Preface With increasing world population and urbanization@ the depletion of natural resources and generation of waste materials is becoming a considerable challenge. As the number of humans has exceeded 7 billion people@ there are about 1.1 billion vehicles on the road@ with 1.7 billion new tires produced and over 1 billion waste tires generated each year. In the USA@ it was estimated in 2011 that 10% of scrap tires was being recycled into new products@ and over 50% is being used for energy recovery@ while the rest is being discarded into landfills or disposed. The proportion of tires disposed worldwide into landfills was estimated at 25% of the total number of waste tires. Likewise@ in 2013@ Americans generated about 254 million tons of trash. They only recycled and composted about 87 million tons (34.3%) of this material. On average@ Americans recycled and composted 1.51 pounds of individual waste generation of around 4.4 pounds per person per day. In 2011@ glass accounted for 5.1 percent of total discarded municipal solid waste in the USA. Moreover@ energy production and other sectors are generating substantial amounts of sludge@ plastics and other post-consumer and industrial by-products. In the pursuit of its sustainability goals@ the construction industry has a potential of beneficiating many such byproducts in applications that could@ in some cases@ outperform the conventional materials using virgin ingredients. This Special Publication led by the American Concrete Institute??s Committee 555 on recycling is a contribution towards greening concrete through increased use of recycled materials@ such as scrap tire rubber@ post-consumer glass@ reclaimed asphalt pavements@ incinerated sludge ash@ and recycled concrete aggregate. Advancing knowledge in this area should introduce the use of recycled materials in concrete for applications never considered before@ while achieving desirable performance criteria economically@ without compromising the long-term behavior of concrete civil infrastructure.