## C rrw3 6TI 67 sacks

The amount of sand required is 2)4 times the cement required, or 15 cu. ft. (2)4 X 6.7 - 15). The amount of gravel or coarse aggregate is three times the amount of cement, or 20.1 cu. ft. (3 X 6.7 = 20.1).

A simple, easy method of very roughly estimating quantities of materials required for small jobs is to assume that the amount of coarse aggregate required will be the same as the total volume of the forms; and that the amounts of sand and cement required will be in the same proportion to the coarse aggregate, as they are in the mix. For example, suppose 10 cu. ft. of concrete is to be made, and the mixture is to be a 1-2)4-3. According to this method, 10 cu. ft. of coarse aggregate will be needed; and the amount of sand needed will be to 10 as 2)4 is to 3, or 7y2 cu. ft. (Sand: 10 = 2)4:3, or, Sand - (10 X 2K) + 3 - 7^). From the proportions it is evident that one-third as much cement is required as coarse aggregate, or 3.3 cu. ft. (sacks). It is obvious that this method indicates more materials than will be needed, but it is valuable for making a quick rough estimate on small jobs when no table is at hand, and where a little surplus is preferable to taking a chance on having to reorder or make a second trip for extra materials.

### Questions

332. (a) Just what takes place when concrete hardens into a permanent mass? (6) Why is it important that too much water not be used in mixing concrete?

333. How should mixtures for concrete be specified? Why?

334. (a) How should the proper proportions of sand and pebbles to cement be determined? (b) In case a mixture is too stiff and harsh, what would you recommend? (c) What are some general rules governing the proportions of sand to pebbles?

335. (a) What is a workable mixture? (b) WW condition may result from the use of insufficient mortar in a mixture? (c) From the use of too much sand? (d) Give examples of construction where the mixture should be more plastic than in other cases?

336. (a) Upon what factor does watertightness depend principally? (b) What other factors are also important?

337. (a) What is meant by aggregate? (6) What is fine aggregate? (c) What is the maximum siae of particles of coarse aggregate that should be used in thin slabs or in wall«?

338. (a) What are the desirable properties of sand? (6) What is meant when it is said that sand should be well graded? (c) Why should it be well graded?

339. What are the desirable properties of coanse aggregate?

340. (a) What is bank-run gravel? (b) Why is it seldom suited for concrete work as it is found? (c) What is the recommended practice where bank-run material is to be used?

341. (a) What is the purpose of the silt test? (6) Just how is it made? (c) What is the maximum allowable amount of silt in a .sample? (d) How may the amount of ailt in sand be reduced?

342. (a) What test can be made to determine the amount of organic matter in sand? (6) Is the teat always reliable? (c) Just how is the test made? (d) Just how may the testing solution be made from common household materials?

343. (a) Describe a simple washing device that may be used for washing sand and gravel. (b) Is it necessary to run tests after washing to determine if the silt or organic matter has been reduced to safe limits?

344. What requirements should be met by water that is to be used in mixing concrete?

345. Describe different convenient methods that may be used to accurately measure the materials used in concrete.

346. (a) What important point, or point« should be observed in mixing concrete with a machine mixer? (b) How large a floor or mixing platform is needed for hand mixing? (c) Describe, step by step, a good method of mixing materials by hand.

347. (a) How long after mixing may concrete be left before placing in the forms? (6) What treatment should the fresh concrete receive as it is placed in forms? Why?

348. (a) Why is a steel trowel not generally used for smoothing the surface of walks and floors in farm buildings? (6) What tool is commonly used for such purposes? (c) How may a floor, like a poultry house floor, be given a very smooth finish? (d) What may result from excessive troweling of a surface?

349. (a) Why should fresh concrete be protected against too rapid drying while curing? (6) How may walks and floors be properly protected? (c) How long should new concrete be kept moist?

350. (a) What important points should be observed in the construction of forms? (ib) Why are wood forms commonly oilod? (c) What kind of oil may be used?

351. (a) In general, how long should forms be left in place after the concrete is poured? (6) What conditions affect the length of time forms should remain in place?

352. (a) Under what conditions should concrete be reinforced? (6) In what part of a concrete beam or lintel should the reinforcing be placed?

353. (a) What precautions should be taken in making concrete in cold weather? (6) How may aggregate be heated?

354. (a) What materials are commonly used for mortar in laying tile, brick, or concrete block walls? (6) In what proportions should they be mixed? (c) What materials and what proportions should be used for mortar where extra strength and density are desired, as in water tanks? (d) Just what property does lime impart to a mortar? (e) Why is thorough mixing especially important?

355. (a) What is the first step in estimating the amounts of materials needed for a concrete job? (6) Explain how tables may be used in estimating quantities.

(c) Estimate the amount of cement, sand, and gravel required for a floor 12 ft. wide, 20 ft. long, arid 4 in. thick, if made of a 1-2^-3 mixture. Use the table«, (d) By use of a different method, estimate the quantities required for the job. (e) Explain a simple, easy rule for roughly estimating quantities, particularly on very small jobs.

### References

Various bulletins of the Portland Cement Association, Chicago, III. Boss, Dent, and White: "Mechanical Training." McMillan: "Basic Principle« of Concrete."

UJ3* Dept. AgricFarmers' Bull. 1772, Use of Concrete on the Farm.

PART VIII

HARNESS, BELT, AND ROPE WORK CHAPTER XXIII HARNESS REPAIR; BELTING; BELT LACING

Repairing of harness is not difficult for one with a moderate amount of mechanical ability or one who commonly does shop work in wood or metal.

Fig. 291.—-Harness repair hardware.

A. Buckle repair clip.

B. Screw hame loop.

C. Bottom hame clip.

D. Screw cockeye.

Q. Buckle attached with con way loop.

There is available on the market a rather wide range of harness hardware, such as buckles, loops, hame staples, repair links, etc., which may be installed on a harness with the use of only such tools as a hammer, vise,

file, cold chisel, and punches. With such pieces of harness equipment, and with a knowledge of harness riveting and leather sewing, a farm boy

Fio. 202.—Harness repair tools.

A. Homemade harness sewing clamp for uso in a vise.

B. Hand machine for using tubular rivets.

C. Lather punch.

### D. Harness sewing awl.

356. Tools and Equipment for Harness Repairing.—Very little special equipment is required for harness repairing. The following list would ordinarily be quite adequate for the farm shop.

1 riveting machine for using tubular rivets.

1 harness sewing awL

1 package assorted harness sewing needles.

1 ball No. 10 linen thread.

1 harness punch.

1 harness sewing clamp (may be homemade).

1 piece harness maker's wax.

Assortment of solid copper rivets and burrs.

### Assortment of tubular rivets.

357. Riveting Leather.—The most secure kind of riveting is done by-punching holes in the leather with a hollow-bit leather punch, inserting a solid rivet, and then placing a burr (washer) on the end and riveting it in place. This kind of riveting is recommended when permanent repairs are being made.

Hollow or tubular rivets are quickly and easily used with the aid of a small hand riveting machine. Such rivets are commonly used for temporary repairs and are excellent for this purpose. Another type of rivet sometimes used Is the split rivet, which has two prongs. It is hammered through the leather, and the prongs are bent over and clinched to hold the rivet in place.

ABC Fig. 293.—Styles of harness rivets. A, solid rivet with burr; B, tubular rivet; C, split rivet.