JP2000169205A - Sludge-recycled concrete, regulation of its setting property, and regulation of its bleeding property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain sludge-recycled concrete by reusing large quantities of sludge on a solid basis produced from fresh concrete so as to reduce its amount to be discarded as a waste to a minimum, to provide a method for regulating the setting characteristics of the subject concrete enabling the initiation/ termination of its setting to be controlled, and to provide a method for regulating the bleeding characteristics of the subject concrete enabling its bleeding level to be controlled. SOLUTION: This concrete is obtained by reusing sludge on a solid basis withdrawn from discarded fresh concrete; in this case, large quantities of sludge can be reused without deteriorating the characteristics of the final concrete by bringing the abundance of such sludge on a solid basis relative to water (sludge mixing ratio) to 15-20 wt.%; wherein the higher the sludge mixing ratio, the sooner the initiation/termination of concrete setting occurs; furthermore, the higher the sludge mixing ratio, the lesser the bleeding level is effected, resulting in earlier bleeding ending time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a concrete using sludge obtained by reusing sludge solids extracted from waste ready-mixed concrete as a raw material for producing ready-mixed concrete, and a method for adjusting the setting and bleeding characteristics of the concrete.

[0002]

2. Description of the Related Art Conventionally, 1-2% of concrete shipped from a ready-mixed concrete plant is returned as concrete.
It has been returned to the manufacturer's raw conplant. The concrete is usually separated into coarse aggregate, fine aggregate, sludge and the like before hardening and discarded, or is subdivided into concrete chunks after hardening. In particular, sludge having a high alkalinity and containing harmful substances such as hexavalent chromium is disposed of in a controlled disposal site or the like. Here, the amount of the sludge to be discarded is 5 to 10 per standard Remicone factory of standard production capacity.
TON / day, and it is desired to reduce the amount of waste sludge.

For this reason, it has been considered to reuse the sludge as a countermeasure.
Japanese Patent No. 3733 proposes a method for removing unhydrated cement from sludge at low cost, and mixing the unhydrated cement with new cement, and a technique for the apparatus. Also,
JIS A 5308 (Lady Mixed Concrete) specifies the amount of sludge mixed.

[0004]

However, the above J
The sludge contamination rate specified by the IS is extremely low, and most of the sludge is still landfilled. In addition, research on sludge has been actively conducted.However, there is little knowledge about the effect of sludge mixing amount and its mixing ratio on concrete properties, and there is no standard of mixing amount and mixing ratio. Reuse methods have not been established.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and a large amount of sludge solids generated from a ready-mixed concrete factory, a concrete product manufacturing factory, and the like is reused in large quantities to minimize the amount of waste. It is an object of the present invention to provide a sludge recycling concrete capable of achieving the above-mentioned purpose, and to provide a setting property adjusting method capable of controlling the start and end of setting in the concrete and a bleeding property adjusting method capable of controlling a bleeding amount.

[0006]

In order to investigate the effects of the sludge mixing ratio on the main properties of concrete, namely, fresh properties, young age properties, strength, and durability, the present inventors set the sludge mixing ratio. Various tests were performed by changing the range from 0 to 20%, and the effects were clarified. As a result, 1
It has been found that in the range of 5 to 20%, it shows characteristics that are equal to or higher than that of no mixing, and the present invention has been completed.

[0007] That is, according to the first aspect of the present invention, the sludge solid content with respect to water (sludge mixing ratio) in sludge recycled concrete obtained by recycling sludge solid content extracted from waste ready-mixed concrete is 15 to 20.
(Weight)%.

In the sludge-recycled concrete having the above-mentioned structure, as shown below, the characteristics of the four concretes are equal to or higher than those of the case where no sludge is mixed. Therefore, a large amount of sludge, which is industrial waste, can be mixed and reused without adversely affecting concrete quality, and the total amount of industrial waste generated from construction activities can be significantly reduced.

