This section is from the book "The Law Of Contracts", by William Herbert Page. Also available from Amazon: Commercial Contracts: A Practical Guide to Deals, Contracts, Agreements and Promises.
Proportioning and Mixing. - Proportioning and mixing shall conform to the respective specifications therefor under head of "Concrete," Items 30, 31 and 32.
Consistency. - The material shall, in all cases, unless otherwise ordered, be mixed wet enough to produce a concrete that will flow readily which can be handled without causing a separation of the coarse aggregates from the mortar.
Placing. - After mixing, the concrete shall be deposited in place immediately. No retempering will be allowed, and concrete which has not been placed within 30 minutes after mixing shall be rejected and removed from the work. Concrete shall be deposited as nearly as possible in its final position. Rehandling of concrete after it has been deposited within the forms shall not be permitted. The concrete shall in no case be dumped or dropped from any great height. Each batch of concrete shall be spread in layers not exceeding four (4) inches in thickness. As soon as one layer is completed the next layer above must be started at once, and the work continued without interruption. As far as possible, the work shall be monolithic. Concrete shall be placed as continuous work between such planes and elevations as the Engineer may direct. When another layer of concrete is placed on one that has already set, the surface of the old concrete must be cleaned of all loose material then roughened, wetted and slushed with neat cement, before placing the new layer; or the bond shall be made by the acid or other approved process, if so directed by the Engineer. When it is necessary to make a joint in monolithic concrete, it shall be made in the middle of a panel at right angles to the beam and by means of a stop-board placed in a vertical position and containing a key on the side next the concrete first placed. Extra twisted or deformed bars shall be placed as directed by the Engineer, to tie old and new work together. When the stop boards are removed, the bond shall be made as above described. No tapered or wedge-shaped slope shall be used. Care must be taken to avoid getting dirt or other foreign matter on concrete surfaces on which other concrete is to be placed, or which has not set. At all stages of the work concrete and mortar must be kept entirely free from dirt of all kind, and if unavoidably mixed with dirt, shall be removed and replaced to the entire satisfaction of the Engineer.
Ramming. - Rammers for use with wet concrete shall be composed of thin blades of steel or iron, about four (4) inches wide. With these the concrete shall be thoroughly spaded and churned to remove all entrained air, and the concrete shall be pushed under and around all bars, corners and obstructions in forms and into all small openings. Care shall be taken in ramming not to displace any bars in forms. Ramming drier mixtures shall be thoroughly done with rammers of such shape and weight as directed, but in no case shall the concrete be mixed dry enough to require very heavy rammers.
Concrete in Freezing and Inclement Weather. - No concrete shall be laid in freezing or inclement weather except by special arrangements with and under the supervision of the Engineer. In case it becomes necessary to lay concrete in freezing weather, special arrangements must be made for heating all materials and maintaining a temperature around the concrete in place which will not allow the concrete to freeze until the same has set. Should any concrete show evidence of being damaged by low temperature, it shall be removed and replaced.
Protection of Concrete. - Whenever required the surface of the concrete shall be suitably protected from cold or frost, but such protection shall not insure the acceptance of the concrete, should it appear to be damaged.
Concrete must be kept moist for one week after depositing; in dry, hot weather it shall be kept covered from exposure to the sun during this time, or else must be constantly sprinkled during the day by a workman especially detailed for this work.
Bonding New Concrete to Old Concrete. - Wherever new concrete is to be joined to old concrete or to concrete already set it shall be done by either of the following methods, as specified:
(1) Bonding new concrete to concrete already set by the Acid Process shall be done as follows:
Thoroughly wash the surface of the concrete with water and then sweep the same from the surface, then cover the surface with diluted muriatic acid in proportions of one part of concentrated acid and three parts of water; allow this to remain until all effervescence has ceased; then flush off entirely with water and sweep clean. A thin coat of neat cement grout of the consistency of thick cream is to be thoroughly spread over the surface immediately after flushing; then spread the new concrete or mortar on the surface thus prepared.
(2) Wherever the specifications shall call for the use of a bonding compound in bonding new concrete to concrete which has taken its permanent set, the bonding compound shall be of approved quality and shall be thoroughly mixed with the new concrete in sufficient quantities to insure good bond between the old and new concrete. Before using such bonding compound the name of the brand and the proportion in which it is to be mixed with the cement shall be submitted to the Engineer and approved by him.
Finish. - This shall be done by careful spading and puddling the plastic concrete for which special tools shall be provided. This must be done with great care that subsequent amount of pointing necessary will be a minimum. Immediately after the forms have been removed, chip off any ridges due to cracks and joints in the lumber, and point the surface with mortar of same proportions as that used for concrete until it is even and smooth. All surfaces must present. a neat, even and smooth appearance, satisfactory to the Engineer, such appearance to be obtained by rubbing with a carborundum brick if deemed necessary by the Engineer.