JP2015048285A - Method for producing premix mortar composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a useful method for recycling residual concrete.SOLUTION: A premix mortar composition that is powder type is produced by mixing: a dried sand obtained by separating sand from residual concrete and by drying the sand; and cement, thickener and powder type surfactant. The drying of sand is carried out such that the water content is 2% or less. The blend ratio preferably is, for 100 pts.mass of cement, 50 to 300 pts.mass of dried sand, 0.1 to 3 pts.mass of thickener, and 0.1 to 3 pts.mass of powder type surfactant. Also in a preferred aspect, the sand after drying is thieved through a thieve having a thieve opening of 0.85 to 2.5 mm and the thieved through portion is used.

Description

  The present invention relates to a method of effectively using sand recovered from residual concrete generated from a ready-mixed concrete factory or a construction site as a raw material for a premix mortar composition.

  The premixed mortar composition is produced by appropriately mixing cement, sand, various inorganic substances, and organic substances so as to obtain desired physical properties. The most important physical property of the premixed mortar is strength development. From the viewpoint of securing strength development, sand is generally used as silica sand that is naturally produced.

  The silica sand used for the premixed mortar is obtained by drying and sieving silica sand collected from nature or ground silica mined from a mine. In any case, it is a natural resource, and in recent years, high-quality silica sand tends to be depleted.

  Application of mountain sand, masa soil, etc. can be considered as substitutes for silica sand, but both are natural resources, and it is becoming difficult to stably obtain products having good quality like silica sand. In particular, there is a problem in ensuring strength development. The use of metal sand such as bauxite is conceivable, but it is not common as a substitute for silica sand because it produces excessive strength against the required quality and increases costs.

  On the other hand, residual concrete or return concrete generated from ready-mixed concrete factories and construction sites is increasing, and reuse is attempted from the viewpoint of effective use of resources or reduction of disposal costs.

  Patent Document 1 discloses a method for recovering dried sludge powder, sand and gravel, which are residues of hydrated cement, from the remaining concrete through steps such as washing, filtration, sieving, and drying. Although the sludge dry powder has been proposed to be used as an alternative to cement, it is difficult to obtain stable strength development because it dries after hydration with cement. Sand and gravel can be used as raw materials for ready-mixed concrete, but their effective use is limited due to the problem of compatibility with ready-made concrete product standards. Therefore, at present, most of the remaining concrete is disposed of without being effectively utilized.

Japanese Patent No. 4447276

  In the premix mortar composition, when an alternative to silica sand is selected, ensuring strength development and particle size configuration are important. Since the type of sand affects the securing of strength development, it is necessary to stably obtain sand of a clear type. A single type is desirable, but a mixed product may be used if the type is clear. The particle size configuration can be adjusted by sieving or the like, but appropriately adjusting the particle size of a plurality of sands is not appropriate because it increases costs.

  As seen in Patent Document 1, the technology for collecting sludge powder, sand and gravel from the remaining concrete has been established, but since the use after collection is limited, many remaining concrete is not reused. It has been disposed of. If there is an application that uses these recovered materials stably, it is considered that reuse of the remaining concrete will proceed.

  In order to achieve the above-mentioned problems, the present inventors have intensively studied. Therefore, since the sand recovered from the remaining concrete was originally quality-controlled as a raw concrete material, it was noted that it was excellent in strength and the grain size configuration was adjusted within a certain range.

  That is, the present inventors have found that sand having the same performance as silica sand that has been conventionally used as a raw material for a premix mortar composition part can be obtained by drying sand recovered from residual concrete.

  Based on this knowledge, a premix mortar comprising a step of separating sand from residual concrete, a step of drying the sand, and a step of mixing the dried sand with cement, a thickener and a powdered surfactant. An invention comprising a method for producing a composition was completed.

  ADVANTAGE OF THE INVENTION According to this invention, the sand which has equivalent quality can be stably obtained as a substitute of the silica sand currently used for the premix mortar composition by drying the sand collect | recovered from the residual concrete. . At the same time, it contributes to the effective use of the remaining concrete, which is mostly discarded.

  The present invention is described in detail below.

  The dry sand used in the present invention is obtained by separating a portion corresponding to a fine aggregate from residual concrete generated at a ready-mixed concrete factory, a concrete product factory, a construction site or the like, and drying after washing.