(1) Fresh properties The slump value tends to decrease slightly as the sludge mixing ratio increases, but at least 20% is a value that does not cause any problem in use in pumping. Further, the air amount is within the set range within a range of 0 to 20%, and there is no problem. Therefore, in the range of 15 to 20%, there is no problem in quality as in the case of no contamination.

(2) Young age properties Due to the increase in the sludge mixing ratio, the bleeding amount is small and the penetration resistance value is relatively large, the bleeding properties and the setting properties are improved, and the properties are better than those without mixing. Further, in the range of 0 to 10%, the effect of the sludge mixing ratio on the strength development is small. Accordingly, the effect of reducing bleeding and the effect of adjusting the penetration resistance (setting time) within the range of 15 to 20% are as good as or better than no mixing.

(3) Strength Changes in compressive strength due to mixing of 0 to 20% sludge under standard underwater curing, on-site underwater curing, and on-site sealed curing, and changes in tensile strength under standard underwater curing are all small. . Further, the change in the static elastic modulus due to the mixing of the sludge in the above range under the standard water curing condition is small. Therefore, 0
In the range of 20%, it is comparable to no mixing.

(4) Durability With respect to the drying shrinkage distortion, the influence of the sludge mixing is small and 0.
There is no inferiority in the range of ２０20%. As for the neutralization, when the sludge mixing ratio is in the range of 15% or more, it is improved to the same level as that of no mixing or higher. Freeze-thaw resistance is improved by mixing sludge. Accordingly, in the range of 15% to 20%, good characteristics are shown, which are comparable to or better than no mixing.

According to a second aspect of the present invention, there is provided the method for adjusting the setting property of concrete utilizing sludge according to the first aspect, wherein the sludge mixing ratio is increased as the start and end of the setting are desired to be advanced. It is assumed that.

According to the above method, the start and end of the concrete setting can be freely set by adjusting the sludge mixing ratio. In other words, the higher the sludge mixing rate, the earlier the onset and termination of the setting, which is mainly useful for adjusting the floor holding time, and can particularly shorten the floor holding time in winter.

According to a third aspect of the present invention, there is provided the method for adjusting the bleeding characteristic of the concrete using sludge according to the first aspect, wherein the bleeding amount is reduced.
The sludge mixing rate is increased.

According to the above method, the bleeding amount of the concrete can be freely set by adjusting the sludge mixing ratio. That is, as the sludge mixing rate increases, the bleeding amount decreases, and the bleeding end time can be shortened, so that the floor holding time can be shortened. Therefore, it is particularly useful for adjusting the floor holding time in winter. In addition, since the amount of bleeding can be adjusted without greatly changing the quality of concrete, it is possible to apply the surface finish condition determined by the delicate balance of the bleeding amount and the seasonal fluctuation of the outside air condition such as humidity and temperature, and it is possible to apply it easily and easily. Becomes

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the properties of the embodiment of the present invention will be described in detail with reference to examples and comparative examples.

Table 1 shows the mixing conditions of the concrete of the test material used for investigating the properties of Embodiment I of the present invention, and Table 2 shows the level of the mixing ratio of the sludge mixed in the test material. Show. Water cement ratio is 40-55% in 5% increments
Was changed within the range. Further, the sludge mixing ratio is a weight ratio of the sludge solid content per unit water amount, and is shown in terms of an outer percentage. The mixing ratio is 0 to 2 in increments of 5%.
0%, 0%, 5% and 10% for the comparative example, and 15% and 20% for the example. Figure 1 shows the particle size distribution of sludge solids.
As shown in the figure, 80% has a particle size of 0.15 mm or less, and all sludges have a particle size of 1.2 mm or less, and is a mixture of fine particles of sand and cement.

As the materials for the test materials, ordinary Portland cement was used as cement, and sea sand off Muroki offshore in Kagawa prefecture (specific gravity 2.56) and Nishijima frame sand in Hyogo prefecture (specific gravity 2.5) as fine aggregate.
8) was mixed at a ratio of 80:20, and Nishijima frame stone (specific gravity 2.63) was used as the coarse aggregate. Also,
As the admixture, a polycarboxylic acid high-performance AE water reducing agent was used, and the mixture was adjusted so that the kneading slump value was matched, and mixed into the sludge water. FIG. 2 shows the kneading procedure, in which a 50 litres biaxial forced kneading mixer was used.

