US2220448A

US2220448A - Method of making concrete blocks and the like

Info

Publication number: US2220448A
Application number: US223300A
Authority: US
Inventors: Henderson Albert
Original assignee: WILLIAM P WITHEROW
Current assignee: WILLIAM P WITHEROW
Priority date: 1938-08-05
Filing date: 1938-08-05
Publication date: 1940-11-05
Anticipated expiration: 1957-11-05
Also published as: GB533216A

Description

NOV. 5, 1940. A, HENDERSQN i l2,220,448

-METHD OF MAKING CONCRETE BLOCKS AND THE LIKE Fled'Aug. 5, 1938 {NVENTOR AZberzHeJzdefJoJz Patented Nov.v 5, 1940 UNITED STATES METHOD F MAKING CONCRETE BLOCKS AND THE LIKE Albert Henderson, Edgewood, ra., minor to William P. Witherow, Pittsburgh, Pa.

Aopuomon August s, 193s, sensi No. 223,34

Clalms.

This invention relates to the manufacture of molded cementitious articles such as blocks,

slabs. etc., and, particularly, to a method of maklng such articles whereby they may be produced 5 more cheaply than heretofore and at the samev time be characterized by superior quality.

This is a continuation in part of my copending application, Serial No. 62,965, filed February 8, 1936, for Apparatus for making concrete articles,

now Patent No. 2,131,474, granted September 2'7,

Concrete blocks and the like have usually been made heretofore bythe so-called dry process. While this process produces blocks 'which are satisfactory for many uses such as foundation wallsand the like where appearance is a secondary consideration, the blocks so made have not been used widely in exposed locations.' Further'objectlons to the previous method of making blocks include the high labor cost resulting from the necessity for handling the blocks individually from the molds to storage piles, as well as the danger of chipping and breakage resulting from such handling. The prior practice has been to 23 store the blocks for aging in any convenient place, without protection from the weather or changes in atmospheric temperature. This causes discoloration of the blocks and renders them generally undesirable from the standpoint so of appearance.

and novelty which will become apparent as the following detailed description of the invention proceeds. In a preferred practice of the invention, I pour liquid concrete into gang moldsr preferably from a traveling hopper. The hopper may conveniently be supplied with concrete from a truck mixer. The blocks or other articles are partly cured in the mold and then removed therefrom to a curing chamber for final curing. After curing, the blocks are dipped to chill them and stored in the same room where molded and cured whereby the waste heat from the molding and curing operations prevents the blocks from being subjected during aging to dangerously low temperatures. A complete understanding of the 5o invention may be obtained from the following Referring in detail tol the drawing, I prefer to carry out the molding, curing and aging of blocks within a single room or building as indicated by slde walls I0, roof Il and suitable end walls. A bridge crane I2 traversing the length 5 of the building facilitates transfer of-the blocks from point to point therein.

,An aisle I3 extends the length of the building, conveniently along one side thereof, and is provided with a paved roadway Il for the passage 10 therealong of a vehicle adapted todeliver mixed concrete, the usual form of such vehicle being a truck mixer as indicated diagrammatically at Il. As is well-known, these vehicles are charged with sand, cement, aggregate and water at cenl5 tral hatching plants and eiect the necessary mixing of such materials while en route to the point 'of delivery.

`Molding apparatus indicated generally at I8 is arranged alongside the aisle I3. This appa- 20 ratus is preferably such as that more fully described and claimed in the parent application above referred to. Briefly. it comprises side rails I1 along which a traveling hopper I8 moves.

Gang molds I9 are spaced along the side rails 25.

and adapted to receive concrete from the hopper in its various positions as it travels along the rails. A water tank 20 is installed beneath the gang molds and is provided with steam pipes 2l whereby heat and moisture may be supplied to so the space surrounding the molds.

In accordance with the invention, concrete is discharged from the truck mixer I5 to the hopper I8 through a chute 22 periodically or continuously as may be desired. The hopper I8 dls- 35 charges concrete to one gang mold I! until the latter is filled to the desired level. Thereupon .the truck mixer and hopper are moved along the aisle to the next gang mold. If desired, a coupling may be provided between the mixer and 40 hopper so thatv the hopper is drawn along the side rails II by the truck mixer in the manner of a trailer.

After the mold Il has been filled, it is subiected to vibration by any suitable means to 45 density and compact the concrete in theA several mold chambers. Steam is then admitted to the pipes 2l in such manner as to maintain the temperature adjacent the mold at about 175 F. 'I'his causes evaporation of the water in the tank 50 2li whereby the desired moisture content is maintained in the air adjacent the mold. The heat supplied by the steam pipes 2| causes partial curing of the molded articles. If too much heat is supplied, the concrete may exhibit undesired expansion or flumngt This impairs the quality -of the nished product. To prevent this result I subject the molded articles, after partial curing, to vibration or compression by any suitable means. and thus again density and compact the articles in the mold.

