JP2006143501A - Aggregate, method of manufacturing the same, and mortar/concrete for spraying - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily obtain aggregate capable of advancing an alkali aggregate reaction without obstructing the hardening performance even in use of mortar/concrete rich in the unit quantity of cement such as mortar/concrete for spraying making a slope or the like having large inclination application objects and the mortar/concrete having properties suitable for the spray application to stabilize the inclined surface of the slope or the like without degrading for a long period of time. <P>SOLUTION: The aggregate is porous aggregate having opened void wherein lithium nitrite is incorporated. The mortar/concrete for spraying contains cement and the porous lightweight aggregate having the opened void in which lithium nitrite is contained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to mortar / concrete having a large amount of unit cement, such as a rock slope protection spray, and more particularly to an aggregate suitable for such spray mortar / concrete.

In order to prevent erosion and weathering of slopes such as rock slopes, the slopes can be stabilized by covering the slopes with structures such as concrete blocks and vegetation, and installing drainage channels, roads, and earth retaining structures. ing. Spraying mortar / concrete is used for the method of stabilizing the slope with a relatively large slope, but spraying mortar / concrete requires early strength development. The cement content is much higher than that used in Moreover, in order to ensure the stability of the spray deposits until it hardens after construction, it is advantageous to use a lightweight aggregate as the aggregate in the mortar / concrete for spraying. Since it is difficult to obtain natural lightweight aggregates that are light in weight aggregates, artificial lightweight aggregates that are fired and manufactured from silicate-based expansive minerals or the like are the mainstream. On the other hand, since such aggregate contains a relatively large amount of siliceous material, it reacts with soluble alkali derived from cement in the presence of water (alkali aggregate reaction) to produce a highly expandable alkali silicate gel. . When the gel is generated, expansion cracks are likely to occur in the cured mortar / concrete, and deterioration of the mortar / concrete occurs, such as a decrease in strength due to the occurrence of cracks and progress of neutralization from cracks. In particular, mortar / concrete having a high cement content also has a high concentration of soluble alkali. Therefore, when used in combination with a high siliceous aggregate as described above, the alkali aggregate reaction increases and the deterioration of the mortar / concrete tends to proceed. As a measure to prevent alkali aggregate reaction of mortar and concrete, (a) avoid the use of reactive aggregate rich in siliceous or use low alkaline special cement. (B) A lithium salt such as lithium nitrite is mixed with mortar / concrete. (For example, refer to Patent Document 1.) (c) Lithium salt is injected or impregnated into a hardened mortar / concrete (for example, refer to Patent Document 2) (d) Lithium-based glass such as calcium lithium aluminosilicate is used as mortar / concrete. (For example, refer to Patent Document 3) and the like are known. However, in the measure (a), the low-silica lightweight aggregate is practically unavailable, and the low-alkaline special cement is not very expensive and can be procured freely. Is not practical. In the measure (b), mortar concrete with a large amount of unit cement requires the addition of a large amount of lithium salt in order to sufficiently suppress the alkali-aggregate reaction, but the excess lithium salt is initially present when Portland cement is used. Depending on the situation, it is not always suitable for spray materials where instantaneous setting is essential. In addition, the measure (c) is not suitable for a wide range of construction cured products, such as sprayed concrete with a slope, and in the measure (d), the raw material preparation is vitrified at a high temperature. Furthermore, it has to be pulverized into a form suitable for mixing, and there still remains a problem such as requiring a great deal of labor and equipment for producing the same.
JP-A 61-256951 JP 2002-173380 A JP 2004-196666 A

  The present invention is intended to solve the above problems, and even when used for mortar / concrete having a large amount of unit cement, such as spraying mortar / concrete having a slope with a large slope, etc. Mortar / concrete with properties suitable for spraying to stabilize slopes such as slopes without easily degrading the aggregate reaction and without deteriorating over a long period of time The issue is to provide

  In order to solve the above-mentioned problems, the present inventors used a porous aggregate rich in open voids in the aggregate, and filled the voids with lithium nitrite, thereby making this a high silica with a large amount of unit cement. Alkaline aggregate reaction can be sufficiently suppressed over a long period of time without affecting the curability even when used in mortar / concrete contents, and such aggregates can be immersed in an aqueous lithium nitrate solution. The present invention was completed because it was easily obtained by the method, and the shotcrete using this kind of lightweight aggregate was excellent in both construction properties and durability after construction.

