JP2006088051A - Production method of back filling material for piping work construction and back filling material for piping work construction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To produce a good quality back filling material for piping work construction from water purification sludge. <P>SOLUTION: In a production method of the back filling material for piping work construction using low moisture content water purification sludge as a raw material, the low moisture content water purification sludge is changed into clay, and then at least one among a water reducing material, cement and a cement-based solidifying material mainly derived from quicklime is added thereto to be granulated. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a method for manufacturing a pipework laying back material, and more particularly, to a method for manufacturing a pipework laying back material from purified water sludge.

  The purified water sludge discharged by the purified water treatment is composed of fine particles such as clay containing a large amount of water and humic acid.

  Conventionally, purified water sludge is reduced to sunlight to be converted into a sun-dried purified water sludge and disposed of as landfill as industrial waste. In addition, the purified water sludge is sometimes dehydrated by a machine to form a machine dewatered cake, which is disposed of as landfill as industrial waste.

  However, in recent years, it has become difficult to secure landfill sites, and this tendency is particularly strong in metropolitan areas where the amount of purified water sludge is large. Therefore, it had to be transported to a distant disposal site, resulting in an increase in processing costs.

  Therefore, a technique for reusing purified water sludge can be considered. For example, a technique is known in which a machine dewatered cake is used as a ground pavement material, horticultural soil, roof tile fixed soil, or cement raw material. However, sun-dried water purification sludge is not reused. The reason why it is not reused will be explained below.

  The water content of the mechanical dewatered cake varies in the range of 90% to 180%. On the other hand, the water content of the sun-drying type purified water sludge varies depending on the region, and varies in a wide range of 50% to 550%.

  Furthermore, the sun-drying type purified water sludge has a large difference in the water content even with sludge in the same dry bed. For example, even if the average water content of the sun-dried water purification sludge is 50%, the water content ratio is 70 to 100%, and the water content ratio is 30% or less. In addition, a large amount of purified water sludge (soil mass) is produced in the portion of the sun-dried purified water sludge having a low water content ratio due to shrinkage accompanying water evaporation.

  Thus, the sun-drying type purified water sludge has not been reused because the water content has a large fluctuation range. In addition, a technique for solidifying by adding a special solidifying material for organic matter to sun-dried water purification sludge is known, but it has not been practically used because of high processing costs.

  On the other hand, natural materials are used as backfill materials for pipe construction. For example, a water supply company purchases natural mountain sand having a specified compaction strength (CBR value) and uses it as a backfill material for pipe construction. However, these natural resources are not inexhaustible. Moreover, problems such as resource reduction and natural destruction have arisen due to mass collection.

  In order to solve this problem, a technique for generating a pipework laying back material (mainly recycled roadbed material or recycled crushed stone) from construction sludge is known.

  For example, a technique is known in which concrete shell and cement are added to and mixed with construction sludge, and the solidified material is crushed to 40 mm or less to be reused as a roadbed material (see, for example, Patent Document 1).

  In addition, cement solidifying agent, water and additives are added to construction sludge, mixed, granulated, and mixed with concrete shell to recycle it as recycled crusher or recycled crushed stone. (For example, refer to Patent Document 2).

JP 2003-342902 A JP 2003-33798 A JP 2003-236520 A

  However, the above-described technology for reusing construction sludge cannot be applied to purified water sludge as it is. This is because purified water sludge is different from the properties of construction sludge.

  Construction sludge is mainly composed of sand and silt and has a lower water content than purified water sludge. Moreover, organic substances, such as humic acid, are hardly contained. Therefore, if the amount of cement added is adjusted according to the moisture content of the construction sludge and solidified (for example, 40 to 60% by weight), the pozzolanic reaction of the cement is not inhibited, so that the construction sludge exhibits strength.

  On the other hand, purified water sludge contains organic acid components such as humic acid (for example, humic acid) in addition to the main component clay. When cement (for example, Portland cement) is added to and mixed with purified water sludge and solidified, the organic acid component of the purified water sludge inhibits the pozzolanic reaction of the cement. For this reason, the strength expression of the purified water sludge is significantly delayed.

  The cause of the pozzolanic reaction inhibition is due to the reaction of calcium ions Ca2 + of calcium hydroxide generated during the hydration reaction of cement with the organic acid component contained in the purified water sludge.

  Moreover, activated water and slaked lime may be mixed in the purified water sludge. This also has a great impact on the reuse of purified water sludge.

  Even if the conventional technology for reusing construction sludge is applied to purified water sludge, there is a problem that a small amount of hexavalent chromium contained in the cement solidified material is eluted when cemented solidified material is added to the purified water sludge. End up.

  The present invention has been proposed in order to solve such problems, and a high-quality backfill material for pipe construction is manufactured at low cost from purified water sludge.

  The present invention relates to a method for producing a backfill material for pipe construction laying using low water content purified water sludge as a raw material, and the low water content purified water sludge is made into clay, and then less of water reducing material, cement and cement-based solidified material led by quick lime. Even one is added and further granulated.

