JP2019026536A - Cement additive and cement composition - Google Patents

Abstract

To provide a cement additive which has excellent solution stability, achieves a good fluidity holding effect and an autogenous shrinkage-reducing effect for cement concrete, and which exhibits immediate and sustained hexavalent chromium reduction; and to provide a cement composition using the same.SOLUTION: This invention relates to a cement additive, comprising: a lime sulphur mixture having a pH of 10 or more and an oxidation-reduction potential (ORP) of -450 mV or less; and one or more grinding aid(s) selected from ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and glycerin, wherein the lime sulphur mixture includes 5 to 15% by mass of Ca in terms of T-Ca, 15 to 30% by mass of S in terms of T-S, and 0.03 to 2.0% by mass of Mg in terms of MgO. This invention further relates to a cement composition, containing cement and the cement additive.SELECTED DRAWING: None

Description

  The present invention relates to a cement additive and a cement composition mainly used in the field of civil engineering and construction.

  In recent years, it has become more difficult to ensure the quality of cement concrete. This is due to the fact that the cement industry accepts various industrial by-products as raw materials, and that the basic unit of acceptance is increasing. This is because the trace components derived from these industrial by-products greatly affect the quality of cement.

In particular, the fluidity and strength developability vary greatly depending on the difference in the content of trace components, and the elution amount of hexavalent chromium also varies greatly.
However, the role of the cement industry to accept industrial by-products as raw materials will continue to be increasingly demanded, so even when using a large amount of industrial by-products, the quality design of cement that can control the effects of trace components is strong. It has been demanded.

In Patent Document 1, calcium polysulfide, which is a compound containing Ca and S, is supported on an immobilizing material such as quicklime, and the elution of harmful heavy metals such as hexavalent chromium without reducing the strength of the improved treated soil. The ground improvement material which added the function which suppresses is disclosed.
Patent Document 2, as a fixing agent used in the containment of heavy metals such as contaminated _{soil, Ca 8 S 5 (S 2} O 3) (OH) and composed mainly of 12 · 20H ₂ O and calcium hydroxide A heavy metal immobilizing agent is disclosed. The above _{Ca 8 S 5 (S 2 O} 3) (OH) 12 · 20H 2 O is to be prepared by the reaction of calcium polysulfide and calcium hydroxide, as the calcium polysulfide, commercial lime sulfur The use is described.
Patent Documents 1 and 2 relate to fixing agents and ground improvement materials used for containment of hazardous heavy metals.

JP 2001-342461 A JP 2004-33839 A

  The present invention provides a cement additive that is excellent in stability, exhibits good fluidity retention effect and self-shrinkage reduction effect of cement concrete, and also exhibits a reducing action of hexavalent chromium having both immediate effect and sustainability And it aims at providing the cement composition using the same.

The present inventor has conducted extensive research to achieve the above object, and as a result, the pH obtained by reacting quicklime, sulfur and water is 10.0 or more, and the oxidation-reduction potential (ORP) is -450 mV. It has been found that the following cement additive containing a specific lime-sulfur mixture and a cement composition using the cement additive achieve the above object.
The present invention is based on the above findings and is summarized as follows.
(1) A lime-sulfur mixture having an oxidation-reduction potential (ORP) of pH 10 or more and −450 mV or less, and one or more grinding aids selected from ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and glycerin. A cement additive comprising (2) The lime-sulfur mixture contains 5 to 15% by mass of Ca in terms of T-Ca, 15 to 30% by mass of S in terms of TS, and 0.03 to 2.0% by mass of Mg in terms of MgO. The cement additive of (1). (3) A cement composition containing cement and the cement additive according to (1) or (2). (4) A cement composition containing 0.01 to 10 parts by mass of a cement additive with respect to 100 parts of cement. (5) The cement composition according to (3) or (4), comprising Portland cement.

  By using the cement additive of the present invention, excellent stability, good fluidity retention effect and self-shrinkage reduction effect of cement concrete can be obtained, and in addition, reduction of hexavalent chromium having both immediate effect and sustainability Effects such as exerting an effect can be obtained.

Hereinafter, the present invention will be described in detail.
In the present invention, “part” and “percent (%)” are based on mass unless otherwise specified.
The cement concrete referred to in the present invention is a general term for cement paste, cement mortar, and concrete.

