180 



STEEL RAILWAY BRIDGES. 



CHAP. IV. 



"(5) Surface coatings, such as cement mortar, asphalt or bituminous mastic, if properly 

 applied to masonry reinforced against cracks produced by settlement, expansion and contraction, 

 may be successfully used for waterproofing arches, abutments, retaining walls, reservoirs and 

 similar structures; for important work under high pressure of water these cannot be recommended 

 for all conditions. 



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50 zd. 



SECT/OHAL ELEVATION 



SECTION S-B 



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EHHj9B 



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DETAIL OF APRON PLATE 



Materials:- 6501m. ft- N? tf Sheet Zinc , 8\ 



135 Gal/on s Tar Paint- 

 Port/and Cement Concrete, /'?' 4 



REIHFORCED COHCRETE FLOOR 



FOR THROUGH 

 C'5-SQ'R-R 



SECTIONAL PLAN A- A- 



FIG. 25. REINFORCED CONCRETE FLOOR FOR THROUGH PLATE GIRDER BRIDGE. 



C. B. & Q. R. R. 



"(6) Surface brush coatings, such as oil paints and varnishes, are not considered reliable or 

 lasting for waterproofing of masonry." 



The membrane method of waterproofing bridge floors will be shown by describing the standard 

 methods of waterproofing in use by two railroads. 



CHICAGO, MILWAUKEE & ST. PAUL RY. SPECIFICATIONS FOR WATERPROOFING. 

 The specifications of the Chicago, Milwaukee & St. Paul Ry. for waterproofing are as follows-. 



The necessary provision for drainage and expansion must be made in designing the structure. 

 The waterproofing should never be compelled to resist hydrostatic pressure, and the membrane 

 should always be protected by a layer of concrete. 



(1) Preliminary. Fill all openings and pockets in the concrete except expansion joints 

 with cement mortar, and round off all sharp corners. Wherever waterproofing stops on a vertical 

 surface the end should be flashed into a groove in the concrete. 



(2) Preparing the Surface. Thoroughly clean and dry the concrete surface using wire 

 brushes and being careful to remove all the laitance. If necessary use hot sand to dry the con- 

 crete. Apply a coat of gasolene to the clean dry surface and follow with a coat of cold primer, 

 spreading the primer evenly with a brush. Omit the primer where tar paper is to be placed and 

 over expansion joints. 



(3) Laying the Burlap. After the primer coat has completely dried, apply a coat of pure 

 hot asphalt, and mop until the layer has a thickness of | in. While the asphalt is still hot begin 

 laying the burlap. Lay the first strip of burlap transverse to the drainage at the lowest point. 

 Lay the strips shingle fashion, as for tar and gravel roofs, and parallel to the first strip working 