  Although it is not possible to collect all the fine aggregates used in concrete production in the separation, washing, and drying processes, there is no practical problem as long as they can be collected.

  In the present invention, the remaining concrete is preferably manufactured and shipped according to JIS A 5308 “Ready mixed concrete”. The standard has provisions on the quality of sand, such as density and particle size, for fine aggregates that are the basis of dry sand, ensuring strength development that is important when used as sand for premixed mortar compositions. It becomes easy.

  In the present invention, the method for separating the fine aggregate (sand) from the residual concrete is not particularly limited, and a known technique can be used. For example, classification using a sedimentation tank or sieving using a vibration sieve can be mentioned. Among these, a method of performing sieving using a vibration sieve after classification in a precipitation tank is preferred.

  In the present invention, a method for drying the separated sand (fine aggregate) is not particularly limited, and a known technique can be used. For example, a rotary dryer such as a rotary kiln, a hot air circulation dryer, or the like can be used. Among these, a method using a rotary dryer provided with a horizontal rotary drum is preferable.

  It is important that the drying is performed so that the moisture content of the sand is 2% or less. The premix mortar composition is composed of dry components such as cement and powdered dispersant. If a large amount of water is present in the fine aggregate, the hydration reaction of the cement proceeds, which is not preferable.

  In the present invention, the sand after drying can be used after sieving. As the mesh opening of the sieve to be used, an arbitrary one of 0.85 mm to 2.5 mm can be preferably used. The lower part of the sieve is mixed with other components to obtain a premixed mortar composition.

  In this invention, the compounding quantity of the dry sand in a premix mortar composition does not have a restriction | limiting in particular, However, 50-300 mass parts is used suitably with respect to 100 mass parts of cement.

  In the present invention, the premixed mortar composition is obtained by mixing the dry sand, cement, thickener and powdered surfactant obtained by the above-mentioned process.

  In the present invention, the cement is not particularly limited as long as it is hydrated with water and develops strength, but various portland cements, blast furnace cements, fly ash cements, silica cements, and eco cements defined in JIS standards are suitable. Can be used. As part of the cement, dry sludge powder recovered from the remaining concrete can be used.

  In the present invention, known thickeners such as those mainly composed of methylcellulose can be used without particular limitation. A suitable compounding quantity is 0.1-3 mass parts with respect to 100 mass parts of cement.

  In the present invention, known powdery surfactants can be used without limitation. Of these, polycarboxylates, naphthalene sulfonates, melamine sulfonates, and lignin sulfonates can be suitably used. A suitable compounding quantity is 0.1-3 mass parts with respect to 100 mass parts of cement.

  In the present invention, dry sand recovered from the residual concrete is used as the sand, but silica sand can also be mixed and used. Depending on the strength development property or particle size constitution of the dry sand, a premix mortar composition with higher performance may be obtained by mixing silica sand rather than using alone.

  As the silica sand, those used as a raw material for the premix mortar composition can be used without any particular limitation. Although there is no restriction | limiting in particular in the usage-amount of silica sand, It is preferable that it is 50 mass% or less of the whole sand from a viewpoint of reduction of the usage-amount of silica sand and ensuring the effective usage-amount of residual concrete.

  In the premix mortar composition of the present invention, an expansion material, blast furnace slag, fly ash, limestone and silica fume can be mixed according to the intended performance. Although the said material can be used for the premix mortar without a restriction | limiting in particular, The thing prescribed | regulated to JIS specification is more suitable.

  Suitable blending amounts of the above materials are 1 to 15% by mass of the expansion material, 2 to 230 parts by mass of the blast furnace slag, 2 to 50 parts by mass of fly ash, and 2 to 2 parts of limestone powder with respect to 100 parts by mass of cement. 50 mass parts and silica fume are 2-40 mass parts.

  The premixed mortar composition of the present invention can be mixed with dry sludge powder obtained by drying sludge water obtained by removing sand and gravel from residual concrete. Since most of the dry sludge powder consists of the unhydrated cement content in the remaining concrete, a certain level of strength can be expected. Moreover, the effective utilization amount of a residual concrete is securable by utilizing the dry sludge powder obtained in the same process as collection | recovery of reproduction | regeneration sand.

