Compositions: coating or plastic – Coating or plastic compositions – Inorganic settable ingredient containing
Reexamination Certificate
2001-03-23
2002-11-12
Marcantoni, Paul (Department: 1755)
Compositions: coating or plastic
Coating or plastic compositions
Inorganic settable ingredient containing
C106S728000, C106S810000, C106S823000
Reexamination Certificate
active
06478869
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention provides methods of improving the flow properties of dry particulate cementitious materials whereby the materials can be readily conveyed out of storage tanks and the like.
2. Description of the Prior Art
Cementitious materials such as hydraulic cements, slag, fumed silica, fly ash and the like having various particle size distributions are often dry-blended and placed in storage tanks. The storage tanks containing the cementitious materials are also often transported by land or sea to locations where the cementitious materials are to be used. During such transportation, the cementitious materials are subjected to vibrations and as a result, the materials are tightly packed under static conditions. One or more of the cementitious materials are often of ultra-fine particle sizes, i.e., sizes in the range of from about 5 to about 100 microns, which causes the tightly packed problem to be more severe. When the cementitious materials are conveyed out of the storage tanks at the locations of use, significant portions of the tightly packed materials are often left in the storage tanks. The incomplete conveying of the materials results in costs for disposing of the materials and increased costs to the person or entity using the cementitious materials.
Cementitious materials have heretofore been treated to make them more flowable. For example, U.S. Pat. No. 2,857,286 issued to Striker on Oct. 21, 1958 discloses a process of treating Portland cement with acetic acid or a water soluble salt of acetic acid whereby the Portland cement becomes more flowable. In accordance with the Striker patent, the treatment of Portland cement with the acid or acetate is carried out either concurrently with, or subsequent to, the grinding of the cement clinker. The acid or acetate can be combined with the cement during grinding or the ground cement can be treated by injecting the acid or acetate into the cement under pressure as a vapor in order to blow the cement and uniformly contact it with the acid or acetate.
U.S. Pat. No. 3,094,425 issued to Adams et al. on Jun. 18, 1963 discloses that most cements compacted by vibration become semi-rigid and will not flow without considerable mechanical effort to break up the compaction. This condition is known as “pack set.” Further, it is stated that it is known that certain polar molecules when added to ground cement will attach to the cement particles and reduce their surface forces. In accordance with the Adams patent, a mixture of calcium acetate and lignin sulfonate is an effective grinding aid and a pack set inhibitor when added to the cement mill and interground with the cement.
U.S. Pat. No. 3,615,785 issued to Moorer et al. on Feb. 2, 1968 discloses a cement grinding aid and pack set inhibitor comprised of polyol and a water soluble salt of an aliphatic acid having no more than 3 carbon atoms.
The above described additives are difficult to handle and must be added to the cement prior to or after grinding. Since commercially available cementitious materials generally do not include such additives, they must be provided, handled and combined with ground cement by the user by spraying, mechanical mixing or other time consuming procedure.
Thus, there are continuing needs for improved methods of enhancing the flow properties of dry cementitious materials which are stored and/or transported in storage tanks.
SUMMARY OF THE INVENTION
The present invention provides improved methods of enhancing the flow properties of a dry particulate cementitious material or a blend of such materials which meet the needs described above and overcome the deficiencies of the prior art. The methods basically comprise dry-blending a particulate flow enhancing additive comprised of a particulate solid adsorbent material having a flow inducing chemical adsorbed thereon with the cementitious materials prior to placing the materials in a storage tank.
The particulate flow enhancing additive of this invention is easily handled, readily dry blended with cementitious materials and enhances the flow properties of the cementitious materials. The presence of the flow enhancing additive in the cementitious materials allows the cementitious materials to be mechanically or pneumatically conveyed out of storage tanks, even when they are tightly packed therein, without leaving significant portions of the cementitious materials in the storage tanks.
A preferred particulate flow enhancing additive useful in accordance with this invention is comprised of precipitated silica powder having a flow inducing chemical comprised of glacial acetic acid adsorbed thereon. The weight ratio of precipitated silica powder to the glacial acetic acid in the flow enhancing additive is in the range of from about 90:10 to about 10:90, and the additive is blended with cementitious materials in an amount in the range of from about 0.01% to about 1.0% by weight of the cementitious materials.
It is, therefore, a general object of the present invention to provide improved methods of enhancing the flow properties of dry particulate cementitious materials.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of preferred embodiments which follows.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present invention provides methods of improving the flow properties of one or more dry particulate cementitious materials such as hydraulic cements, slag, fumed silica, fly ash and the like. The methods of the invention are particularly suitable for improving the flow properties of a dry particulate cementitious material or a blend of such materials which are of fine or ultra-fine particle size and are tightly packed under static conditions in a storage tank from which they must be conveyed. This invention also provides methods of storing one or more dry particulate cementitious materials in a storage tank, transporting the storage tank and cementitious materials therein to a location of use and then conveying the cementitious materials out of the storage tank without unintentionally leaving a significant portion of the cementitious materials in the storage tank. The term “significant portion” is used herein to mean a portion of the stored cementitious material that is above about 15% thereof by volume.
The methods of this invention are basically comprised of dry-blending a particulate flow enhancing additive comprised of a particulate solid adsorbent material having a flow inducing chemical adsorbed thereon with one or more cementitious materials. Thereafter, the blend of the cementitious materials and flow enhancing additive can be placed in a storage tank and readily conveyed therefrom, either mechanically or pneumatically, without leaving a significant portion of the cementitious materials in the storage tank.
A variety of particulate solid adsorbent materials can be utilized for forming the flow enhancing additive of this invention. Examples of such adsorbent materials include, but are not limited to, precipitated silica, zeolite, talcum, diatomaceous earth and fuller's earth. Of these, precipitated silica is presently preferred. The adsorbent material utilized must be capable of adsorbing the flow inducing chemical utilized.
The flow inducing chemical utilized in accordance with this invention can be any of the heretofore known chemicals which produce polar molecules that react with cementitious materials and increase their flow properties. Examples of polar molecule producing chemicals which can be utilized include, but are not limited to, organic acids such as alkyl and/or alkene carboxylic acids and sulfonic acids, salts of the foregoing acids formed with weak bases and acid anhydrides such as sulfur dioxide, carbon dioxide, sulfur trioxide, nitrogen oxides and similar compounds. The most preferred flow inducing chemical for use in accordance with this invention is glacial acetic acid. While the exact cause for the flow enhancement of cementit
Crook Ronald J.
Fitzgerald Russell M.
Heathman James F.
Reddy Baireddy R.
Sweatman Ronald E.
Dougherty, Jr. C. Clark
Halliburton Energy Services, inc.
Marcantoni Paul
Roddy Craig W.
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