Application of Fly Ash in ASHphalt Concrete : from Challenges to Opportunities
Fly ash has been effectively used for many years in producing high performance concrete, with limited use in asphalt pavements. This is possibly because the performance benefits that fly ash provides to asphalt mixtures are under-investigated. The reported research investigated the interaction of fly ash with different types of asphalt binders and documented important improvements found in the critical properties of asphalt. Microstructural investigation demonstrated in previous work, that crack-arresting behavior was successfully induced by evenly distributed fly ash particles within the bitumen matrix. Investigation of the rheological performance of blends of asphalt binders with different types of ash using dynamic shear rheometer confirmed the feasibility of using fly ash to improve the performance of asphalt
Recycling of Waste Glass in Eco-Cement
been used for more than 9000 years. Because of its easy availability, cost effectiveness and unique mechanical, chemical, thermal and optical properties, glass is currently found in many applications. In the United States, ~20 million tons of glass products are manufactured annually with a shipment value of about $29 billion.1 Theoretically, glass is a 100% recyclable material: it can be indefinitely recycled without loss of quality. According to EPA official statistics,2,3 the municipal solid-waste (MSW) stream in the United States contains ~5.5% of waste glass, or 12.8 million tons. In 2000, only 23% of this volume was recycled.2–6 This means that, despite the apparent simplicity of glass recovery, its recycling rate is among the lowest (at an average MSW recovery level of 30%).3 Waste glass comes from various sources: glass containers (bottles and jars), construction glass (windows) and electrical equipment (lamps, monitors and TVs). Most (89%) of the waste glass comes from various containers (Figs. 1 and 2).2,3 Generally, recovered glass containers are recycled as new glass containers; other recovered glass is used in newly emerging sectors, such as fiberglass insulation, abrasives, light-weight aggregates, concrete and asphalt.2–27 Recycling of waste glass is attractive to glass manufacturers, because it decreases the costs associated with raw materials and technological processes. Recycling also lowers energy consumption and eliminates the need to dump waste glass in landfills. However, to recycle waste glass effectively within the glass industry, it must contain glass of similar composition, which has been separated from contaminants that can decrease the quality of new glass products.2 The following contaminants affect recycling of waste glass:2,3,7–11 • Glass of fluctuating composition or color (compared with the main stream); • Ceramics (dishware, porcelain, pottery, brick, concrete); • Metals (including container lids or seals); and • Organics (paper, plastics, cork, wood, plants, food residue (especially sugar)). Evaluation of the effect of various groups of waste glass
Mechanical behaviour and durability of high volume fly ash cementitious composites
The purpose of this research is to separate different morphological particles of ASTM class F fly ash, and study their effect on mechanical behaviour and durability of high volume cementitious mixtures. In this research wet separation of raw fly ash is carried out, which resulted in three layers of different morphological particles. The first layer of particles float, comprise of about 1-5% of fly ash, is identified as cenospheres or hollow spheres. The second layer of particles is measured to be 55-60% of raw fly ash and consisting of porous spherical and rounded particles rich in Si and Al. The third layer particles is measured to be about 35-40% of raw fly ash. High volume fly ash cementitious composites containing second or third layer particles are tested under compression and bending, highlighting a higher strength and ductility in comparison to cementitious ones containing raw fly ash particles. KEYWORDS. Cementitious matrix; Raw fly ash; Second layer particles; Third layer particles.