JP2003329561A - Method for estimating water retention capacity of fine- aggregates and design method of mixing concrete using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain desired workability without executing a trial kneading at every time when fine-aggregates are changed. <P>SOLUTION: In the method for estimating a water retention capacity, water/ fine-aggregate mixed materials are made up by mixing water with the fine- aggregates being objects to be estimated at three fine-aggregate/water ratios of (a%, b% and c% different from each other, and each consistency is measured respectively. In the measurement, each slump value of the water/fine-aggregate mixed materials corresponding to the three fine-aggregate/water ratios is obtained. The obtained slump values are plotted and represented by a graph in figure 1 (a). Then, a relativity between the fine-aggregate/water ratio and the slump value of the water/fine-aggregate mixed material is determined from the measured slump values. It is also preferable that the relativity between the fine-aggregate/water ratio and the slump value is determined relatively by referring to previous data relating to other fine-aggregates A, B and C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention mainly evaluates the water retention of fine aggregates that have arrived at ready-mixed concrete factories, and the water retention of fine aggregates that is used when designing concrete mix based on the evaluation. The present invention relates to a property evaluation method and a concrete mix design method using the same.

[0002]

2. Description of the Related Art In manufacturing concrete,
It is necessary to perform a mix design in advance that determines the usage ratio of cement, water, aggregate and admixture, but in the mix design of concrete, the unit water amount should be within the range that has the required strength, durability, watertightness and workability. It is important to reduce the amount as much as possible and to appropriately select the ratio of fine aggregate and coarse aggregate for that purpose.

That is, if the proportion of fine aggregate is reduced,
The amount of unit water required to obtain concrete with the required consistency is reduced, the amount of expensive cement used is reduced, and it becomes economical, but if the proportion of fine aggregate is too small, material separation increases and workability is improved. Since it becomes bad concrete, it is important to find the optimum ratio of fine aggregate and coarse aggregate.

Although there are various methods for designing the composition, the method of determining the composition by carrying out test kneading is the most practical method and is still widely used.

By the way, in the mix design of concrete, generally, the mix strength is first determined as the strength in which the variation in quality is taken into consideration in the design standard strength, and the maximum size of the coarse aggregate (in the case of general RC is used). Is 20 or 25 mm,
If the cross section is large, 40 mm is set as a guide, and then the consistency represented by slump (generally 5 to 12 cm for RC vibration and 3 to 10 cm for a large cross section) is set. Establish.

Next, the unit water amount, the air amount and the fine aggregate ratio for the test composition are determined, and the water-cement ratio is determined based on the strength and the like.

Next, a unit amount of cement is determined from the water-cement ratio and the unit amount of water, and a test kneading is carried out. While properly correcting each value for the above-mentioned test formulation, a specific formulation satisfying a predetermined slump or the like. Determine.

[0008] Finally, it is a general procedure that the on-site composition is separately determined so as to obtain the concrete of the concrete composition in consideration of the particle size of the aggregate on the site, the state of the surface water, and the usage method of the admixture. .

[0009]

Here, the required strength,
In order to produce durable and watertight concrete, it is important to reduce the unit water volume as much as possible within the range where workability suitable for concrete pouring work is obtained as described above. In order to obtain the required consistency of concrete, the unit water volume required for concrete is
It greatly differs depending on the particle size and shape.

Therefore, every time the fine aggregate is changed, it is necessary to carry out a test kneading to design the directional composition, which causes a problem that a great deal of labor and labor is required.

The present invention has been made in consideration of the above circumstances, and newly defined water retention of fine aggregate as an index affecting the workability of concrete, and evaluated it. Based on the evaluation, The purpose of the present invention is to provide a water retention evaluation method for fine aggregates that can estimate the unit water volume that can obtain the required workability without performing test kneading for each fine aggregate, and a concrete mix design method using the same. And

[0012]

In order to achieve the above object, the water retention evaluation method for fine aggregates according to the present invention, as described in claim 1, comprises at least two different types of fine aggregates and water. The fine aggregate ratio is mixed to prepare a water-fine aggregate mixture, and the consistency of the water-fine aggregate mixture is measured to determine the consistency of the water-fine aggregate ratio and the water-fine aggregate mixture. The relationship with the tenacity is grasped, and the water retention of the fine aggregate is evaluated based on the relationship.