  That is, this invention is the mortar concrete for spraying represented by the aggregate represented by following (1)-(2), the manufacturing method of the aggregate represented by (3), and also (4)-(5). (1) A porous aggregate having an open void, wherein the void contains lithium nitrite. (2) The aggregate according to (1), wherein the water absorption is 5 to 30%. (3) A method for producing an aggregate, comprising dipping an aggregate having an open gap in a lithium nitrite solution. (4) Spraying mortar / concrete comprising cement and porous lightweight aggregate having open voids and lithium nitrite contained in the voids. (5) Porosity in which the amount of lithium ions contained in the open void tone of the porous lightweight aggregate is 100 to 120% of the ion content of alkali metals and alkaline earth metals excluding lithium in the mortar concrete for spraying The spraying mortar / concrete as described in (4) above, using a lightweight aggregate.

  According to the present invention, it is possible to sufficiently prevent the alkali aggregate reaction that starts from the vicinity of the aggregate surface without affecting the curability of the mortar and concrete for spraying, and it is difficult for deterioration to proceed over a long period of time. A strong spray layer can be formed. In addition, since the specific gravity of the mortar and concrete for spraying of the present invention is low, the unit volume mass is small, and it is easy to obtain high adhesion even on slopes and slopes with relatively steep slopes. It is also excellent in suppressing rebound and spraying off.

  The aggregate of the present invention is one in which lithium nitrite is contained in the void of the porous aggregate having an open void. The aggregate containing lithium nitrite is not limited as long as it has open pores, and may contain a large amount of silica. In addition, the aggregate type may be natural aggregate such as volcanic gravel, refined by-product aggregate such as slag, artificial aggregate obtained by firing expanded shale or slate, etc. A porous artificial lightweight aggregate as a raw material is suitable. The opening void amount of the porous aggregate is not particularly limited, but a water absorption rate of 5 to 30% is preferable because it can include lithium nitrite sufficient to suppress the alkali aggregate reaction, and more preferably a water absorption rate of 10 to 10%. It shall be 25%. It is difficult to secure lithium nitrite that can suppress alkali-aggregate reaction even with mortar and concrete with a common unit cement amount for porous aggregates with a water absorption rate of less than 5%, and with aggregates exceeding 30% It becomes brittle in strength and is not suitable for use in spraying construction to stabilize slopes and walls. Furthermore, when the lithium nitrite is efficiently supported in the voids and the supported lithium ions diffuse to prevent the alkali aggregate reaction due to the presence of moisture, the diameter of the open voids on the aggregate surface is about 10 nm to It is preferably 100 μm.

  In addition, 100% of the open space of the porous aggregate is not necessarily occupied by lithium nitrite, and the lithium ion content of lithium nitrite contained in the space excludes lithium in mortar and concrete. It is desirable that the total amount of ions of alkali metal and alkaline earth metal is approximately equal to or about 120% of the total amount of ions of alkali metal and alkaline earth metal. If the amount of lithium ions is larger than this, when it is used in combination with Portland cement or the like, predetermined workability may not be ensured. Moreover, when the amount of lithium ions is less than the total amount of ions of alkali metal and alkaline earth metal excluding lithium in mortar and concrete, the alkali aggregate reaction may not be sufficiently suppressed. Here, the total amount of alkali metal ions and alkaline earth metal ions excluding lithium refers to alkali metal ions and alkaline earth metal ions excluding lithium ions in cement, aggregate and other admixtures constituting the mortar and concrete. Is the total amount.

  In the method for producing an aggregate of the present invention, the porous aggregate may be immersed in an aqueous solution of lithium nitrite. The immersion time is about 24 hours to 1 week. For dipping, the aggregate may be simply left in the liquid at room temperature or in the vicinity thereof. However, in order to infiltrate the lithium nitrite aqueous solution to the deep part of the opening gap, for example, a reduced pressure water supply method by vacuum treatment or 150 ° C. or less. This can be dealt with by performing the hot water absorption method. Commercially available reagents can be used as lithium nitrite to be used, but other materials may be used. In addition, the concentration of lithium nitrite in the aqueous solution in which the porous aggregate is immersed is such that at least the lithium ion content of lithium nitrite contained in the aggregate voids excludes alkali metal ions and alkaline earth metals excluding lithium in mortar and concrete The concentration should be such that an equivalent or more than the total amount of ions can be easily obtained. It is desirable to wipe off the liquid adhering to the surface of the aggregate after immersion, for example, with a dehydrator or the like, and to make it dry if possible.

