. Practical concrete work for the school and home. in nature, or from the source of their origin, beenexposed to high heat, hence will stand such exposure in theconcrete. Clean Materials Necessary.—Attention has been called else-where to the necessity for using aggregates that are matter such as clay is particularly objectionable whenin the form of a coating on the particles. Where they are socoated, the cement cannot come in contact with the surface ofthe particles and therefore cannot bind them together. Washing Materials Sometimes Necessary.—\\hcre theonly sand and pebbles obt
. Practical concrete work for the school and home. in nature, or from the source of their origin, beenexposed to high heat, hence will stand such exposure in theconcrete. Clean Materials Necessary.—Attention has been called else-where to the necessity for using aggregates that are matter such as clay is particularly objectionable whenin the form of a coating on the particles. Where they are socoated, the cement cannot come in contact with the surface ofthe particles and therefore cannot bind them together. Washing Materials Sometimes Necessary.—\\hcre theonly sand and pebbles obtainable contain foreign matter, it isnecessary to wash them before using them in a concretemixture. This can readily be done by building a trough 20 PRACTICAL CONCRETE WORK like shown below. Materials to be washed are shoveledinto the trough at the high end, while water is applied at thesame end through a hose connected to a pipe. Plenty ofwater flowino- down the trousfh will cause the materials to be , Bof//e -it>i7r!y ■..■;.: Peib/ea. A simple homemade device for washing sand and pebbles and for separating the twci from each other. cleaned by tumbling and rolling about. At the lower end ascreen is placed to separate the sand from the pebbles. Thewater carries off the foreign material. Wedge-shaped cleats(riffles) are nailed on the bottom of the trough inside to assistin tumbling the materials as they roll down. The foregoing description of aggregates and their physicaland other requirements to fit them for use in concrete workapplies particularly to the broad applications of concrete inbuilding construction. There is another aspect of the sub-ject of aggregates which pertains particularly to the use ofconcrete in the making of some small ornamental objects orwares, none of which is to be subjected to such tests ofstrength as is demanded of concrete in certain portions of PRACTICAL CONCRETE WORK 21 buildings. For instance, a concrete window flower box neednot have a
Size: 1997px × 1252px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookidpracticalcon, bookyear1917