The lime sulfur mixture contained in the cement additive of the present invention is mainly composed of calcium polysulfide (CaS _X , where _X represents the number of sulfur atoms). It is a yellowish brown liquid obtained by using quicklime, sulfur and water as raw materials, reacting them in an autoclave, and solid-liquid separation. Conventionally, lime-sulfur mixtures are mainly known as fruit tree pesticides.
The lime-sulfur mixture can have various composition ratios and characteristics depending on the use ratio of raw lime, sulfur and water and reaction conditions in the autoclave. Therefore, the use ratio of quick lime, sulfur and water as raw materials is preferably 1.2 to 3 parts of sulfur, 2.5 to 5 parts of water, and 1.5 to 2 parts of sulfur with respect to 1 part of quick lime. 3 to 4 parts of water are particularly preferred. Moreover, it is preferable to perform reaction at 140-180 degreeC on the pressurization conditions of 3.5-10 atmospheres.

  It is important that the lime-sulfur mixture of the present invention has a pH of 10 or more. If the pH is less than 10, the effects of the present invention, that is, the solution stability, fluidity retention effect, hexavalent chromium reduction effect, and further the self-shrinkage reduction effect may not be sufficiently obtained. The pH of the lime sulfur mixture is more preferably 11 or more, and particularly preferably 12 or more. Although the one where the pH value of a lime sulfur mixture is large is preferable, 13 or less is preferable on the safety of operation.

  Moreover, the oxidation-reduction potential (ORP: vs Ag / AgCl) which the lime sulfur mixture of the present invention has is preferably −450 mV or less. If ORP is not lower than −450 mV, the main effects of the present invention, the fluidity retention effect, the hexavalent chromium reduction effect, and the self-shrinkage reduction effect may not be sufficiently obtained. The ORP is more preferably −500 mV or less. The lower limit value of the ORP of the lime-sulfur mixture is not particularly limited as long as it does not impair the effects of the present invention.

The lime-sulfur mixture of the present invention contains 5-15% of Ca in terms of T-Ca, 15-30% of S in terms of TS, and 0.03-2.0% of Mg in terms of MgO. It is preferable.
The Ca content is determined by JIS R5202 “Cement Chemical Analysis Method”, the S content is determined by a carbon / sulfur analyzer, and the MgO content is determined by ICP emission spectroscopic analysis.

When the Ca content is less than 5%, the pH of the lime-sulfur mixture deviates from the alkaline region, whereas when it exceeds 15%, the pH may exceed 13. The Ca content is more preferably 6 to 9%, and further preferably 7 to 8%.
If the S content is less than 15%, the hexavalent chromium elution amount may increase. On the other hand, if it exceeds 30%, the hexavalent chromium elution amount may increase. The S content is more preferably 17 to 28%, and particularly preferably 20 to 26%.
If the Mg content is less than 0.03%, the fluidity retention effect, the hexavalent chromium reduction effect, and the self-shrinkage reduction effect may not be sufficiently obtained. The content of Mg is more preferably 0.07% or more, and particularly preferably 1.0% or more. The content of Mg is preferably as high as possible, but is preferably 2.0% or less because it may be altered by substitution with Ca in the cement hydrate.

As the grinding aid used in the present invention, one or more selected from ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol and glycerin can be used.

When lime sulfur mixture comes into contact with carbon dioxide in the atmosphere for a long period of time, the pH is lowered, precipitates are formed, the stability of the solution is lowered, the fluidity retention effect and the hexavalent chromium reduction effect, Furthermore, there are cases where the effect of reducing self-shrinkage cannot be obtained sufficiently.
In this invention, stability of a solution can be improved by mixing a grinding | pulverization adjuvant with a lime sulfur mixture. The amount of the grinding aid used in the present invention is preferably 0.5 to 30 parts, more preferably 1 to 20 parts, based on 100 parts in total of the lime sulfur mixture and the grinding aid. If the amount used is lower than 0.5 parts, the stability of the solution may be insufficient. On the other hand, if it exceeds 30 parts, the fluidity retention effect, the hexavalent chromium reducing effect, and the self-shrinkage are reduced. The effect may not be sufficiently obtained.

  As the cement used in the present invention, various portland cements such as normal, early strength, ultra-early strength, low heat, medium heat, etc., various mixed cements obtained by mixing blast furnace slag, fly ash, or silica with these portland cements, limestone Examples include filler cement mixed with powder, blast furnace slow-cooled slag fine powder, and the like. Furthermore, portland cements such as environmentally conscious cement (eco-cement) manufactured using municipal waste incineration ash and sewage sludge incineration ash as raw materials can be mentioned. In the present invention, one or more of the above can be used.

