WO2017085688A1

WO2017085688A1 - Cementing material formulation for obtaining mortars with reduced alkali-silica reaction

Info

Publication number: WO2017085688A1
Application number: PCT/IB2016/056974
Authority: WO
Inventors: Hector Leonardo ROMERO MENDOZA
Original assignee: Cementos Argos S.A.
Priority date: 2015-11-19
Filing date: 2016-11-18
Publication date: 2017-05-26

Abstract

The invention relates to a cementing material formulation for obtaining mortars with reduced alkali-silica reaction that comprise aggregates such as sea sands and basaltic sands, the formulation helping to reduce the expansion of concretes in order to prevent the deterioration thereof and increase the durability of same.

Description

A FORMATION OF CEMENTING MATERIAL FOR THE OBTAINING OF MORTARS WITH REDUCED ALKAL-SILICON REACTION

STATE OF THE ART OF THE INVENTION

Field of the Invention

The present invention relates to the field of the cement industry, and more particularly it relates to a formulation of cementitious material that includes additions and / or supplementary cementing materials, which reduces the alkali-silica reaction in mortars made with reactive sands for purposes. to reduce the expansion of concrete and avoid premature deterioration.

Description of the prior art

To better understand the object and scope of the present invention, it is convenient to describe the current state of the art in reference to the mortars and the inconveniences they present.

It is well known in the art field that the alkali-silica reaction affects the durability of hydraulic concrete structures, causing premature deterioration in concrete made with reactive stone aggregates. The mechanism of damage to the concrete starts when the cement alkalis react with the silica of the aggregates, producing a gel that expands in the presence of moisture, generating an increase in the internal pressure of the cementitious matrix and causing cracking of the concrete.

Furthermore, it is known that siliceous materials are highly reactive and if they are used as aggregates for concrete, for example gravel or sand, they could have negative effects in combination with a cement with a high alkali content. For these reasons, the reactions that occur are located on the surface of the reactive aggregates, are punctual and of great intensity, exceeding the resistant capacity of the concrete and causing its deterioration.

In turn, in the siliceous materials, being finely pulverized and evenly distributed in the cement and concrete in the form of pozzolans, the effect generated is contrary because the reaction of the alkalis, like any other chemical reaction, occurs preferably in the active materials of greater specific surface, that is, with greater finesse. Consequently, the expansive reactions develop in an infinite plurality of points evenly distributed in the mass, so that the intensity of the reaction at each point is very weak and the concrete can absorb the stresses caused without deterioration.

Although, a variety of methods and formulations have been developed to improve the durability of concrete, which have shown good results in practice, the disadvantage of the alkali-silica reaction still exists.

Under the current state of the art available for concrete, it would be very convenient to have a new formulation that reduces the alkali-silica reaction to avoid the subsequent expansion of the concrete and its deterioration, and which also allows it to increase its durability.

BRIEF DESCRIPTION OF THE INVENTION

It is therefore ur. object of the present invention to provide a new formulation of cementitious material for obtaining mortars with reduced alkali-silica reaction.

It is yet another object of the present invention to provide a formulation of cementitious material that improves the durability of the concretes.

It is still another object of the present invention to provide a formulation of cementitious material for obtaining mortars with reduced alkali-silica reaction, being mortars comprising fine aggregates such as marine sands and basaltic sands, where the formulation It comprises between 70% and 80% of Portland cement, between 10% and 25% of fly ash, and between 5% and 35% of pozzolana, where the pozzolana is ground in a granulometric degree that passes through a 325 mesh.

It is also another object of the present invention to provide a mortar comprising e) a fine aggregate comprising: basaltic sand, and b) a cementitious material formulation comprising: between 70% and 80% Portland cement, between 10% and 25% of fly ash, and between 5% and 15% of pozzolana, where the pozzolana is ground in a granulometric degree that passes through a 325 mesh.