When the articles have set sumciently to be self supporting, which condition is attained in a relatively short time, because of the rapidity at which curing proceeds in the temperature maintained adjacent the mold, I partially remove the articles from the chambers of the mold, by means of the apparatus described and claimed in the parent application referred to above. This breaks the bond between the articles and certain of the mold parts and thereby facilitates the final removal of the articles from the mold.

A final curing chamber is located alongside the mold I9 and may conveniently take the form of a liftable,`open-bottomed box 22. Buccessive layers of articles formed in the mold il are deposited over a water tank 24 having steam pipes 2l therein and enclosed by the cover 22 forming a final curing chamber. Steam is supplied to the pipes 25 in such manner as to maintain in the chamber a temperature even higher than that to which the articles were initially.

subjected, e. g., 225 to 250 l". I have found that molded concrete articles, after initial curing, may safely be exposed to such temperature to accelerate the completion of the curing cycle without danger of expansion orfflumng.

On completion of the curing, the articles are separated from the mold portions which were removed from the mold with them to provide a unitary liftable mass including a plurality of articles, and piled on skips 2l for further handling en masse. In order to prevent excessive dehydration of the heated 'articles on exposure to the air, by evaporation of such free water as remains in them, I dip them in a tank` 2I of cold water. This dipping operation chills the blocks and thusprevents excessive dehydration on subsequent exposure to the air. Heat-exchange pipes 28 may be connected to a convenient source of heating or cooling fluid to maintain the bath in the tank 21 at the proper temperature. Instead of plain water, the tank 21 may contain a. coloring, sealing or hardening liquid.

Since the pores. of the articles are open when they are heated, such liquids will readily penetrate the articles on dipping. After dipping, the skip loads of articles are piled as indicated at 29 for gradual shrinkage. This process as previously can'ied out required a considerable length of time. I reduce the time required for shrinkage by storing the articles in the same room in which they are molded and cured and close enough to the heated molding and curing chamber so that the waste heat therefrom maintains the blocks in storage at a temperature of above 40 F. and accelerates the shrinkage process.

'I'he articles produced in accordance with the individually. This procedure is carried out even in delivering the articles to the job, as the loaded skips 2| may conveniently be placed on a delivery truck and the blocks removed at the job in the most convenient location. The empty skips are then returned from the job for reloading.

'I'he vibration of the mold after initial curing of the articles therein produces a stronger product with a lower absorption coefficient than has been obtainable heretofore. This is because the vibration eliminates the cells formed in the cement -paste by the quick hydration thereof resulting from heat applied in the curing. As already indicated, the chilling of the blocks when cured prevents excessive loss of moisture therefrom and also permits the application of coloring, sealing or hardening agents. The sudden chilling of the articles produces no observable ill effects. By protecting the articles during aging against abnormally low temperatures, the

strength of the finished article is increased and an attractive color imparted thereto, viz., al-- but a preferred practice -of my method, it will be understood that changes in the procedure disclosed may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

l. Inl method `of making concrete articles, the steps including poln'lng concrete into the mold, vibra-ting the mold, heating the mold and the concrete therein, and vibrating the mold and its contents after partial setting of the latter.

2. In a method of making concrete articles, the steps including molding the articles, subjecting the articles to heat to accelerate the hydration of the cement in the concrete by the available water. and, before elimination of all the free water, wetting the articles with a liquid at a temperature substantially below that to which the articles are heated, while they are hot from the curing, thereby chilling them and inhibiting excessive dehydration.

3. The method defined by claim 2 characterized by dipping the articles in the water.

4. In a method of making concrete articles, the steps including depositing concrete in a mold, heating the concrete in the mold, thereby effecting a partial curing of the article, vibrating the article to reduce the voids formed by the removal of surplus water in curing, removing the article from the mold, subjecting it to further heating adjacent the mold to complete the curing, wetting the article while hot from the curing with water at a tempera-ture below that of the article, thereby cooling it and inhibiting excessive dehydration, and storing the article near enough to the mold so that the waste heat from the curing operation expedites volume change in the article in storage.

5. In a method of making concrete articles, the steps including depositing a cementitious mix in. a mold, curing the formed articlesfby applying heat to the mold, said heat driving off surplus water in the articles, and reducing the voids left by the removal ofsaid surplus water, by vibrating the articles.

ALBERT HENDERSON.