Concrete block for pavement and method for producing same

Abstract

Provided is a concrete block for pavement composed of a cured body of a curable composition that contains a binder, aggregate and water. The concrete block is characterized in that the binder contains a powder component and an alkali source, wherein a blast furnace slag fine powder is contained as the powder component, and an alkali metal silicate is contained as the alkali source.

Description

Paving Concrete Block and Method for Manufacturing the Same

[0001] The present invention relates to CO ２ emission-reduced paving concrete block and a method for manufacturing the same.

[0002] In the construction industry, CO ２ emission reduction is an urgent issue. Particularly in reinforced concrete structures, CO ２ emissions generated throughout the life cycle when placing concrete on site to construct a structure are said to be about 80% attributable to the manufacturing of constituent materials, about 10% attributable to construction, and the remainder attributable to demolition and disposal. Among these, CO ２ cement is cited as one of the main causes of emissions, and there is a demand for constituent materials for concrete manufacturing that further reduce CO ２ emissions.

[0003] Similarly, the precast concrete products industry is also working on CO ２ emission reduction (Non-Patent Document 1).

[0004] Hideaki Karasawa, "Initiatives for CO2 Reduction in Precast Concrete Product Manufacturing", Concrete Engineering Vol. 48, No. 9, September 2010, p. 102, Japan Cement Association, Outline of Cement LCI Data, April 2024

[0005] For example, for a paving concrete block using cement as a binder, which is a type of precast concrete product, when calculated from the data described in Non-Patent Document 2, 1 m ３ of the block emits about 320 kg of CO ２ . Therefore, it is also necessary to reduce cement-derived CO ２ emissions in paving concrete blocks.

[0006] An object of the present invention is to provide a paving concrete block that can be manufactured without using cement as a binder, and a method for manufacturing the same.

[0007] The present inventors have studied CO ２We have conducted intensive research to reduce emissions, and by using a binder containing a powder component and an alkali source as an alternative binder to cement, material-derived CO ２ We have found that it is possible to obtain a paving concrete block with reduced emissions, and have completed the present invention.

[0008] That is, the first aspect of the present invention is a paving concrete block composed of a cured product of a curable composition containing a binder, aggregate and water, wherein the binder is a binder containing a powder component and an alkali source, the binder contains ground granulated blast furnace slag as the powder component, and contains an alkali metal silicate as the alkali source. The paving concrete block of the present invention can be used as an interlocking block.

[0009] The second aspect of the present invention is a method for producing a paving concrete block, comprising: preparing a curable composition containing a binder that includes a powder component and an alkali source, wherein the powder component includes ground granulated blast furnace slag and the alkali source includes an alkali metal silicate, aggregate, and water; then molding the composition and demolding after molding. According to the production method of the present invention, an interlocking block can be produced by immediately demolding the prepared curable composition after vibration pressure molding.

[0010] In the present invention, the powder component includes ground granulated blast furnace slag and fly ash, and it is preferable that the relationship between the volume percentage of ground granulated blast furnace slag (X (%)) in the total volume of ground granulated blast furnace slag and fly ash and the molar ratio of the sum of alkali metal ions and silicon ions contained in the alkali source to water in the curable composition: (Al+Si) / W (molar ratio) (Y) satisfies the following relational expression. Y≧-0.004X+0.27 (X is 5 or more and 65 or less)

[0011] It is also preferable that the alkali source in the binder includes an alkali metal silicate and an alkali metal carbonate.

[0012] It is preferable that the alkali metal silicate is sodium silicate, and it is preferable that the alkali metal carbonate is sodium carbonate.

[0013] In the paving concrete block and the method for producing the same according to the present invention, a binder containing ground granulated blast furnace slag as a powder component and an alkali metal silicate as an alkali source is used without using cement which is generally used as a binder. This maintains the strength required for a paving concrete block, while reducing CO ２ emissions significantly, for example, by up to about 80%, compared to the case where cement is used as the binder.

