US1682687A - Concrete block or slab and method of making the same - Google Patents

Description

Aug. 28, 1928.

' F. W. SAMPSON CONCRETE BLOCK 0R SLAB AND METHOD OF MAKING THE SAME Filed July 28, 1926 Patented Aug. 28, 1928 UNITED srA res PATENTOFFICE.

FRANK w. sarvrr sorv, or ATLANTA; Gunners. 9

coucnnrn sneer; on snan AND Mnrncon or MAKING THE sears.

. Application filed July 28,

This inventionurelates to concrete blocks or slabs and methods of making the same,-

and, particularly a to concrete roads and methods of laying the same.

It has been the common practice to construct concrete roads of a mixture consisting of coarse rock aggregates and motar which is poured over the sub-grading and planed or smoothed to the desired surface contour. In

using such a mixture, a certain proportion of mortar must be employed to fill the voids the mass thus forming rock clusters and con- I sequent mortar pockets in the finished pave ment surface. It is Well known that the cement and sand mortars of all concrete paven'ients possess less resistance against destruction under surface Wear and impact than the coarse aggregates of granite,1trap rock, limestone and other coarse pieces of stone of natural structure, while selected graclings of more durable stone suchas those mentionedpossess higher and more uniform Wear resisting qualities than gravel conglomerate. It is Well known by engineers and road builders that the impact of heavy loads is the quickest and surest destroyerof roads, and conseqeuntly engineers are requiring that the surfaces of concrete roads be planed to a substantially perfect contour and grade line in order that the road surfaces may be" protected as far as possible against the damaging impact that starts immediately at the point of any surface imperfection. In the concrete pavements built by ordinary methods, as referredto above, the perfectly planed surface afiords only temporary protection against destruction by impact, as the tractive thrusts of highway vehicles grind dust and grit against the pavement surface, thus causing continual frictional Wear.

19%. seriarno; 125,567.

This frictional Wear eventually disintegrates the finish coat of surplus mortar on the pavement until the coarse; aggregate of natural durable stone is reached. Since the stone is more resistant'to abrasionthan the mortar the rate of Wear is very materially reduced in areas Where the stones happento be prescut atthe surface-ofthelroad in close proxi a mitytoeachother, While abrasive Wear continues at a relativelyrapid rate over areas in the surface Where mortar pockets exist or Where the stone may "be Widely separated by the mortar, or Where the stone may be" sunkbelow the uniform surface elevation inthe surplus mortar, Atthis point in the life of the concrete road of ordinary construction, the variablerate of Wear will soon create unevenness in the pavement surface whichwill greatly lncrease theimpact forces to whrchthe surface of the road is subjected and hence hastens the destruction of the road. t

It also has been proposed to construct con crete roadsby laying a sub-base of a mixture containing a lean mortarmixture and rock aggregates of a low grade, and permit ting the sub-base to set, after which the sur face course is laid and planed. The use of lean mortar mintureand low grade aggregates in the sub-base permits the read more economically to be built, but it has been found that a very imperfect bond is probase has set, i a

i It also has been proposed to construct concrete roads with ordinary mixtures contammg an excess amount of mortar by pouring vided between the sub-base and surface" the concrete in position and then subjecting it to vibration to cause a Wedging actionto take place in the aggregates. In the method referred: to, and, which has been commonly practiced, a layer of concrete mixture ontaininrr a surplus of mortar is poured over the sub-grade. A layer of clean high grade aggregates is then spread over the concrete mixture after which the road is subjected to vibration to tampdown the surface aggregates. It has been found in actual practice that the tamping to which the road is subjected causes someof the higher grade surface aggregates to be driven downwardly a material distance below the road surface,

while some of the lower grade base aggrebaseand surface course employing low grade and high grade aggregates respectively, and wherein the higher grade aggregates are definitely maintained at the surface of the road to present a durable wearing surface.