  According to the present invention, a pipe laying backfill material can be produced at a lower cost using purified water sludge having a large water content ratio fluctuation range and containing organic components such as activated carbon and humic acid. The produced pipework laying back material has a particle size of 10 mm or less, has a certain compaction strength, is harmless to the environment, and can be used satisfactorily as a substitute for mountain sand.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  In addition, the purified water sludge of this Embodiment is not limited to a drying method, A sun-drying type purified water sludge and a machine dewatering cake are included. Moreover, the purified water sludge of this Embodiment is not limited to the kind of the injection material added during the water purification process, Activated carbon and slaked lime may be mixed.

  First, the process of manufacturing a backfill material for pipe construction laying from low water content purified water sludge will be described.

  FIG. 1 is a flowchart of a process for manufacturing a pipework laying back material from a low water content purified water sludge according to an embodiment of the present invention.

  Here, the low water content purified water sludge is a purified water sludge having a water content ratio of less than 300%. For example, low-moisture sun-dried purified water sludge or mechanical dehydrated cake can be used.

  In the manufacturing process of the pipework laying back material, first, the low water content purified water sludge is made into clay (process A). Claying is performed by an apparatus used for crushing ordinary water purification sludge. For example, it is an apparatus such as a roll crusher in which the gap between the rolls is adjusted to 10 mm or less, or a kneading mixer for crushing and kneading purified water sludge. Thus, it becomes possible to mix uniformly the solidification material added at the process C mentioned later by making into clay.

  Next, quick lime is added and kneaded to the crushed low water content purified water sludge (step B). Kneading is performed, for example, for about 1 to 3 minutes using a kneading mixer or the like. The kneading mixer is not particularly limited, and is, for example, a biaxial paddle mixer or a kneading mixer with an arm and a roller.

  As a result, the added quicklime is hydrated to become slaked lime (calcium hydroxide). Slaked lime neutralizes and destroys humic acid in low water content purified sludge and improves the organic properties of low water content purified sludge. This eliminates the inhibition of the polazone reaction by humic acid, thereby improving the strength of the pipework laying back material produced.

  Quicklime evaporates (reduces) the water content of the low water content purified water sludge by the heat generated by the hydration reaction. Furthermore, since ettringite is produced by the hydration reaction, a cross-link is formed between the particles to solidify the low water content purified water sludge.

  In addition, when the water content of the low water content purified water sludge is low, the process B can also be skipped. If omitted, it is necessary to improve the organic properties by adding quick lime in step D described later.

  Next, a reducing fixative is added and kneaded together with cement or cement-based solidifying material (cement or the like) to the low water content purified water sludge to which quick lime has been added and kneaded, and sufficient stirring and kneading are performed with a kneading mixer (step C). In addition, cement etc. are not specifically limited, A commercially available thing can be used. For example, the cement or the like is Portland cement, blast furnace cement, or a general-purpose cement-based solidifying material.

  The reason for adding cement or the like in step C is that the backfill material for pipe construction laying has fluidity and compaction strength, which are the characteristics of natural mountain sand. In order to ensure fluidity, the pipework laying back material must be aligned with a particle size distribution of 10 mm or less like natural mountain sand. In addition, the backfill material for pipe construction laying needs to have a compaction strength that can support a vehicle of 10 tons or more on the pavement. That is, it is desirable that the pipework laying backfill material has a compaction strength of 20% or more in terms of CBR value.

  However, adding cement or the like to low water content purified water sludge is an economical and effective means for increasing the compaction strength, but there is a concern about the elution of hexavalent chromium. Therefore, by adding and kneading the reducing and fixing agent developed by the present applicant (see Patent Document 3) together with cement or the like, elution of hexavalent chromium from the pipework laying back material can be suppressed.

  This reduced fixing agent is 0.7 to 1.0% by weight of ferrous sulfate (reagent deer grade 1, manufactured by Kanto Chemical Co., Ltd.), an aqueous solution of sodium silicate (J sodium silicate No. 3, manufactured by Nippon Chemical Industry Co., Ltd.). 14) to 21% by weight, water and a stabilizer. The reduced fixing agent was prepared by first adding and mixing ferrous sulfate in water at a predetermined ratio, and further adding and mixing an aqueous solution of sodium silicate and a stabilizer at a predetermined ratio.

  When returning to the manufacturing process, the granulated powder material led by quick lime is added and kneaded to the low water content purified water sludge having finished the process C, and granulated into particles of 10 mm or less (process D). Granulation can be performed by a kneading mixer having a granulation function. For example, there are a mixing mixer manufactured by Kitagawa Iron Works Co., Ltd. (experimental machine brand name Bellegaya) and a biaxial paddle mixing mixer manufactured by Nikko Corporation (experimental machine brand name ECB).

  In the process D, the plasticity of the low water content purified water sludge can be adjusted by adding and mixing the granulated powder material which leads quicklime. This is because granulation is performed before the pozzolanic reaction of cement or the like occurs, so that plasticity is required for the low water content purified water sludge.

