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Filling the Joints

sand, grout, bricks, filler, pavement and filled

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There is much difference of opinion amongst munici pal engineers concerning the best material to use in filling the joints in a brick pavement. The materials commonly employed are sand, Portland-cement grout, and asphaltic or coal-tar paving-cement. Certain patent fillers of more or less the same character are also some times employed.

Sand Filler. In using sand as a filler, a thin layer of sand is spread over the pavement and raked or swept into the joints until they are thoroughly filled. In some instances the sand is artificially dried before putting it upon the bricks, but ordinarily, in mod erately dry weather, the sand may be spread in a thin layer on the bricks and allowed to dry before sweep ing in. After the joints are well filled a light layer of sand is placed on top of the pavement and it is opened to traffic. The jarring of the traffic will cause the sand to settle more or less in the joints for a considerable time, and the sand cover should be retained for several weeks. The sand used for filling should be fine and sharp, free from loam and dirt. It must not pack or cake on top of the brick under traffic. In many instances sand has been used as a filler with satisfactory results and given good service even under moderately heavy traffic. It makes a practically impervious joint and holds the bricks quite firmly in place. It seems desirable in the use of sand filler to employ round-edge bricks, as the edges are not held so firmly as with a rigid filler, and if sharp are more likely to be chippedoff,while the round edges aid in thoroughly filling the joints with the sand.

Portland-cement Filler. For filling joints with Port land cement a grout composed of equal parts of cement and sand is commonly employed. This grout is mixed in a tight box to a condition such that it will readily flow into the joints, and is swept in with brooms until the joints are thoroughly filled. The easiest method of securing the complete filling of the joint is probably that of applying the grout in two parts, mixing the first part very wet and filling the joints nearly full. As the

grout begins to stiffen, the draining out of the water causes it to settle somewhat, but thoroughly fills and seals the lower part of the joint. The second part may then be mixed a little stiffer and the upper part of the joint be readily filled flush with the top of the bricks.

In handling the grout it is necessary that it be mixed quickly and applied at once without giving it time to settle, in order that it may retain its consistency and no separation of its materials take place. A pavement so filled becomes practically a monolithic mass, as the bricks are firmly held together and the joint is filled flush with the edges of the bricks with a material which soon becomes about as hard as the bricks themselves.

A serious objection to the cement filler is the rumbling usually resulting from filling the pavement solidly with cement grout, which is doubtless due to the expansion of the mortar in the joints. This has been doubted by some, on the ground that the rumbling is no worse in hot than in cold weather; but the expansion which causes rumbling is probably that due to the natural swelling of the cement mortar rather than that due to temperature. It is well known that Portland-cement mortar when kept in a damp condition expands considerably for several months after it has set. It is also subject to consid erable changes in dimension with variations in ure, and probably the least effect of expansion, rather than the greatest, is to be expected in hot, dry weather.

The rumbling of the pavement may be largely obviated by using expansion-joints along each curb and at intervals across the street. These joints are com monly made by putting a wooden strip between the courses of brick in laying and afterward removing the board and filling the joint with asphaltic or coal-tar paving-cement before applying the cement grout to the pavement.

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