Afurther object is to provide a concrete roadwhich economically may be constructed due to the use of relatively low grade aggregates in the sub-base, and wherein a perfect bond is effected between the sub-base chlnes now 111 use, and the vibrating action and surface course.

A further object is to provide a road of the character above mentioned wherein a relatively high percentage of the road surface is made up of stone aggregates, as distinguished from the usual concrete road surface which is composed largely of surplus mortar, whereby greater resistanceto impact and abrasion is obtained. a t

A further object is to provide a method of constructing concrete roads wherein greatly increased beam strength and improved surface wearing qualities are obtained, thus materially increasing the life of the road by minimizing cracking of the road and destruction of the surface.

A further object is to provide a method of constructing concrete roads wherein a distinct deficiency of mortar mixture isemployed as distinguished from the usual prac tice of employing an excess of the mortar mixture to obtain a more uniform distribution of aggregates throughout the mixture,

thus preventing the formation of mortar pockets.

A further object is to provide a method of the character outlinedwherein a cement containing sub-base is laid over the sub-grade and is subjected to a vibrating action to wedge the aggregates together and to pour a surface course of mortar and rock aggregates over the sub-base before the latter has set, and to sub ect the surface course to a vibrating action to cause a wedging action of the rock aggregates therein.

A further object is to provide a method of the character just mentioned wherein the aggregates employed in the surface course are preferably of the flat elongated type whereby an increasedlateral wedging takes place under the influence of the vibration to increase the beam strength of the road.

A further object is to provide a method of coloring the road to a substantial depth below its surface without disturbing the surface, whereby the road glare usually present on concrete roads is eliminated.

In the practice of the method, the road is sub-graded in the usual manner and the road width is defined by mold boards or suitable preconstructed curbing, as desired. A mass is then mixed containing relatively low grade aggregates and a relatively lean mortar mixture, and the proportion of the mortar mixture used is somewhat less than that required to fill the normal voids in the loose aggregates. It is also preferred to use a mortar mixture of the stifi'est workable plasticity. After the proper preparation and mixing, the material is deposited upon the prepared sub-grade and compacted to the physical limit of vertical and lateral wedg ing of the stone aggregates by means of vibration Any suitable means of vibration may be employed, such asthe vibrating maneed not be dcscribedin detail. It should be borne in mind, however, that the vibrating action to which the surface of the sub-base is subjected takes place together with considerable pressure. The portion of the vibrating apparatus which directly contacts .ing or pushing it by rakes or the like to spread it evenly over the sub-base to the proper thickness. The mixture for the surface course consists of a relatively rich mortar mixture and high grade aggregates such as granite, trap rock or the like. The pro portion of the mortar n'iixture employed is less than that required to fill the voids in the loose aggregates. This deficiency in mortar is important in the practice of the invention as will becomeapparent. In selecting the aggregatesto be employed, it is preferred that relatively flat elongated stones be employed in order that increased lateral wedging may be obtained. After the surface course is laid in the manner described, it is subjected to vibration and pressure. The subjection of the sub-base and surface courses to vibrationand pressure causes the aggregates to be driven into close contact with each other whereby they are wedged together. This wedgingaction materially reduces the naturalvoidswhereby the mortar in the mixtures,which was originally deficient in proportion is suflicient to fill the reduced voids and a compact mass results in which there is an even distribution stones are closely compacted, being separated by relatively thin veins of mortar. It will 1 be apparent that the placing of the surface course-loosely upon the sub-base causes the aggregates of the surface course to assume different. relative positions, but when the sur face course is subjected to vibration and pressure, the aggregates tend to flatten out horizontallyand overlap each other whereby great beam strength is provided.

