Appeal from the District Court of the United States for the District of New Jersey; William Clark, Judge.
Before BUFFINGTON, DAVIS, and THOMPSON, Circuit Judges.
BUFFINGTON, Circuit Judge.
The primary question in this case is the validity of patent No. 1,684,671, granted September 18, 1928, to Harold P. Hayden, assignor to Barber Asphalt Company, the present plaintiff, for "method of preventing evaporation from concrete during curing." The practice of the art prior to the patent in suit, the objections thereto, the novel means the patentee disclosed to overcome these objections, their effectiveness and money saving, are set forth in his patent specification, which we adopt, in view of the proofs, as the facts of the case, to wit:
"In modern cement concrete construction it is desirable to retard the evaporation of water from the concrete after it is placed and during the curing period in order to insure thorough hydration of the cement and thus produce a concrete of maximum strength.
"Heretofore various methods of protecting concrete during the curing period, especially in roadway and the like construction where the concrete has a large exposed surface, have been used, for example, one well known method used in roadway and the like construction involves the application of wet burlap to the exposed surface of the concrete immediately after finishing, the burlap being kept wet, as by sprinkling, until the concrete has set, or at tained a rigidity such as to withstand a substantial weight without marring, after which the burlap is removed and the surface covered with earth, or straw, which is maintained wet until the expiration of the stipulated curing period, when the earth, or straw, is removed. Another method, which has been attempted, involves the spreading of tar on the surface of concrete after the concrete has set, or attained a rigidity such as to enable workmen to walk on it without marring the surface. Still another method involves the provision of dikes about the concrete for maintaining a pond of water on its surface until it is ready for use.
"The methods heretofore used for protecting concrete during the curing period are open to numerous objections, more especially in that they involve substantial expense and are ineffective in preventing the evaporation of water from the concrete during the critical period before the concrete has set, or the protection of the concrete is not attempted until substantially after the critical period has passed, as is evidenced, for example, by the occurrence of hair cracking, which is avoided by the practice of the method according to my invention.
"I have discovered that if cement or cement concrete be treated, after it is finished, i.e., smoothed off, or broomed if so finished, and before it has set, i.e., before it will support a substantial weight, such as that of a man walking on it, without marring, by the formation on the exposed surface thereof a water impervious film, which preferably will adhere to the concrete, and the concrete be then permitted to set and cure without disturbance, the concrete will cure without hair cracking, and when cured will be found to have greatly increased strength, durability and resistance to weathering as compared to concrete treated by the methods heretofore known.
"In accordance with my invention, I apply the water impervious film to the exposed surface of cement or concrete to be cured before it has set, by which, as has been indicated, I mean before the concrete has attained a condition of firmness or rigidity such that it will support a substantial weight without marring of the surface, as for example, the weight of a man walking on it. Preferably, the film is applied as soon as practical after the cement or concrete is laid and finished; however, it must be applied before the concrete has set, as indicated above, if the benefits of my invention are to be obtained.
"In accordance with my invention, the water impervious film, when applied before the cement or concrete has set, as indicated, acts to prevent evaporation of water from the cement or concrete, and especially from exposed surface thereof, or to retain sufficient original water in the cement or concrete, during that period in which the continuous presence of requisite water is essential for the hydration of the cement and the avoidance of hair cracking of the surface.
"As illustrating different applications of the principle of my invention I will give the following examples: --
"A bituminous paint such as ordinary liquid asphalt paint, consisting of a residual asphalt base of twenty to thirty penetration at 77 deg. F., or native asphalt, dissolved in a volatile petroleum solvent may be used as the coating for this purpose. Such a paint when applied, for example at the rate of one gallon per 100 sq. ft. as soon as practical after pouring and finishing of the concrete, but in any event before the concrete has set, will form a satisfactory protective impervious film, and prevent evaporation of water from the concrete during curing.
"Ordinary linseed oil paint will also form a satisfactory impervious film if applied in sufficient quantity after the superficial water has subsided after pouring and finishing of the concrete.
"Stil another method of practicing my invention, and one that is distinctly preferred possesses further advantages. To the surface of wet unset concrete and preferably as soon as practical after laying and finishing I apply, as by means of a spray, a water-external-phase bituminous emulsion such as is often called in paving practice 'cold repair cement.' Such emulsion possesses the property of breaking after a short exposure to the air inconsequence of the evaporation of the water, with the formation of a water impervious adherent film of bitumen on the surface of the concrete.
"I have found that cement concrete which has thus been protected by the application thereto, when freshly placed, or before it has set, of a water impervious and preferably adherent film possesses a remarkably higher tensile strength after curing or aging than is possessed by the ...