linking method is applied. Radial Distribution Functions (RDFs) show that the cross-links are the hydrophilic part of hydrogel. RDFs and mechanical properties are reported for different water amounts. The results show that an increase in water content leads to a decrease in elastic modulus of the hydrogel.

Formulation for the effect of dissipation of excess pore water pressure on one-dimensional advective-diffusive transport of solutes in clays is presented. The formulation is based on the effect of the rate of consolidation or swelling and excess pore pressure or suction dissipation on transient, nonlinear advective component of transport through clay. One partial differential equation is presented for advective diffusive transport that is dependent upon soil/solute properties and transient hydraulic head gradient, which is calculated from the Terzaghi consolidation equation. Finite difference method is used to solve the system of partial differential equations for consolidation and solute transport. Four hypothetical cases are evaluated to demonstrate the effect of consolidation under loading and swelling under hydraulic gradient on advective-diffusive transport and breakthrough in single and double drainage clay layer. The results show that consolidation in doubly drained clay impacts concentration profiles, but does not significantly impact breakthrough of the diffusive flux. Consolidation under single drainage conditions, significantly impacts the diffusional flux. When drainage path is the same as the diffusional flux, consolidation accelerates transport and breakthrough time can be less than 5% of the diffusional breakthrough time under no consolidation. Swelling under hydraulic gradient application can either accelerate or retard the advective diffusive flux, depending upon the ratio of the effective diffusion coefficient relative to the coefficient of consolidation. Higher the effective diffusion coefficient and lower the coefficient of consolidation result in an increase in the effect of pressure dissipation on transport.

This special section includes a selection of original research papers focused on the mechanics of nanocomposites and nanostructures. The September issue includes the first set of papers on the subject. Most of the papers were also presented at the Nanomechanics and Nanocomposites Symposium at the 2012 Conference of the Engineering Mechanics Institute of the American Society of Civil Engineers held at Notre Dame University in South Bend, Indiana. The Nanomechanics and Nanocomposites Symposium provided a unique venue for researchers exploring the intersections of applied and computational mechanics within the field of materials science at the nanoscale. In this area, there are both tremendous challenges and opportunities. It is humbling to consider the limitations of our current knowledge about the structures and properties of materials at the smaller scales. On the other hand, it is bewildering to consider all of the possibilities for breakthroughs in the engineering disciplines that might be achieved by understanding our world and employing that knowledge to make advances in the materials we use. Although this symposium featured papers on a wide variety of topics, mechanics of materials at the nanoscale was a dominant theme discussed. Indeed, four of the five papers in this first series were devoted entirely to nanomechanical behavior of materials, and a majority of the remaining papers also focused, at least in part, on aspects of nanomechanics. Accordingly, we are pleased to publish this collection of papers in the similarly themed Journal of Nanomechanics and Micromechanics. We believe these papers represent some of the wide scope seen in the field.