JPH0377764B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for preparing a mixture of hydraulic substances, in which sand, which is an essential material for preparing a mixture of mortar or concrete, is mixed with powder of a hydraulic substance such as cement or gypsum. The purpose of the present invention is to provide a method for determining a reasonable amount of water when mixing and kneading such fine aggregates, and thereby obtaining a kneaded material with stable characteristics in terms of fluidity, breathing, etc. Adding and mixing fine aggregate (and coarse aggregate, fiber materials, and other auxiliaries or additives) and mixed water to hydraulic substance powder such as cement to prepare a ready-mixed material such as mortar or concrete. Although this has been widely practiced in the past, it is inevitable that there will be some variation in the quality characteristics of the green kneaded material prepared in this way or the various products obtained by molding and hardening the green kneaded material. As is well known. In particular, when using the shell kneading (divided kneading) method developed by the present inventors, it is necessary to accurately determine the amount of primary water (or the subsequent amount of secondary water), which will affect the quality characteristics. However, it is large. This is due to the fact that the amount of water adsorbed or attached to the fine aggregate cannot be accurately determined as described above, and in fact, the amount of water adsorbed or attached to the sand piled outdoors varies widely. It is clear from practice that when sand with different amounts of water is used, the above-mentioned quality or characteristics will vary greatly. By the way, regarding such fine aggregate, JIS
A1109 "Method for testing specific gravity and water absorption of fine aggregate" is specified, that is, a specified flow cone is set on a table, a sample is filled into the flow cone in a specified manner, and then the flow cone is The time when the fine aggregate slumps for the first time when the aggregate is pulled up is called the Saturated surface-dry state.
condition), and the moisture contained in the fine aggregate in this state is that the voids inside the fine aggregate are filled with water (saturated), and the surface is dry with no water. When preparing such a green kneaded product, the water absorption rate obtained in the above test is used as the ineffective water content of the fine aggregate itself, and the water content of such fine aggregate does not play a role in the blending. The values excluded when determining the blended water are used. However, as a result of the present inventors' study of aggregates in the surface dry saturated state specified by JIS, it is unreasonable to determine the blended water by treating the surface dry saturated state as described above as ineffective water. I came to the conclusion that there is. That is, the present inventors used C sand, E sand, and crushed sand from Oigawa River, and mixed them with water using a vacuum mixer under a reduced pressure of 730 mmHg so as not to leave any air on the sand surface, and then mixed them with water to a predetermined moisture content. A sample was prepared, filled into an acrylic container in the specified precise state, placed on a flow test table, and compacted by moving up and down 15 times. After measuring the weight, the moisture content and voids were determined. rate (in absolute dry condition)
Figure 1 summarizes these measurement results and also shows the moisture content of these fine aggregates in the above-mentioned surface dry saturated state (hereinafter referred to as surface dry state) according to JIS regulations. be. According to Figure 1 of the cover, in each fine aggregate as described above,
Even below the above-mentioned surface dry state, changes in bulking (porosity) are clearly shown due to changes in moisture content. In addition, results similar to this have also been found in the influence of particle size due to changes in water absorption of fine aggregate that has been sieved separately, or in centrifugal force tests. In the saturated state (Q), it is still bound by a certain amount of aggregate on the aggregate surface and has a critical surface adsorption water rate (SW lim) beyond which it will not be dehydrated unless it is specially handled or dried. I have to say it's amazing. That is, the surface dry water saturation state Q is determined by the internal water saturation rate (Q ₀ ) and the critical surface adsorption water (SWlim).
The sum Q=Q ₀ +SWlim. By the way, the surface dry saturated state Q as mentioned above,
In order to determine the critical surface adsorption water SWlim, etc., it is basic to measure them and determine at least the Q value. For example, this condition can be achieved by storing the fine aggregate that is sufficiently hydrated in a closed container and holding it for a long period of time (for example, about one month). Although it is certain that the objective can be achieved even if the measurement is carried out in a timely manner, requiring such a long time would consume a period of months to obtain a single measurement value, and a large amount would be consumed in mass production. However, it is not possible to obtain measurement results that meet the demand conditions for fine aggregate (sand), which inevitably comes in many varieties. Therefore, the present inventors confirmed that for the above-mentioned fine aggregates, there is something that should be called the maximum surface adsorption water rate SWmax, in addition to the above-mentioned SWlim.
This Sw max was estimated to be the ineffective water content that does not affect or have any effect on separation breathing, fluidity, or workability in the actual kneaded product. In other words, the present inventors have repeatedly studied how to clarify the relationship between SW lim and Sw max within a relatively short period of time, and have developed a centrifugal force mechanism in which properly moistened fine aggregate is housed in a closed container. The separated water is separated from the fine aggregate, and whether it is subjected to centrifugal force or stopped, it is properly managed so that it does not become adsorbed or attached to the fine aggregate again. We have devised a measurement method to prevent this from occurring. The details of the water separation test device for fine aggregate using centrifugal force, which was designed and used by the present inventors based on this concept, are shown in Figure 2. The height is 10 with an acrylic plate 11 attached to one end of a 5 mmφ PVC pipe 10.
A second isometric body 1 with the same dimensions as the first cylindrical body of cm and a height of 5 mm
0, a wire mesh 12 made of metal wire with a diameter of 0.15 mm, a filter paper 13, and a perforated punched iron plate 14 with a thickness of 1.6 mm.