  In addition, you may add and mix a reinforcing material with a granulated powder material as needed. By adding a reinforcing material to the low water content purified water sludge, the strength of the manufactured backfill material can be reinforced. Furthermore, since the usage-amount of quicklime, cement, etc. can be reduced, the backfill material for pipe construction laying can be manufactured cheaply. In addition, the reinforcing material should just be a powder material with little moisture. For example, mountain sand, coal ash, stone powder, dust, fine powder of granulated slag, and the like.

  Next, the granulated low water content purified water sludge is cured for a certain period (step E). Curing is done by placing the sheets on top of each other. The curing period in this case is about 3 weeks, but is preferably about 4 weeks. During the curing period, cement etc. absorbs the water in the low water content purified sludge and performs pozzolanic reaction. The strength of the pipework laying back material generated is improved by this polazone reaction.

  Next, the cured purified water sludge is divided into particles larger than 10 mm and particles smaller than 10 mm by a classifier (process F). The classifier is, for example, a vibration sieve machine. The classified particles of 10 mm or less are collected as a backfill material for pipe construction. On the other hand, particles larger than 10 mm are crushed by a crusher such as a roll crusher. And the particle | grains crushed to 10 mm or less are collect | recovered as a backfill material for pipe construction installation.

  In this Embodiment, 90% or more of the produced | generated products become a particle | grain of 10 mm or less by adjusting the compounding quantity of the quicklime added at the process B to an appropriate range. In this case, it is possible to manufacture the pipework laying back material even if the classification step (step F) is omitted.

  In addition, process AD can be implement | achieved as follows using a kneading mixer.

  The materials are charged into the kneading mixer as follows. First, when low water content purified water sludge is thrown in, the weight of low water content purified water sludge is measured using a measurement control apparatus. Then, when the measured weight reaches the set value, a predetermined amount of reducing lime, cement, and the like are automatically charged sequentially, and a reinforcing material is charged as necessary.

  A kneading mixer performs process AD for about 5 to 8 minutes, for example. And the low water content purified water sludge which passed through process AD moves using a belt conveyor, and is cured in another place.

  Next, the addition amount of the material added to the low water content purified water sludge of this Embodiment is demonstrated.

  The addition rate (%) of quicklime ((weight of additive / volume of purified water sludge) × 100) is 3% or more and 20% or less, more preferably 5% or more and 15% or less with respect to the volume of the low water content purified water sludge. Set. When the addition rate of quick lime is less than 5%, the amount of quick lime is too small, so that the reduced water content of the low water content purified water sludge, the organic property improvement and the granulation effect cannot be fully exhibited. On the other hand, if it exceeds 15%, the water content of the purified water sludge is excessively reduced, which affects the pozzolanic effect of cement and the like.

  The addition rate (%) of cement and the like ((weight of additive / volume of purified water sludge) × 100) is 2.5% or more and 20% or less, more preferably 5% or more and 15 with respect to the volume of the low water content purified water sludge. Set to% or less. If the addition rate of cement or the like is less than 5%, the amount of cement or the like is too small, and thus the effect of solidifying the low water content purified water sludge cannot be sufficiently exhibited. On the other hand, if it exceeds 15%, the low water content purified water sludge is excessively solidified, which further increases the cost. In addition, you may adjust the addition rate of cement etc. with the water content ratio of a low water content purified water sludge.

  Next, the process of manufacturing the backfill material for pipe construction laying from high water content purified water sludge is demonstrated.

  FIG. 2 is a flowchart of a process for producing a pipework laying back material from the high water content purified water sludge according to the embodiment of the present invention.

  Here, the high water content purified water sludge is a purified water sludge having a water content ratio of 300 to 600%. For example, sun-drying type purified water sludge with high water content or sun-drying type purified water sludge mixed with activated carbon can be used.

  First, high water content purified water sludge needs to be reduced before solidifying and granulating. Then, quick lime is added and kneaded to the high water content purified water sludge to reduce the water (step I). In addition, by adding and kneading quicklime, humic acid is neutralized and destroyed, and the organic properties are improved, as in the case of the low water content purified water sludge described above. Moreover, since an ethrin guide is produced | generated by hydration reaction, a bridge | crosslinking is formed between particle | grains and a high water content purified water sludge is solidified.

  The high water content purified water sludge kneaded with quicklime is stirred using a kneading mixer or a backhoe. The water content of the stirred high water content purified water sludge is reduced by the heat generated by the quick lime hydration reaction.

  It is desirable that the stirred high water content purified water sludge be further reduced in the sun. In addition, when there is no place to reduce water in the sun, the high water content purified sludge may be reduced by field loading.

  This process I is performed in about 1-3 days, for example. In addition, it is desirable that the water content of the high water content purified water sludge subjected to the water reduction treatment is 150% or less.

  Moreover, you may add and knead a reinforcing material with quick lime as needed. The type and amount of the reinforcing material to be added are adjusted according to the water content ratio of the high water content purified water sludge. By adding a reinforcing material to the high water content purified water sludge, it is possible to reinforce the strength of the pipework laying material produced. Furthermore, since the usage-amount of quicklime, cement, etc. can be reduced, the backfill material for pipe construction laying can be manufactured cheaply.

