JPS61127655A - Operation improvement for cement plaster - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for improving the workability of cement plaster containing aggregate.

BACKGROUND OF THE INVENTION Cement plasters, such as Portland cement and Stucco plaster, are used for protective and decorative finishes on walls, floors and ceilings, both outdoors and indoors. They are hard, high strength, fire resistant, and resistant to wet-dry or freeze-thaw weather cycles.

Cement plasters generally contain cementitious binders,
Consists of aggregate (e.g. sand), plasticizer, and water. Additionally, certain admixtures may be added to improve coating and rheological properties. Cement plasters are most desirably operated at the highest aggregate (eg, sand) to cement ratio to reduce the risk of shrinkage and cracking of the dry silaster. However, excess sand impairs the workability of Shirastar. For example, when using a pressure pump, excess sand can clog the pump, requiring costly and time-consuming repairs to the hoses, and during which work is stopped.

Single admixtures of cellulose ether and polyvinyl alcohol improve the workability, binding, adhesion and water retention properties of Shirastar. In U.S. Pat. No. 4,265.beta.74, an additive consisting essentially of a water-soluble cellulose ether and a low-foaming surfactant, such as a block-rimer of polypropylene oxide and ethylene oxide, is added to Portland cement silaster. This additive increases the pumpability of the plaster when used in pressure pumps.

U.S. Pat. No. 2,950,206 discloses a finishing mortar consisting essentially of an inorganic fine filler that is marble powder or chalky dry slaked lime, a water-soluble cellulose ether, and bentonite clay as a lubrication agent. Disclosed.

The amount of ingredients is 64 to 79 parts of marble powder, 2 to 4.1 parts of chalk, 1.9 to 4.2 parts of dried slaked lime, and 0 parts of cellulose ether.
．． 4 to 0.7 parts, bentonite clay 1.5 to 3 parts, and water 15 to 24 parts. The cellulose ether is mixed separately with some water and the clay is dispersed in a separate container and then mixed with additional water along with the remaining dry ingredients cellulose ether and clay.

U.S. Pat. No. 4,131,480 discloses Bon! containing lightweight aggregate! Operable cementitious compositions are disclosed. Sulfonated melamine formaldehyde is used with water-soluble cellulose ethers as a dispersant for cement particles and to reduce water absorption by aggregates under pressure. It is possible to use expanded clay as a lightweight aggregate. The amount of cellulose ether used is 0.012 percent of the dry mixture. Cellulose ether and dispersant are added separately in powder form to the mixture.

Kaolin clay used for forming cement mixtures is disclosed in JP-A-58-15053. This work Mho, 2' -L 10 i
Improved by adding a certain amount of clay. Optionally, 0 to 0.05 parts by weight of water-soluble cellulose ether can be added to the dry mixture to improve the water retention and adhesion properties of the cement.

British Patent No. 1484057 discloses that an inert filler 3
0 to 80, emulsifier 10 to 40eI, and water retention agent 5 to
A self-smoothing mortar composition is disclosed that is a uniform dry powder of 60 mm. Kaolin clay can be an inert filler, hydroxyalkyl cellulose can be a water retention agent. This composition is present in an amount of 0.7 to 4.5 weight percent of the total weight of the mortar, which consists of a large amount of I Rutland cement.

In industrial practice, cement plaster is manufactured in large patches in mixers. The addition of small amounts of admixtures to improve the properties of the plaster was an imprecise process, causing the polymer to be unevenly dispersed and the plaster to harden.

In view of the shortcomings of the prior art, it has been proposed to improve the rheological properties and paintability of glastar while improving workability, providing control over desired properties, and increasing the ability of glastar to retain aggregate. It is highly desirable to provide admixtures.

[Means for solving problems]

Surprisingly, the method of the present invention increases the ability of cement plaster to accept aggregate while remaining workable. That is, the present invention provides a method for improving the workability of a cement plaster composition comprising a hydraulic binder and a major amount of aggregate, the method comprising: (a) water-soluble cellulose added to the mixture of the hydraulic binder and aggregate; The method involves adding a small amount of a substantially dry homogeneous mixture of the ether and (b) clay clay in an amount equal to or greater than the weight of the cellulose ether.