It is yet another object of the present invention to provide a mortar comprising a) a fine aggregate comprising between 30% and 50% of basaltic sand, and between 50% and 70% of sea sand, and b) a cementitious material formulation comprising between 70% and 80% of Portland cement, between 101 and 25% of fly ash, and between 5% and 15% of pozzolana, where the pozzolana is ground in a granulometric degree that passes through a 325 mesh.

BRIEF DESCRIPTION OF THE DRAWINGS

For clarity and understanding of the object of the present invention, it has been illustrated in several figures, in which some examples of embodiment have been represented, all by way of example, where:

Figures 1 to 4 show a view of some basaltic and marine sand particles respectively;

Figures 5A through bE show views of the sands classified by size, material retained in meshes 4, 8, 16, 30, 50 and 100, respectively, while Figure 5F shows a view of the cementing material;

Figures 6 and 7 show a view of the specimens corresponding to two mortar mixtures before being tested, in accordance with ASTM C 1260 and / or ASTM C 1567;

Figures 8 and show a view of the differences existing both at the surface and microscopic level of a mortar bar with low expansion; Y

Figures 10 and 11 show a view of the differences existing both at the surface and microscopic level of a mortar bar with high expansion.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the invention, it consists of a new formulation of cementitious material for obtaining mortars with reduced alkali silica reaction, which prevents the cracking expansion of concrete, providing greater durability to it, being that said formulation may comprise:

between 70% and 80% of Portland cement,

between 10% and 25% fly ash, and

er.tre 5% and 15% of pozzolana,

where the pozzolana is ground in a granulometric degree that passes through a 325 mesh.

Thus, from the cementitious material formulation of the invention, different mortars with reduced alkali-silica reaction were obtained, being in a first preferred embodiment, that the mortar may comprise:

a) a fine aggregate comprising:

basaltic sand, and

b) a formulation of cementitious material comprising:

between 70% and 80% of Portland cement,

between 10% and 25% fly ash, and

between 5% and 15% of pozzolana,

While, in another preferred embodiment, the mortar may comprise:

a) a fine aggregate comprising:

between 30% and 50% basaltic sand, and between 50% and 70% marine sand, and

b) a formulation of cementitious material comprising:

between 70% and 80% of Portland cement,

between 10% and 25% fly ash, and

between 5% and 15% of pozzolana,

In this way, various formulations according to the present invention have been prepared which have been effective and on which the non-limiting examples of the invention will be given below. Such examples comprise the components and their test percentages that are within the ranges indicated above.

For this, different mortar mixtures were first evaluated using combinations of sands and mineral additions using ASTM Standard C1260 or C1567. Likewise, the type and severity of the mortar bars damage was evaluated using a method found in the literature, which allows to find a damage index (DRI). Where, a higher index value indicates greater visual damage of the mortar specimen. The composition of the mortar mixtures, the expansion of the bars after 14 Test days and weighted DRI are presented in the examples of the invention.

It is highlighted that, in order to assess the damage condition of the mortar bars in the petrography laboratory, the DRI methodology, Damage Rating Index, developed by Grattan-Bellew, was used. This method is applicable to laboratory prisms and also to concrete cores extracted from structures in service. The measurement is based on the division of the analysis area into 225 mm ² analysis tables, which are evaluated with a stereomicroscope at an increase of 16X, evidencing and classifying the damages found.

Thus, three bars of each of the mixtures produced were studied and evaluations on polished 3,600 mm ² surfaces were performed for each mortar bar, an analysis area was held for each type of mixture of 10,800 mm ^2. The damages were evaluated in the different categories and each damage has an incidence factor that is used to calculate the weighted DRI.

Likewise, the considerations of ASTM C1260 - 1567, appendix ΧΓ, which say that the expansions will be:

Potentially safe for values less than 0.10% at 14 days; Potentially reactive and harmful for values greater than 0.20% at 14 days; Y

Between 0.10% and 0.20% additional examinations of the material such as inspection and petrographic analysis are required.

