In all specifications for materials to be used in paving, curbing, and guttering of every kind, a city shall establish a standard or standards of strength and quality, to be demonstrated by physical, chemical, or other tests within the limits of reasonable variations. In every instance the materials shall be so described in the specifications, either by standard or quality, to permit genuine competition between contractors so that there may be two or more bids by individuals or companies in no manner connected with each other and no material shall be specified which shall not be subject to such competition.
Neb. Rev. Stat. §§ 14-3,124