[0014] Furthermore, when the relationship between the volume ratio of ground granulated blast furnace slag (X (%)) to the total volume of ground granulated blast furnace slag and fly ash contained in the powder component, and the molar ratio of the sum of alkali metal ions and silicon ions to water in the curable composition: (AL + Si) / W (molar ratio) (Y) satisfies the following relational expression, the durability of the paving concrete block can be improved, and a flexural strength of 3.0 N / mm at 14 days of age ２ or higher can be achieved, so the block can also be used as an interlocking block. Y≧-0.004X + 0.27 (X is 5 or more and 65 or less)

[0015] It is a diagram showing the 14-day flexural strength at a given age relative to the relationship between the volume ratio of ground granulated blast furnace slag (X (%)) to the total volume of ground granulated blast furnace slag and fly ash contained in the powder component of the binder, and the molar ratio of the sum of alkali metal ions and silicon ions contained in the alkali source to water in the curable composition: (AL + Si) / W (molar ratio) (Y). The region above the straight line indicated by the solid line (including the solid line) corresponds to a 14-day flexural strength of 2.0 N / mm ２ or higher, and the region above the straight line indicated by the dotted line (including the dotted line) corresponds to a 14-day flexural strength of 3.0 N / mm ２ or higher.

[0016] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to these embodiments. Note that, in this specification, "parts" and "%" are based on mass unless otherwise specified.

[0017] In the present invention, the paving concrete block refers to all concrete blocks used for paving roads, sidewalks and the like.

[0018] In this invention, an interlocking block is a type of concrete block used for paving, where load transfer and load distribution between blocks are achieved through the interlocking effect of joint sand or similar fine-grained material filled in the gaps between the blocks. It is manufactured by a method of immediate demolding after vibration and pressure molding.

[0019] The concrete block for paving according to the present invention consists of a hardened body of a hardening composition containing a binder, aggregate, and water.

[0020] <Binding Agent> In the concrete block for paving of the present invention, the binding agent comprises a powder component and an alkali source. The total content of the powder component and alkali source in the binding agent is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably substantially 100% by mass (consisting of the powder component and alkali source). The powder component includes blast furnace slag fine powder, and the alkali source includes alkali metal silicate.

[0021] (Blast furnace slag fine powder) Blast furnace slag fine powder is a by-product of pig iron production, and is CaO, SiO ２ Al ２ O ３ It contains MgO as its main component. Examples of blast furnace slag fine powder include those containing calcium in an amount of 20% to 60% by mass on an equivalent basis of calcium oxide (CaO). In particular, using blast furnace slag fine powder 4000 for concrete as specified in JIS A 6206 is more preferable from the viewpoint of strength development and shrinkage at room temperature of paving concrete blocks manufactured using the resulting hardened body. Carbonated blast furnace slag fine powder may also be used to adjust the pot life.

[0022] In the present invention, the powder component of the binder may contain blast furnace slag fine powder, but it is preferable to include fly ash in addition to blast furnace slag fine powder in order to ensure long-term durability, prevent rapid hardening during manufacturing, and improve workability.

[0023] (Fly Ash) Fly ash is the fine ash that is collected from the exhaust gas by a dust collector, which is a by-product of combustion residue when coal, biomass fuel, or both are burned in boilers at thermal power plants, etc. ２ Al ２ O ３ Fly ash for concrete, which has as its main component and is standardized into types I to IV according to JIS A 6201 based on particle size and flow value, is preferred. The standard is not particularly limited, but types I and II, which have fine particle size and are highly reactive, are more preferred.

[0024] When the powder component includes blast furnace slag fine powder and fly ash, the total content of slag fine powder and fly ash in the powder component is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably substantially 100% by mass.

