WO2017179121A1

WO2017179121A1 - Cement additive and cement composition

Info

Publication number: WO2017179121A1
Application number: PCT/JP2016/061808
Authority: WO
Inventors: 将貴宇城; 盛岡　実; 啓史原; 雅昭渡辺
Original assignee: デンカ株式会社
Priority date: 2016-04-12
Filing date: 2016-04-12
Publication date: 2017-10-19
Also published as: JPWO2017179121A1

Abstract

Provided are a cement additive and a cement composition that maintain the favorable fluidity of cement concrete, that reduce autogeneous shrinkage, and that exhibit an immediately effective and long-lasting hexavalent chromium reduction effect. (1) A cement additive that comprises a lime-sulfur mixture having a pH of 10 or more and that has an excellent ability to maintain the fluidity of cement concrete and reduce autogeneous shrinkage. (2) The cement additive indicated in (1), wherein the lime-sulfur mixture has an oxidation-reduction potential (ORP) of -450 mv or less. (3) The cement additive indicated in (1) or (2), wherein the lime-sulfur mixture contains 5-10% of Ca in terms of T-Ca, 15-30% of S in terms of T-S, and 0.5-2.0% of Mg in terms of MgO. (4) A cement composition containing cement and one of the cement additives indicated in (1) to (3). (5) The cement composition indicated in (4), wherein the cement additive content is 0.005-1 part with respect to 100 parts of cement. (6) The cement composition indicated in (4) or (5), wherein the cement contains Portland cement.

Description

Cement additive and cement composition

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

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 the acceptance unit is increasing. This is because the trace components derived from these industrial by-products greatly affect the quality of cement.

In particular, fluidity and strength development vary greatly depending on the content of trace components. There are also significant differences in the elution amount of hexavalent chromium.
However, since the role of the cement industry to accept industrial by-products in various directions will continue to be increasingly demanded, cement quality design methods that can control the effects of trace components are strong even when large amounts of industrial by-products are used. 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 quick lime, and harmful heavy metals such as hexavalent chromium are eluted without reducing the strength of the improved treated soil. A ground improvement material to which a remarkably suppressing function is added is disclosed. Specifically, Patent Document 1 discloses a ground improvement material obtained by loading calcium polysulfide on quick lime, which is an immobilizing material, and then mixing it with a water-related component composed of cement and gypsum.
Patent Document 2, as a fixing agent for use in the containment of heavy metals contained etc. 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.
However, these Patent Documents 1 and 2 both relate to a heavy metal fixing agent and a ground improvement material for containment of toxic heavy metals, and have absolutely no effect on retaining the fluidity of cement concrete and reducing self-shrinkage. There is no description.

Japanese Unexamined Patent Publication No. 2001-342461 Japanese Unexamined Patent Publication No. 2004-33839

The present invention provides a cement additive and a cement composition that exhibit a good fluidity retention effect and self-shrinkage reduction effect of cement concrete, and in addition, exhibit a hexavalent chromium reducing action having both immediate effect and sustainability. The purpose is to provide.

The 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 preferably the redox potential (ORP). It has been found that a cement additive containing a specific lime-sulfur mixture having a -450 mv or less and a cement composition to which the cement additive is added achieve the above-mentioned object.
The present invention is based on the above findings and is summarized as follows.
(1) A cement additive comprising a lime-sulfur mixture having a pH of 10 or more and excellent in maintaining fluidity and reducing self-shrinkage of cement concrete. (2) The cement additive according to the above (1), wherein the lime-sulfur mixture has an oxidation-reduction potential (ORP) of −450 mV or less. (3) Lime-sulfur mixture containing 5 to 10% of Ca in terms of T-Ca, 15 to 30% of S in terms of TS and Mg being 0.5 to 2.0% in terms of MgO The cement additive as described in (1) or (2) above. (4) A cement composition containing cement and the cement additive according to any one of (1) to (3) above. (5) The cement composition according to (4), wherein the cement additive is contained in an amount of 0.005 to 1 part with respect to 100 parts of cement. (6) The cement composition according to (4) or (5), wherein the cement contains Portland cement.

By using the cement additive of the present invention, good fluidity retention effect and self-shrinkage reduction effect of cement concrete can be obtained, and in addition, it exhibits the reducing action of hexavalent chromium having both immediate effect and sustainability, etc. The effect is obtained.

