JPS604150B2 - Method for preventing cement-based shrinkage by adding carbonaceous materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to improved methods and compositions for preventing shrinkage of cementitious systems during setting and hardening.

As used herein, the term "cement-based" refers to setting hydraulic cements containing aggregate and water, such as concrete, mortar, grout and products made therefrom, hydraulic coal, gypsum, etc., and mixtures thereof. means.

Methods and apparatus for preventing shrinkage of hydraulic cement mixtures during setting and hardening have previously been proposed.

Additional techniques include the addition of various expanding agents, such as aluminum powder, iron filings, during cement mixing. However, these methods are not practical. The reasons for this are, among other things, the drawback of not being able to properly control the expansion. It is also theorized that certain special materials can eliminate shrinkage in proper concrete, the principle of which is to adsorb water from the cement system and release trapped gases from the porous particulate material. There is.
Materials such as combinations of petrochemical by-products fluidized coke and delayed coke, fluidized coke alone and porous granular materials, so-called industrial adsorbents, are used with various cement mixtures. to effectively prevent shrinkage. U.S. Patent No. 3503767, U.S. Patent No. 351944, U.S. Patent No. 3
Please consider No. 794504 and US Reissue No. 26597 as reference examples. The effective use of certain materials as anti-shrinkage agents in cementitious systems is not foreseen.

For example, considering that fluid coke is a carbonaceous material, its success as an anti-shrinkage agent without being harmful to cement systems is surprising. Therefore, US Reissue Patent No. 26,597 states that other types of coke or carbon other than fluid coke are not effective in expanding cement in certain systems. The patent also states that although the coal mass may undergo expansion, a harmful amount is required for this to occur, and that "the amount to be added is adjusted because expansion is related to the sulfur content of the fired mass." Although competitive agglomerates and coke powder are added to cement systems as aggregates, concrete technology, Volume 1, John Wiley and Sons.
& Sons), New York, 1962, 146-1
As pointed out on page 47, the combustible materials, primarily carbon, in these materials have the undesirable result of excessive expansion when used as concrete aggregates. This expansion is exceptional and furthermore it is not possible to control this expansion. This is because when drying, shrinkage occurs and the humidity fluctuates. Carbonaceous materials are currently used in cement compositions for very limited and specialized purposes, such as in peripherally cemented oil well applications.

Accordingly, U.S. Pat. No. 2,609,882 discloses adding activated carbon to a cement composition for solidifying an oil well with the cement, thereby offsetting the harmful effects of mud additives used to bore the oil well. There is. U.S. Pat. No. 3,375,146 describes adding natural lignite, bituminous coal, anthracite, graphite, coal coke, coke or carbon to a cement composition to provide a low density composition for cementing oil wells. It is being

All of the above patents dealing with oil well cement bonding do not mention any advantages or disadvantages of carbon materials other than those mentioned therein. It is still believed that the addition of carbon materials such as coal or lignite to general applications is detrimental to concrete. For example, ``Concrete Construction Handbook,'' by Joseph J. Q. Waddell and McGraw Hill.
ph). Wadell, McGraw Hm), 2nd edition, pages 236-237, points out hazardous substances and restricted ranges of coarse aggregate for concrete and lists coal and lignite as hazardous additives. The present invention is groundbreaking enough to break through the traditional concepts as described above.

According to the present invention, unexpected carbonaceous materials such as coal are specially treated to render them favorable for use as additives in cement systems, and at the same time when added to such systems, they It acts to adjustably prevent shrinkage that typically occurs during solidification and hardening.

The process according to the invention activates carbonaceous materials, such as coal, which have been known for some time to possess properties useful for anti-shrinkage, and which are obtained with known coal anti-shrink agents such as fluid coke. It enhances results.

The effective results vary depending on the carbonaceous material.The adjustment range for anti-shrinkage is therefore determined by the selection of the appropriate working material depending on the desired purpose. This may or may not be due to the amount of carbon in the material, although it varies depending on the type of carbonaceous material.The anti-shrinkage is due to the release of gas from the surface and the porosity of the carbonaceous material when added to the cementitious system as a granular solid. It is.