The first cylindrical body is filled with 200 g of sample fine aggregate, and the second cylindrical body 10 is filled with absorbent cotton 16, and the vinyl tapes 15 are joined facing each other as shown in FIG. As shown in FIG. 4, a receiver is attached to a rotary plate 22 in a case 20 with a lid 21 so as to be tiltable about a shaft 25. More than half of the water is contained in the container 24, and a predetermined centrifugal force is applied by rotating the rotary plate 22 in this state, and the separated and discharged water from the first cylinder is transferred to the second cylinder. The moisture absorbed by the absorbent cotton 16 of the cylindrical body is designed to prevent the moisture thus absorbed by the absorbent cotton 16 from flowing back when the rotary plate 22 stops rotating for testing. It should be noted that sealing the tubes 10, 10 with vinyl tape 15 or the like as described above is important in determining the critical surface adsorption water rate SWlim and surface dry saturated state as described above in the present invention.
When centrifugal force is applied to a container that is simply covered with a test material, the air inside the container is released to the outside under the conditions in which the centrifugal force is applied, and the pressure inside the container is generally reduced. The conversion flow of air between the inside and outside of the container is repeated,
Moisture is also diffused and discharged due to the conversion flow of air between the inside and outside of the container, and the reduced pressure conditions also increase moisture dispersion. It is necessary to appropriately prevent the vaporization and discharge of moisture associated with such air flow conversion and apply centrifugal force to obtain measurement results, and for this reason, the formation of the sealed state is important. However, using the above-mentioned device, for example, E sand from Oigawa (FM = 3.23, porosity ε = 33.8%)
The Q value measured by JISA1109 above is
The amount of water landing on this item is 1.39%.
Once dried at a temperature of 110°C for 24 hours, dry in a vacuum mixer at -730mmHg from 1Q.
Prepare materials with varying moisture content in a range of 10Q, apply a centrifugal force of 453 g (g is gravity acceleration) to these materials for 120 minutes,
The results of the moisture separation treatment are summarized and shown in FIG. 5, with the horizontal axis (processing time) plotted on a logarithmic scale. In other words, according to the results shown in Figure 5, at least 5Q
For the following water contents, the water content decreases in an orderly manner in approximately proportion to the centrifugal action time, and for 1Q, there is almost no decrease in the water content. On the other hand, in the case of 6Q or higher, the decline is rapid within the first 5 minutes, but after that it is a slow decline, and at least 5
After 10 minutes, the moisture content decrease behavior is almost the same as that in the case of 5Q or less. In other words, there is clearly an inflection point on this horizontal logarithmic graph for anything above 6Q, and the maximum state where the inflection point is difficult to recognize is the maximum surface adsorption water rate.
It can be said that water adhering above the maximum surface adsorption water rate, which is recognized as SWmax, is an inflection point, and is separated relatively easily, whereas water below that is separated slowly. . Incidentally, this kind of phenomenon is observed in almost the same way in all other types of sand, although the specific values are different.
3.01, the Sagami River sand with a porosity ε = 33.0% is as described above.
The Q value according to JISA1109 is 3.12%, which is considerably higher than the case shown in Figure 5, but the results of a completely similar test and measurement for this product are summarized in the same way as shown in Figure 6. . In other words, in the case of this Sagami River river sand, in the same horizontal axis logarithmic graph as in Figure 5 above, the water content decreases in a nearly linear manner up to 3Q, but above 4Q, there is a clear decrease at the position of 5 minutes of centrifugal force action. An inflection is observed, and in this case, it is recognized that the above SWmax exists around 3Q. In addition, each of the above-mentioned fine aggregates and other representative 5
Figure 7 shows the results of a similar centrifugal force separation test on seed fine aggregates whose initial moisture content was adjusted to around 1Q, with some fluctuations observed. However, it was confirmed that all fine aggregates remained almost unchanged regardless of the length of the separation treatment time, and from this result, the test results according to JISA1109 (Q) were confirmed.
can be said to be stable in terms of moisture content. However, in the actual kneaded material, such surface dry state (Q)
It is natural that the water is restricted to this extent, and it is clear that the amount of water that causes fluctuations in breathing and fluidity is greater than this Q value (in Figure 5, even 5 minutes of centrifugal force action exceeds 4Q). From the results shown in Figures 5 and 6 mentioned above, the amount of water affected by breathing and fluidity is determined by the maximum surface adsorption water rate.
It is considered that Sw max has been exceeded, and when Sw max is expressed as a multiple of the Q value, it is recognized from the results shown in FIGS. 5 and 6 that it falls within the range of 2Q to 5Q. It should be noted that for the above-mentioned test measurements, it is important to perform the addition of incidental water under reduced pressure conditions as mentioned above in order to carry out measurements within a short period of time. If the pressure is reduced to -730 mmHg, the air adhering to the surface of the fine aggregate can be effectively removed, and if water is added and mixed in this state, the added water will damage the structure of the fine aggregate. The water is effectively permeated into the inside, and the attached moisture becomes stable and constant. On the other hand, when water is simply added and mixed in the atmosphere, there is a high possibility that the adhering water is unevenly distributed on the surface of the fine aggregate.
Therefore, it is unstable and the measurement results fluctuate. For example, the results of the same centrifugal separation treatment of the Oigawa E sand, which was kept in an absolutely dry state and mixed with water under the reduced pressure conditions in a vacuum mixer, and with water added in the air, are shown in Figure 8. Even if the processing time is the same, the measurement results may vary.
Those mixed with water in the atmosphere have low moisture content and considerable variation. Those using reduced pressure conditions are almost stable and have almost no fluctuation even in the repeated test results, and similar results were obtained with any of the above-mentioned Sagami River sand, water slag sand, or standard sand. Therefore, it is essential to add water and mix under reduced pressure conditions to obtain a predetermined Q value in order to obtain accurate measurement results. It is necessary to maintain a constant state. Furthermore, to explain the results of examining various types of fine aggregates for centrifugal force separation as described above, the 11 types of fine aggregates shown in Table 1 below each typically contain moisture equivalent to 3Q. These fine aggregates were prepared in the same way as above.
The results of centrifugal force separation treatment using a gravitational acceleration of 453 g are also shown in the lower part of Table 1 in relation to the elapsed treatment time.