Although the usage-amount of the cement additive of this invention in cement concrete is not specifically limited, Usually, 0.01-10 parts are preferable with respect to 100 parts of cement, and 0.05-5 parts are more preferable. When the amount of the cement additive used is less than 0.01 part, the effects of the present invention, that is, the fluidity retention effect, the hexavalent chromium reduction effect, and the self-shrinkage reduction effect may not be sufficiently obtained. is there.
In the present invention, cement and a cement additive are blended to form a cement composition.

  The form of the lime-sulfur mixture of the present invention is not particularly limited, and may be any form as long as the effects of the present invention are not impaired. The liquid can be used as it is, or the liquid can be used after being dried.

  The cement composition of the present invention includes fine aggregates such as sand and coarse aggregates such as gravel, as well as expansion materials, rapid hardening materials, AE agents, dispersants, antifoaming agents, thickeners, rust inhibitors, Antifreezing agents, shrinkage reducing agents, setting modifiers, clay minerals such as bentonite, anion exchangers such as hydrotalcite, slag such as granulated blast furnace slag fine powder and blast furnace slow-cooled slag fine powder, limestone fine powder and other admixtures It is possible to use together 1 type or 2 types or more of the group which consists of in the range which does not inhibit substantially the objective of this invention.

The cement composition of the present invention may be partially or wholly mixed in advance. Any existing device can be used as the mixing device. For example, a tilting mixer, an omni mixer, a Henschel mixer, a V-type mixer, a proshear mixer, a nauta mixer, and the like can be used.
In addition, when the cement additive of the present invention is used as a grinding aid for cement clinker, the above-described effects of the present invention are more remarkably exhibited.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, this invention is not limited to these.

(Experimental example 1)
Various lime-sulfur mixtures A to G and grinding aids A to H shown below are mixed at a ratio shown in Table 1 to prepare a cement additive, and 0.5 part is added to 100 parts of cement to make cement. A composition was prepared.
The cement additive was sprayed and mixed into the cement using a hand spray (for spray coating, made of polycarbonate, manual type, 2 liters in volume), and previously blended with the cement.
In Experiment No. 1-9, the cement additive of Experiment No. 1-4 was sprayed on the normal Portland cement clinker using the above hand spray, and gypsum (added 4% to the cement clinker in an internal ratio) The mixture was pulverized together with a specific surface area of 3300 cm ² / g.

Next, a concrete having a unit cement composition amount of 500 kg / m ³ , a water / cement composition ratio of 33%, a fine aggregate volume ratio to the total aggregate volume of 46%, an air amount of 4.5%, and a slump of 21 cm is prepared. did. At this time, 1.4 parts of the high performance water reducing agent was added to 100 parts of the cement composition. With respect to this concrete, slump change over time (slump loss), self-shrinkage, and hexavalent chromium reduction effect (elution amount of hexavalent chromium) were measured.
The stability of the solution was also evaluated. The results are shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, Blaine specific surface area 3210 cm ² / g, commercial product (Denka).
Ordinary Portland Cement _{Clinker: 3CaO · SiO 2 58.1%,} 2CaO · SiO 2 18.7%, 4CaO · Al 2 O 3 · Fe 2 O 3 10.0%, 3CaO · Al 2 O 3 10.2%. (Fired at 1350 ° C in kiln)
Gypsum: 2 water gypsum, commercial product

Lime sulfur mixture AG changed the use ratio of quicklime, sulfur, and water, made it react in the autoclave on conditions of 5 atmospheres and 150 degreeC, and carried out solid-liquid separation.
Lime sulfur mixture A: Lime sulfur mixture, pH 11.0, ORP-540 mV, MgO content 1.0%, T-Ca content 13%, TS content 26%.
Lime sulfur mixture B: Lime sulfur mixture, pH 10.5, ORP-500 mV, MgO content 1.0%, T-Ca content 12%, T-S content 24%.
Lime sulfur mixture C: Lime sulfur mixture, pH 10.0, ORP-450 mV, MgO content 1.0%, T-Ca amount 11%, T-S amount 22%.
Lime sulfur mixture D: Lime sulfur mixture, pH 10.5, ORP-500 mV, MgO content 0.05%. T-Ca amount 10%, T-S amount 21%.
Lime-sulfur mixture E: Lime-sulfur mixture, pH 10.5, ORP-500 mV, MgO content 2.0%, T-Ca amount 8%, T-S amount 19%.
Lime sulfur mixture F: Lime sulfur mixture, pH 11.0, ORP-540 mV, MgO content 1.0%, T-Ca content 13%, TS content 26%.
Lime sulfur mixture G: Lime sulfur mixture, pH 8.0, ORP-450 mV, MgO content 1.5%, T-Ca content 13%, TS content 26%.
Lime-sulfur mixture H: A mixture obtained by mixing 25 parts of lime-sulfur mixture with a ball mill on 100 parts of quicklime (brene specific surface area 3460 cm ² / g).
The lime-sulfur mixture H is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-342461) and is not solid-liquid separated.