Chemical mend plaster generally consists of a hydraulic binder, a large amount of aggregate, and optionally various additives such as plasticizers and water.

Hydraulic binders are compositions that are capable of bonding materials upon contact with water. Typically, Portland cement and plastering cement are used as hydraulic binders for cement silaster.

Aggregate is a durable coarse granular material. Preferably, the aggregate has a fine particle size so that the aggregate-based plaster can be delivered through the hose to the target surface with one ounce of pressure. The aggregate is preferably fine structural sand. This cement plaster uses the main amount of aggregate. That is, the component present in the largest amount in cement plaster is aggregate. Typically, about 4 parts aggregate per part hydraulic binder is used.

Optionally, it is possible to add certain additives to the silaster in small amounts in order to impart desired properties to the plaster. Typical additives are plasticizers, which improve the workability of Shirastar when it is wet and applied to the target surface. A preferred plasticizer is hydrated lime. Hydrated lime improves the workability of wet plaster when applied and also acts as a secondary bonding agent when the glaster is applied to the target surface. Compared to the amounts of hydraulic binder and aggregate used in cement plaster compositions, only smaller amounts of plasticizer are required to achieve its benefits. Typically, about one-half part plasticizer per part of hydraulic binder will be used.

Cellulose nitrates that can be used in the present invention are water-soluble cellulose ethers, such as hydroxyethylmethylcellulose, hydroxyethylcellulose, methylcellulose, and methylcellulose. Preferred cellulose ethers have about 0 hydroxyglobil molecular substitutions.
．． 05-0.4 and methoxy substitution degree 1.1-2.0
of hydroxypropyl methylcellulose. Most preferred are hydroxyglobil molecular substitutions of about 0.1 to 0.33 and methoxy substitution degrees of 1.12 to 1.64.

The clays used in the present invention are platy clays, ie clays whose natural form is found as stacks of platelets. Bentonite clay and kaolin clay are readily commercially available clays that can be used in the present invention.

Powdered water-soluble cellulose ether is mixed with an equal or larger amount of powdered cellulose ether,
A substantially dry, homogeneous mixture, ie, a carefully mixed blend of the compositions, is provided. A substantially dry, homogeneous powder is obtained.

Based on the total weight of this homogeneous mixture, the cellulose ether can be about 10-50% and the clay about 5%
It can be from 0 to 90 inches. Preferably, the homogeneous mixture is a dry blend of hydroxypropyl methylcellulose with a hydroxyglobil molecular substitution of about 011 to 0.33 and a methoxy degree of substitution of 1.12 to 1.64, and kaolin clay.

In this preferred homogeneous mixture, the hydroxypropyl methylcellulose is about 25 parts by weight and the kaolin clay is about 75 parts by weight.

As mentioned above, it is desirable for the cement silaster to contain as much aggregate as possible in relation to the amount of binder. However, there are limitations to the ability of cement plaster compositions to contain aggregate and remain workable. The use of excess aggregate in cement plaster compositions renders the cement silaster unworkable. That is, the cement plaster becomes dry and brittle and cannot be applied or adhered to the target surface.

The workability of cement plasters containing aggregates is increased by adding a substantially dry homogeneous mixture of water-soluble cellulose ether and platy clay during the manufacture of cement plasters. This homogeneous mixture is limited to the extent that it can be incorporated into the cement silaster composition and completely dispersed.
, may be added at any time prior to applying the cement silaster to the target surface. One method of adding a homogeneous mixture is to first mix the hydraulic binder with a relatively large amount of aggregate. Optionally, sufficient water may be added to form a slurry of binder and aggregate.

To this mixture or slurry is added a small amount of a substantially dry homogeneous mixture of water-soluble cellulose ether and clay clay. This homogeneous mixture is unexpectedly capable of and suitable for increasing the workability of cement silaster with increased amounts of aggregate. More specifically, by using this homogeneous mixture, it is possible to add a larger amount of aggregate to the cement silaster composition than before without impairing the workability of the cement plastic. Only a small amount of homogeneous mixture must be added to achieve the benefits of the present invention. Additionally, the chemistry of this homogeneous mixture physically limits the amount that can be used. If too much of the homogeneous mixture is added, the final cement plaster composition becomes a sticky, gluey material that becomes too sticky to work with.

