Expansive soils are prevalent world over and cause significant hazards and monetary losses due to infrastructure damages caused by their swelling and shrinking behavior. Expansive soils have been conventionally treated using chemical additives such as lime and cement, which are known to significantly improve their strength and volume-change properties. The production of lime and cement is one of the highest contributors of greenhouse gas emissions worldwide, because of their energy-intensive manufacturing processes. Hence, there is a pressing need for sustainable alternative chemical binders. Geopolymers are a relatively new class of aluminosilicate polymers that can be synthesized from industrial by-products at ambient temperatures. Geopolymer-treated soils are known to have comparable strength and stiffness characteristics of lime and cement-treated soils. This study evaluates the sustainability benefits of a metakaolin-based geopolymer treatment for an expansive soil and compares its results with lime treatment. Test results have shown that geopolymers have significantly improved strength, stiffness, and volume-change properties of expansive soils. Increased dosages and curing periods have resulted in further property enhancements. Swell and shrinkage studies also indicated reductions in these strains when compared to control conditions. The sustainability benefits of both geopolymer and lime treatment methods are evaluated using a framework that incorporates resource consumption, environmental, and socio-economic concerns. This study demonstrates geopolymer treatment of expansive soils as a more sustainable alternative for expansive soil treatments, primarily due to metakaolin source material. Overall results indicated that geopolymers can be viable additives or co-additives for chemical stabilization of problematic expansive soils.

In this paper we employ a dataset of three dimensions - state, sector, and year - to estimate the short- and long-run price elasticities of state-level electricity demand in the United States. Our sample covers the period 2003-2015. We contribute to the literature by employing instrumental variable estimation approaches, using the between estimator, and pursuing panel specifications that are able to control for multiple dimensions of fixed effects. We conclude that state-level electricity demand is very price inelastic in the short run, with a same-year elasticity of -0.1. The long-run elasticity is near -1, larger than often believed. Among the sectors, it is industry that has the largest long-run price elasticity of demand. This appears to in part be due to electricity-intensive industrial activities clustering in low-price states.

German Dieses Diskussionspapier beleuchtet die PRME-Verpflichtung der Hochschule Pforzheim und die daraus resultierenden Probleme (Abschnitt 2)

If global photovoltaics (PV) deployment grows rapidly, the required input materials need to be supplied at an increasing rate. In this paper, we quantify the effect of PV deployment levels on the scale of metals production. For example, we find that if cadmium telluride {copper indium gallium diselenide} PV accounts for more than 3% {10%} of electricity generation by 2030, the required growth rates for the production of indium and tellurium would exceed historically-observed production growth rates for a large set of metals. In contrast, even if crystalline silicon PV supplies all electricity in 2030, the required silicon production growth rate would fall within the historical range. More generally, this paper highlights possible constraints to the rate of scaling up metals production for some PV technologies, and outlines an approach to assessing projected metals growth requirements against an ensemble of past growth rates from across the metals production sector. The framework developed in this paper may be useful for evaluating the scalability of a wide range of materials and devices, to inform technology development in the laboratory, as well as public and private research investment.

This paper empirically investigates the possible market power effects of vertical integration proposed in the theoretical literature on vertical foreclosure. It uses a rich data set of cement and ready-mixed concrete plants that spans several decades to perform a detailed case study. There is little evidence that foreclosure is quantitatively important in these industries. Instead, prices fall, quantities rise, and entry rates remain unchanged when markets become more integrated. These patterns are consistent, however, with an alternative efficiency-based mechanism. Namely, higher productivity producers are more likely to vertically integrate and are also larger, more likely to survive, and charge lower prices. We find evidence that integrated producers’ productivity advantage is tied to improved logistics coordination afforded by large local concrete operations. Interestingly, this benefit is not due to firms’ vertical structures per se: non-vertical firms with large local concrete operations have similarly high productivity levels.