Various tests were conducted in order to investigate the characteristics of the examples and the comparative examples which were prototyped under the above conditions and procedures. Table 3 shows the outline of the entire test. A slump test (JIS A 1101) and an air volume test (JIS A 1128) were performed as a fresh test, and a bleeding test (concrete pump construction guidelines and Explanation Appendix 5, JIS A 1123) and setting test (JIS A 6204 appendix), compressive strength test (JIS A 1108) and tensile strength test (JIS A 1113) as strength tests, and durability test Drying shrinkage test (JIS A 1129), neutralization acceleration test (High durability reinforced concrete construction design and construction guideline 1), and freeze-thaw resistance test (JIS A 1129)
6204 Appendix 2).

Basically, the quality of the working example was judged as good if there was no inferiority on the basis of the characteristics of concrete without sludge. Hereinafter, the test results will be described step by step.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

[Table 3]

Table 4 shows a list of the results of the fresh test. Even when the sludge mixing ratio is changed in the range of 0 to 20%, the air amount is within the set range.
It can be seen that there is no problem with 0% mixed concrete. Also, there is no problem in terms of the unit mass and the concrete temperature without mixing with the embodiment.

FIG. 3 shows the relationship between the water cement ratio, the sludge mixing ratio, and the slump value. The change in the slump value with respect to the water cement ratio is almost negligible. Therefore, the water cement ratio is 5
Looking at the effect of the mixing ratio under a constant condition of 0%, the slump value decreases as the mixing ratio increases. However, if the sludge mixing ratio is 20% or less, a slump value capable of pumping can be secured, and the quality is improved. It turned out to be no problem.

From the above, it was confirmed that there was no problem in this embodiment regarding fresh properties.

[0028]

[Table 4]

Table 5 shows the test items and levels relating to the young age property test, and FIG. 4 shows the results of the bleeding test when 50 kgf / cm ² was applied as a pressure and when no load was applied.
And FIG.

[0030]

[Table 5]

The pressure bleeding amount hardly changes at the sludge mixing ratio of 0 to 20%, but the no-loading greatly decreases with the increase of the mixing ratio. The effect is recognized.

FIG. 6 shows the results of a penetration resistance test performed as a setting test. From the data of the sludge mixing ratio of 10%, it is understood that the influence of the water cement ratio is small, and the setting is controlled by the mixing ratio. When compared with a water cement ratio of 50%, a remarkable effect of improving the coagulability is obtained, in which the start and end are earlier by about 2 hours for every 10% increase in the mixing ratio.

FIG. 7 shows the change in compressive strength during standard curing as an evaluation of the strength development, but there is no significant difference regardless of the sludge mixing ratio. Therefore, it is considered that the young age strength, which is a problem in workability after concrete casting, is secured.

As described above, the present embodiment has a
It was confirmed that the bleeding suppression and the setting effect were remarkably improved, and the strength expression was comparable. In other words, it was confirmed that the properties of the young-aged material showed good characteristics more than no mixing.

Next, the strength test will be described. The compressive strength test was carried out based on JIS A1108 under standard underwater curing, on-site underwater curing, and on-site sealed curing, and the tensile strength test was carried out under standard underwater curing under JIS A1113, both of which were 100 mm in diameter and 200 mm in length. Specimens were used. The static elastic modulus was measured for a standard water-cured specimen of 13 weeks of age.

FIG. 8 shows the results of the compressive strength test under standard underwater curing conditions, and FIG. 9 shows the results of the compressive strength test under the conditions of in-situ underwater curing and on-site sealing curing. The strength is almost determined by the water-cement ratio. In the range of 0 to 10%, the change in compressive strength with respect to the mixing of sludge is small. FIG.
0 shows the change in the tensile strength of the standard water-cured specimen in the above range, but the change is similarly small.