[Table] Figure 9 is a diagram that summarizes these results. In this figure, the horizontal axis is on a logarithmic scale up to 90 minutes, but between 90 minutes and 120 minutes. The interval is made larger because there are complicated parts, but the value taken at the 0 minute position on the horizontal axis on the vertical axis in Figure 9 is the value corresponding to 3Q for each fine aggregate. , the moisture content of these materials decreases with each treatment time, but Sagami River sand (X...
With the exception of X) and North American sand, the water content decreases due to the treatment action are in an almost orderly parallel relationship, and with the exception of the Sagami River sand and North American sand, the surface dry saturated water structure vs. Q of 2 was treated for 120 minutes. The water content is approximately twice as high, and it is recognized that it is hardly affected by the coarse grain ratio FM or the porosity ε shown in Table 1. However, Figure 10 shows the above results organized by the multiplier of Q, and it is clear that there is a linear correlation between the Q value and the processing time of 30 minutes. , 60 minutes and 120 minutes are arranged as shown in Figures 11 a to c. In other words, the slope of the linear relationship between the water content after centrifugal force and the Q value of the fine aggregate is 2.5 at 30 minutes, 2.3 at 60 minutes,
It is 2.0 at 120 minutes and is approximately regular, and becomes smaller as the processing time increases, but most of the measurement points are located neatly on the straight line of SW = 2.5Q, 2.3Q, and 2.0Q on the diagram. ing. However, if we consider the aforementioned Sagami River sand and sand from North America, which deviate to some extent from the straight line of Q = 2.5, 2.3, or 2.0 on the chart, the reason why values deviate from the standard line in this way can be explained. It is recognized that this is due to the internal water saturation rate (Q ₀ ) of the fine aggregate, and this deviation from the reference line becomes approximately the same after centrifugation for at least 30 minutes. Therefore, in order to shorten the time required for test measurement and to obtain a substantially stable SWmax (or Q ₀ ) value, it is generally sufficient to take about 5 minutes, but it may take up to 30 minutes, such as with Sagami River sand or North American sand. Since there are special cases in which the separation process is performed using centrifugal force as described above, it is practical to set the time to 5 to 30 minutes. According to the present invention, the critical surface adsorption water rate Swlim (Q) obtained as described above and the maximum surface adsorption water rate SWmax, which are unique to each sand, are within a range of 2 to 5 times the Q value. The amount of mixed water is determined by taking the water content at a substantially constant rate as the non-effective water percentage, and using the amount of water above this non-effective water percentage as the effective water percentage. In such cases, cases where the internal water saturation rate _Q0 is significantly affected are excluded from application as they are exceptional cases, and if applicable, the above-mentioned centrifugal force treatment for at least 30 minutes or more should be applied. Adopt the value given. It is natural that the sand actually used has a certain water content, so in order to obtain the actual amount of water added to the actual sand using the amount of water mixed in the present invention determined as above, Naturally, the value is obtained by subtracting the water content of the actual sand described above from the amount of water mixed. Specific examples and comparative examples of the method according to the present invention will be described below. Sand with physical properties according to JIS as shown in Table 2 below was used.