This has been theorized, but the inventor does not want to be bound by it. The favorable results obtained are therefore due to the desorption of gases retained on the active surface of the material. This release occurs when water from the cement system is adsorbed onto the particle surfaces, returning or displacing gases. The exact way in which this occurs, whether physical or chemical, is not fully understood. It is surprising that carbonaceous materials possess these advantages and superior properties, especially when specially treated according to the present invention. This is because coal, for example, is generally ineffective as an anti-shrinkage agent when added to cement, and is still considered to have deleterious consequences for general purposes. It is not known whether physical or chemical changes or both have occurred in the material as a result of the special treatment of the present invention, and there is no need to standardize the carbonaceous material. We think it sufficient to point out how the process may be carried out with favorable results.

According to the invention, the carbonaceous material is heated to a high temperature, for example in the presence of air in an open air, and its anti-shrinkage ability is further enhanced by contacting it with steam at this high temperature. The heating temperature is well above that which merely causes drying of the carbonaceous material, and although some material volatilization is clearly occurring here, this process may cause other effects such as pyrolytic densification and crystallization. It cannot be said with certainty that the burning twill phenomenon will occur. The carbonaceous particulate material is added to the cement mixture prior to the addition of water, and while in contact with the water the cement mixture sets and hardens, releasing its gases. The action of the material is that it releases gas, so that when it is sufficiently dry it retains the gas and then adsorbs water and releases the gas. Carbonaceous granular materials have the advantage that they can be used in a wide range of applications in cementitious systems with different setting times. Therefore, they can be effectively used for cement types that set quickly as well as for cements that set within a certain period of time. Thus, by choosing a carbonaceous particulate material appropriate for the desired use, both the amount and duration of shrinkage prevention of the cementitious system can be more effectively controlled.
Therefore, the purpose of the present invention is to add carbonaceous material to cement system,
The purpose of this addition is to prevent such shrinkage of the cement system. Another object of the present invention is to specially treat carbonaceous materials to render them useful or to improve their effectiveness as anti-shrinkage agents in cementitious systems.
An unexpected property of the carbonaceous material added to the cementitious system according to the present invention is that it reduces undesirable breathing, the phenomenon of water rising to the surface that occurs simultaneously with precipitation of solid material.

Breathing is particularly undesirable for applications such as mechanical grouting and the like. This is because the breathing creates a water-filled cavity beneath the substrate and reinforcing fins. When dry, these voids remain and the adhesive strength is reduced. The release of gas by the carbon additive of the present invention not only prevents shrinkage, but also helps reduce breathing that typically occurs with methods other than the present invention. Although this is an observable fact,
It is not understood whether this is due to expansion of the cement against a solid surface, due to drainage of water from the cement, or for other reasons. It is therefore a further object of the present invention to provide a method and composition that reduces pleating during setting of cementitious systems.

Particulate materials useful in this invention are carbonaceous materials and are used in the specific process of this invention.

Carbonaceous materials are known to have anti-shrinkage properties, such as fluid coke, and this property can be enhanced by the present invention. Advantageously, this carbonaceous material is not generally known to have unique anti-shrinkage properties when added to adhesive systems in acceptable amounts, such as delayed coke, or to cement, such as coal. considered to be harmful at times. Fluid coke is made by the method described in U.S. Pat. No. 2,881,130,
Delayed coke is described in US Pat. No. 2,835,605.

The effectiveness of these materials as anti-shrink agents is described in US Reissue No. 26,597. According to the patent, although fluid coke is effectively used in cement compositions to prevent shrinkage, day-laid coke does not cause expansion and does not swell in the sand despite having a chemical composition very similar to fluid coke. It acts similarly to inert additives such as Further, as stated in U.S. Reissue Patent No. 26,597, carbon, which is believed to be a strong surfactant, is easily wetted by water and expansion would be expected given the results with fluid coke. , it actually has no expansion effect. The results in the present invention are therefore both surprising and unexpected. Coal is generally classified based on its quality as a fuel, ie, the amount of carbon it contains and the state of the carbon.