FIG. 11 shows the relationship between the compressive strength of the 13-week standard underwater curing and the static elastic modulus. The static elastic modulus of the sludge mixing ratio of 0 to 20% substantially matches the static elastic modulus estimation formula of the Architectural Institute of Japan shown by the wavy line in the figure, and is within the range of variation. The effect is small.

From the above, it was confirmed that there was no incompatibility with the present embodiment in terms of strength.

Table 6 shows the test items and levels of the durability test. A 100 × 100 × 400 mm specimen was demolded at a material age of 1 day, and thereafter subjected to standard water curing until a predetermined material age of each test. The drying shrinkage strain was measured by a contact gauge method.
The accelerated neutralization test was conducted at a temperature of 20 ± 2 after 56 days of age.
The evaluation was performed by measuring the neutralization depth under the conditions of ° C., relative humidity of 60 ± 5%, and carbon dioxide concentration of 5 ± 0.2%. As a freeze-thaw resistance test, a change in relative dynamic elastic modulus up to 300 cycles was measured.

[0040]

[Table 6]

FIG. 12 shows the measurement results of the drying shrinkage for the water cement ratio of 50%. The change in drying shrinkage strain in the range of the sludge mixing ratio of 0 to 20% is about 100 × 10 ^−6, which is sufficiently small, and there is almost no influence of the sludge mixing.

FIG. 13 shows the neutralization depth of 91 days of age for a water cement ratio of 50%. In order to suppress the progress of neutralization to be equal to or less than that of non-contamination, the mixing ratio may be 15% or more, and a remarkable neutralization suppressing effect is recognized in the above range. It is unknown why 10% makes it easier to neutralize,
It is necessary to investigate the cause in the future. However, the reason why the neutralization suppressing effect is improved by increasing the amount of sludge is qualitatively considered to be due to the large amount of cement in the sludge.

FIG. 14 shows the results of the freeze-thaw resistance test.
It can be seen that the relative dynamic elastic modulus of the concrete mixed with sludge is smaller than that of the concrete mixed without sludge, and the freezing and thawing resistance is improved by mixing.

As described above, the present embodiment has a
It was confirmed that there was a marked improvement in neutralization inhibition and freeze-thaw resistance, and that drying shrinkage was comparable. In other words, it was confirmed that the device exhibited good characteristics in terms of durability, which was better than no contamination.

As described above, it was confirmed that the present example exhibited the same properties as fresh properties, early age properties, and strength durability, which are the main properties of concrete, or excellent properties equal to or better than no mixing.

However, from the viewpoint of the pumpability of concrete, the slump value is more preferably about 18 cm, and it is desirable to effectively impart viscosity in order to increase resistance to material separation. Cement is also contained in the sludge solid content, and its effect can be expected by mixing it.

Next, a method of adjusting the setting property of concrete by the sludge mixing ratio according to Embodiment II of the present invention will be described with reference to the results of a penetration resistance test shown in FIG. As described in the description of Embodiment I, the penetration resistance value is less affected by the water cement ratio and is mainly governed by the sludge mixing ratio.
For each% increase, the onset and termination of coagulation are advanced by about 2 hours. From this result, it can be seen that the start and end of concrete setting can be freely set by adjusting the sludge mixing ratio. If the data in FIG. 6 is accumulated by changing environmental conditions such as materials, temperature, and humidity, the setting start time during floor holding work under various environmental conditions can be adjusted, and especially, the floor holding work in winter can be easily performed. I do.