  Cement and the like and a reducing fixative are added and kneaded to the reduced water content purified water sludge, and sufficient stirring and kneading are performed with a kneading mixer (step J). In addition, the process J is the same as the process C in the case of the low water content purified water sludge mentioned above, and detailed description is abbreviate | omitted.

  Next, the kneaded high water content purified water sludge is cured for a certain period (step K). In addition, the process K is the same as the process E in the case of the low water content purified water sludge mentioned above, and detailed description is abbreviate | omitted.

  Next, the cured high water content purified water sludge is crushed and granulated into particles of 10 mm or less (step L).

  Specifically, first, the cured high water content purified sludge is crushed to about 200 mm with a backhoe, and then crushed to 40 mm or less with a roll crusher with a nail. Then, the crushed material is passed through a vibration sieve of 10 mm net, and particles of 10 mm or less are collected as backfill material. On the other hand, particles larger than 10 mm are crushed to 10 mm or less with a roll crusher and collected as a backfill material.

  Next, the addition amount of the material added to the high water content purified water sludge of embodiment of this invention is demonstrated.

  The addition rate of quicklime (%) ((weight of additive / volume of purified water sludge) × 100) is 5% or more and 25% or less, more preferably 5% or more and 15% or less with respect to the volume of the high water content purified water sludge. Set. When the addition rate of quick lime is less than 5%, the amount of quick lime is too small, so that the effect of reducing the water content and improving the organic properties cannot be fully achieved. On the other hand, if it exceeds 15%, the water reduction and organic property improvement effect of the high water content purified water sludge does not change, so only the cost increases.

  Addition rate (%) of cement, etc. ((weight of additive / volume of purified water sludge) × 100) is 5% or more and 20% or less, more preferably 5% or more and 15% or less with respect to the volume of high water content purified water sludge. Set to.

  When the addition rate of cement or the like is less than 5%, the amount of cement or the like is too small, and the solidification effect of the high water content purified water sludge cannot be sufficiently exhibited. On the other hand, if it exceeds 15%, the high water content purified water sludge is excessively solidified, which further increases the cost.

  Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following examples.

Example 1
In this example, a production test of a backfill material for pipe construction was conducted using sun-dried purified water sludge as a raw material. The water content of the sun-dried water purification sludge was around 60%.

Table 1 is a table | surface which shows the experimental result of Examples 1-3 of this invention. Table 1 lists the type of sludge, test items, test number, and average water content of the purified water sludge. Moreover, the addition rate of quicklime, cement, and a reduction | restoration fixing agent added to the purified water sludge by the test is described by% (weight%) of the weight ratio of the additive with respect to the volume of the purified water sludge. For example, when 3 t of quick lime is added to 100 m ³ of purified water sludge, the addition rate of quick lime becomes 3%. Moreover, the addition rate of the mountain sand added by the test to the purified water sludge is described in% (volume%) of the volume ratio of the mountain sand to the volume of the purified water sludge. For example, when 10 m ³ of mountain sand is added to 100 m ³ of purified water sludge, the addition rate of mountain sand becomes 10%. Moreover, the particle size distribution and strength characteristic (CBR test value) of the pipework laying back material generated in the test are described.

  That is, in the test numbers 1 and 2, the addition rate of quick lime (powder quicklime, manufactured by Tagen Lime Industry Co., Ltd.) was 3%, and the addition rate of mountain sand as a reinforcing material was 30%. And, the addition rate of Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) was 7.5% (reduced fixing agent 3.8%) in test number 1, and 10% (reduced fixing agent 5%) in test number 2, The effect of solidification due to the difference of cement addition rate was investigated. The addition rate of quicklime is the sum of the addition rates used in the water reduction process and the granulation process.

  In Test Nos. 3 and 4, the addition rate of quick lime was 5%, the addition rate of Portland cement was 5%, and the reducing fixative was 2.5%. Then, the addition rate of mountain sand was set to 30% in test number 3 and 40% in test number 4, and the solidification effect due to the difference in the addition rate of mountain sand was examined.

  In the production of the backfill material for pipe construction laying in this example, first, the sun-dried clean water sludge was made into clay using an experimental biaxial mixer. In addition, the kneading time of the mixer for converting to clay was 2 minutes. Next, the properties of reduced water and purified water sludge were improved by adding quick lime to clay-dried sun-dried purified water sludge. The mixer kneading time at this time was 1 minute.

  Next, Portland cement and a reducing fixative (a liquid mainly composed of ferrous sulfate and sodium silicate) are added to sun-dried purified water sludge with reduced water and kneaded for 2 minutes. And after confirming that Portland cement and the reduction | restoration fixing agent were knead | mixed with purified water sludge uniformly, the mixture was granulated for 1 minute, adding the quicklime which is a granulated powder material with a biaxial mixer. Next, mountain sand as a reinforcing material was mixed with the granulated sun-dried water purification sludge and cured at room temperature for 4 weeks to obtain a backfill material for pipe construction.

  And the strength characteristic (CBR test value) and particle size distribution of the obtained pipework laying back material were measured, respectively. The particle size distribution was measured according to JIS A 1204. The CBR test was measured according to JIS A 1211 (the same applies hereinafter). The measurement results are shown in Table 1.

