98 HIGHWAY CONSTRUCTION 



Joint Filling. The character of the material used in filling the 

 joints between the brick has considerable influence on the success and 

 durability of the pavement. Various materials have been used such 

 as sand, coal-tar pitch, asphalt, mixtures of coal-tar and asphalt, and 

 Portland cement, besides various patented fillers, as "Murphy's 

 grout' '/which is made from ground slag and cement. Each material 

 has its advocates, and there is much difference of opinion as to which 

 gives the best results. 



The best results seem to be obtained by using a high grade of 

 Portland cement containing the smallest amount of lime in its composi- 

 tion, the presence of the lime increasing the tendency of the filler to 

 swell through absorption of moisture, causing the pavement to rise 

 or to be lifted away from its foundation, and thus producing the roaring 

 or rumbling noise so frequently complained of. 



The Portland cement grout, when uniformly mixed and carefully 

 placed, resists the impact of traffic and wears well with brick. When a 

 failure occurs, repairs can be made quickly; and, if made early, the 

 pavement will be restored to a good condition, If, however, repairs " 

 are neglected, the brick soon loosens and the pavement fails. 



The office of a filler is to prevent water from reaching the founda- 

 tion, and to protect the edges of the brick from spalling under traffic. 

 In order to meet both of these requirements, every joint must be filled 

 to the top, and must remain so, wearing down with the brick. Sand 

 does not meet these requirements. Although at first making a good 

 filler, being inexpensive and reducing the liability of the pavement to 

 be noisy, it soon washes out, leaving the edges of the brick unprotected 

 and consequently liable to be chipped. Coal-tar and the mixtures of 

 coal-tar and asphalt have an advantage in rendering a pavement less 

 noisy and in cementing together any breaks that may occur through 

 upheavals from frost or other causes ; but, unless made very hard, they 

 have the disadvantage of becoming soft in hot weather and flowing 

 to the gutters and low places in the pavement, there forming a black 

 and unsightly scale and leaving the high parts unprotected. The 

 joints, thus deprived of their filling, become receptacles for water, mud, 

 and ice in turn ; and the edges of the brick are quickly broken down. 

 Some of these mixtures become so brittle in winter that they crack 

 and fly out of the joints under the action of traffic. 



The Portland cement filler is prepared by mixing two parts of ' 