Liquid grinding aid A: ethylene glycol, primary reagent liquid grinding aid B: propylene glycol, primary reagent liquid grinding aid C: diethylene glycol, primary reagent liquid grinding aid D: triethylene glycol, primary reagent liquid grinding aid E: Glycerin, primary reagent liquid grinding aid F: triethanolamine, primary reagent liquid grinding aid G: triisopropanolamine, primary reagent liquid grinding aid H: liquid grinding aids A and C mixed in equal amounts

Fine aggregate: river sand from Himekawa, Niigata Prefecture, particle size: under sieve 5 mm, coarse particle ratio 2.82, specific gravity 2.64.
Coarse aggregate: crushed stone from Himekawa, Niigata Prefecture, maximum particle size 25 mm, coarse particle ratio 6.98, specific gravity 2.62.
High-performance water reducing agent: polycarboxylate, commercially available (BASF, MELFLUX 2651F).

<Test method>
Stability of the solution: Cement additive mixed with lime sulfur mixture and liquid grinding aid is put into a 100 ml beaker and stored for one week with the top open in an environment of 20 ° C and 60% relative humidity. The presence or absence of precipitates and the volume ratio of the precipitates were confirmed visually.
Slump loss: Slump was measured according to JIS A 1150, and the amount of change in the measured value 30 minutes and 90 minutes after immediately after kneading was examined.
Self-shrinkage: Measured according to JCI Self-Shrink Research Committee report. Expressed as self-shrinkage strain at age 56 days.

Elution amount of hexavalent chromium: A hexavalent chromium standard solution is diluted to prepare a solution having a hexavalent chromium concentration of 100 mg / l, and the hexavalent chromium solution is made to be 2 liters per 1 m ³ of concrete. The water was replaced with kneading water. The amount of elution from fresh concrete that has not yet solidified and the amount of elution from hardened concrete were investigated.
The amount of elution from fresh concrete (immediate effect) was determined by adding hydrochloric acid to pure water after filtering the supernatant obtained from bleeding water and centrifugation 30 minutes after kneading, and the hydrogen ion concentration index (PH) was 5.8. The solution adjusted to 6.3 or less was mixed at a volume ratio of 10%, and measured by ICP emission spectroscopic analysis according to JIS K0102.
The amount of elution from the hardened concrete (sustainability) was measured by crushing the hardened concrete after 28 days of age and using a sample 2 mm below according to the Environmental Agency Notification No. 46 method. However, the residual concentration of hexavalent chromium was measured by ICP emission spectroscopic analysis according to JISK 0102.

  From Table 1, it can be seen that the cement additive of the present invention is excellent in the effect of maintaining the stability and fluidity of the solution, and further has the effect of reducing self-shrinkage and the effect of reducing hexavalent chromium.

(Experimental example 2)
The same procedure as in Experimental Example 1 was performed except that the cement additive of Experiment No. 1-4 was used and the amount of cement additive used was changed as shown in Table 2. The results are shown in Table 2.

  From Table 2, it can be seen that by using an appropriate amount of the cement additive of the present invention, the fluidity retention effect and the hexavalent chromium reduction effect are obtained, and the self-shrinkage is also reduced.

  By using the cement additive and cement composition of the present invention, good fluidity retention effect and self-shrinkage reduction effect can be obtained, and in addition, effects such as exerting the reducing action of hexavalent chromium can be achieved. Suitable for a wide range of applications, mainly in the civil engineering and construction industries.

Claims (5)

Contains a lime-sulfur mixture having an oxidation-reduction potential (ORP) of pH 10 or more and −450 mV or less, and one or more grinding aids selected from ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, and glycerin. Cement additive. The lime-sulfur mixture contains 5 to 15% by mass of Ca in terms of T-Ca, 15 to 30% by mass of S in terms of TS, and 0.03 to 2.0% by mass of Mg in terms of MgO. The cement additive according to claim 1. A cement composition comprising cement and the cement additive according to claim 1 or 2. The cement composition according to claim 3, comprising 0.01 to 10 parts by mass of cement additive with respect to 100 parts by mass of cement. The cement composition according to claim 3 or 4, comprising Portland cement.