Typically, a cement silastar composition consisting of about 17 bw widths of Deltland cement, about 78 bw widths of fine structural sand, and about 5 bw widths of hydrated lime on a dry weight basis is combined with about 0. ．．
05-0.35 weight bone width preferably about 0.15-0.2
Adding a homogeneous mixture of 5 weight widths The following examples are set forth to further illustrate the invention without limiting its scope. All departments and sections are by weight unless otherwise specified.

〔Example〕

a substantially dry powder of hydroxyzolobyl methylcellulose and a substantially dry powder of kaolin clay having a hydroxygloxyl molecular substitution of about 0.1 to 0.33 and a degree of methoxy substitution of about 1.12 to 1.64; A substantially dry homogeneous mixture is prepared by mixing.

The final homogeneous mixture consists of about 25 parts by weight of hydroxyzorobyl methylcellulose and about 75 parts by weight of kaolin clay.

Cement plaster + mixing at a construction work site.

A commercially available mortar mixer with a 2 inch outside diameter (5 cIn) hose for pumping, 1 part Portland cement (1 cubic foot), 1/2 part lime (1/2 cubic foot, 0.02 m''), construction Super fine sand 18~
Add 20 cubic feet (approximately 4 cubic feet) and a construction grade mixture of water to provide the proper consistency (water/cement ratio of approximately 0.6).

The initial cement plaster composition is prepared according to building industry specifications without adding the homogeneous mixture described above.

The second cement plaster composition is prepared according to building industry specifications and with the addition of a small amount of the homogeneous mixture described above. A second cement plaster composition is formulated as follows. Mix half of the specified amount of Portland cement with half of the specified amount of sand (approximately 10 shovels). Add water so that you get a slurry of cement and sand. To this slurry is added 0.01 part of the above homogeneous mixture based on the weight of Portland cement. While stirring, add the remaining specified amount of cement.

Add sand, hydrated lime and water.

The first cement plaster composition was coated with a 2 inch outer diameter (5 m
) to the painted surface.

Add sand to the composition until the hose is snug. The hose is plugged with 20 shovels of sand.

A ninth second cement plaster composition prepared according to the method of the present invention is delivered in one stroke to the painted surface through a 2 inch (5α) outer diameter hose. Add sand to the composition until the hose is clogged.

The hose was covered in sand like a shovel 28.

By the method of the invention the workability of the cement plaster composition can be kept compatible with an increase of 40 cents in the amount of sand.

Claims (1)

[Claims] 1. A method for improving the workability of a cement plaster composition having a hydraulic binder and a major amount of aggregate, comprising: (a) a water-soluble 1. A process characterized by adding a small amount of a substantially dry homogeneous mixture of a cellulose ether and (b) an equal or greater amount of clay based on the weight of the cellulose ether. 2. The homogeneous mixture is based on the total weight of the homogeneous mixture,
about 10 to 50% by weight of the cellulose ether and about 50% by weight of the cellulose ether;
90% by weight of said clay plate. 3. The method according to claim 2, wherein in the homogeneous mixture, the water-soluble cellulose ether is methyl cellulose, and the plate clay is kaolin clay. 4. In the homogeneous mixture, the water-soluble cellulose ether has a hydroxypropoxyl molecule substitution of about 0.05 to
3. The method of claim 2, wherein the platy clay is a kaolin clay. 5. The homogeneous mixture is based on the total weight of the homogeneous mixture,
5. The method of claim 4, comprising about 25% by weight of said hydroxypropyl methylcellulose and about 75% by weight of said kaolin clay. 6. The method of claim 5, wherein said homogeneous mixture is present in an amount of about 0.05 to 0.35% by weight based on the total weight of dry ingredients of said cement plaster composition. 7. The hydraulic binder is Portland cement,
2. The method of claim 1, wherein the aggregate is fine structural sand. 8. The method of claim 1, wherein a sufficient amount of water is added to the mixture of hydraulic binder and aggregate to form a slurry. 9. The method according to claim 8, wherein a plasticizer is added to the slurry of hydraulic binder and aggregate. 10. The method of claim 9, wherein the plasticizer is hydrated lime, the binder is Portland cement, and the aggregate is fine structural sand.