[Table] The sand shown above was dried at 110℃ for 24 hours, and -
Water absorption treatment was carried out for 5 minutes under reduced pressure of 730 mmHg to obtain a water content equivalent to 3 times the above Q value.
A surface-dry version according to JISA1109 was prepared.
Then, each of these sands has a volume ratio of 1 part cement.
On the other hand, the mixing was adjusted by setting the sand to 2.6 and keeping the water-cement ratio, W/C = 68%, including the moisture content. The kneading method was to add primary water to the sand and knead it for 30 seconds, then add cement and mix it for 90 seconds, then add secondary water and knead it for 60 seconds to obtain the desired kneaded product. The specific formulation relationships for these kneaded products are shown in Table 3 below, together with those on a surface dry basis according to the conventional method.

[Table] On the other hand, according to the present invention, about 2.5Q is regarded as ineffective water that does not affect breathing or fluidity, and the water above that point is considered to be effective water. Absolutely dry W/C in Table 3 above is 68
The formulation of the present invention, which was determined so that W/C = 57%, which approximately corresponds to Quantity.

[Table] For each of the formulations in Tables 3 and 4 above, the blended water is added by dividing it into the primary and secondary stages, and the kneading time in each process is also constant as described above. The desired kneaded product was obtained. Further, each of the kneaded products obtained as described above was subjected to the following tests in order to confirm its characteristics and properties. Surface breathing…1 in a φ71 x ^H 200 container
Internal breathing every hour until the end point...Measure the amount of dehydration 90 minutes after filling. Settlement test: Immediately after kneading in 2 squares using a φ20m/m sinking rod Table flow: Measure immediately after kneading in a constant temperature and humidity system according to JIS regulations. Unit volume weight: 2 squares Strength test: 4 x 4 x 16 mm test piece, 7 days old, 28 days old bending and compression In other words, the results of each of the above tests are as follows for those in Table 3. Table 5 shows the results, and those in Table 4 are shown in Table 6.