j The deficiency in the mortar prevents it fromffalling away from the aggregates to form surface pools on the sub-base as well as thesurface course, and very little free moisture is present. It has been found therefore that a perfect bond may be obtained between I course wherebythey are effectually prevented from separating. In the impacting action, use is inade'of the factthat the semiplastic mortar which coats the stones acts as a lubricant thereby permitting the stones to slide into the closest possible interlocking co-relation under the process of compacting,

and thus the aggregates, as loosely measured before mixing, after being lubricated and tightly wedged together will have then,

physical volume reduced materially in their final position of rest in the concrete mass. This reduction lIl VOllllTlG reduces the voids between the stones, thus maintaining the in close proximity to each other.

aggregates It has been found that the flattening out of the aggregates in the surfacecourse, and the use of a deficiencyin mortar, permits a completed road to be formed wherein the surface a is made up of as high asapproximately 90 per cent stone. In practice I prefer to employ stone having a relatively deep color in order that the surface glare may be materially reduced.

As prev1ously stated,the surface course is placed over the sub-base immediately after the latter has been properly subjected to vibration and pressure. The preparation of the concrete mixture of the base in the manner above described, and the compacting of. the base to the limits of vertical and lateral wedging of the stone aggregates quickly renders the base fully and uniformly stable and rigid while the cement in the base is fresh and unset. It has been found that the base, constructed as described, is highly stable, and the materials for the surface course maybe transported thereover without loosening any of the base aggregates or materially disturbing the surface thereof in any manner. that the vibrating action to which the surface course is subjected will notcause the base aggregates to riseto the top of the surface course, and the higher grade aggregates of the surface course will be prevented from being driven downwardly into the base.

the sub-base and surface The stability of the base is such The compacting of the base and the great stability thereof forms a firm support for the readily are caused to assume substantially horizontal positions by the vibration and pressure to which they are subjected, and the lateral wedging of the aggregates is materially increased.

It will be obvious that only small amount of mortar can be present on the top of the surface course after the completion of the process above described. The finished road surface is thenmade by brushing over the top ofthe surface course before the mortar therein has set. In practice, it is preferred to permit the semi-completed road to remain approximately one hour after the completion of the vibrating action before the surface thereofis brushed In the brushing operation, Tprefer to place a smallamount of saw dust, sand, or other absorbing medium on the surface coat, and the brushing action carries the absorbing medium over the top of the surafcecoatand takes up the excess inois ture and the relatively small amount of surface cement present. The surface thus presented has been found to be made up of as high as90 per cent stone, the remaining surface being made up by the thin veins of mortar between the aggregates. The durable stone employed in the surface course provides a true surface and the stones are held rigidly in their relative positions by the integral character of the road whereby it will be apparent that the road is adapted to be subjected to considerable impact and surface abrasionwithout injury to the road.

I have found that the mortar adjacentthe surface ofthe road constructed in accordance wlth the present invention readily may be colored to a substantial depthj without road. Mineral mortar swept over the completedroad surface before the cement therein has attained its final set, and while the mortar isyet moist from mixing; It has been found that the color will penetrate the moist mortar to a sufficient depth to leave a permanent color. Mineral mortar colorings will all fade, but ithas been found that the present method leaves a dull tone of the desired coloring, thus eliminating the pavement surface. a

In the drawings I have shown several sunlight and motor headlight glare from forms ofroad constructed in accordance with a a completed road, 1

igure 2 is an enlarged vertical sectional view of a portion of the road, and,

Figure 3 is a similar view of a modified form of roads Referring to the drawings the numeral 10 designates curbings arranged at the sides of the road. As previously stated these curbings may be dispensed with and ordinary mold boards may be employed for confining the road during its construction. A sub-base 11 is arranged between the curbings, and includes rock aggregateslQ, preferably of a low grade regardless of their hardness, and the aggregates are bound together by mortar, as indicated at 13. As previously stated, a. deficiency in mortar is employed, but the mortar is suflicient to completely fill the voidsafter the base is subjected to the vibrating action previously referred to. The base is laid on the usual sub-grading 14:,which is crowned in the usual manner and the base also may be crowned as indicated at 15. A A