[0025] Furthermore, it is preferable that the volume ratio (X (%)) of blast furnace slag fine powder to the total volume of blast furnace slag fine powder and fly ash be 5% or more and 65% or less, and more preferably 10% or more and 65% or less from the viewpoint of durability of paving concrete blocks. Moreover, it is preferable that it be 10% or more and 55% or less from the viewpoint of workability during the manufacture of paving concrete blocks. Setting it to 5% or more allows for good strength development of the geopolymer composition cured body in the initial stage. Setting it to 65% or less is preferable because it allows for good fluidity to be maintained when water and binder are mixed, making it easier to obtain sufficient workability, and also from the viewpoint of expanding the effective utilization of fly ash.

[0026] (Alkali source) The alkali source contains alkali metal ions (Li) as constituent ions. ＋ , Na ＋ , K ＋The alkali metal salts include alkali metal silicates, alkali metal carbonates, alkali metal hydroxides, etc. Typical alkali metal salts include alkali metal silicates, alkali metal carbonates, alkali metal hydroxides, etc. In the present invention, the alkali source of the binder includes alkali metal silicates. The combination of alkali metal silicates and alkali metal carbonates is preferable because the heat of dissolution is relatively low, it does not adversely affect the mixing process, and a concrete block for paving with excellent flexural strength can be obtained by curing at room temperature. The alkali source, such as alkali metal silicates and alkali metal carbonates, may be in liquid or powder form, and may be in anhydrous, hydrated, or aqueous solution form of the salt. Powder form is preferable due to its high transportability and workability.

[0027] Alkali metal silicate powders include sodium silicate powder (SiO₂ ２ / NaO ２ Examples include sodium silicate powder (molar ratio: approximately 1.95 to 3.4), sodium metasilicate powder (type 1, type 2), potassium silicate powder, potassium metasilicate powder, and lithium silicate powder. Sodium silicate powder (SiO₂) is used because it exhibits excellent strength development and durability, and is a relatively inexpensive powder material. ２ / NaO ２ Molar ratio: approximately 1.950 to 2.2, H ２ O = approximately 20% by mass is preferred.

[0028] Alkali metal carbonate powders include sodium carbonate (Na ２ CO ３ ), potassium carbonate (K ２ CO ３ ), lithium carbonate (Li ２ CO ３ Examples of powders include those listed above. Sodium carbonate powder is preferred because it is relatively inexpensive, shows high reactivity to slag fine powder, and exhibits good strength development in a short period of time.

[0029] When alkali metal silicates and alkali metal carbonates are used in combination, the content of alkali metal carbonates relative to the total mass of alkali metal silicates and alkali metal carbonates is preferably 5% to 50% by mass, as this improves early strength development and reduces viscosity during the mixing process, making the work easier.

[0030] (Aggregates) The aggregates used in the concrete blocks for paving according to the present invention can be any known aggregates used in general concrete manufacturing without any particular limitations. Specifically, these include crushed stone, crushed sand, river gravel, hill sand, sea sand, limestone aggregate, etc.

[0031] The amount of aggregate used in this invention is not particularly limited as long as it is within the range used in general paving concrete blocks, and specifically, it is about 30% to 90% of the volume of the paving concrete block.

[0032] (Water) The water used in the concrete blocks for paving according to the present invention is not particularly limited, and any water commonly used for concrete, such as tap water, deionized water, or pure water, can be used.

[0033] (Other) In the concrete block for paving of the present invention, various admixtures and additives can be added to the curable composition in addition to those mentioned above, as long as they do not impair the effects of the present invention. Examples include known materials used in concrete such as fluidizers, shrinkage reducers, rust inhibitors, waterproofing agents, setting retarders, defoamers, efflorescence inhibitors, dust reducers, pigments, and calcium carbonate powder.

[0034] In the present invention, it is preferable to adjust the material ratio in the binder and the amount of water used so that the relationship between the volume ratio (X (%)) of blast furnace slag fine powder in the binder's powder component to the total volume of blast furnace slag fine powder and fly ash, and the molar ratio of the sum of alkali metal ions and silicon ions contained in the alkali source to water in the curable composition: (AL + Si) / W (mol ratio) (Y) satisfies the following relationship. Note that the water in Y refers to the total water in the concrete block, and includes, for example, water contained in the alkali source.

