US1832875A - Method of preparing concrete - Google Patents

Description

Patented Nov. 24, 1931 UNITED ST OFF METHOD PREPARING, ;C.0NCRETE No Drawing.

Our invention relatesto the artof'malringj concrete and hasfor its object the provisionof an. improved methodor process of'preparing the same to insure itsproper strength"- after hardening or setting. 1 The invention consists in regulatingthe amount or proportion; of moisture in a given quantity of miX- tnre by the removal of substantially all excess free molsture from the mass after the mixing operation has-been performedfand lVith a view to aclearer,understandingpf the present modeof treatment and its etlect, some preliminary observations as to the usual practices in making., concrete are desirable. The quantities ofthe various solid ingredients, includingicement and inert matter, em

ployed. in preparing a mixture .fora defin te Work orstructure are usually fixed upon "in advance of the undertaking, each being as signed a definite relative'proportion or value in termsusually of bulk or Weight, this estiao mate .beingbased. upon common experience.- Comparatively slight consideration is given in any given undertaking tothe correct rela;- tive proportion of fwater employed for effecting the necessary chemical chang'e :in th'ecement togive it theproperstrengtln Too much or-too little Water .are1bothldetrimental to thedesiredfresult, itibeingralvvays self evident that insufficient. moisture Would. fail in eliecting the chemical change inthe pow- 49 dered cement necessary to give itzadhesive strengthand solidifying properties, whileit is now increasingly appreciatedlby those. engaged with the commercial use .offfconcrete that any large excess of water is also destruc'- As a, corrective ,i measure tive in its effect.

the quantity v of. Water supplied .the .mixing chamber is only roughly estimated 7 with respect to the volume of the :solidiingrediients employed, irrespective oftheir characterano condition. The results, whileepartiallycon Applicationifiled;October:1, 1930. SeriaI'No. 485,658.

rective in many instances, are notnniformly soand ifarffrom approximating iscientifieac-j curacy and dependability. This is attributed tothe factthat'moisture is always presemxto aVaryingQeXtentin or on'the inert-"matter as" usedin commercial practice, and it cannot Practicably be determined in advance of the actual mixing; operation What is the" proper quantity of water to'be used in eachiindiv'idnal mixture;

i From laboratory tests of "samples of dif ferent batches taken from the same const-ruo-v tion job, alike in so far as therelative propor tions of solid matter are involved butdifir ing in the content'ofwater', it'h'as been shown that'the compressive strength of the mass" after 'like'periods of setting sh'ovv a'variance' sometimes amounting'to 50%, the resultant product in some instances being belowthat required for safety and durability,

While commercial practices do not favor tl eattainment of absolute accuracyin ap portioning materials in making concrete, a reasonable range" of variation, whilerelag tively smallin correct practice, is permis'sible in the. proportion of water to th'e remain ing ingredients for 'difler'ent batchesfionzth'e'; same job. Keep'ingi within" the'- allowable range ofvariation', We have discovered, can bestoe attained-by" removing the excessfree moisture from each batch;separately'fafter' the .mixing operation :has been substantially comlfletedand'whilelthe "mass is still in a' fluid fsta-te, preliminary to setting or 'hard'eni-i ing; The removal 'of this excess moisture may b'e accomplished with practical success in various Ways such as; forexa'mple, by centrifuging,f"absorption, filtration, etcJ, ora' combination thereof.

In practicing our method or 1 process of making concrete, an intimate'mixture 'ofce ment', suchas Portland'cement or othemuto solidifying substance, with an aggregate comprising one or more inert substances such as sand and/or gravel, in" the pres; enoe of 'Water,jsupp1ied in accordancewith any usual or approvednformula, s uch, fo1"v example, astwo'parts bygvolume of sandran'd: four parts; of gravel to-onei art of cement,"

with sufficient"water'-to rea ilyformamo hesive fluid mass, is first made up in the usual manner. The mixing operation may be performed either by hand or with machinery, including any suitable mixing devices.

5 And while it is indispensable to the production of a good quality of concrete that approved practices regarding the use of ingredients of approved character, in proper proportion and properly mixed be observed,

our improvements in the art are more directly concerned with the condition and treatment of concrete in the mixed mass while in a fluid state, than with the mixing operation itself.

. It is not essential to the utility of our method that the quantity of water employed in the mixture during the mixing operation be accurately measured before introduction to ,,the mixing chamber. It may even largely exceed the amount necessary to properly hydrate the cement. Nor is it necessary that the inert ingredients be heated or otherwise dried out before introduction to the mixing chamber. It is, however, important that the mixing operation be substantially fully performed before commencement of the operation of removing the excess water, in order to insure the thorough conversion of the re- .ment from an inert to an active state, and that after such conversion the excess water in and throughout the mixture be removed before the cement sets. By the term excess water we refer to that portion of the total volume of water or moisure present in the mixed mass which, if not removed at or before the commencement of setting or hardening of the mass, impairs the strength and quality of the concrete after setting, such excess being substantially that portion of the water not required to properly hydrate the cement and to moisten the inert matter preliminary to hardening or placing of the concrete.

