Читать книгу The Library of Work and Play: Mechanics, Indoors and Out - Fred. T. Hodgson - Страница 5

Fig. 7. Floats and trowels

The floating operation is laborious, for it must be done at once, while the operator is on his knees. Fred and Nick, however, worked away at it until they made a good job of the portion that they were putting down. All of the walk they could finish at one time was about sixteen or eighteen feet, so that the whole job required a number of days to complete.

The first instalment being done, so far as the floating was concerned, it was now in order to make joints in the walk across the face, firstly for the purpose of marking it off into flag sizes, four feet square; secondly to prevent expansion. If there were no joints made in the walk, it would "lift" up, crack, break, and ultimately be destroyed. Fred, who knew that the walk would contract in cold and expand in warm weather, explained this peculiarity to George and Nick, and having a "jointer" along with the floats which the father had sent, he, with Nick's help, ran some joints, at four-foot intervals, across the walk, while Nick pushed his spade through the joints to the ground, actually cutting cement and concrete into sections of four feet each. This would allow for expansion or contraction, and even admit the raising of some of the sections above the others, without cracks or breaks occurring.

The first instalment of the walk being made, it was left to George to wheel damp sand and scatter it over the face of the walk about an inch thick, to keep the sun and rain from injuring it.

Then he received instructions to wet the surface every morning for a week. At the end of two or three days the cement was hard, or "set" enough to bear walking on, and in a week it was cleaned off for use. One peculiarity about concrete or cement work is, that it improves and gets stronger with age.

The walk was complete in due time, in sections of about sixteen feet long, and proved quite satisfactory. Mr. Gregg was pleased with it, and he explained to Fred, George, and Jessie that it might have been made more ornamental, as there were many tools for rounding off the edges, indenting the surface, to make it less slippery, or for laying the flags off in panels; but in this case all were pleased with the way the boys had finished it.