US2795470A

US2795470A - Device and method for curing concrete compression test cylinders

Info

Publication number: US2795470A
Application number: US410189A
Authority: US
Inventors: Randolph A Lonier
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-02-15
Filing date: 1954-02-15
Publication date: 1957-06-11
Anticipated expiration: 1974-06-11

Description

R. A. LONlER METHOD June 11, 1957 2,795,470

DEVICE AND FCR CURINC CONCRETE CouPREssIoN TEST CYLINDERS Filed Feb. 15, 1954 'EIE DEVICE AND METHD FOR CURING CONCRETE COMPRESSION TEST CYLINDERS Randolph A. Lonier, Riverside, lli. Application February 15, 1954, Serial No. 410,189 2 Claims. (Cl. S12-31) This invention relates to improvements in the curing of. concrete test specimens and more particularly to a novel device and method for use in curing of such specimens.

As is well known, in order to develop optimum structural properties in concrete, it is necessary that the concrete be cured Curing involves hydration of the cement by means of water, such hydration being necessary so that the concrete will retain its structural strength. It is customary when a concrete structure is poured or formed to keep the concrete wetted down for a number of days to insure that the structure is properly cured.

For the same reasons, in evaluating the structural properties of a particular concrete mix it is customary to form in a mold a cylindrical test specimen which is then cured and tested for its compression strength and other properties according to various well known procedures and specifications as established by interested groups. Heretofore, the curing of such concrete test specimens has been carried out in either of two ways. In the laboratory, a special room or cabinet is provided and maintained at controlled temperature and humidity conditions for the required length of time, usually a matter of days or weeks. In the eld, the test specimen is cured by a less satisfactory technique such as by placing the specimen in a wooden box and covering it with Wet sand.

It will readily be seen that the curing techniques heretofore used have been relatively inconvenient and, at least in the case of laboratory methods, have been relatively expensive. My invention supplies a long felt need for a simple and inexpensive yet elective curing technique which is especially adapted for use in the field.

Accordingly, a primary object of the invention is to provide novel means for curing concrete compression test specimens, said means being characterized by a high degree of simplicity, convenience, and effectiveness as contrasted with the procedures heretofore employed.'

A further object of the invention is to provide a novel and relatively simple device for use in curing concrete compression test specimens.

Another object of the invention is to provide a novel curing method for use in the preparation of concrete compression test specimens.

An additional object of the invention is to provide novel means for controlling temperature and moisture conditions during the curing of concrete compression test specimens.

Other objects and advantages of the invention will become apparent from the subsequent detailed description taken in conjunction with the accompanying drawing wherein:

Fig. l is a perspective view of a structure comprising one specic embodiment of the invention;

Fig. 2 is a longitudinal sectional view on an enlarged scale taken along the line 2 2 of Fig. l;

Fig. 3 is a transverse sectional view line 3 3 of Fig. 2;

taken along the 2,795,470 Patented June 11, 19,57

Fig. 4 is a perspective exploded view showing certain elements of the structure seen in Figs. 1 to 3; and

Fig. 5 is a fragmentary sectional view illustrating certain modications of the invention.

Proper curing of concrete test cylinders is a function of both moisture and temperature. During the initial stages of curing, temperature is a particularly important consideration. At low temperatures, usually below 60 F., the rate of hydration of the cement declines and as the temperature approaches the freezing point of Water hydration may stop entirely. At higher temperatures, i. e. above 60 F., the rate of hydration increases with temperature and excessively high temperatures may result in a high early strength of the test cylinder but a low ultimate strength due to drying' out of the concrete. Consequently, during initial curing it is quite important to protect the test specimen from extremely high and extremely low temperatures. In the field or at the job site a temperature of from about 60 F. to about 80 F. will normally give proper curing, and in the laboratory a temperature of from about 65 F. to about 75 F. is desirable.

The initial moisture content of the specimen and its paper mould is usually adequate for proper hydration during the early portion of the curing period, especially in the case of field or job site tests in cool Weather. However, in warm weather or under other conditions it is necessary to supply additional moisture and retain a high moisture environment for the test cylinder over any excan is formed from relatively light gauge metal such as galvanized sheet metal but a suitable plastic or resinous material or waterproof paper or fiber or the like may also be used. The interior of the can is lined with a cellular porous material having good thermal insulating properties and also a high capacity for absorbing and retaining water. In this instance, the liner is made of cellulose sponge and is in two parts as best seen in Fig. 4 where.

the liner is illustrated in detached exploded relation. One part of the liner is a disk 12 of cellulose sponge which tits against the cap 11 at the closed end of the can, and

theother part of the liner is a rectangular sheet 13 of,

cellulose sponge rolled into a tube with the longitudinal edges 14 merely butted together Without any permanent attachment. The tube 13 is inserted into the can so that its inner end abuts the disk 12, and the inherent resiliency of the curled or rolled sheet holds the tube snugly in the can, with the disk 12 thereby also being retained in position as clearly seen in Fig. 2. If desired, an adhesive may be interposed between the liner and the can but the detachable assembly herein shown has the advantage of readily permitting the liner to when necessary.