  According to test numbers 1 and 2, when the addition rate of quick lime is 3% and the addition rate of mountain sand is 30%, the addition rate of Portland cement is 7.5%, The CBR value was 7.7%, and no strength was developed. On the other hand, when the addition rate of Portland cement is 10%, the backfill material for pipe construction laying has a CBR value of 68% and develops strength. In addition, although the addition rate of the reducing fixative is different between Test Nos. 1 and 2, the effect of the reducing fixative on the strength of the pipework laying back material is very small and can be ignored.

  According to Test Nos. 3 and 4, when the addition rate of quick lime is 5%, the Portland cement is 5%, and the backfill material for pipe construction has a CBR value of 81.4% and 71.3%. And develops strength. That is, when this result is compared with Test No. 1, it can be seen that when the addition rate of quick lime is increased, the strength of the pipework laying back material is developed even if the addition rate of Portland cement is lowered.

  Furthermore, when test numbers 3 and 4 are compared, when the sand sand addition rate is 30%, the CBR value of the pipework laying backfill material is 87.4%, and when the sand sand addition rate is 40%. The CBR value of the pipework laying back material was 71.3%. From this result, it can be understood that the strength of the pipework laying back material does not always increase in proportion to the unilateral increase in the sand sand addition rate.

  Moreover, the backfill material for pipe construction laying produced in this example has a gravel content and sand content of 10 mm or less as main components, and has a particle size distribution similar to mountain sand.

(Example 2)
In this example, a production test of a pipework laying back material was performed in the same process as in Example 1 using sun-dried water purification sludge as a raw material. The water content of the sun-dried water purification sludge was around 55%. The addition rate of each additive in the present example is shown in Table 1.

  In Test Nos. 5 to 7, Portland cement was 5%, the reducing fixative was 2.5%, and the addition rate of quick lime was 5 to 7%. Then, the addition rate of mountain sand was changed to 0% in test number 5, 10% in test number 6, and 30% in test number 7, and the solidification effect due to the difference in the addition rate of mountain sand was investigated.

  According to Test No. 5, when the addition rate of quick lime is 5%, the addition rate of Porland cement is 5%, and the mountain sand is 0%, the backfill material for pipe construction laying has a CBR value of 8.9. %, And no strength was developed. On the other hand, according to Test No. 6, when the addition rate of mountain sand is increased to 10%, the backfill material for pipe construction laying has a CBR value of 46% and develops strength. Further, according to test number 7, when the addition rate of mountain sand was increased to 30%, the CBR value of the backfill material for pipe construction laying was 90%, which further increased the strength. From this result, it was found that the desired strength can be obtained in the low water content purified water sludge even when the cement addition rate is low, by adjusting the mountain sand addition rate.

  Moreover, the pipework laying back material produced in this example was mainly composed of gravel and sand of 10 mm or less, and obtained a particle size distribution similar to mountain sand.

(Example 3)
In this example, a production test of a pipework laying back material was performed in the same process as in Example 1 using sun-dried water purification sludge as a raw material. The water content of the sun-dried clean water sludge was around 57%. The addition rate of each additive in the present example is shown in Table 1.

  In test numbers 8 and 9, blast furnace cement type B (manufactured by Taiheiyo Cement Co., Ltd.) was used. In test number 10, a general-purpose organic-compatible cement-based solidifying material (trade name GS-10, manufactured by Taiheiyo Cement Co., Ltd.) was used.

  Test Nos. 8 to 10 were 15% for blast furnace cement type B or organic-compatible cement-based solidified material and 7.5% for reducing fixative, and examined the solidification effect due to changes in the addition rate of quicklime and mountain sand.

  According to Test No. 8, when the addition rate of quick lime is 5%, the addition rate of blast furnace cement type B is 15%, and the addition rate of mountain sand is 25%, the backfill material for pipe construction has a CBR value of 186. %, And strength was developed. Further, according to test number 9, the addition rate other than mountain sand is the same as test number 8, and even if the addition rate of mountain sand is reduced to 20%, the backfill material for pipe construction has a CBR value of 137%. Thus, sufficient strength was obtained.

  On the other hand, according to Test No. 10, when the addition rate of quick lime is 0%, the addition rate of organic-compatible cement-based solidified material is 15%, and the addition rate of mountain sand is 20%, the same as Test No. 9, pipe construction The backfill material had a CBR value of 34% and exhibited strength, but a sufficient strength improvement effect was not obtained as compared with Test Nos. 8 and 9.

  Based on the above results, pipes with 5% quick lime added to the same amount of blast furnace cement and mountain sand combination from the backfill material for pipe construction laying produced by the combination of organic cement-type solidification material and mountain sand The backfill material for construction laying was able to greatly improve the strength. Therefore, it was suggested that quicklime has the effect of improving the organic properties of purified water sludge.

  Moreover, the pipework laying back material produced in this example was mainly composed of gravel and sand of 10 mm or less, and obtained a particle size distribution similar to mountain sand.