Further, in the water retention evaluation method for fine aggregates according to the present invention, the water retention is evaluated by the ratio of water fine aggregates when the consistency of the water fine aggregate mixture becomes substantially zero. The water retention at that time is taken as the water retention limit value.

According to a third aspect of the present invention, there is provided a concrete mixing method for mixing concrete, wherein the fine aggregate to be mixed and water are mixed in at least two different fine aggregate ratios. A mixture of aggregates is prepared, and the consistency of the mixture of fine aggregates is measured to grasp the relationship between the ratio of the fine aggregates and the consistency of the mixture of fine aggregates. The water retention of the fine aggregate to be compounded is evaluated based on the property, and the water retention of the fine aggregate to be compounded is collated with the association data between the water retention and the unit water amount obtained in advance. A concrete mix design method for estimating a unit water amount required when using a target fine aggregate, wherein the association data is used to calculate the grain shape, the grain size, and other arbitrary indexes that affect the workability of concrete. Fine While evaluating the water retention of each of the materials, the unit water amount required when using each fine aggregate is obtained by test kneading, respectively, data showing the relationship between the water retention and the unit water amount Is created in advance.

Further, in the concrete mix designing method according to the present invention, the water retention is evaluated by the ratio of the fine aggregates when the consistency of the fine aggregate mixture becomes substantially zero, The water retention capacity at that time is used as the water retention limit value.

In the water retention evaluation method for fine aggregates and the concrete mix design method using the same according to the present invention,
First, fine aggregate, and if the composition is designed, the fine aggregate to be mixed and water are mixed at at least two different water fine aggregate ratios (ratio of water to fine aggregate). A mixture is prepared and its consistency is measured. The consistency can use, for example, a slump value as an index.

Next, the relationship between the fine aggregate ratio and the consistency of the fine aggregate mixture is ascertained based on the measurement result of the consistency.

The applicant of the present invention has conducted an experiment on this relationship with various fine aggregates, and as the ratio of the fine aggregates increases, the consistency of the mixture of fine aggregates increases, and at the same time, the fine aggregates become finer. It was found that when the ratio was too small or too large, the measurement accuracy of the consistency decreased.

Further, when experimental values were plotted with the horizontal aggregate as the horizontal aggregate and the vertical axis as the consistency, the plot was almost along a straight line rising to the right, and the same consistency was obtained. It was also found that the finer the aggregate of water fine aggregates required to obtain, the more gradual the slope of the straight line described above.

Even if the fine aggregate has the same density, actual volume, or sampling location, the relationship between the water-fine aggregate ratio and the consistency results in a different result. It is considered that it is caused by the grain size or grain shape of the aggregate, and the above-mentioned relationship is defined as the water retention property of the fine aggregate according to the deformation state of the fine aggregate mixture, in other words, the fine aggregate mixture is predetermined. The water-aggregate ratio when the water-aggregate mixture is at a given consistency is considered as the characteristic value of the water-aggregate that retains water between particles when it is maintained in its deformed state. , Which is defined as the water retention characteristic of fine aggregate.
The Applicant defines the water-fine aggregate ratio when the consistency becomes zero, in particular, as a water retention limit value.

As described above, if the water retention is evaluated based on the relationship between the ratio of fine aggregate to the consistency, the grain size of fine aggregate can be examined by sieving or the grain shape can be examined. Even if only the relationship between the consistency of the fine aggregate and the fine aggregate ratio is investigated by the above-mentioned procedure, the deformability when the fine aggregate is mixed with water, and thus when the fresh concrete is used. It becomes possible to use it as an index to evaluate the workability of, and it becomes possible to manage the fine aggregate with higher quality.