Hereinafter, the present invention will be described in detail. In the present invention, “parts” and “percent (%)” are shown on a mass basis 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), and contains quick lime, sulfur and water. It is a yellow-brown liquid that is a solid-liquid separation obtained by reacting these in an autoclave as raw materials. Conventionally, lime-sulfur mixtures are mainly known as fruit tree pesticides.
The lime-sulfur mixture has various composition ratios and characteristics depending on the ratio of use of raw lime, sulfur, and water, which are raw materials, and the reaction conditions in the autoclave. That is, the ratio of quick lime and sulfur: water as raw materials is preferably 1.2 to 3 parts of sulfur and 2.5 to 5 parts of water with respect to 1 part of quick lime, particularly preferably 1.5 to 2 parts of sulfur and 3 to 4 parts of water are used. The reaction is preferably carried out under a pressurized condition of 3.5 to 10 atmospheres, preferably 140 to 180 ° C. The reaction is preferably carried out in an autoclave.

It is important that the lime-sulfur mixture of the present invention has an alkaline region having a pH of 8.0 or higher. If the pH is less than 8.0, 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. Especially, 9.0 or more are preferable and, as for pH of a lime sulfur mixture, 10.0 or more are especially preferable. Although the one where the pH of a lime sulfur mixture is larger is preferable, 13.0 or less is preferable from a viewpoint on the safety of operation.

Further, the redox potential (ORP) of the lime-sulfur mixture of the present invention is preferably −450 mV or less. If the ORP is not in the range of −450 mv or less, 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. Among these, ORP is preferably −500 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.

In the lime-sulfur mixture of the present invention, Ca is preferably contained in an amount of 5 to 10% in terms of T-Ca, S is preferably contained in an amount of 15 to 30% in terms of TS, and Mg is preferably in terms of MgO. Is contained in an amount of 0.5 to 2.0%.
The Ca content here is determined by JIS5202 “Cement Chemical Analysis Method”, the S content is determined by a carbon / sulfur analysis system, and the MgO content is determined by ICP emission spectroscopic analysis.

If the Ca content is less than 5%, it becomes difficult to have an alkaline region, while if it exceeds 10%, the pH may exceed 13. Among these, the Ca content is more preferably 6% or more, particularly preferably 7% or more, and more preferably 9% or less, and particularly preferably 8% or less.
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. Among these, the S content is more preferably 17% or more, particularly preferably 20% or more, and more preferably 25% or less, and particularly preferably 28% or less.
When the Mg content is less than 0.5%, the fluidity retention effect, the hexavalent chromium reduction effect, and the self-shrinkage reduction effect may not be sufficiently obtained. Among these, the Mg content is more preferably 0.7% or more, and particularly preferably 1.0% or more. A higher Mg content is preferable, but 2.0% or less is preferable because it may be replaced with Ca in the cement hydrate to promote alteration.

As the cement used in the present invention, various portland cements such as normal, early strength, ultra-early strength, low heat, medium heat, and the like, 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.

The amount of the cement additive of the present invention used in cement concrete is not particularly limited, but is usually preferably 0.005 to 1 part, more preferably 0.05 to 0.5 part with respect to 100 parts of cement. preferable. When the amount of the cement additive used is small, 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.
In the present invention, cement and a cement additive are blended to form a cement composition.

The form of the lime-sulfur mixture contained in the cement additive of the present invention is not particularly limited, and any form may be used as long as the effect of the present invention is not impaired. It is possible to use the liquid as it is or to use a dried liquid.

In the cement composition of the present invention, in addition to cement and cement additives, fine aggregates such as sand and coarse aggregates such as gravel, as well as expansion materials, rapid hardening materials, water reducing agents, AE water reducing agents, high performance Water reducing agent, high performance AE water reducing agent, antifoaming agent, thickener, conventional rust preventive agent, antifreeze agent, shrinkage reducing agent, setting modifier, clay minerals such as bentonite, anion exchanger such as hydrotalcite, blast furnace One or two or more of a group consisting of admixtures such as slag such as granulated slag fine powder and blast furnace slow-cooled slag fine powder, limestone fine powder, etc. are used in a range that does not substantially impair the object of the present invention. It is possible.

The cement composition of the present invention may be partially or wholly mixed with the above components used therein. Any existing apparatus can be used as a mixing apparatus for mixing various components. For example, a tilting cylinder 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.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

"Experiment 1"
Cement additives A to G composed of various lime-sulfur mixtures shown below were used. This cement additive was used in an amount of 0.1 part per 100 parts of cement in a cement composition comprising cement and cement additive.
The cement additives A to E were mixed by spraying the cement additives onto the cement using a hand spray (for spray application, made of polycarbonate, manual type, volume 2 liters), and were previously blended with the cement.
The cement additive F is sprayed on a normal Portland cement clinker using a hand spray (for spray coating, made of polycarbonate, manually operated, 2 liters in volume), and then gypsum (4 parts divided with respect to the cement clinker). Cement (Brain specific surface area 3300 cm ² / g) was prepared by pulverization and mixing.