[0035] Y ≥ -0.004X + 0.23 ...Equation (1) (X is between 5 and 65)

[0036] Preferably, the following relationship is satisfied: Y ≥ -0.004X + 0.27 ...Equation (2) (X is between 5 and 65)

[0037] By satisfying the above relationship, a bending strength of 2.0 N / mm² is achieved at 14 days of age.２ Preferably, the above is 3.0 N / mm ２ This makes it possible to achieve the above properties and obtain a highly durable concrete block for paving, which can be used as an interlocking block. In this case, in order to secure working time and improve workability, it is preferable that the Y value be 0.30 or less when considering the pot life.

[0038] Here, the above relational equation is an equation calculated based on the results of the examples described later (see Figure 1). That is, equation (1) above was determined based on the results of Examples 1 and 2, and in Figure 1, the region above the straight line shown by the solid line of this determined equation (1) (including the solid line) is the region with a bending strength of 2.0 N / mm at 14 days of age. ２ This represents the region shown above. Furthermore, based on the results of Examples 3 to 6, the above formula (2) was determined, and in Figure 1, the region above the straight line indicated by the dotted line of this determined formula (2) (including the dotted line) has a bending strength of 3.0 N / mm at 14 days of age. ２ This represents the area indicated above.

[0039] In the concrete blocks for paving according to the present invention, the method for producing a hardening composition by mixing a binder, aggregate, water, and other materials as needed can be any conventional method used in ready-mix concrete plants or precast concrete product plants, without any particular limitations.

[0040] In the concrete blocks for paving according to the present invention, a mixer that is generally used for mixing mortar or concrete can be used as the mixing device for mixing each of the above materials. Specifically, examples include pan mixers, forced twin-shaft mixers, tilt mixers, mortar mixers, and hand mixers.

[0041] In this invention, a hardening composition is prepared by mixing a binder, aggregate, water, and other materials as needed. Then, the hardening composition is filled into a predetermined mold and allowed to harden to produce concrete blocks for paving. The manufacturing method can be any conventional method used in concrete secondary product factories without any particular limitations. Specifically, for example, when manufacturing interlocking blocks, the prepared hardening composition is filled into a mold of a predetermined shape, compacted by vibration or other means (such as vibration pressure molding), and then immediately demolded. After demolding, the material is cured to allow the properties of the present invention to fully develop. Alternatively, it is also possible to compact the material in the same way as general ready-mixed concrete, leave it in the mold, and then demold and cure it after it has hardened.

[0042] Furthermore, in the concrete paving blocks of the present invention, cement mortar can be used in the surface layer for the purpose of improving aesthetics. When a surface layer is provided, the manufacturing method involves manufacturing the base layer using the procedure described above, then filling it with the cement mortar for the surface layer, and similarly compacting, demolding, and curing. In addition, a double-layered concrete paving block can be made by forming the surface layer on the bottom and the base layer on top, except that the order in which the base layer concrete and the surface layer mortar are filled is reversed.

[0043] The surface mortar forming the surface layer can be a known general mortar, for example, prepared by mixing a cement-based binder, fine aggregate, coarse aggregate such as river gravel or crushed rock with an average particle size of 5 mm or more, and other water-retaining agents and efflorescence inhibitors with water. Instead of a cement-based binder, a binder consisting of powder components and an alkali source, used in the concrete blocks for paving according to the present invention, may be used.

[0044] The curing method can be any conventional curing method used in ready-mix concrete plants or precast concrete product plants, without any particular restrictions. Specifically, this includes wet curing, underwater curing, steam curing, autoclave curing, and air curing.