(Comparative Example 1)
In Comparative Example 1, a sun-drying type purified water sludge was used as a raw material, and a production test of a pipework laying back material was performed in the same process as in Example 1. The water content of the sun-dried clean water sludge was around 57%. The addition rate of each additive in the present example is shown in Table 1.

  That is, without adding quicklime, the reducing fixative was fixed at 7.5%, and the addition rate of Portland cement and mountain sand was changed to examine the solidification effect.

  According to Test Nos. 11 to 14, when quick lime is not added, the addition rate of mountain sand is 0 to 30%, and the addition rate of Portland cement is 5 to 15%, the backfill material for pipe construction is CBR value. Was 1.7 to 4.5%, and none of them exhibited strength. This result also suggested that quick lime exerts an effect of improving the organic properties of the purified water sludge and has a great influence on the solidification effect of cement.

Example 4
In this example, a machine dehydration cake into which lime was injected during the water purification treatment was used as a raw material, and a production test for a pipework laying back material was conducted. The water content of the mechanically dehydrated cake was 91.2% or 93.8%. Since the dehydrated cake of this example contained lime in advance, it is determined that it is not necessary to add quick lime to improve the organic properties of the cake. Therefore, in this example, a production test was performed using cement.

  Table 2 is a table | surface which shows the experimental result of Example 4 of this invention.

  That is, in test numbers 15 to 18, the addition rate of the portant cement was 15%, the addition rate of the reducing fixing agent was 7.5%, and the solidification effect due to the difference in the addition rate of mountain sand was examined.

  In the production of the pipework laying back material in the present example, first, the mechanical dewatered cake is made into clay using an experimental biaxial mixer. In addition, the kneading time of the mixer for converting to clay was 3 minutes. Next, Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) and a reducing fixative (a liquid mainly composed of ferrous sulfate and sodium silicate) were added to the pulverized mechanical dewatered cake and kneaded for 2 minutes. . Next, using a twin-screw mixer, the granulated powder material mixed with 50% quicklime and 50% stone powder was granulated for 1 minute while being added to the mechanical dehydrated cake. And the mountain sand which is a reinforcing material was mixed with the granulated mechanical dewatering cake, and it cured at room temperature for 4 weeks, and obtained the backfill material for pipe construction construction.

  The strength characteristics (CBR test value) and particle size distribution of the obtained pipework laying back material were measured. The measurement results are shown in Table 2.

  According to Test Nos. 15 to 18, when the addition rate of cement is 15% and the addition rate of reducing fixative is 7.5% in the mechanical dewatered cake, the pipe construction obtained when the addition rate of mountain sand is increased The strength of the backfill material for laying continues to increase. However, according to the test numbers 17 and 18, even when the addition rate of mountain sand is 40%, the strength of the backfill material for pipe construction is greatly improved as compared with the case where the addition rate of mountain sand is 30%. I couldn't.

  Moreover, the pipework laying back material produced in this example was mainly composed of gravel and sand of 10 mm or less, and obtained a particle size distribution similar to mountain sand.

(Comparative Example 2)
In Comparative Example 2, a machine dehydration cake was used as a raw material, and a production test of a pipework laying back material was performed in the same process as in Example 4. The water content of the mechanically dehydrated cake was 93.8%. The addition rate of each additive in the present Comparative Example 2 is shown in Table 2.

  That is, the addition rate of Portland cement was 10%, the addition rate of reducing fixative was 7.5%, and the addition rate of mountain sand was 20%, and the solidification effect was examined.

  Then, the manufactured pipework laying back material had a CBR value of 45% and was able to exhibit strength. When this result is compared with the result of test number 15, even if the addition rate of Portland cement is reduced, the backfill material for pipe construction laying can be obtained with the same strength by increasing the addition rate of mountain sand. I understood.

  That is, by increasing the addition rate of mountain sand, even if the addition rate of Portland cement is reduced, the target strength can be obtained, so that the pipework laying backfill material can be manufactured at low cost.

(Example 5)
In this example, a production test of a backfill material for pipe construction was conducted using sun-dried high water content purified water sludge mixed with activated carbon as a raw material. The water content of the sun-drying high water content purified water sludge was 532.9% or 580.3%.

  Table 3 is a table | surface which shows the experimental result of Example 5 of this invention.

  That is, in the test numbers 20 to 25, the addition rate of Portland cement is 15%, the addition rate of the reducing fixing agent is 7.5%, the addition rate of quick lime is 5 to 15%, and the addition rate of mountain sand is 20 to 30. % And the addition rate of coal ash were changed to 10 to 20%, and the solidification effect was examined.

  In the production of the backfill material for pipe construction laying in this example, first, quick lime, mountain sand and coal ash are added to the sun-dried high water content purified water sludge and kneaded for 3 minutes using an experimental biaxial mixer. Then, the kneaded sun-dried high water content purified sludge is reduced in air. In addition, the water reduction period of the test numbers 20-23 was 3 days, and the water reduction period of the test numbers 24 and 25 was 6 days.