  The method for obtaining the sludge water is not particularly limited, and a known technique can be used. For example, classification using a sedimentation tank or sieving using a vibration sieve can be mentioned. Among these, a method of performing sieving using a vibration sieve after classification in a precipitation tank is preferred.

  In the present invention, the method for obtaining the solid content by filtering the sludge water obtained by the above method is not particularly limited, and a known technique can be used. For example, filtration by a screw press, a filter press, a centrifugal dehydration apparatus, and the like can be mentioned. Among them, a method by a filter press is preferable.

  The drying of the solid content is not particularly limited, and a known technique can be used. For example, a rotary dryer such as a rotary kiln, a hot air circulating dryer, or the like can be used. Among them, heating drying is preferable, and a method using a rotary dryer provided with a horizontal rotary drum is particularly preferable. It is important that the degree of drying is performed so that the moisture content is 2% or less.

  The suitable compounding quantity of the said dry powder is 1-15 mass parts with respect to 100 mass parts of cement.

  In the present invention, a known method can be used as the production method of the premixed mortar composition without limitation. Examples thereof include a method of simultaneously mixing raw materials weighed in a predetermined amount, a method of individually mixing arbitrarily selected raw materials, and further mixing the mixed raw materials. The mixer can be used without particular limitation as long as the raw materials can be sufficiently mixed. The product form of the premixed mortar composition after mixing is not particularly limited, but it is preferably packed in a container that can be weighed in a predetermined amount and can prevent moisture from entering, such as a paper bag or a flexible container bag.

  The premix mortar composition in the present invention is in a powder form and is used as a mortar composition mixed with a predetermined amount of water. The method of kneading with water is not particularly limited, and a known machine such as a hand mixer or a mortar mixer can be used.

  The premix mortar composition in the present invention can also be produced in a mobile mortar mixer for the purpose of supplying a mortar composition kneaded with water.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(1) Materials used / cement: Ordinary Portland cement / Recycled sand: Recovered from ready-mixed concrete manufactured according to JIS A 5308 “Ready mixed concrete”. Maximum particle size: 5.0 mm, coarse particle ratio: 2.83, density: 2.57 g / m 3, fine particle fraction: 0.22%, moisture: 0.1% or less, silica sand: No. 4 silica sand, expansion Material: Lime-based expansive material, powdered surfactant: Polycarboxylic acid-based high-performance AE water-reducing agent, thickener: Methyl cellulose-based thickener, sludge dry powder: Manufactured according to JIS A 5308 “Ready mixed concrete” Recovered from ready-mixed concrete.

(2) Production of premix mortar Premix mortar was produced so as to have the composition shown in Table 1. The materials were weighed to a predetermined amount and mixed with an omnimixer.

(3) Performance evaluation of mortar Premixed mortar having the composition shown in Table 1 and water were mixed to evaluate the performance of the mortar. 4.15 kg of water was added to 25 kg of premixed mortar. The J funnel flow time was measured as an indicator of fluidity. Compressive strength was measured as an index of strength development. The test material age for compressive strength was 1 day, 3 days, and 28 days, and 20 ° C water curing was performed until a predetermined material age.

(4) Test results Table 2 shows the test results. It can be seen that the blend using reclaimed sand has the same fluidity and high strength development compared to the blend using silica sand alone.

Claims (7)

A process of separating sand from residual concrete,
A method for producing a premixed mortar composition comprising a step of drying the sand, and a step of mixing the dried sand with cement, a thickener and a powdery surfactant.   The method for producing a premixed mortar composition according to claim 1, wherein the concrete is a residue of concrete produced in accordance with JIS A 5308 "Ready mixed concrete".   The method for producing a premixed mortar composition according to claim 1 or 2, further comprising mixing silica sand.   The premixed mortar composition according to any one of claims 1 to 3, wherein after the sand is dried, the sand is sieved with a sieve having an opening of 0.85 to 2.5 mm, and the lower part of the sieve is mixed with other components. Method.   Furthermore, the manufacturing method of the premix mortar composition of any one of the Claims 1 thru | or 4 which mix an expansion | swelling material.   The method for producing a premixed mortar composition according to any one of claims 1 to 5, wherein at least any one selected from blast furnace slag, limestone, fly ash and silica fume is further mixed.   The method for producing a premixed mortar composition according to any one of claims 1 to 6, wherein dry sludge powder obtained by separating and drying sand and gravel from residual concrete is mixed.