Moreover, the mortar concrete for spraying of this invention contains the porous lightweight aggregate which has the opening space | gap containing the cement and the said lithium nitrite. As the lightweight aggregate, an aggregate having a specific gravity of about 2.0 or less is applicable. The cement to be used is usually a variety of portland cements such as early strength, ultra-early strength, low heat, moderate heat, etc., and also mixed cement, white cement, etc. mixed with various portland cements such as fly ash, blast furnace slag or limestone powder. Special cements such as eco cement may be used. The mortar concrete for spraying of the present invention is preferably a mortar having a unit cement amount of 400 to 450 kg / m ³ or a concrete having a unit cement amount of 300 to 400 kg / m ³ , and cement (C) and lithium nitrite are used. The blended weight ratio of the included porous lightweight aggregate (fine aggregate; S, coarse aggregate; G) is not limited, but is generally C: S = 1: 4 for mortar and generally C: for concrete. G: S = 1: 1: 4 is recommended. Unit amount cement in 400 Kg / m ³ under mortar and 300 Kg / m ³ under the concrete may become insufficient strength as a spray, mortar or the unit amount of cement weight unit cement exceeds 450 kg / m ³ is 400 Kg In concrete exceeding / m ³ , the viscosity becomes high and the pumpability may be reduced.

  The mortar concrete for spraying of the present invention can contain components other than the porous lightweight aggregate having an open space containing cement and lithium nitrite as described above, as long as the effect of the present invention is not lost. For example, water-reducing agent, high-performance water-reducing agent, high-performance AE water-reducing agent, fluidizing agent, setting modifier, fiber, thickener, swelling material, pigment, white-fade inhibitor, waterproofing agent, polymer resin for cement, water-repellent agent In addition, one or two or more rapid setting agents may be included. The amount of blended water is preferably 40 to 60 parts by weight with respect to 100 parts by weight of cement for both mortar and concrete. If it is less than 40 parts by weight, it is difficult to obtain a fluid state suitable for spraying unless water reducing agents are used in combination, and workability is lowered. Moreover, when it exceeds 60 weight part, intensity | strength expression will fall and it is unsuitable for spraying.

  The method for producing the mortar / concrete for spraying according to the present invention is not particularly limited, but as a preferred example, aggregate, cement, water containing lithium nitrite produced as described above, and an admixture as necessary A predetermined amount of the material may be put into a pressure tank type spraying device all at once and kneaded. Also, the spraying method for spraying mortar / concrete of the present invention is not particularly limited, and examples thereof include a wet method in which the kneaded material is pneumatically fed to a spray nozzle through a single transport pipe.

[Adjustment of aggregate]
Porous natural and artificial lightweight fine aggregates were immersed in an aqueous solution having a concentration of 10% by weight obtained by diluting lithium nitrite (commercial reagent) with distilled water at a temperature of 20 ° C. for 24 hours. Moreover, the porous artificial lightweight coarse aggregate was immersed in an aqueous solution having a concentration of 40% by weight obtained by diluting lithium nitrite (commercial reagent) with distilled water at a temperature of 20 ° C. for 24 hours. During the immersion, the aggregate was not moved and left in the liquid. After 24 hours, the aggregate was taken out from the lithium nitrite aqueous solution, the excess liquid adhering to the aggregate surface was wiped off with a cloth, and the porous natural solution containing 10% by weight lithium nitrite aqueous solution shown in Table 1 in the voids Fine aggregate (S1), porous natural fine aggregate (S2) containing 10% by weight lithium nitrite aqueous solution in the void, and porous coarse aggregate (G1) containing 40% by weight lithium nitrite aqueous solution in the void ) In addition, Table 1 also shows the value of the content of lithium nitrite ions in the aggregate voids by immersion calculated from the amount of change in aggregate weight before and after immersion. For comparison, a fine aggregate made of non-porous river sand was prepared by performing a similar immersion treatment with a 10% by weight aqueous lithium nitrite solution (S3), and further subjected to an immersion treatment with an aqueous lithium nitrite solution. Details are given in Table 1 along with the non-porous natural fine aggregate that was not found in the river sand (S4).

[Manufacture of spraying mortar]
Using the fine aggregates S1 to S3 shown in Table 1 immersed in lithium nitrite, three types of fresh mortars M1 to M3 for spraying were prepared for each fine aggregate to be used by the following composition and method. Fine aggregate 100.0Kg, ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) 25.0Kg and tap water 12.5Kg were weighed and put into a mixer of a mixer built-in sprayer (manufactured by Sanwa Sangyo Co., Ltd.). . After the entire amount was added, the mixture was kneaded for 60 seconds to obtain fresh mortar.

  For reference, 100.0 kg of fine aggregate S4 represented in Table 1 not immersed in lithium nitrite, 25.0 kg of ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.), and 12.5 kg of tap water are weighed. This was put all at once into a mixer of a mixer built-in sprayer (manufactured by Sanwa Sangyo Co., Ltd.) and kneaded for 60 seconds to produce fresh mortar M4. Further, 100.0 kg of fine aggregate S4 represented in Table 1 not immersed in lithium nitrite, 25.0 kg of ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.), 1250 g of lithium nitrite powder (purity 99%; commercially available reagent) And 12.5 kg of tap water was weighed, and this was put all at once into a mixer of a mixer built-in sprayer (manufactured by Sanwa Sangyo Co., Ltd.) to prepare fresh mortar M5 kneaded for 60 seconds.

