A concrete laborer or layer sets up the forms in which concrete is poured to create walkways, walls, pillars and other structures. Concrete laborers can have a workers compensation injury from a single traumatic lifting incident or fall at work, resulting in a herniated disc for example. Or they can incur degenerative disc disease over time in part from the heavy physical labor required by the job duties. Laborers lift and carry rebar or wire mesh to reinforce the concrete, often bending over to use trowels and other tools to spread and smooth concrete, and mold expansion joins and edges. Curing time varies by temperature, wind and other environmental factors, so laborers must monitor the material to ensure it hardens to a durable finish. Laborers may add color to the concrete, small stones for decoration, or apply waterproofing and other sealants often by hand in sweeping and twisting repetitive motions.