  After confirming that the water content of the sun-dried high water content purified sludge after water reduction is 150% or less, Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) and reducing fixative (ferrous sulfate and sodium silicate A liquid containing the main component (made by the present inventor) is added and kneaded for 3 minutes using an experimental biaxial mixer. The kneaded sun-dried high water content purified water sludge was aged at room temperature for 4 weeks, further crushed and granulated, and collected through a 10 mm sieve as a backfill material for pipe construction laying.

  The strength characteristics (CBR test value) and particle size distribution of the obtained pipework laying back material were measured. Table 3 shows the measurement results.

  According to Test Nos. 20 to 23, when the cement addition rate is 15%, the pipework laying back material to which quicklime, mountain sand and coal ash are added has a CRB value of 106.8% or more and is large. Strength was developed. On the other hand, according to the test numbers 24 and 25, even when the cement addition rate was the same 15%, the pipework laying back material added with quick lime and mountain sand without adding coal ash developed strength. However, the CBR value was lower than the pipework laying back material produced by adding coal ash in test numbers 20 to 23.

  From this result, the strength of the backfill material for pipe construction is improved by adding quick lime and Portland cement to the sun-dried high water content purified water sludge mixed with activated carbon, and further adding a reinforcing material. Can do. In particular, by adding coal ash as the reinforcing material, the strength of the pipework laying back material can be significantly improved.

  Moreover, the pipework laying back material produced in this example was mainly composed of gravel and sand of 10 mm or less, and obtained a particle size distribution similar to mountain sand.

(Comparative Example 3)
In Comparative Example 3, a production test of a pipework laying back material was performed in the same process as in Example 5, using sun-dried high water content purified water sludge mixed with activated carbon as a raw material. The water content of the sun-dried clean water sludge was 532.9%. The addition rate of each additive in Comparative Example 3 is shown in Table 3.

  That is, without adding quick lime, the addition rate of Portland cement was 15%, the addition rate of reducing fixative was 7.5%, the addition rate of mountain sand was 30%, and the solidification effect was examined.

  Then, the backfill material for pipe construction laying had a CBR value of 6.1% and did not exhibit strength. When this result is compared with the results of Test Nos. 20 to 23, it can be determined that the quick lime was not added. This is because in this comparative example 3, quick lime was not added, so that the organic properties of the high water content purified water sludge could not be improved. In other words, it can be seen that by improving the organic properties, purified water sludge can be solidified even with Portland cement.

(Example 6)
In the present Example, the production test of the backfill material for pipe construction laying was performed by using as a raw material the sun drying type purified water sludge or the sun drying type high water content purified water sludge mixed with activated carbon.

  Table 4 is a table | surface which shows the experimental result of Example 6 of this invention.

  The backfill material for pipe construction is manufactured in the same process as in Example 1 when sun-dried low water content purified sludge is the raw material, and Example 5 when the high water content purified water sludge mixed with activated carbon is the raw material. It is manufactured in the same process.

  And the elution amount of the hexavalent chromium of the manufactured pipework laying back material was investigated, respectively. The measurement results are shown in Table 4. The elution amount of hexavalent chromium was measured by diphenicarbazide absorptiometry in accordance with Environmental Agency Notification No. 46 (environmental standard related to soil contamination).

  According to Test Nos. 27 to 43, the elution amount of hexavalent chromium was reduced in all tests by setting the addition rate of cement to 5 to 15% and the addition rate of reducing fixative to 1/2 of the addition rate of cement. The soil environmental standard value was suppressed to 0.05 mg / l or less.

(Comparative Example 4)
In Comparative Example 4, a sun-drying type high-purity purified water sludge mixed with sun-dried water purification sludge or activated carbon was used as a raw material, and a production test of a pipework laying backfill material was performed in the same process as in Example 6. . In Comparative Example 4, a production test of a pipework laying back material was performed without adding a reducing fixative. Table 4 shows the addition ratio of each additive in Comparative Example 4.

  According to Test Nos. 44 to 46, when no reducing fixative is added, the elution amount of hexavalent chromium exceeds the soil environment standard value (0.05 mg / l).

  From this result, elution of hexavalent chromium in the manufactured pipe laying backfill material was made by adding a reducing fixator when manufacturing the pipe laying backfill material from the purified water sludge using cement solidifying material. It can be seen that can be kept below the environmental standard value. That is, by adding a reducing fixing agent, a highly safe backfilling material for pipe construction can be manufactured.

(Example 7)
In this example, a sun-drying type purified water sludge mixed with bottom sand was used as a raw material, and a production test for a pipework laying back material was conducted. This sun-dried water purification sludge was forced to evaporate water by changing the top and bottom of the sludge in the dry bed with a tractor several times during the sun drying period. In such an upside-down work, a part of the bottom sand laid by the tractor blades on the bottom of the dry floor is dug, and the bottom sand is mixed into the sun-dried clean water sludge. When the sun-dried water purification sludge is mixed with bottom sand, the moisture content is reduced. Furthermore, the sun-drying type purified water sludge has an effect of improving the strength as in the case where mountain sand is added as a reinforcing material.

  In addition, the water content ratio of the sun-dried clean water sludge mixed with bottom sand in this example was around 43%.

