From bricks to cobblestones to recycled rubber, there are plenty of material options for sidewalks. But concrete is likely the cheapest.
"For most American cities, concrete is the go-to choice for building sidewalks. It's relatively cheap to install - only about $12 per square foot - and it's very solid. Its pale color reflects light, reducing nighttime illumination costs for cities compared to darker-hued alternatives. Plus, if adequately maintained, concrete can last up to eighty years.
Yet concrete also has its downsides: Manufacturing it has a high carbon footprint, since its fabrication requires the energy-intensive heating of limestone; it has a tendency to crack when tree routes grow underneath it; and it has no porosity, depriving the ground under it of essential ground water and increasing runoff problems."