【table】

[Table] Comparing the results of Tables 5 and 6, even though there are some differences due to the use of different sands in each case, the breathing rate of the surface layer in Table 5 is 1.05. ~6.10%, but those in Table 6 are significantly lower at 0.71~2.97%, and the variation range is also small. Regarding the internal breathing rate, those in Table 5 range from 7.8 to 18.5%, while those of the present invention shown in Table 6 range from 8.03 to 12.87%, which is a small variation range. Furthermore, regarding the sedimentation test, Table 5 shows
0.28~1.81g/ ^cm2 , but in Table 6 it is 1.02~3.5
It was confirmed that it had preferable fluidity in terms of g/cm ² and that Table 6 showed less variation in table flow. According to the present invention as explained above, it is possible to appropriately obtain a kneaded material of this type of hydraulic material that uses a certain amount of different types of fine aggregate and has stable characteristics or properties with a small range of variation. This invention is industrially very effective because it can be used to tighten the system.

[Brief explanation of drawings]

The drawings show the technical contents of the present invention, and Fig. 1 is a chart showing the relationship between the surface dry saturated state and porosity according to JIS regulations for various fine aggregates, and Fig. 2 is a chart created by the inventor of the present invention. An explanatory diagram showing the disassembled state of the closed container used in the centrifugal force action method proposed by , which was proposed for short-time measurement, in cross-section and plan view. Figure 3 is a cross-sectional view of the assembled state, and Figure 4 is Figure 5, which is a cross-sectional view of the entire test equipment, summarizes the relationship between centrifugal force action time and water content when measurements are taken using the equipment shown in Figures 2 to 5 for fine aggregates with various amounts of adhering water. Figure 6 is a diagram showing the results of similar measurements made on fine aggregates different from those shown in Figure 5, and Figure 7 is a diagram showing the results of measurements made in the same way for fine aggregates different from those shown in Figure 5. Graph showing similar centrifugal force separation test results for the
The figure is a chart showing the results of similar centrifugal separation treatments for water added in the atmosphere and water added under reduced pressure conditions. Figure 9 is a graph summarizing the results of centrifugal separation treatment for various fine aggregates. Figure 10 is a chart showing the results of arranging the initial moisture content of Figure 9 using the multiplier of the Q value. FIG. 11 is a chart showing the results further organized for processing times of 30 minutes, 60 minutes, and 120 minutes. In these drawings, 10 is a synthetic resin pipe, 11 is an acrylic plate, 12 is a wire mesh, 13 is filter paper, 14 is a perforated iron plate, 15 is an adhesive tape, and 16
20 is absorbent cotton, 20 is a case, 21 is a lid, 22 is a rotating plate, 23 is a rotating shaft, 24 is a receiver, and 25 is a shaft.

Claims (1)

[Claims] 1. Determine the critical surface adsorption water rate of fine aggregate such as sand to be mixed into the hydraulic substance kneaded material, and determine the critical surface adsorption water rate within the range of 2 to 5 times the critical surface adsorption water rate The method is characterized in that a moisture content of a substantially constant ratio obtained by measuring fine aggregate of A method for adjusting a hydraulic material kneaded product. 2. The moistened fine aggregate is placed in a closed container, and a centrifugal force is applied to the closed container for a predetermined period of time to separate adhering water, and after the separation treatment by this centrifugal force, the remaining adhering water is removed from the fine aggregate. The method for preparing a hydraulic material kneaded material according to claim 1, wherein the critical surface adsorption water content is determined by measuring the water content. 3. A method for preparing a hydraulic material kneaded material according to claim 1, in which the critical surface adsorption water rate is determined according to the specific gravity and water absorption rate test method of fine aggregate specified in JIS A1109.