54 research outputs found

    A laboratory study on cold-mix, cold-lay emulsion mixtures

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    This paper describes laboratory experiments and presents results for the performances of cold-mix, cold-lay emulsion mixtures. The main objective of the experiments was to evaluate and improve the properties of the cold mixtures. The mixture properties evaluated were: volumetric properties, indirect tensile stiffness modulus (ITSM), repeated load axial creep and fatigue. These properties were compared with conventional hot asphalt mixtures not containing any waste/recycled materials. To optimise the performances of the mixtures, a target of ITSM value of 2000 MPa was selected. At full curing conditions, the stiffness of the cold mixes was found to be very similar to that of hot mixtures of the same penetration grade base bitumen (100 pen). Test results also show that the addition of 1–2% cement significantly improved the mechanical performance of the mixes and significantly accelerated their strength gain. The fatigue behaviour of the cold mixes that incorporated cement was comparable with that of the hot mixtures

    Managed Aquifer Recharge as a Tool to Enhance Sustainable Groundwater Management in California

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    A growing population and an increased demand for water resources have resulted in a global trend of groundwater depletion. Arid and semi-arid climates are particularly susceptible, often relying on groundwater to support large population centers or irrigated agriculture in the absence of sufficient surface water resources. In an effort to increase the security of groundwater resources, managed aquifer recharge (MAR) programs have been developed and implemented globally. MAR is the approach of intentionally harvesting and infiltrating water to recharge depleted aquifer storage. California is a prime example of this growing problem, with three cities that have over a million residents and an agricultural industry that was valued at 47 billion dollars in 2015. The present-day groundwater overdraft of over 100 km3 (since 1962) indicates a clear disparity between surface water supply and water demand within the state. In the face of groundwater overdraft and the anticipated effects of climate change, many new MAR projects are being constructed or investigated throughout California, adding to those that have existed for decades. Some common MAR types utilized in California include injection wells, infiltration basins (also known as spreading basins, percolation basins, or recharge basins), and low-impact development. An emerging MAR type that is actively being investigated is the winter flooding of agricultural fields using existing irrigation infrastructure and excess surface water resources, known as agricultural MAR. California therefore provides an excellent case study to look at the historical use and performance of MAR, ongoing and emerging challenges, novel MAR applications, and the potential for expansion of MAR. Effective MAR projects are an essential tool for increasing groundwater security, both in California and on a global scale. This chapter aims to provide an overview of the most common MAR types and applications within the State of California and neighboring semi-arid regions

    What Do Community Benefits Agreements Deliver? Evidence From Los Angeles

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    Using compost from urban solid waste to prevent erosion in road embankments

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    This paper describes how compost, a by-product generated by solid waste treatment plants, can be usefully applied to road embankments to prevent erosion. Our study analyzed this process in terms of the following variables: (1) location and orientation; (2) embankment slope; (3) soil and compost characteristics; (4) compost dosage; (5) vegetation species; (6) plot dimensions; and (7) planting method. The results ob- tained focus on the vegetation survival rate, plant growth and germination; colonization of other species; cover crop for plots; and erosion estimation. It was found that when greater quantities of compost were added to embankments, soil loss was decreased. The addition of this material also produced a marked increase in plant growth, the survival rate of manually planted vegetation, the colonization of other species, as well as the cover crop. However, we observed that compost seemed to hinder the germination of hydroseeded species, whereas colonizing plants germinated more quickly. The side slope was not found to be a significant factor for manually planted species, but turned out to be crucial for hydroseeded varieties.Department of Civil Engineering, University of Granada, Spai
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