Next, the unit cement composition amount is 500 kg / m ³ , the water / cement composition ratio is 33%, the fine aggregate volume ratio (s / a) to the total aggregate volume is 46%, the air amount is 4.5%, and the slump. 21 cm of concrete was prepared. At this time, 1.4 parts of the high performance water reducing agent was added to 100 parts of the cement composition.
This concrete was confirmed for the change of slump with time, self-shrinkage, and reduction effect of hexavalent chromium. The results are also shown in Table 1.

<Materials used>
Cement: Ordinary Portland cement, Blaine specific surface area 3210 cm ² / g, a commercially available product (Denka Co., Ltd., ordinary Portland cement) is used.
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 degrees in kiln)
Gypsum: 2 water gypsum, commercial product

Cement additive A: Lime sulfur mixture, pH 11.0, ORP-540 mv, MgO content 1.0%, T-Ca content 13%, TS content 26%.
Cement additive B: Lime sulfur mixture, pH 10.5, ORP-500 mv, MgO content 1.0%, T-Ca content 12%, TS content 24%.
Cement additive C: Lime sulfur mixture, pH 10.0, ORP-450 mV, MgO content 1.0%, T-Ca content 11%, TS content 22%.
Cement additive D: Lime sulfur mixture, pH 10.5, ORP-500 mv, MgO content 0.5%. T-Ca content 10%, TS content 21%.
Cement additive E: Lime sulfur mixture, pH 10.5, ORP-500mv, MgO content 2.0%, T-Ca content 8%, TS content 19%.
Cement additive F: Lime sulfur mixture, pH 11.0, ORP-540 mv, MgO content 1.0%, T-Ca content 13%, TS content 26%.
Cement additive G: A mixture obtained by mixing 25 parts of lime sulfur mixture with a ball mill with 100 parts of quicklime (Blaine specific surface area 3460 cm ² / g).
The above cement additives A to F are used in various reaction ratios of quick lime, sulfur and water, and reacted in an autoclave at a pressure of 5 atm and 150 ° C., respectively. Is a lime-sulfur mixture consisting of a liquid material obtained by separating a solid material like a filter press.
The cement additive G is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-342461), and the lime-sulfur mixture used there was not solid-liquid separated.

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 2651 F).

<Test method>
Change in slump with time: Slump was measured according to JIS A 1150, and the amount of change in the measured value 30 minutes and 90 minutes after the 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 the fresh concrete was determined by adding hydrochloric acid to pure water from a sample obtained by filtering the supernatant obtained from bleeding water or centrifugation after 30 minutes of kneading, and a hydrogen ion concentration index of 5.8 or more. It was mixed with a solution having a volume ratio of 3 or less at a ratio of 10% by weight, and measured by ICP emission spectroscopic analysis according to JIS K0102.
The amount of elution from the hardened concrete was measured in accordance with the Environmental Agency Notification No. 46 method by crushing hardened concrete after 28 days of age and using a sample 2 mm below. However, the residual concentration of hexavalent chromium was measured by ICP emission spectroscopic analysis according to JIS K0102.

ND: Not detected

From Table 1, when the cement admixture G (Experiment No. 1-8) in which a conventionally known calcium polysulfide (lime sulfur mixture) is supported on quicklime powder by using the cement additive of the present invention is used. Compared with, the fluidity retention effect is excellent, the reduction effect of hexavalent chromium is both immediate and sustainable, and self-shrinkage is also reduced. It turns out that a more remarkable effect is acquired by using it (experiment No. 1-7).

"Experimental example 2"
The same procedure as in Experimental Example 1 was conducted except that the cement additive A was used and the amount of the cement additive used was changed as shown in Table 2. The results are shown in Table 2.

ND: Not detected

From Table 2, by using an appropriate amount of the cement additive of the present invention, a fluidity retention effect can be obtained, a reduction effect of hexavalent chromium can be achieved both with immediate effect and sustainability, and self-shrinkage is also reduced. You can see that.

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, it exhibits the reducing action of hexavalent chromium that has both immediate effect and sustainability. It is suitable for a wide range of applications mainly in the civil engineering and construction industries.

Claims

A cement additive comprising a lime-sulfur mixture having a pH of 10 or more and excellent in maintaining fluidity and reducing self-shrinkage of cement concrete.
The cement additive according to claim 1, wherein the lime-sulfur mixture has an oxidation-reduction potential (ORP) of -450 mV or less.
The lime-sulfur mixture contains 5-10% of Ca in terms of T-Ca, 15-30% of S in terms of TS, and 0.5-2.0% in terms of Mg, The cement additive according to claim 1 or 2.
A cement composition comprising cement and the cement additive according to any one of claims 1 to 3.
The cement composition according to claim 4, wherein the cement additive is contained in an amount of 0.005 to 1 part per 100 parts of cement.
The cement composition according to claim 4 or 5, wherein the cement contains Portland cement.