Although some of the carbon in the coal is fixed and some of the carbon is combined with hydrogen and nitrogen as volatile hydrocarbon compounds that can be vaporized, heating in the retort cannot drive this carbon out. do not have. The ratio of volatile hydrocarbons to fixed carbon in coal is called the fuel ratio, and the general classification based on this standard is lignite, bituminous coal, semi-bituminous coal, semi-bituminous coal, and anthracite coal. , the carbon content increases and the fuel ratio increases in this order. Head coal, or lignite, is brown in color and has a specific gravity of 0.5 to 1.5. Bituminous coal, or soft coal, is black in color and has a specific gravity of 1.25 to 1.4. Anthracite, also called hard coal, has a specific gravity of 1.3 to 1.75 and is black in color.
be. The carbonaceous particulate additive is selected to have a substantially uniform size or a certain range of sizes depending on various purposes of use. Since all the materials are charcoal-based, various materials can be mixed together during use. As will be understood by those skilled in the art, the selection of the particular carbonaceous material, particular processing steps and particle size will vary depending on the cementitious system and intended use.
Appropriate selections and amounts to be used are readily determined in accordance with the mathematics of the present invention and based on routine observation and measurement of the following parameters. When carrying out the process of the invention, a suitable amount of carbonaceous material is added at any time before or at the time of the addition of water.
It is added to the cement or cement mixture and mixed to form an aqueous cement mixture.

For example, in the production of grouts and mortars, the additives are mixed with cement or a mixture of cement and bone marrow to form a dry cement mixture. This dry cement mixture is thoroughly mixed with the appropriate amount of water to form a grout or mortar. Similarly, when producing fresh concrete, additives are mixed with cement and aggregate to form a dry mixture.
This mixture is then used to produce fresh concrete in a stationary or truck mixer. On the other hand, mixing all ingredients, including additives, in a stationary mixer or truck mixer to produce fresh concrete is simple and convenient to operate. The amount of additive used in a cement system is calculated based on the amount of cement in the system, making it convenient and possible to mix the additive directly into the cement before shipping it to the user. be.

In order to further illustrate the invention, some examples are described below.

The performance of the additive is that it is mixed with water and at a depth of 8.9c (
The expansion and contraction of the adhesive system is determined by the expansion and contraction of the adhesive system when poured into a 3.5 inch cylindrical mold leaving 10% of the exposed surface of the mold. The expansion and contraction of the casting mold is measured by the longitudinal movement of the top surface. To obtain a high degree of accuracy, an optical test submitted to ASTM's C-9 committee for approval was used to measure top surface movement. This test uses a focused light beam to reduce the shadow on the top surface by 2.54 cm.
The image is projected onto a screen with a vertical scale in units of (1 inch). The magnification is 88 times. The movement of the top surface on the screen is recorded to within a few inches at short intervals for each pillar until the final set. Casting usually takes about 3 to 4 hours for long-curing materials and about 6 hours for short-curing adhesive compositions. A thin layer of oil coats the surfaces of the cement pillars in the mold to prevent evaporation and retard hardening.

To facilitate observation of the movement of the top surface, a sphere is placed on the top surface, and the expansion and contraction of the Western shape is measured from the movement of the apex of the shadow projected on the screen. The cement system in each example was formulated by mixing 42.5 parts Type 1 cement, 5 parts sand, and 7.5 parts carbonaceous additive by weight, and according to the present invention, 704.4 qo (13000 F ) to 815
．． It is heated to 6°C (1500T) and water is sprayed at this temperature.

Processing time is not a critical factor; a heating time of 1 to 2 hours is sufficient. Experiments with untreated material were also performed as a reference standard for comparative purposes. Additionally, experiments using activated alumina in place of carbonaceous additives were conducted to determine the effectiveness of the special process of the present invention without the use of carbonaceous additives.
Each of the compositions was thoroughly mixed with about 9 quarts of water per 100 pounds of formulation, cast as described above, and observed for expansion or contraction. Example 1 (Sample A
(Sample H) The carbonaceous materials that were crushed to the extent that they passed No. 16 and were mixed in the above proportions are as follows.

A. Fluid coke B.

Daylaid Coke C, Anthracite ○, Lignite E, Bituminous Coal F, Activated Carbon results are set out in Table 1 and are also expressed in light test measurements every 2.54 k (1 inch). The measured values were obtained by using carbonaceous materials that were specially treated according to the invention.

The results also demonstrate the effectiveness of these materials as anti-shrink agents when processed according to the process of the present invention.
Results using activated alumina (G) as a shrinkage control additive without carbonaceous material are also shown. Dry heat treatment consists of heating the carbonaceous material or other shrink preservative or control in an electric furnace.

The above-mentioned electric furnace is manufactured by Thermolin (Dubique, Iowa, USA), for example.
1400 type electric furnace made by Thermolyne, Inc., which is equipped with a bamboo heater inside the wall that is controlled to a predetermined temperature by an on-off cycle timer. Heating takes place in the presence of a dilution of air due to slight leakage around the furnace door.

