Solidia Technologies (United States)

Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-à-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution (SiO2-to-Na2O ratio or Ms of 1–2) to provide a total alkalinity of 0.05 (Na2O-to-binder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on Ms, (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.

Solidia/CCSM received funding for further research and development of its Low Temperature Solidification Process (LTS), which is used to create hydrate-free concrete (HFC). LTS/HFC is a technology/materials platform that offers wide applicability in the built infrastructure. Most importantly, it provides a means of making concrete without Portland cement. Cement and concrete production is a major consumer of energy and source of industrial greenhouse gas (GHG) emissions. The primary goal of this project was to develop and commercialize a novel material, HFC, which by replacing traditional concrete and cement, reduces both energy use and GHG emissions in the built infrastructure. Traditional concrete uses Portland Cement (PC) as a binder. PC production involves calcination of limestone at {approx}1450 C, which releases significant amounts of CO{sub 2} gas to the atmosphere and consumes a large amount of energy due to the high temperature required. In contrast, HFC is a carbonate-based hydrate-free concrete (HFC) that consumes CO{sub 2} gas in its production. HFC is made by reaction of silicate minerals with CO{sub 2} at temperatures below 100 C, more than an order-of-magnitude below the temperature required to make PC. Because of this significant difference in temperature, it is estimated that we will be able to reduce energy use in the cement and concrete industry by up to 30 trillion Btu by 2020. Because of the insulating properties of HFC, we believe we will also be able to significantly reduce energy use in the Building sector, though the extent of this saving is not yet quantified. It is estimated that production of a tonne of PC-based concrete requires about 6.2 million Btu of energy and produces over 1 tonne of CO{sub 2} emissions (Choate, 2003). These can be reduced to 1.9 million Btu and 0.025 tonnes of CO{sub 2} emissions per tonne of HFC (with overall CO{sub 2}-negativity possible by increasing carbonation yield). In this way, by replacing PC-based concrete with HFC in infrastructure we can reduce energy use in concrete production by 70%, and reduce CO{sub 2} emissions by 98%; thus the potential to reduce the impact of building materials on global warming and climate change is highly significant. Low Temperature Solidification (LTS) is a breakthrough technology that enables the densification of inorganic materials via a hydrothermal process. The resulting product exhibits excellent control of chemistry and microstructure, to provide durability and mechanical performance that exceeds that of concrete or natural stone. The technology can be used in a wide range of applications including facade panels, interior tiles, roof tiles, countertops, and pre-cast concrete. Replacing traditional building materials and concrete in these applications will result in significant reduction in both energy consumption and CO{sub 2} emissions.

Future battlefield networks such as FCS and WIN-T will rely on mobile ad hoc networks (MANETs) to satisfy their communications requirements. Thus there is a critical need for systematic techniques based on formal methodologies to design MANETs to meet mission requirements. However, given the complexity of MANETs, the variety of applications they need to support, and the associated performance measures, it is extremely challenging to perform such an engineering design of MANETs. The challenges stem both from the large number of design choices that can be made for any given mission, and, more importantly, from the lack of a systematic body of principles that a network designer can rely upon to guide these choices. To address this critical need, a joint effort has been initiated between Telcordia and CERDEC to formulate a Network Engineering Design Analytic Toolset (NEDAT) that applies formal network science-based approaches to systematically and accurately design, analyze and predict the performance of MANETs. In this paper, we present the results from the first phase of this joint effort.

Creating a hierarchy to meet certain constraints and optimize objective functions can greatly improve scalability, performance and robustness of large networks. However, as constant optimization would result in excessive reconfiguration and signaling overhead, existing hierarchy maintenance protocols are only invoked after detecting constraint violations (e.g., when a node cannot directly reach other nodes in its part of the hierarchy). This passive approach minimizes overhead, but will, over time, result in declining network optimality, particularly in dynamic MANET networks. This paper investigates a new active approach to maintaining a hierarchy, which maintains better network optimality, while balancing the reconfiguration and signaling overhead. Our active approach is performed only at border routers that, at random intervals, perform a local optimization based on the objective functions globally optimized during the hierarchy generation. Using an example of creating balanced size domains (clusters), our simulation results show that active localized decisions can maintain the hierarchy close to the optimal value even after much network dynamics; this is in marked contrast to passive local maintenance which allows the network to deteriorate dramatically.

Asynchronous Transfer Mode (ATM) is a communications architecture for the provision of broadband integrated services digital networks. Two fundamental features of ATM networks are hierarchical routing and statistical multiplexing. This paper addresses the problem of laying out virtual paths (VPs), which are logical network links that provide direct connections between certain nodes. A bi-criteria integer-programming model is developed that includes a throughput-maximization objective, a delay/overhead minimization objective, and a diversity constraint whereby link-disjoint VPs are found so as to provide fault tolerance. The formulation employs a new model for approximating the effects of statistical multiplexing. An approximate solution method is developed, which employs constraint generation for bound tightening, and heuristics based on rounding of a linear programming solution.