Next, a method of adjusting the bleeding amount of concrete according to the sludge mixing ratio according to Embodiment III of the present invention will be described with reference to FIG. As described in the description of Embodiment I, the bleeding amount with no load is greatly reduced with an increase in the sludge mixing ratio, and a remarkable bleeding suppressing effect is recognized. From this result, it is understood that the bleeding amount can be freely set by adjusting the sludge mixing ratio. However, when used at the construction site, the amount of bleeding will vary depending on the cement raw material and its fineness, concrete temperature, size of aggregate, chemical admixtures such as AE agent and water reducing agent. It is desirable to collect and accumulate data on the relationship between the sludge mixing rate and the bleeding amount under the materials and conditions used, and formulate the data if possible. In addition, since there is an effect on the above-described setting characteristics at the time of construction, it is necessary to confirm whether there is any problem.

In general, when the temperature is low, the amount of bleeding increases. Therefore, this method is used particularly for adjusting the floor holding time in winter, and the bleeding amount is reduced by increasing the sludge mixing rate, and the bleeding end time is reduced. As a result, the floor holding time can be shortened, and the construction period can be significantly shortened.

Furthermore, since the amount of bleeding can be adjusted without greatly changing the quality of concrete, the surface finish condition determined by the delicate balance between the external air condition such as humidity and temperature that fluctuates seasonally and the bleeding amount can be excellently and easily. It is possible to construct. This will be described with a specific example. Assuming that there is no significant change in temperature and humidity during the same season, the season determines the evaporation rate of water from the concrete surface. If the evaporation rate is higher than the bleeding rate, initial cracks will occur on the surface and re-cleaning will be required. Conversely, if the evaporation rate is lower than the bleeding rate, the construction time will be long. According to the third embodiment, since the optimum bleeding amount can be set for each season, the evaporation rate and the bleeding rate can be balanced, and the surface finish can be satisfactorily and easily performed.

In this embodiment, each season is set. However, in order to further improve the surface finish, the target bleeding amount may be set by measuring the evaporation rate on that day or at that time. Absent.

[0052]

As described above, according to the invention relating to the sludge-recycled concrete according to the first aspect, when the waste solid concrete or the sludge solids taken out from a concrete product factory or the like is recycled into the ready-mixed concrete, The mixing ratio of sludge solids to water is 15-20.
%, The following effects are obtained.

By remixing a large amount of sludge, which has a high alkalinity and has been discarded as industrial waste, into concrete, the total amount of industrial waste generated from construction activities can be maintained without deteriorating the quality and properties of the concrete. Can be greatly reduced and suppressed.

Since the sludge contains a large amount of cement, if the mixing ratio of the sludge exceeds 15%, a large effect of suppressing neutralization is exhibited. For this reason, in the case of reinforced concrete (hereinafter abbreviated as RC), steel-frame concrete (hereinafter abbreviated as SC), steel-reinforced concrete (hereinafter abbreviated as SRC) and steel tube concrete (hereinafter abbreviated as CFT), it is possible to maintain the strong alkalinity of concrete,・ Corrosion of the steel pipe is suppressed and durability is improved.

By mixing the sludge solid content into the concrete, the volume of the concrete is increased, and the unit price of the concrete can be relatively reduced.

Particularly in poor mix, the amount of cement paste increases due to an increase in the sludge mixing ratio, which has the effect of improving the properties of fresh concrete, increasing the viscosity, and pumping even concrete that tends to separate between cement and aggregate. It will be easier. In addition, since the cement and the aggregate are hardly separated due to the increase in viscosity, jumper hardly occurs, and the quality after casting is improved.

The amount of bleeding can be reduced by increasing the mixing ratio of sludge, and it is particularly effective for concrete for CFT and concrete for floor slab. Also, RC ・ S
In the case of C, SRC, and CFT, it is possible to suppress a decrease in the bonding strength between the reinforcing steel, the steel frame, the steel pipe and the concrete due to excessive bleeding, thereby improving the construction reliability. Furthermore, since the bleeding end time is shortened, the construction period can be significantly shortened. In addition, since the water bleeding due to the bleeding and the water film can be suppressed, the waterproofness is improved and the corrosion of the reinforcing steel, the steel frame, and the steel pipe is significantly suppressed by the synergistic effect with the neutralization suppressing effect, and the durability is greatly reduced. improves.