Such doors, for example, are not very tightly closed, but are not large enough to allow a sheet of paper to pass through. However, the theoretical understanding is that the foggy atmosphere inside an electric furnace quickly becomes comprised of carbon monoxide, carbon dioxide and traces of oxygen as a result of carbon oxidation. Furthermore, the presence of air not only does not adversely affect the results of the process, but as detailed below, it actually enhances these results. The steam heat treatment consists of a dry heat step followed by an injection step using a steam nozzle to eject steam at this temperature. Table 1 × 2.54 伽 (1 inch) unit per unit of Fuku test measurement value × 1
・O quart of water used Linghui 0.5 quart of water used
Unlike the results stated in Table 1, using 11 quarts of water as a control instead of carbonaceous material.
The above water-based cement mixture (H
) was measured for shrinkage in the same manner as above and the value was -3.375 inches.

Although the special process of the present invention is particularly advantageous with carbonaceous materials, activated alumina has not shown any improvement in effectiveness when treated with this special process.
Although it is still widely believed that carbonaceous materials such as coal and lignite are undesirable in concrete, the inventors have determined that the compressive strength of representative compositions produced according to the method described above is acceptable. I discovered what is within.

Taking into account the expansion obtained, the fact that the compressive strength per unit volume is somewhat lower than that of a single sand-cement mixture without any additives makes it difficult for the required application and results. It does not have a significant impact. Example 2 In this example, the heating effect in the presence of large amounts of air was confirmed.

Heating delayed coke 'B} and anthracite coal (C},
The conditions in this case were the same as in Example 1 except that the door was not closed but opened 0.64 mm (1'4 inch). Cement systems were prepared and measured in the optical test as described in Example 1. In the presence of this large amount of air, 704 qo (130
Cement systems containing anthracite heated to 00F) are shown in Table 1.
It expanded 113.5 inches compared to the 114 inch expansion shown in Figure 1, with no significant change when heated in dilute air. However, in a large amount of air, 704℃ (130℃)
A cement system containing delayed coke heated to 00F) expanded 117.5 inches compared to the expansion of only 18.8 inches shown in Table 1, and when heated in dilute air, this coke expanded showed high effectiveness as an anti-shrinkage agent. In order to more clearly explain the results obtained by the special process of the present invention, the results selected as representative examples are illustrated graphically in FIGS. 1 to 7.

These Figures 1 to 7 represent the expansion or contraction obtained according to the optical test described above, with the ordinate indicating the cured state after casting and the abscissa indicating time. The notation attached to each curve describes the processing conditions to which the material was subjected. The term drying is used to remove moisture.
This means that it was heated to 100 degrees Fahrenheit (2500F).
When interpreting the graphs of FIGS. 1-7 and the results shown in Table 1, it must be kept in mind that expansion or contraction is expressed in inches.

The inch unit corresponds to the scale in the diagram used for light testing to reflect variations in the casting surface. This test is highly sensitive to changes in the casting surface, magnifying these changes by a factor of 88. As a result, differences of one or two units do not seem to be particularly significant when comparing the results of different treatments or different materials. Nevertheless, Figures 1 to 6 show the effectiveness of anti-shrinkage agents through proper selection of the materials treated according to the invention, some of which actually swell.

Many bonds can control not only the amount of deflation or expansion, but also the onset time or duration. This is advantageous in view of the fact that many types of cement are required, each having different properties such as setting time. For example, a curve with an arrow at the right end means that the effect continues long enough for the material to expand or prevent contraction beyond the limits of the abscissa. This means that the trapped gas continues to be released. The results depicted in Figures 1 through 6 were neither expected nor predicted.

As can be seen, even within this class of materials, ie carbonaceous materials, the results are variable. These results are further discussed regarding the specific materials used. The foregoing has demonstrated that carbonaceous materials can be modified into effective cementitious anti-shrinkage materials by heat treatment and heat treatment with steam or water mist. If the carbonaceous material already has anti-shrinkage properties, these properties are further greatly enhanced by the treatment of the present invention. This is strange and unexpected. This is because there is no physical identity between the various effective carbonaceous materials when they are in their final state. Therefore, fluid coke has large awning-like D-globe structures resulting from increased foaming, while delayed coke is spongy, neither layered nor spherical. However, coal differs from fluid coke and dilaid coke in that its structure is in the form of stacked sheets. Chemically, these substances are considered to be the same in that they all contain carbon. However, when they are treated, they behave differently, albeit effectively. The anti-shrinkage effect between untreated materials is fundamentally different from each other. The anti-shrinkage properties of the fluid coke are increased by heating, which heating may be sufficient to drive off moisture so as to dry the material. Delayed coke from refineries has no effect on shrinkage prevention when added to cement systems in acceptable amounts.

