JPH0512294B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an alkali aggregate reactivity test method and specimen thereof, and particularly to a test method and specimen thereof for simply and quickly determining the alkali silica reactivity of aggregate. [Prior Art] Alkaline aggregate reaction is one of the causes of early deterioration of concrete structures. This is a reaction between the silica potentially contained in the aggregate and the alkali contained in the concrete, resulting in a product that absorbs water and expands, causing cracks in the concrete. This alkali aggregate reaction test method uses a mortar bar and is widely used. This method uses alkaline additives (eg, sodium hydroxide, NaOH) to adjust the alkaline content (R ₂ O) of the base cement. Through these adjustments, a mortar bar as a specimen is prepared from a combination of aggregate, cement, NaOH, and tap water. The length change of this mortar bar is measured, and if the expansion rate (elongation rate) after 6 months is less than 0.10%, it is determined to be harmless, and if it is 0.10% or more, it is determined to be harmful. Regarding the alkali aggregate reaction test method,
There are regulations such as JISA 5308 (Annex 8) and ASTM C-227. [Problems to be Solved by the Invention] However, the above method is limited to low-alkali cement in which the alkali content (R ₂ O) of the cement used is 0.6% or less, and the R ₂ O of the cement is reduced by adding NaOH to this. There was a problem in that it had to be adjusted to 1.2%, and there was also a problem in that it took a long time to make a determination. The purpose of the present invention was to solve the above-mentioned problems, and it is an object of the present invention to provide a simple alkali aggregate reaction test method and a specimen thereof, which allows for early determination. [Means for Solving the Problems] In order to achieve the above object, the present invention provides an alkali-silica reaction system that determines the alkali-silica reactivity potentially present in aggregate by measuring changes in the length of mortar bars. The present invention provides an aggregate reaction test method, characterized in that seawater is used as mixing water for kneading the aggregate and cement to create the mortar bar. Further, the specimen of the present invention is characterized in that, in the specimen for the alkali aggregate reaction test, seawater is used as mixing water for mixing the aggregate and cement. And these cements have an alkali content of 0.6
% (low alkalinity) or more than 0.6% (high alkalinity). Further, as the seawater, not only natural seawater but also artificial or standard seawater can be used. [Operation] According to the above configuration, when creating a specimen,
By using readily available seawater as mixing water, NaOH (alkaline additive) for adjusting R ₂ O is not required, and adjusting the R ₂ O of cement by adding NaOH is also unnecessary. Furthermore, there is no need to measure the R ₂ O of cement, and the test can be performed regardless of whether it is a low-alkali or high-alkali cement. [Example] Examples of the present invention will be described below with reference to tables and drawings. Regarding the six types of aggregates G ₁ to G ₆ shown in Table 1 below, the same aggregate was used in the case of seawater mixing in which the present invention was implemented, and the case of cement mixing with tap water and an alkaline additive (NaOH). The elongation rate of the mortar bar was compared for the conventional case in which R ₂ O was adjusted to 1.2%. In addition, aggregates G ₁ and G ₂ are aggregates having alkali silica reactivity, and G ₃ to _{G 6} are non-reactive aggregates.

【table】

[Table] The five types of cement used were C ₁ to C ₅ as shown in Table 2 below, with C ₁ to C ₃ being low alkali, C ₄ ,
_C5 is a high alkaline cement.

[Table] However, R ₂ O (%) = Na ₂ O (%) + 0.658K ₂ O (%)
When using conventional tap water and adding NaOH as water for mixing cement and aggregate,
The formulation in the case of using seawater according to this example is shown in Table 3 below. In this example, natural seawater collected in Sentai Taipei and commercially available artificial seawater are used as the seawater.

[Table] _Each aggregate (G Table 4 shows the combinations of cement ( _C1 to _C5 ) and cement ( _C1 to _C5 ). For aggregates G ₁ and G ₂ , tests were also conducted using high alkali cements C ₄ and C ₅ .

[Table] The components of the seawater used in this example are shown in Table 5.

〔Effect of the invention〕

As described above, according to the test method or specimen of the present invention, by using seawater as mixing water, it is possible to carry out an alkaline aggregate reaction test that is simple and allows for early determination.

[Brief explanation of the drawing]

FIGS. 1 to 6 are graphs showing a comparison of elongation rates between an example of the present invention and a conventional example, and each representing a change in elongation rate over time for each type of aggregate used. 2... Growth rate of conventional example with R ₂ O = 1.2% adjustment, 4
...Natural seawater kneading (low alkali) elongation rate, 6...
Natural seawater kneading (high alkali) elongation rate, 8...Artificial seawater kneading (low alkali) elongation rate, 10...Artificial seawater kneading (high alkali) elongation rate, 12...Limit elongation rate.

Claims (1)

[Claims] 1. In an alkali aggregate reaction test method for determining the alkali silica reactivity potentially present in aggregate by measuring changes in the length of a mortar bar, the aggregate and cement are kneaded together. An alkaline aggregate reaction test method characterized in that seawater is used as mixing water for preparing the mortar bar. 2. The method according to claim 1, wherein the cement has an alkali content of 0.6% or less. 3. The method according to claim 1, wherein the cement has an alkali content of more than 0.6%. 4. The method according to claim 1, wherein the seawater is natural seawater. 5. The method according to claim 1, wherein the seawater is artificial seawater. 6. The method according to claim 1, wherein the seawater is standard seawater. 7. In a specimen for an alkali aggregate reaction test, which is prepared by mixing aggregate and cement and determining the alkali silica reactivity potentially present in the aggregate, as mixing water for mixing the aggregate and cement. A specimen for an alkaline aggregate reaction test characterized by the use of seawater. 8. The specimen according to claim 7, wherein the cement has an alkali content of 0.6% or less. 9. The specimen according to claim 7, wherein the cement has an alkali content exceeding 0.6%. 10. The specimen according to claim 7, wherein the seawater is natural seawater. 11. The specimen according to claim 7, wherein the seawater is artificial seawater. 12. The specimen according to claim 7, wherein the seawater is standard seawater.