OCR Text |
Show Concrete Slabs Will Be Given Series of Tests (Prepared by the United States Department of Agriculture.) To determine the relative efficiency of several designs of concrete pavements pave-ments and to develop more "exact knowledge of the amount and distribution distribu-tion of stress In pavement slabs resulting re-sulting from loads applied to them In various positions, the bureau of public roads of the United States Department of Agriculture Is constructing numerous numer-ous full-size concrete pavement slabs at the experiment farm of the department depart-ment at Arlington, Va. The slabs will Jater be subjected to an elaborate series of tests. Some slabs will be of uniform thickness, thick-ness, throughout. Tests on these are expected to furnish information regarding re-garding the relation between loads applied ap-plied at various points and the stress mid strain of the concrete at all points In the loaded cross section, and the relation between load resistance and slab thickness. Other slabs will be thickened at the edgos and for a certain distance from the edges In accordance with the different dif-ferent designs now used in several states. In some slabs the thickening will be provided for by excavating the subgrade under their edges. In others the surface of the concrete slab will be raised at the edges so as to form a low, rounded lip curb. In still others the Up curb will be combined with a thickening of the edge of the slab at the bottom. Observations of these sections sec-tions will furnish Information regarding regard-ing the relative load-resisting properties prop-erties of designs now in use in various va-rious states. The test slabs, which will be 20 feet wide by 40 feet long, will have central longitudinal and transverse Joints. The object of one test Is to determine de-termine the efficiency of various methods meth-ods in use for transferring load across these joints. Other experiments will Include bond tests of dowel bars to determine the length of embedment necessary; the measurement of subgrade friction, with particular attention to the effect of edge thickening of transverse joints on resistance to the sliding of the slabs on the supporting surface; and |