It is therefore understood that delayed coke expands only when added to a cement system in an amount of approximately one needle tone, the amount required to achieve the same results as fluid coke. It is true that delayed coke from refineries is ineffective, but when this coke is subjected to heat treatment and a fine atomization process with water or steam, it becomes as effective as or more effective than fluid coke. Anthracite is effective even when sent from an oil refinery, and becomes an even better anti-shrinkage agent when heated and in contact with a fine mist of water. The normal anti-shrinkage ability of anthracite changes when natural anthracite is present in water and releases gases. In addition, the inventor has a surprising fact that 81 bi○ (15000F)
The addition of 1% natural anthracite coal heated to 1% and steam atomization is more effective as an expanding agent in cement systems than fluid coke added at a rate of 1%. Bituminous coal is essentially ineffective when it leaves the refinery, but is effective when processed. In contrast, it is surprising that polar coal exhibits certain effects even in its untreated state. Furthermore, this effect is enhanced by treatment. These variations allow for the selective combination of different carbonaceous materials, compensating each other in properties to meet specific requirements, resulting in additives with favorable degrees of shrinkage. Therefore, the selection and adjustment to change the expansion rate and expansion capacity are
possible over a wide range. Other carbonaceous materials such as candle charcoal, charcoal, etc. are also used and processed here. Furthermore, the compressive strength is unexpectedly satisfactory, taking into account the preconceptions of those skilled in the art that coal in the cement has an adverse effect on this strength.

The benefit of anti-shrinkage therefore outweighs the inconvenience of expansion and/or addition of lignite to the cement. The surprising ability of carbonaceous materials to minimize breathing in adhesive systems is also illustrated in Example 3.

Example 3 Breathing was observed when preparing three cement compositions.

The three compositions were made by mixing 42.5 parts Type 1 cement and 57.5 parts sand by weight, preparing three 100-pound portions of this mixture and adding 9 quarts, 8 quarts, and 7 quarts of water, respectively. Add quarts and mix. No carbonaceous material was used. Each of these cementitious systems showed the least amount of breathing with 9 quarts of water added, followed by 8 quarts of water, and the least amount of breathing with 7 quarts of water added, and shrinkage of 7 quarts. The one with the least amount of water added was the least (same order as above). Breathing and shrinkage are eliminated by replacing 3 parts sand with 3 parts fluid coke. Also, fluid coke 2
．． While 5 parts removed the breathing, as little as 2 parts did not. However, even this small amount was sufficient to prevent shrinkage. Therefore, the amount required to eliminate breathing can be readily confirmed by observation. This is because pleading can be identified by the exposure of water on the Western-style surface. Also, the amount excluding breathing can be easily determined according to the type of cement, water content and carbonaceous material used. However, the carbonaceous material must be resistant to shrinkage.

[Brief explanation of drawings]

The drawings are curves showing the expansion and contraction states with respect to hardening time for cement systems containing various carbonaceous materials of the present invention. Figure 1 shows anthracite, Figure 2 shows lignite, Figure 3 shows fluid coke, and Figure 4 5 is a curve diagram for delayed coke, FIG. 5 is for activated carbon, FIG. 6 is for activated alumina, and FIG. 7 is for bituminous coal. FIG. l FIG. 2 FIG. 3 FIG. 4 FIG. 5 FIG. 6 FIG. 7

Claims (1)

[Claims] 1 Select one or more of granular fluid coke, day-laid coke, anthracite, bituminous coal, and lignite, and heat the material at a temperature of 121°C (250°F) or higher, except in the case of said day-laid coke, 816°C (1500°F). °F) and adding said heat-treated granular material to the cement system simultaneously with or prior to the addition of water in an amount that prevents shrinkage of the cement system.
A method of preventing shrinkage of water-based hydraulic cement systems during curing.