182 



STEEL RAILWAY BRIDGES. 



CHAP. IV. 



parts fine gravel graded from in. to fine sand. The top of the mastic shall be leveled off with 

 wooden floats and mopped with waterproofing asphalt. 



(5) Expansion Joints. At all expansion joints in the concrete a fold to allow for the ex- 

 pansion of the structure shall be formed by laying the burlap and felt over a one-inch pipe; the 

 pipe being removed as the mat is being completed. 



(6) Splices and Flashing. Where the work is stopped before being completed at least 3 feet 

 of burlap at the end and one-half the width of the burlap at the side shall be left exposed to form a 

 splice. 



Special care shall be taken to seal the waterproofing at the sides and ends of the bridge. The 

 burlap and mastic shall be carried up the parapet walls at the sides and the ends of the burlap 

 shall be concreted into a recess in the walls so that no water can enter. The burlap shall be 

 carried down over the back-walls at the ends of the bridge to cover all construction joints and 

 shall run into a line of tile to facilitate the escape of the water. 



(7) Materials. Burlap. The burlap is to be 8 oz. open mesh high grade burlap saturated 

 with an asphalt meeting the specifications for waterproofing asphalt. It shall come in rolls 

 which shall be placed on end for shipment and storage, and shall not stick together in the roll. 



Felt. The felt shall be a good quality of wool felt saturated and coated with an asphalt 

 meeting the specifications for waterproofing asphalt. It shall come in rolls which shall be placed 

 on end for shipment and storage, and shall not stick together in the roll. It shall not weigh less 

 than 15 Ib. per 100 sq. ft. 



Primer. The primer shall be an asphaltic compound of approved quality and capable of 

 adhering firmly to the concrete. 



Waterproofing Asphalt. The waterproofing asphalt shall meet the following requirements. 



1. The specific gravity of the asphalt desired shall be greater than 0.95 at 77 degrees F. 



2. The flowing point shall not be less than 100 degrees F. nor more than 140 degrees F. 



3. The flash point shall not be lower than 450 degrees F. 



Broken 

 Stone 

 Filling \ 



Abutment 

 **~~Drain Tile 



Mortar-'' Corners of Slab \ 



(b) SECTION OF EXPANSION JOINT AT 

 OFFSET IN WATERPROOFING SURFACE 



Concrete t \ Expanded Mefak 3 Layers ef Burlap. 



* ~-U * ..... i t i . i . L . . . J 



Woun</i>ff Corners 



\Round off Slope-' W' Mortar \ 

 | D J 



(c) SECTION OF FIXED JOINT AT OFFSET 

 IN WATERPROOFING SURFACE- 



Surface of Waterproofing to 

 conform to surface of Hase--^ \ 



^- Groove 



Asphalt'' f e) TRANSVERSE SECTION OF SLAB- 



3 Layers of Burhp-~^ 



3 Layers of Burlap ' 



i \ 



1 ! 



II "-Burlap 

 J| j j / Layers or\\ Tar Papery ( 



(f) LONGITUDINAL SECTION OF WATERPROOFING (g) DETAIL OF SUMMIT (h) SECTION OF EXPANSION JOINT 



FIG. 26. STANDARD METHOD OF WATERPROOFING BRIDGE FLOORS. C. M. & ST. P. RY. 



4. The penetration at 80 degrees F. for a period of 30 seconds shall be at least 15 millimeters 

 and must not exceed 20 millimeters. This penetration to be measured with a Vicat needle weighing 

 300 grams, one end being one millimeter in diameter for a distance of 6 centimeters. 



5. When heated to a temperature of 325 degrees F. for 7 hours the loss in weight shall not 

 exceed 2 per cent and the penetration of the residue at 80 degrees F. and for the period of 30 

 seconds using the same instrument as described above shall not be reduced more than 50 per cent. 



6. The total soluble in carbon bisulphide shall not be less than 99 per cent. 



7. The total soluble in 88 degree naptha shall not be less than 70 per cent. 



8. The total inorganic matter or ash shall not exceed one per cent. 



9. Cold Test. 



a. A cube of the asphalt one inch on edge shall be soft and malleable at a temperature of 

 zero degrees F. 