In using the devi-ce, a concrete test cylinder Yor specinien 15 is disposed other at supporting surface and the lined can is placed in inverted relation over the test cylinder to enclose the specimen in spaced relation therewith. Such test cylinders are usually formed in a heavy paper or cardboard mold (not 4shown), and the mold may be left on the cylinder or removed, as desired, prior to curing. The test cylinder usually is 6 inches in diameter and l2 inches long in which case the outer shell of the curing can may be removed and replaced in upright fashion Ona-floor 16 or beL aboutv 8, inches. inxdiameter, and about 13%. inches.

is essential for satisfactory curing, itv is quite important thaty theY annularedge ofthe open'lower end ofrthe curing can have a continuous uninterruped sealing` engagement with thesupporting surface 16; To insure as good seal at this point, I' preferably; provide; aninwardly ex-l tending flange 17 at the lower endP of* thecylinder 10 which is turned upwardly; to a slight extent as shown in Fig. 2. Thus, ak minimumj contact areajbetween the annular edge ofI the can and' the: surface 16fis established which approximates a line contactiY Consequently,vk the effect of irregularities;A bumps, or other unevenness in either the supportingy surface or the open end of the can is minimized and thereV islittle.- opportunity for the. occurrence ofV gapsy or openV spaces'betweentheend of the can and theA supportinggsurfaceV whichl would detract from theeffectiveness of the can inmaintainingproper temperature and highmoist-ure contentin thespace around the specimen. Also, the inturned flange 17 assists in retaining the liner 13 within thecylinder 10:

As previously mentioned the internal liner of the can has both good thermal insulating properties and also high water-absorptive and water-retentive properties. As also explained above, temperature control ofA the test specimen is frequently the most important consideration, particularly during` the-initial curingV period. Consequently, in many instances the curing can will `be used in a dry condition, i. e. without prior saturation of the liner with water. Since the liner is a good thermal insulator, the initial heat of the test specimen will be conserved and in addition the heat generated by the exothermic hydration reactions during curing will be largely'retained. For example, curing of test specimens on the job site in winter or cool weather is often` a diicult problem. With my invention the test cylinder can readily be cured in an unheated shack on the job site by reason of the thermal insulating quality of the lined enclosure or can. Under other conditions, such -as in summer or warm weather, it may also be necessary to provide additional moisture for effecting extended curing of test cylinders. In this case, the lining of the curing'can is irst saturated with water and then placed over the test specimen. With a commercially available grade of coarse pore cellulose sponge about 1A. inch thick as a liner for a curing can of the previously mentioned dimensions, I have found that the liner will soak-up andv retain about one gallon of water and that even after two weeks use in curing the liner willV still contain about two quarts of water.

In addition to cellulose sponge,` other porous cellular materials having the required `properties may also be used for theican liner. In some cases it may also be desirable to provide speciall supporting sheets, slabs, or the like for supporting the test specimen and curing device. In this way a dat even supporting surface is insured over long curing periods regardless yoft the condition of the ground, door, or other surface at the curing site.

In Fig. 5, I have illustrated a modification of the invention wherein the external water tight cylinder has an outwardly extending flange 18 and the upper end cap or closure issecured to the cylinder by crimping the edge of the cap, as at 19, around and underneath the fiange 18. More importantly, I have shown a doublelayer internal liner for the can consisting of a' Ifirst layer 20 of thermal insulating material of any suitable type and aminnermostlayer 21 ofv water absorptiveandV retentivematerial. The use 0f the device is the same as hereinbefore described. The separate layers 2li and 21 may be adhesively secured to the outer container and to each other or they may be merely frictionally retained as in Fig. 2.

From the foregoing, it will be seen that my invention provides a novel and vastly improved means for curing concrete test cylinders which is equally adapted for use in the laboratory and in the field. The curing device itself is simple and inexpensive and is very convenient to use.V The needfor elaborate and costly humidity controlled cabinets or rooms is avoided. The test specimens are kept clean. andintact with themarkings thereon legible at all times. The method insures a substantially uniform control of curing conditions even over extended periods and the device itself can be used over and over depending upon the carewhicliit receives.

Although the invention has been described with par-- ticular reference to certain, preferred structural embodiments, it is to be understood that various modifications and alternatives may be resorted to without departing from the scope-of theinventi-on as dei-ined in the appended claims.

I claim:

1. A curing can `for 4concrete testV specimens comprising a Water tight enclosure having'a closed end and an open end whereby to permit said enclosure to be disposed in inverted relation over an upright test specimen with the open end of the enclosure engaging the supporting surface for saidspecimen, means at the open end of said enclosure-for insuring. a substantially sealed relation between the enclosure and the supporting surface, said means comprising an inwardly extending radial `lange slanted axially inwardly from said` open endv to minimize the surface contact area of the annular edge of said open end, anda liner provide-d at'the inside of said enclosure andcomprising a thermal insulator and a water absorptive and retentive material, said liner being adapted to prevent excessive temperature changes in the specimen during curing thereof and also being adapted to be saturated with water for insuring proper moisture content of the specimen during curing thereof.

2. A curing device for concrete test specimens cornpiising an elongated generally cylindrical water tight can, said can having a closed end and an open end whereby to permit the can to be inverted over an upright test specimen for enclosing the same, and a porous cellular liner extending around the interior of the can, said liner comprising a disk portion disposed against the closed end of the can and a separate tubular portion extending around the cylindrical Wall of the `can and frictionally retained therein and abutting said disk portion, the open end of said can having an inwardly turned flange portion engaging the end of the tubular liner portion for. retaining the same in the can.

References Cited in the le of this patent UNITED STATES PATENTS 412,461l Canon Oct. 8, 1889 552,526 Gronwald Ian. 7, 1896 1,857,018 Hanson May 3, 1932 1,999,152 Finley Apr. 23, 1935 2,215,479 Sair Sept. 24, 1940 2,573,772 Ny-sten Nov. 6, 1951