THE IRRIGATION AGE. 



777 



MIXING CONCRETE ON THE 

 FARM 



How to Select Your Materials and Mix Your 

 Own Concrete 



On account of its cheapness, uniformity, and quick de- 

 velopment of strength, the only cement practically used at 

 present is the kind called "Portland." There are almost as 

 many brands of Portland cement as there are of wheat flour. 

 For farm work choose some brand guaranteed by the local 

 dealer to meet the standard specifications of the American 

 Society for Testing Materials, which standards are approved 

 by the National Government. 



Cement takes water so easily that care must be exercised 

 in storing it. Upon the regular floor of a good building 

 place timbers close together, as a support for a false floor, 

 upon which the cement should be piled. 



=/K 

 SJ/VO 



7 



CO/VC/ffTF 



Proportion of Materials and Resulting Concrete. 



KEEP THE CEMENT DRY. 



Cement is heavy; do not overload the floor of the build- 

 ing by piling it too high, and do not store it against the side 

 walls. Keep it covered with canvas or roofing paper. Cement 

 once wet sets up and is unfit for use. However, lumps due to 

 pressure in the store house must not be mistaken for set-up 

 cement Such lumps are easily crumbled and may then be used. 



DO NOT BUY STONE 



SCREENED TO ONE 



SIZE. 



Concrete is a mixture of Port- 

 land cement and particles of stone. 

 The stone should vary in size 

 from pieces one inch in diameter 

 to sand grains. By so grading 

 the stone, the smaller particles fit 

 in the spaces between the larger 

 pieces, thereby producing the most 

 compact and the .strongest mix- 

 ture. 



The best stone for crushed 

 rock is one which is clean, hard, 

 and breaks with sharp angles. 

 Trap, granite, and hard limestone 

 are among the best; the use of 

 shale, slate, and soft limestones 

 and sandstones should be avoided. 

 The crushed rock should be 

 screened on a J4~inch screen to 

 remove the fine particles. These 

 small particles should be con- 

 sidered as sand; and, if insuffi- 

 cient in quantity to make the 

 proper proportion of the concrete, 

 as is described later, enough sand 

 should be added to them to pro- 

 duce the required amount. 



WELL-GRADED GRAVEL GOOD. 



Gravel well graded in sizes is at least equally as good 

 for concrete as crushed stone. Bank-run gravel just as duy 

 from the pit, seldom runs even and rarely has the right 

 proportion of sand and pebbles for making the best con- 

 crete. The mixture most suitable has one part sand to 

 two parts gravel, measured by volume, in which all sizes 



passing through a 1-inch-mesh screen and retained on a 

 .'4-inch screen are considered gravel. As there is usually 

 too much sand for the gravel, it is both advisable and 

 profitable to screen the material and to remix them in the 

 proper proportions. Gravel should have no rotten stone 

 and should be clean, so that the cement may adhere to it 

 tightly. 



SAND MUST BE CLEAN. 



With dirty sand, no amount of cement will make strong 

 concrete. Generally sand is clean, but if not, it can easily be 

 washed by playing a hose or flushing water upon thin layers 

 of sand placed on a tight-jointed inclined wooden board. In 

 size of grain it should vary uniformly from fine to coarse. 

 All particles passing a J/t-inch screen may be considered sand. 



Any good-tasting drinking-water is suitable for concrete. 



NO GREAT EXPENSE FOR TOOLS. 

 The tools and equipment necessary for making concrete 

 in moderate quantities are already at ' hand on a well con- 

 ducted farm, or will be used afterward for other purposes. 

 The list: 



2 square pointed "paddy" shovels, No. 3. 

 1 round pointed tiling shovel or 1 garden spade. 

 1 heavy garden rake. 



1 sprinkling can or bucket or 1 spray nozzle for 

 hose. 



1 water barrel or 1 length of hose. 

 1 sidewalk tamper or home-made wooden 

 tamper. 



1 sand screen made of a section of j4-inch wire 

 mesh nailed to a wooden frame. 



1 measuring box or frame. See description fur- 

 ther along in article. 



1 mixing board. 



2 wheelbarrows with steel trays. 



PROPER PROPORTIONS FOR FARM WORK. 



For farm work the following proportions are most suit- 

 able: 



For concrete necessarily waterproof. 1 : 2 : 4 or 1 : 4 

 For all other ordinary purposes....! : 2*/2 : 5 or 1 : 5 

 Such proportions of three parts, as 1 : 2 : 4 indicate that 



Mixing Board, Tools, Ktc. 



the concrete is to be .mixed 1 part cement to 2 parts sand 

 to 4 parts screened gravel or crushed rock; and 1 : 4 that 

 it is to be mixed 1 part cement to 4 parts bank-run gravel. 

 Measurement by counting shovelfuls is poor and uncer- 

 tain practice. To avoid splitting of bags of cement, make 

 as the unit of measurement 1 cub : c foot, the amount of 

 loose cement contained in one cement bag. Such measure- 