After the completion of the sub-base, a surface course 16 may be placed in position. The surface course also is crowned as indicated at 17, and the sides thereof are arranged fiush with the inner portions of the curbing as will be a parent. The surface course is made up 0 preferably flat elon- 'ated aggregates 18bonded by mortar 19. The amount of mortar employed in the surface course also is less than the amount necessary to fill the normal voids in the surface aggregates, but is sufii'cient to fill such A voids after they have beenreduced by the action of the vibration and pressure to which the surface course is subjected in the manner previously described.- As shown in Figures 1 and 2, the relatively flat elongated aggregates 18 are caused to assume substantially horizontal positions underthe-force of the vibratory impacting, and overlap each other throughoutthe surface course, thus greatly increasing the beam strength of the road. The top surfaces ofthe upper aggregates 18 form a large percentage of the actual road surface as indicated at 20. A

A In Figure 3 of the drawings I have shown aroad constructedin the manner illustrated in Figures 1 and 2, exceptgthat coloring matter is provided for the surface portions of the cement between the surface aggregates. As previously stated, a solution of a mortar coloring is brushed over the surfaceof the road and this coloring has been found in actual practice to penetrate to a substantial depth as indicated at 21. Due to the depth to which it penetrates, the coloring will not wear off and thus the road glare is substantially permanently eliminated.

From the foregoing it will be apparent that the present invention contemplates the provision of a road laid in two courses, to

reduce the cost of construction. The aggregates used in the base are of a relatively low grade, while a relatively lean cement mixturepreferably is employed. The vibratory action to which the sub-base is subarated only byrelatively thin veins of mortar. The provision of a road surface made up to a great extent of closely placed stones greatly increases the wearing qualities of the road whereby the latter will not be so highly subject to the destructive action of impact and abrasion. In this connection attention is invited to the fact that it is the customary practice to employ some means for preventing the escape of the original moisturefrom the mortar to permit the latter to properly cure. In connection with the present method, it should be noted that inasmuch as the surface of the road is made up principally of rock, the rapid evaporation of the original moisture from the mortar is prevented and consequently no outsidemeans is necessary to assist in properly curing the road.

The placing of the coloring matter as shown in Figure 3, together with the use of colored stones provides a road which some what resembles a black pavement in physical appearance, thus materially reducing road g are. 1

While I have described the method as being particularly applicable to the building of roads, it will be apparentthat slabs or blocks of any desired size may be constructed in accordance with the invention for use in other ways, as in building constructions and the like. i

It is to be understood that the structure of the road and the methods outlined are to be taken as preferred examples of the same and that various changes may be made therein without departing from the s irit of the invention or the scope of the su joined claims. a

I claim: A i

1. The method of making concrete structures which consists in placing a base containing aggregates and an insufficient quantity of mortar to fill the normal voids of the aggregates, vibrating the aggregates of the base whereby the mortar content thereof will be sutficient to fill the voids, placing a surface course containing mortar and aggregates on the base before the latter has set,

and vibrating the aggregates of the surface course. i

2. The method of making concrete structures Whichconsists in placing abase con taining aggregates and an insu'fiicient quan tity of mortar to fill the normal voids of the aggregates, subjecting the base to vibration and pressure to reduce the voids substantially to the volume of the mortar, placing on said base before it has set a relatively thin surface course containing inortar and relatively flat elongated aggregates,

and subjecting the surface course to vibra tion and pressure.

3. A concrete construction having an outer portion formed of a relatively large percentage of relatively flat elongated coarse aggregates and a relatively small percentage of mortar, said aggregates lying in close relationship to each other throughout the mass of said outer portion and substantially parallel to each other and to the surface of said outer portion and overlapping each other, the surface of said outer portion being formed of substantially 90 per cent coarse aggregates. i

In testimony whereof I affix my signature.

FRANK W. SAMPSON.

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