Puffed Wheat Highways

Thud, thud, thud, go automobiles over many a brand-new concrete highway which looks as smooth as a table. Reason for this phenomenon, which has exasperated many a driver, is the bulging of the substance filling the expansion joints between the big rectangles of concrete. Like most solids, concrete expands in hot weather, contracts in cold. Hence the joints require a resilient substance which will fill the gap completely no matter how the concrete behaves. Most substances tried by road-builders have had two faults--they bulged in hot weather, left openings for seepage in cold.

Last week a company called Parabond Corp. of America, in Cambridge, Mass., disclosed its novel solution, which has been adopted by Connecticut, Rhode Island, Massachusetts. Parabond is a rubber latex compound poured into the expansion joints, where it jells. To prevent the usual separation from the concrete, it has a strong adhesive mixture. To prevent bulging, it is thickly interlarded with puffed wheat. The porous globules of puffed wheat constitute bubbles in the mixture, permitting the latex to give without forming a ridge across the highway.

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