Next, when designing the mix composition of concrete using such a water retention evaluation method for fine aggregates, first, the association data between the water retention property and the unit water amount is created in advance before the mix design.

Data relating the water retention and the unit water amount are
For any fine aggregate with different grain shape, grain size and other indicators that affect the workability of concrete,
The water retention of each of them is evaluated, and the unit water amount required when each fine aggregate is used is obtained by test kneading, and this is used as data showing the relationship between the water retention and the unit water amount.

The water retention may be a ratio of fine aggregate in any consistency. In addition, it is desirable to create the above-mentioned association data using as many fine aggregates as possible.

Next, in order to design the mix composition of concrete using such association data, the water retention of the fine aggregate to be mixed is evaluated by the above-described procedure, and then the water retention of the fine aggregate is evaluated. The preliminarily created association data between the water retention capacity and the unit water amount is collated, and the unit water amount required when the fine aggregate to be blended is used is estimated by the collation.

Here, in evaluating the water retention of the fine aggregate, the water-fine aggregate ratio at the consistency adopted when creating the association data is used. For example, if the association data is associated with the unit water amount by the water-fine aggregate ratio when the slump value is 5 cm, when the water retention of the fine aggregate to be mixed is evaluated, when the slump value is 5 cm, If the water fine aggregate ratio of is evaluated as its water retention property and the water fine aggregate ratio when the slump value is 0 cm, that is, the water retention limit value is associated with the unit water amount, the fine aggregate to be blended is Also when evaluating the water retention of the above, the water retention of the fine aggregate is evaluated by the water retention limit value.

By doing so, even if the test kneading is not performed every time the fine aggregate is received or carried into the ready-mixed concrete plant, the water retention of the fine aggregate can be evaluated by the above-mentioned procedure. It is possible to easily know the amount of unit water required when mixing fresh concrete with fine aggregate.

The above-mentioned association data need only be obtained with respect to the reference slump value, and if the slump value to be designed is different from the reference slump value when the association data was created, the slump value is obtained. A known conversion table showing the increase / decrease value of the unit water amount corresponding to the increase / decrease of may be appropriately used.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a water retention evaluation method for fine aggregates and a concrete mix design method using the same according to the present invention will be described below with reference to the accompanying drawings. It should be noted that parts and the like which are substantially the same as those of the conventional technique are designated by the same reference numerals and the description thereof is omitted.

(First Embodiment)

In the water retention evaluation method for fine aggregates according to the present embodiment, first, three fine aggregate ratios, a%, b% and c%, which are different from each other in fine aggregate and water to be evaluated, are used. To prepare a water-fine aggregate mixture, and measure the consistency of each. In this embodiment, the consistency is evaluated by the slump value.

FIG. 1 (a) is a graph showing a state in which the slump value of the water-fine aggregate mixture is obtained for three water-fine aggregate ratios and plotted.

In order to measure the slump value, first, the surface water ratio of the fine aggregate is measured, and then water is added so as to obtain a predetermined fine aggregate ratio, and then a fine aggregate mixture is prepared. The slump value may be measured by kneading the water-fine aggregate mixture with a mortar mixer for about 30 seconds and then putting it in a mini slump cone. In order to prevent the water-fine aggregate mixture from separating into water and fine aggregate, for example, 20 to 30% by mass of stone powder with respect to the fine aggregate is added as a separation reducing agent.

Next, based on the measurement result of the slump value, the relationship between the fine aggregate ratio and the slump value of the fine aggregate mixture is grasped. In understanding the relationship between the fine aggregate ratio and the slump value, it is good to pay attention to the increase of the slump value with respect to the increase of the fine aggregate ratio.

In order to understand the relationship between the water-fine aggregate ratio and the slump value, it is also desirable to relatively understand it by referring to the data on other fine aggregates performed in the past.

In FIG. 1 (b), the results of the above-described fine aggregate to be evaluated are superimposed on another fine aggregate A, fine aggregate B, and fine aggregate C, and the respective test values are appropriately set. It is a straight line drawn.