[0045] (Other Embodiments) The concrete blocks for paving according to the present invention are not limited to the embodiments described above, and various modifications may be made without departing from the spirit of the present invention. Furthermore, parts of certain embodiments may be deleted. Also, well-known technologies may be added to the configuration of certain embodiments.

[0046] The present invention will be described in more detail below with reference to specific examples. However, the present invention is not limited to the following examples.

[0047] (Materials used) ・Powder components (1) Fly ash (FA): Fly ash type II (compliant with JIS A 6201) (2) Blast furnace slag fine powder (BS): Blast furnace slag fine powder 4000 (compliant with JIS A 6206) ・Alkali source (3) Powdered sodium silicate (Ns): Sodium silicate powder (SiO ２ / Na ２ O molar ratio = 1.98, H ２ O = about 20% by mass, Na mol concentration 1219 mol / t, Si mol concentration 1203 mol / t, H ２ (4) Soda ash (Nc): Sodium carbonate powder (manufactured by our company) (5) Portland cement (NC): Ordinary Portland cement (compliant with JIS R 5210) (6) Eco cement (EC): Eco cement (compliant with JIS R 5214) Other materials (7) Fine aggregate (S): Crushed sand (compliant with JIS A 5005) (8) Coarse aggregate (G): Crushed stone No. 6 and No. 7 (compliant with JIS A 5005) (9) Water (W): Tap water (compliant with JIS A 5308 Annex C)

[0048] In this embodiment and reference example, interlocking blocks were manufactured as concrete blocks for paving. For manufacturing, first, a mixture of tap water added to each material according to the proportions shown in Table 1 was kneaded in a soil mixer with a capacity of approximately 10 L to obtain a curable composition. The kneaded curable composition was poured into a metal mold measuring 10 cm on the short side, 20 cm on the long side, and 6 cm in height, and vibrated and compressed using a trowel-type vibrator. The manufactured blocks were cured for 14 days in an air environment at a temperature of 20 ± 3°C and a humidity of 60 ± 5%. Then, according to the method described in JIS A 5371 (Precast Unreinforced Concrete Products) Annex B Recommended Specification B-3, the blocks were placed with their top surfaces facing upwards in a concrete compression strength testing machine equipped with a jig for bending strength testing. Rubber plates were inserted into the pressure and support surfaces to ensure even load distribution, and a load was applied. The bending strength was calculated from the load at the point of block failure. Table 3 shows the bending strength at 14 days of age. In this case, the loading span was set to more than twice the thickness of the block, and the load was applied at a single point in the center between the supports.

[0049] Furthermore, a comparison between conventional concrete blocks for paving and the concrete blocks for paving according to the present invention, 1m ３ Winning CO ２ The emissions were calculated and compared. Table 2 shows CO2 emissions. ２ The emissions were shown. ２ Emissions are calculated based on the amount of each material used (kg / m³). ３ ), CO ２ CO2 emissions per kg (kg / kg) for each material ２ The CO emissions were calculated and then totaled. ２ For emission intensity (kg / kg), the data described in Non-Patent Document 2 was used. Also, the CO2 values ​​in Reference Examples 1 and 2 were used. ２ Table 3 shows the reduction rates relative to emissions.

[0050]

[0051]

[0052]

[0053] Reference Example 1 is a concrete block for paving using conventional ordinary Portland cement, with 1 m of concrete. ３ CO2 derived from materials used in the manufacturing process ２ The calculated emission result is 318 kg / m³ ３ That was the case.

[0054] Reference Example 2 is derived from the formulation in Reference Example 1, but with CO2 ２ To reduce emissions, eco-cement was used, and 60 parts by mass of the binder were replaced with blast furnace slag powder. (Reference Example 2: 1 m of concrete) ３ CO2 derived from materials used in the manufacturing process ２ The calculated emission result is 137 kg / m³ ３ That was the case.