In carrying out our invention we provide a suitable receptacle, which may be of any convenient size or shape, to receive the concrete after the mixing operation has been fully or subtantially performed. It is not essential to the successful application of our invention that the original mixing chamber or apparatus be used for this purpose, although it may conveniently serve, nor that the entire mass be uniform in density or in water content with respect to itself or other batches.

We prefer, in fact, to employ a separate receptacle of suitable proportions and conveniently arranged to readily accommodate periodic discharges from the mixing apparatus or other source of supply. lVithin this ultimate receptacle are placed or provided suitable water removing means, as, for example,

a pipe or conduit (not shown) having an inlet and provided with a filtering nozzle extending into the body of the mixture and an outlet end extending beyond the mixture and connected to suitable mechanism for producing suction of a predetermined strength adequate to remove the excess moisture within and throughout the mixture but none of the moisture required to fully hydrate the cement and moisten the inert substances. Said filtering nozzle should be designed to effectively reach and drain substantially all parts of the interior, including the entire mass of concrete contents, of excess moisture.

Although a substantial portion of the excess water may rise to the surface of the mass if the latter be permitted to stand undisturbed a sufficient length of time, whether this result be accomplished by gravity alone or in conjunction with tamping or other artificial means, this gravitational or settling method is found to be unnecessarily timetaking, deficient in thoroughness and otherwise objectionable. By our present method or means the entire mass mixture is penetrated and drained simultaneously and thoroughly before commencement of the hardening or setting of the concrete.

In the application of our improved method or process of preparing concrete it is important that the dewatering operation, by whatever means effective for the ends described this be accomplished, should be commenced, adequately performed and fully completed within certain limitations in point of time namely, immediately or shortly after the exposed or accessible surfaces of all particles of inert materials have become moistened and the entire body of cement or other auto-solidifying substance has been completely hydrated, and before the latter has appreciably begun to set or harden. It is equally important that the dewatering operation be extended to all parts of the mixture, as well within and throughout the same as the exposed surfaces. It should be further pointed out that whatever means are employed for removal of the excess moisture, it is important also that the coercive force applied should be so regulated or controlled that only the excess moisture, and none of the moisture necessary to moisten the inert matter and fully hydrate the cement, be remove It will be understood that our invention is not restricted to the precise details of the operations herein described but embraces 0bvious modifications thereof, and is commensurate with the scope of the appended. claims.

lVe claim as our invention:

1. The method of preparing concrete, consisting of intimately mixing an auto-solidifying substance with an aggregate, in the presence of water, then allowing the autosolidifying substance to become hydrated, and thereupon applying dewatering means to exert a coercive force tending to extract excess water from the mixture said force being regulated and applied to and throughout the body of the mixture.

Ill)

2. The method of preparing concrete, consisting of intimately mixing an auto-soliditying substance with an aggregate, in the presence of water then allowing the autosoliditying substance to become fully hydrated, and then applying suctional dewatering means to all parts of the mixture to remove the excess water before the mixture has begun to harden.

3. The method or process of preparing concrete, consisting of intimately mixlng an auto-solidifying substance with an aggregate consisting of one or more inert substances, in the presence of water, then allowing the auto-solidifying substance to become fully hydrated, and thereupon removing the excess water by dewatering means adapted to exert a predeterminable extractive force applied throughout the mixture.

4,. The method or process of preparing concrete, consisting of intimately mixing an auto-solidifying substance with an aggregate, consisting of one or more inert substances, in the presence of water, then allowing the auto-solidifying substance to become fully hydrated, and thereupon filtering and removing excess moisture from the mixed mass by suctional means.

5. The method or process of preparing concrete, consisting of intimately mixing an auto-solidifying substance with an aggregate consisting of one or more inert substances, in the presence of water, then allowing the mixture to remain undisturbed for a limited period of time, and thereupon removing the excess water from the mixed mass by means of filtration involving suction.

6. The method or process of preparing concrete, consisting of intimately mixing an auto-solidifying substance with an aggregate, in the presence of water, then allowing the auto-solidifying substance to become fully hydrated, and then dewatering the mixture by removing the excess moisture by filtration induced by suction havinga predetermined coercive force.

7. The method or process of preparing concrete, consisting of intimately mixing an auto-solidifying substance with an aggregate, in the presence of water, then allowing the auto-solidifying substance to become fully hydrated, and then applying controlled dewatering means to exert a regulated extractive force to and throughout the mixture to remove only the excess water.

8. The method or process of preparing concrete, consisting of intimately mixing an auto-solidifying substance with an aggre-o gate, in the presence of water, then allowing the auto-solidifying substance to become fully hydrated, and then dewatering the mixture by filtration induced by suction having only suflicient coercive force to remove all the moisture in excess of requirements for moistening the aggregate material and for fully hydrating the auto-solidifying substance.

In testimony whereof, we have signed our names to this specification.

MARTIN A. MORRISSEY. ALMER F. MOORE.