"Concrete should not be dressed (tooled) until 30 days old, under normal conditions—preferably not under 60 days. Before casting the several classes of block, it should be agreed between the contractor and the in spector as to the method of handling the block, so that there will be no dog or lewis holes in the showing faces. I found on my own work that this question is overlooked frequently in the design and moulding of the blocks. "Lewis holes should be cast in the blocks where prac ticable. Bear in mind that lewis holes must be so made as not to bring excessive pressure on the concrete. par ticularly near the mortar facing or near the arrises of the block. Remember that you are not handling granite. Be careful not to handle large blocks with lewises or dogs when they are green, as you will meet with dis aster. The contractor must provide wood blocks and rag cushions in turning over the blocks; otherwise the arrises will be broken.
"One-quarter to %-in. should be allowed beyond all neat lines for dressing. All arrises should be chiseled.
Better work can be got by using hand hammers than machine ones; and concrete details subject to close inspection by the public should be hammered by hand.
All arrises excepting those of abutting joints should be rounded to approximately a %-in. radius. If this is not done, the public will eventually knock off the fine arrises. Use metal templets for cutting important details.
"Modify all blocks which you are unable to cast sat isfactorily. Inspectors should report all blocks which in their judgment need additional reinforcement. Check all forms just before moulding, and keep a record of the blocks cast, and see that they are being cast in the order required on the work. Paint the date of casting on each block, and keep careful record of them.
"Cover all blocks in warm weather with rags, bags, etc., keeping same covered and damp for ten days. Do not cast blocks in freezing weather (particularly thin ones) without taking extraordinary precautions to pro tect the concrete from the cold.
"Concrete Mass Work. The inspector in charge of the mass work shall, before the mass concrete work is begun, receive from the form inspector an approval of the forms or shall personally examine them to see that they conform to line and grade, and that they are in accordance with the approved plan. He shall note, before beginning this work, that all laitancc, mud, chips, and dirt have been cleaned off the surface of the concrete, and that the forms (for finished work) are also cleaned of all dirt and cement. A very unsightly face is often
produced by leaving the mortar on the forms, which has resulted by the throwing of concrete into the forms in the previous day's work. He shall be governed by inspections from the assistant engineer as to the height which the contractor may be permitted to carry up a day's work.
"Concrete shall be placed in 9-in, courses on finished work. With the consent of the assistant engineer, con crete may be placed in courses of 2 ft. on heavy mass unfinished work.
"On finished work each day's work shall be brought accurately to horizontal and vertical surfaces. If this is not clone, the lipping which nearly always shows will be ragged and therefore unsightly. The positions of bulkheads and the height to which the finished work shall be carried shall be so selected as to assure a neat bonding appearance in the finished work. The con tractor should so arrange his work that the concrete may be brought up at least 2 ft. in a day's work.
"Don't finish the day's work too close to an orna mental detail. You will find, if you do, that you have lipping where you can least afford it.
"In waterproofing flat concrete surfaces with con secutive layers of tar or other similar material, apply the layers so that they will be shingled with the direc tion of the flow of water, and iron well. Don't apply waterproofing material rich in water—that is, which is full of water bubbles.
"On extra work, the contractor is entitled to pay for moving his plant or machinery to and from another part of the work, provided the extra job is on a part of the work previously declared finished by the engineer.
"Breaking into the contractor's gangs for men on odd extra jobs should not be resorted to unless abso lutely necessary. However, the contractor must, as a general rule, have enough elasticity in his force and plant to handle the current extra work with the same degree of facility and economy as the contract work proper. Extra work must not be continually sacrificed to the contract work proper.
"In paying for the use of machines under extra work, the engineer will agree with the contractor on the price per hour complete in operation, or, where extra work is continuous, on the basis of the price per day. Inspectors should compare the time of men and plant on all extra work with the foremen every night, and a similar com parison should be made by the superintendent and assistant engineer twice a month.