Since the water and the water film due to the bleeding can be suppressed, the waterproofness is improved, and the permeability of permeated water and chemical erosion is reduced, so that the freeze-thaw resistance is improved.

According to the second aspect of the invention, the start and end of the concrete setting can be freely set by adjusting the sludge mixing ratio.
In other words, the higher the sludge mixing ratio, the earlier the onset and termination of the setting, which is mainly useful for adjusting the floor holding time and the time of demolding, and especially the floor holding time in winter can be shortened, greatly shortening the construction period Is possible.

According to the third aspect of the present invention, the bleeding amount of the concrete can be freely set by adjusting the sludge mixing ratio. That is, as the sludge mixing rate increases, the bleeding amount decreases, and the bleeding end time can be shortened, so that the floor holding time can be shortened. Therefore, it is particularly useful for adjusting the floor holding time in winter. In addition, the amount of bleeding can be adjusted without greatly changing the quality of concrete,
A surface finish state determined by a delicate balance between the outside air state such as temperature and the bleeding amount can be favorably and easily applied.

[Brief description of the drawings]

FIG. 1 is a particle size distribution diagram of sludge solid content used in sludge recycling concrete according to the present invention.

FIG. 2 is a conceptual diagram showing a procedure of mixing sludge recycled concrete according to the present invention.

FIG. 3 is a graph showing an influence of a water cement ratio and a sludge mixing ratio on a slump value.

FIG. 4 is a graph showing the influence of the water cement ratio and the sludge mixing ratio on the amount of pressurized bleeding.

FIG. 5 is a graph showing an effect of a sludge mixing ratio on a bleeding amount with no load.

FIG. 6 is a graph showing the effect of the water cement ratio and the sludge mixing ratio on the setting properties.

FIG. 7 is a graph showing the effect of a water cement ratio and a sludge mixing ratio on compressive strength development characteristics.

FIG. 8 is a graph showing the effect of the water cement ratio and the sludge mixing ratio on compressive strength under standard underwater curing conditions.

FIG. 9 is a graph showing the effect of water cement ratio and sludge mixing ratio on compressive strength under on-site underwater curing and on-site sealing curing conditions.

FIG. 10 is a graph showing the effect of the water-cement ratio and the sludge mixing ratio on the tensile strength under standard underwater curing conditions.

FIG. 11 is a graph showing the relationship between compressive strength and static elastic modulus under standard underwater curing conditions.

FIG. 12 is a graph showing an effect of a sludge mixing ratio on drying shrinkage.

FIG. 13 is a graph showing the effect of the sludge mixing ratio on neutralization.

FIG. 14 is a graph showing the effect of the water cement ratio and the sludge mixing ratio on the relative dynamic elastic modulus.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenichi Ichinose 4-640 Shimoseito, Kiyose-shi, Tokyo Co., Ltd. Inside the Obayashi Corporation Technical Research Institute (72) Inventor Yasuhiro Fuchida 4-640 Shimoseito, Kiyose-shi, Tokyo Co., Ltd. Inside the laboratory (72) Inventor Hidekazu Mine 1-2-14 Kamishinjo, Higashiyodogawa-ku, Osaka-shi, Osaka F-term (reference) 4G012 PA04 PA30 PB16 PC02 PC03 4G056 AA25 CB35

Claims (3)

[Claims] 1. A concrete in which sludge solid content taken out from waste ready-mixed concrete is reused, wherein the amount of sludge solid content relative to water (sludge mixing ratio) is 15%.
Sludge recycled concrete, characterized in that the amount is from 20 to 20% by weight. 2. The method for adjusting the setting properties of concrete using sludge according to claim 1, wherein the sludge mixing ratio is increased as the starting and ending of setting are desired to be advanced. Method for adjusting the coagulation characteristics. 3. The bleeding characteristic of the sludge-recycled concrete according to claim 1, wherein the sludge mixing ratio is increased as the amount of bleeding is reduced. Adjustment method.