[0055] Examples 1 to 6 are concrete blocks for paving according to the present invention. None of them use Portland cement, and 1 m of concrete ３ CO2 derived from materials used in the manufacturing process ２ The emission calculation result for Example 1 was 72 kg / m³. ３ In Example 2, the load was 50 kg / m². ３ In Example 3, the load was 83 kg / m². ３ In Example 4, the load was 61 kg / m³. ３ In Example 5, the load was 51 kg / m³. ３ In Example 6, the load was 57 kg / m³. ３ As a result, CO2 is 74-84% compared to Reference Example 1 and 40-64% compared to Reference Example 2. ２ It has the effect of reducing emissions.

[0056] Furthermore, from Table 3, the volume ratio (X (%)) of blast furnace slag fine powder in the total volume of blast furnace slag fine powder and fly ash contained in the powder component, the molar ratio of the sum of alkali metal ions and silicon ions contained in the alkali source in the curable composition to water: (AL + Si) / W (mol ratio) (Y), and the flexural strength at 14 days of age are found to be in the relationship shown in Figure 1. If the following relationship is satisfied, the flexural strength at 14 days of age is 3.0 N / mm² in accordance with JIS A 5371 "Recommended Specifications B-3 for Precast Unreinforced Concrete Products". ２It is possible to create the above interlocking blocks, and it is possible to create concrete paving blocks that have a low environmental impact and excellent durability. Y ≥ -0.004X + 0.27 (X is between 5 and 65)

Claims

1. A concrete paving block comprising a hardened body of a curable composition containing a binder, aggregate, and water, wherein the binder is a binder containing a powder component and an alkali source, the powder component containing blast furnace slag fine powder, and the alkali source containing an alkali metal silicate.

2. The concrete paving block according to claim 1, which is an interlocking block.

3. The concrete block for paving according to claim 1 or 2, wherein the powder component comprises blast furnace slag fine powder and fly ash, and the relationship between the volume ratio (X (%)) of the blast furnace slag fine powder to the total volume of the blast furnace slag fine powder and fly ash and the molar ratio (AL + Si) / W (mol ratio) (Y) of the sum of alkali metal ions and silicon ions contained in the alkali source in the curable composition to water satisfies the following relationship: Y ≥ -0.004X + 0.27 (X is 5 or more and 65 or less) 4. The concrete block for paving according to claim 1 or 2, characterized in that the alkali source in the binder contains alkali metal silicate and alkali metal carbonate.

5. The concrete block for paving according to claim 1 or 2, characterized in that the alkali metal silicate is sodium silicate.

6. The concrete block for paving according to claim 4, characterized in that the alkali metal carbonate is sodium carbonate.

7. A method for manufacturing concrete blocks for paving, comprising preparing a curable composition containing a binder, aggregate, and water, and then demolding after molding, wherein the binder is a binder containing a powder component and an alkali source, the powder component containing blast furnace slag fine powder, and the alkali source containing an alkali metal silicate.

8. The method for manufacturing a concrete block for paving according to claim 7, characterized in that the prepared curable composition is immediately demolded after vibration pressure molding to produce an interlocking block.

9. A method for producing a concrete block for paving according to claim 7 or 8, wherein the powder component comprises blast furnace slag fine powder and fly ash, and the relationship between the volume ratio (X (%)) of the blast furnace slag fine powder to the total volume of the blast furnace slag fine powder and fly ash and the molar ratio (AL + Si) / W (mol ratio) (Y) of the sum of alkali metal ions and silicon ions contained in the alkali source in the curable composition to water satisfies the following relationship: Y ≥ -0.004X + 0.27 (X is 5 or more and 65 or less) 10. The method for manufacturing a concrete block for paving according to claim 7 or 8, characterized in that the alkali source in the binder contains an alkali metal silicate and an alkali metal carbonate.

11. The method for manufacturing a concrete block for paving according to claim 7 or 8, characterized in that the alkali metal silicate is sodium silicate.

12. The method for manufacturing a concrete block for paving according to claim 10, characterized in that the alkali metal carbonate is sodium carbonate.

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