As can be seen from the figure, the fine aggregate to be evaluated has a higher water retention than the fine aggregate A, and therefore requires a large amount of water to realize the same slump value.
It can be seen that the amount of water for realizing the same slump value is smaller than that of the fine aggregate B and the fine aggregate C because the water retention is lower.

As described above, according to the water retention evaluation method for fine aggregates according to the present embodiment, the water retention described above is evaluated based on the relationship between the ratio of water fine aggregates and the slump value. For example, even if the grain size of the fine aggregate is not examined by sieving or the grain shape is examined, just by examining the relationship between the slump value and the fine aggregate ratio of the fine aggregate by the above-mentioned procedure, It becomes possible to use it as an index for evaluating the deformation performance when fine aggregate is mixed with water, and further the workability when it is made into fresh concrete, and it becomes possible to manage fine aggregate with higher quality.

In the present embodiment, the magnitude of the slump value when evaluating the water retention is not mentioned, but in evaluating the water retention of the fine aggregate, a range in which the slump value can be accurately measured, for example, It is desirable to appropriately select the slump value in the range of 5 cm to 10 cm and evaluate the water retention as the fine aggregate ratio at that time, but the size of the slump value when evaluating the water retention is arbitrary in the first place, and evaluated. From the viewpoint of uniformity, the water-aggregate ratio at which the slump value of the water-aggregate mixture becomes substantially zero may be evaluated as water retention. In this case, the water retention when the slump value is zero can be considered, so to speak, a water retention limit value.

(Second Embodiment)

Next, the second embodiment will be described.

In designing the mix composition of concrete according to the second embodiment using the water retention evaluation method for fine aggregates described in the first embodiment, first, the water retention and the unit water amount are related to each other before the mix design. Create data in advance.

In order to create the association data between the water retention capacity and the unit water content, first, in the first embodiment, with respect to arbitrary fine aggregates having different grain shapes, grain sizes, and other indexes affecting concrete workability, Each of these water retentions is evaluated according to the procedure described.

FIG. 2A shows three types of fine aggregates, that is, fine aggregate A, fine aggregate B, and fine aggregate C, as arbitrary fine aggregates having different indexes affecting the workability of concrete. It is a graph which evaluated water retention.

Next, these three fine aggregates A, B,
The unit amount of water required when using the fine aggregate C is obtained by test kneading, and this is used as data showing the relationship between the water retention capacity and the unit amount of water.

As in the case of the first embodiment, the water retention may be a fine aggregate ratio at an arbitrary slump value, for example, 5 cm. For convenience of explanation, only three fine aggregates are used in the present embodiment, but it is desirable to create the above-described association data using as many fine aggregates as possible.

In FIG. 2 (b), the unit amounts of water required when using the fine aggregate A, the fine aggregate B, and the fine aggregate C were obtained by test kneading, and these were respectively indicated by ○, △, □. 2 is a graph showing a state of being plotted with, and such a graph becomes data showing the relationship between the water retention capacity and the unit water amount.

Next, in order to carry out a concrete mix design using the created association data, for example, the same procedure as that of the first embodiment is applied to the fine aggregate to be mixed or received in the ready-mixed concrete plant. To evaluate water retention.

Next, the water retention of the fine aggregate is collated with the above-mentioned association data between the water retention and the unit water amount, and the unit water amount required when the fine aggregate to be blended is used by the collation. To estimate. For example, referring to FIG. 2B, if the water retention of the fine aggregate to be blended is 15%,
It can be seen that the unit water amount of concrete is 170 kg / m ³ .

Here, in evaluating the water retention of the fine aggregate, the water fine aggregate ratio at the slump value adopted when creating the association data is used. For example, if the association data is associated with the unit water amount by the water-fine aggregate ratio when the slump value is 5 cm, when the water retention of the fine aggregate to be mixed is evaluated, when the slump value is 5 cm, The water-fine aggregate ratio is evaluated as its water retention.

