Sand Filler. Sand was the first filler employed for brick pavements, and in the Middle West is even yet almost exclusively used. The sand should• be fine and dry, and be worked into the joints by sweeping it over the pavement, which also should be dry. A few cities specify that the sand shall be heated to dry it, before being swept into the joints. Although the sand is nominally always swept into the joints, it is spread upon the surface and left to be worked in by traffic, which is undesirable since the joints are then partially filled Ni 'h manure and street dirt. The sand can be swept into the join effectively and economically with a revolving machine sweeper. After the joints have been filled, the surface of the pavement is covered with a layer of sand I to inch thick, which is left on for a crew weeks after the street is thrown open to traffic, to secure th thorough working down of the sand into every joint. The cost of sweeping the pavement and filling the joints with sand is 0.15 to 0.25 cent per square yard, and the cost of a finch layer of sand at $1.08 per cubic yard is 1.5 cents per square yard. To cover waste and contingencies, the sand joint filler is usually estimated at 2 cents per square yard.
The advantages of a sand filler are: 1. It is cheap, usually costing about 2 cents per square yard. 2. The pavement may be thrown open to traffic as soon as the bricks are laid. 3. The pave ment may be taken up easily and without breakage of the brick. 4. It is practically water tight, particularly after being in service a short time. Whenever a brick pavement having a sand filler is opened, the sides of the brick are always found dry and clean a little distance below the wearing surface.
The disadvantages of a sand filler are: 1. It does not protect the edges of the brick from chipping. 2. It may be washed out on steep slopes. 3. It is removed from the top of the joints by the street sweeper—either the broom or the pneumatic.
The cost depends upon the locality and the closeness of the joints. Usually tar costs from 6 to 8 cents a gallon; and one gallon is generally sufficient for one square yard of pavement. The total cost of the filler varies from 10 to 12 cents per square yard of pavement.
Tar is superior to sand in that it makes a perfectly water tight joint; and it is superior to hydraulic-cement grout in that it is not so rigid and therefore makes a more quiet pavement.
Tar costs more than sand, and does not protect the edges of the brick as well as hydraulic-cement grout.
The objections to tar are: 1. In summer it is likely to melt and run out of the joints; and in winter it is brittle and likely to chip out of the joints. 2. The heating of it makes unpleasant odors on the street.
Sometimes asphalt is mixed with the tar to make it less susceptible to changes of temperature, and sometimes asphalt is substituted for the tar. Unfortunately a mixture of tar and as phalt is often referred to as tar and also as asphalt, and frequently as pitch—a term also applied to tar or asphalt;—and consequently it is difficult to determine the practice in different cities. A com mon composition of "asphalt" filler is: refined asphalt, 20 parts, residuum oil, 3 parts; and coal-tar distillate No. 4, 100 parts. It is not clear that using a thicker tar and entirely omitting the asphalt and the residuum oil would not give an equally good filler. The different asphalt paving companies sell an asphalt paving filler.