[Blowing of spraying mortar and alkali-aggregate reaction test of sprayed hardened material]
Fresh mortars (M1 to M5) prepared as described above were pneumatically fed to the spray nozzles with a compressor, respectively, and placed on a wooden formwork with a bottom of 50 cm in length, 80 cm in width, 20 cm in depth and installed vertically on the horizontal ground. Were sprayed uniformly at a distance. The presence or absence of rebound occurrence at the time of spraying was examined visually, but only a very small amount of rebound was observed in any mortar. After spraying, it was left to stand for 7 days, and the presence or absence of peeling of the sprayed material during that period was visually examined. Next, the cured sprayed material after 7 days was cut out with a concrete cutter so that a 10 × 10 × 40 cm rectangular parallelepiped specimen was obtained. Three test specimens were prepared for one type of mortar. The prepared cured mortar test specimens were immersed in a saturated aqueous sodium chloride solution and continuously cured at 50 ± 1 ° C. for 7, 30, 90, and 180 days using a thermostatic bath. The change in length of the specimen was examined at a predetermined age, and the amount of expansion (average value of three specimens for each type) was calculated. From this result, it was determined that an expansion amount of about 0.02% or less and substantially no expansion was determined to be “no” for the alkali aggregate reaction, and the other was determined to be “having” for the alkali aggregate reaction. The above results are shown in Table 2.

[Manufacture of spray concrete]
100.0 kg of porous fine aggregate S1 immersed in lithium nitrite, 25.0 kg of porous coarse aggregate G1 immersed in lithium nitrite, 25.0 kg of ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) And 12.5 kg of tap water was weighed and put into a mixer of a mixer built-in type sprayer (manufactured by Sanwa Sangyo Co., Ltd.). After the entire amount was added, the mixture was kneaded for 60 seconds to produce fresh concrete for spraying (C1).

[Blowing of sprayed concrete and alkali aggregate reaction test of sprayed hardened material]
Fresh concrete for spraying (C1) is pneumatically fed to the spray nozzle by a compressor, and is evenly spaced at a distance of 1.5 m on a wooden formwork that is 50 cm long, 80 cm wide, 20 cm deep and has a bottom surface installed vertically on the horizontal ground. Sprayed. After spraying, it was allowed to stand for 7 days, and the presence or absence of peeling of the sprayed material during that period was examined visually. The cured spray after 7 days of standing was cut out with a concrete cutter so that a 10 × 10 × 40 cm rectangular parallelepiped specimen was obtained. Three test specimens were prepared for one type of concrete. The produced hardened concrete specimens were immersed in a saturated aqueous solution of sodium chloride, and were continuously cured at 50 ± 1 ° C. for 7, 30, 90, and 180 days using a thermostatic bath. The change in length of the test specimen was examined at a predetermined age, and the amount of expansion was calculated. From this result, it was determined that an expansion amount of about 0.02% or less and substantially no expansion was determined to be “no” for the alkali aggregate reaction, and the other was determined to be “having” for the alkali aggregate reaction. The above results are shown in Table 3.

  From Table 2, since the mortar for spraying using the aggregate of the present invention (M1 and M2) did not show any expansion associated with the alkali aggregate reaction, the deterioration progressed for a long time after spraying. I find it difficult. On the other hand, since non-porous fine aggregates can hardly be impregnated with lithium nitrite, spray aggregate mortar (M3) using this has caused an alkali aggregate reaction. Moreover, the spraying mortar (M4) based on the prior art in which lithium nitrite is mixed and added has a higher expansion amount than the spraying mortar concrete (M1, M2 and C1) according to the present invention, and has the effect of suppressing the alkali aggregate reaction. This is lower, but this is because the reactive component in the aggregate (mainly silica) that progresses from the vicinity of the aggregate surface compared to the case where lithium nitrite is supported in the aggregate voids compared to the case where it is added. It can be seen that the alkali-aggregate reaction between the cement and the alkali derived from cement is efficiently suppressed, and the suppression effect is high.

Claims (5)

A porous aggregate having an open void, wherein the void contains lithium nitrite. The aggregate according to claim 1, wherein the water absorption is 5 to 30%. A method for producing an aggregate, comprising immersing a porous aggregate having an open space in a lithium nitrite solution. A mortar-concrete for spraying comprising a cement and a porous lightweight aggregate having an open void and lithium nitrite contained in the void. Porous lightweight aggregate in which the amount of lithium ions contained in the open void tone of the porous lightweight aggregate is 100 to 120% of the ion content of alkali metal and alkaline earth metal excluding lithium in the mortar concrete for spraying The mortar concrete for spraying according to claim 4, wherein