As described above, according to the concrete mix designing method of the present embodiment, the fine aggregate is not required to be subjected to a test kneading every time when the fine aggregate is received or carried into the ready-mixed concrete plant. If the water retention property is evaluated by the procedure described in the first embodiment, it becomes possible to easily know the unit water amount required when compounding fresh concrete using the fine aggregate.

In the present embodiment, the evaluation of water retention and the creation of association data were performed with the data when the slump value was 5 cm, but this was performed with the water retention limit value, that is, the data when the slump value was zero. May be.

In such a case, as shown in FIG. 3 (a), a straight line approximating the water retention of the fine aggregate A, the fine aggregate B, and the fine aggregate C is extended toward the X axis, and the intersection point The fine aggregate ratio is set to the water retention limit values a '%, b'%, and c '%, and the test kneading is performed for these water retention limit values as shown in FIG. It is sufficient to obtain unit water amounts by plotting them, plot them, and draw a straight line that approximates them to obtain the association data.

The water retention of the fine aggregate to be compounded may be evaluated in the same manner as in FIG. 3 (a).

[0055]

As described above, according to the water retention evaluation method for fine aggregates and the concrete mix design method using the same according to the present invention, the particle size of fine aggregates can be examined by sieving or the particle shape can be determined. Even if you do not investigate, just by examining the relationship between the consistency of the fine aggregate and the fine aggregate ratio by the procedure described above, the deformation performance when mixing the fine aggregate with water It becomes possible to use it as an index to evaluate the workability when it is made into concrete, and it becomes possible to manage fine aggregate with higher quality, and it is tested every time fine aggregate is received or delivered to the ready-mixed plant. Even without kneading, if the water retention of the fine aggregate is evaluated by the above-mentioned procedure, it is possible to easily know the unit water amount required when blending fresh concrete using the fine aggregate. Possible That.

[0056]

[Brief description of drawings]

FIG. 1 is a graph showing an implementation procedure of a water retention evaluation method for fine aggregate according to the present embodiment.

FIG. 2 is a graph showing an implementation procedure of a concrete mix design method according to the present embodiment.

FIG. 3 is a graph showing an implementation procedure of a concrete mix design method according to a modification.

Claims (4)

[Claims] 1. A fine aggregate and water are mixed in at least two different fine aggregate ratios to prepare a fine aggregate mixture, and the consistency of the fine aggregate mixture is measured. Grasping the relationship between the ratio of the fine aggregate to the consistency of the fine aggregate mixture, and evaluating the water retention of the fine aggregate based on the relationship. Water retention evaluation method. 2. The water retention is evaluated by a fine aggregate ratio at which the consistency of the fine aggregate mixture becomes substantially zero, and the water retention at that time is defined as a water retention limit value. The water retention evaluation method of the fine aggregate according to claim 1. 3. At least two fine aggregates and water to be blended
The water-fine aggregate mixture is prepared by mixing two different water-fine aggregate ratios, and the consistency of the water-fine aggregate mixture is measured to obtain the water-fine aggregate ratio and the water-fine aggregate mixture. Grasping the relationship with the consistency of the body, evaluating the water retention of the fine aggregate of the compounding target based on the relationship, the water retention of the fine aggregate of the compounding target, the water retention obtained in advance Is a concrete mix design method for estimating the unit water amount required when the fine aggregate to be mixed is used by matching with the association data of the unit water amount and the association data, the grain shape, the grain size In addition to evaluating the water retention of each of the fine aggregates that have different indicators that affect the workability of concrete,
A concrete mix designing method characterized in that a unit water amount required when using each fine aggregate is obtained by test kneading, and is created in advance as data showing a relationship between the water retention property and the unit water amount. . 4. The water retention is evaluated by a fine aggregate ratio at which the consistency of the fine aggregate mixture becomes substantially zero, and the water retention at that time is defined as a water retention limit value. The method for designing concrete mix according to claim 3.