  Table 5 shows the addition ratio of each additive in this example.

  In Table 5, the addition rate of quicklime added to the purified water sludge in the test is described in% (% by weight) of the weight ratio of the additive to the volume of the purified water sludge. Moreover, the addition rate of the mountain sand added by the test to the purified water sludge is described in% (volume%) of the volume ratio of the mountain sand to the volume of the purified water sludge. Moreover, the particle size distribution and strength characteristic (CBR test value) of the pipework laying back material generated in the test are described.

  That is, in the test number 47, the addition rate of quick lime was 10%, and the addition rate of mountain sand as a reinforcing material was 40%. Moreover, in the test number 48, the addition rate of quicklime was 15%, and the addition rate of mountain sand which is a reinforcing material was 30%. Thus, in the present Example, the solidification effect by adding only quicklime and mountain sand without adding cement or the like was examined.

  In the production of the backfill material for pipe construction laying in this example, first, sun-dried clean water sludge mixed with bottom sand was made into clay using a laboratory mixer for 2 minutes. Next, by adding quick lime to sun-dried purified water sludge mixed with bottom sand, the organic properties of the reduced water and purified water sludge were improved in 2 minutes.

  Next, the mixture was granulated for 1 minute from a biaxial mixer while adding quicklime as a granulated powder material to sun-dried clean water sludge mixed with bottom sand. Next, mountain sand as a reinforcing material was mixed with the granulated bottom sand-mixed sun-dried water purification sludge and cured at room temperature for 3 weeks to obtain a backfill material for pipe construction.

  And the strength characteristic (CBR test value) and particle size distribution of the obtained pipework laying back material were measured, and the results are shown in Table 5.

  According to test number 47, when the addition rate of quick lime was 10% and the addition rate of mountain sand was 40%, the obtained backfill material for pipe construction laying had a CBR value of 71.5%. Moreover, according to the test number 48, the CBR value of the backfill material for pipe construction laying obtained with the addition rate of quick lime being 15% and the addition rate of mountain sand being 30% was 93.7%.

  From this result, even if no sentiment is added to sun-dried water purification sludge mixed with bottom sand, quick lime is added at an addition rate of about 10%, and mountain sand is added at an addition rate of about 30%. It was found that it was possible to produce a pipe laying backfill material with a strength exceeding the target value. Moreover, it turned out that the intensity | strength of the produced backfill material for pipe construction laying can be improved by increasing the addition rate of quicklime.

  Further, the pipework laying back material generated in this experimental example has a gravel content and sand content of 10 mm or less as main components, and has a particle size distribution similar to mountain sand.

  According to the present invention, it becomes possible for a water purification treatment contractor to recycle without discarding the purified water sludge.

It is a flowchart of the process of manufacturing the backfill material for pipe construction laying from the low water content purified water sludge of embodiment of this invention. It is a flowchart of the process of manufacturing the backfill material for pipe construction laying from the high water content purified water sludge of embodiment of this invention.

Claims (11)

In the manufacturing method of the backfill material for pipe construction laying using low water content purified water sludge as a raw material,
Backfilling material for pipe construction laying characterized in that the low water content purified water sludge is made into clay, and then at least one of a water reducing material led by quick lime, cement and cement-based solidified material is added, and further granulated. Manufacturing method.   Adding at least one of the water-reducing material led by quick lime, cement and cement-based solidifying material is to add a water-reducing material driven by quick lime and cement or cement-based solidifying material. The manufacturing method of the backfill material for pipe construction laying of Claim 1.   The method for producing a backfill material for pipe construction laying according to claim 1 or 2, wherein the low water content purified water sludge is granulated and then subjected to curing and classification.   The method for producing a backfill material for pipe construction laying according to any one of claims 1 to 3, wherein a reinforcing material is added to the low water content purified water sludge. In the manufacturing method of the backfill material for pipe construction laying using high water content purified water sludge as a raw material,
A method for producing a backfill material for pipe construction laying, comprising adding a water-reducing material led by quick lime and cement or a cement-based solidifying material to the high water content purified water sludge.   The method for producing a backfill material for pipe construction laying according to claim 5, wherein after adding the cement or cement-based solidifying material, the high water content purified water sludge is cured, and then crushed and granulated.   The method for producing a backfill material for pipe construction laying according to claim 5 or 6, wherein a reinforcing material is added to the high water content purified water sludge.   The said reinforcing material is at least 1 sort (s) selected from mountain sand, coal ash, stone powder, dust, and slag fine powder, The manufacturing method of the backfill material for pipe construction laying of Claim 4 or 7 characterized by the above-mentioned.   The method for producing a backfill material for pipe construction laying according to any one of claims 1 to 8, wherein a reducing fixing agent is added together with the cement or cement-based solidifying material.   The method for producing a backfill material for pipe construction according to claim 9, wherein the reducing fixing agent contains ferrous sulfate and sodium silicate as main components.   A pipework laying back material manufactured by the manufacturing method according to claim 1, wherein the particle size is 10 mm or less and the hexavalent chromium elution amount is 0.05 mg / l or less. Backfill material for pipe construction laying.

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