EXAMPLE 1

In a first preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

100% basaltic sand,

70% Portland cement,

25% fly ash, and

5% of pozzolana.

Under this combination of percentages and components, a 14-day expansion of 0.067% has been surprisingly obtained, with a DRI of 107. This being _/ a potentially harmless expansion in accordance with ASTM C 1567.

EXAMPLE 2

In a second preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

100% basaltic sand, 70% Portland cement,

20% fly ash / y

10% of pozzolana.

Under this combination of percentages and components, a 14-day expansion of 0.120% has been surprisingly obtained, with a DRI of 140. Thus, an expansion that must be analyzed by petrographic inspection in accordance with ASTM C 1567.

EXAMPLE 3

In a third preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

100% basaltic sand,

70% Portland cement,

15% fly ash, and

15% of pozzolana.

Under this combination of percentages and components, a 14-day expansion of 0.092% has been surprisingly obtained, with a DRI of 116. This being a potentially harmless expansion in accordance with ASTM C 1567. EXAMPLE 4

In a fourth preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

30% basaltic sand _/

70% marine sand,

75% Portland cement,

15% fly ash, and

10% of pozzolana.

Under this combination of percentages and components, a 0.229% 14-day expansion has been surprisingly obtained, with a DRI of 81. This being a potentially reactive and harmful expansion in accordance with ASTM C 1567.

EXAMPLE 5

In a fifth preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

30% basaltic sand,

70% marine sand,

80% Portland cement,

15% fly ash, and

5% of pozzolana. Under this combination of percentages and components, a 14-day expansion of ^] 0.219% has been surprisingly obtained, with a DR1 of 85. This being a potentially reactive and harmful expansion in accordance with ASTM C 156?

EXAMPLE €

In a sixth preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

50% basaltic sand,

50% marine sand,

75% Portland cement,

15% fly ash, and

10% of pozzolana.

Under this combination of percentages and components, a 0.260% 14-day expansion has been surprisingly obtained, with a DRI of 133. This being a potentially reactive and harmful expansion in accordance with ASTM C 1567.

EXAMPLE 7

In a seventh example of preferred and merely illustrative embodiment, the mortar obtained from the invention It has been prepared with the following components and percentages:

100% marine sand,

80% Portland cement, and

20% fly ash.

Under this combination of percentages and components, a 0.080% 14-day expansion has been surprisingly obtained, with a DR1 of 44. Thus, a potentially harmless expansion according to the Morma ASTM C 1567.

EXAMPLE 8

In an eighth preferred and merely illustrative embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

100% basaltic sand,

80% Portland cement, and

20% of pozzolana.

Under this combination of percentages and components, a 14-day expansion of 0.149% has been surprisingly obtained, with a DRI of 59. Thus, an expansion that must be analyzed by petrographic inspection in accordance with ASTM C 1567. EXAMPLE 9

In a ninth example of preferred and merely illustrative embodiment, the mortar obtained from the invention has been prepared cor. The following components and percentages:

50% basaltic sand,

50% marine sand,

80% Portland cement, and

20% fly ash.

Under this combination of percentages and components, a 0.223% 14-day expansion has been surprisingly obtained, with a DRI of 92. Thus, a potentially reactive and harmful expansion in accordance with ASTM C 1567.

EXAMPLE 10

In a tenth preferred and merely illustrative embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

100% marine sand, and

100% Portland cement.

Under this combination of percentages and components, a 14-day expansion of 0.325% has been obtained, with a DRI of 141. This being an expansion potentially reactive and harmful according to ASTM C 1260.

EXAMPLE 11

In a eleventh preferred and merely illustrative embodiment, the mortar obtained from the invention has been prepared cor. The following components and percentages:

100% basaltic sand, and

100% Portland cement.

Under this combination of percentages and components, a 14-day expansion of 0.527% has been obtained, with a DRI of 882. Thus, a potentially reactive and harmful expansion in accordance with ASTM C 1260.

EXAMPLE 12

In a twelfth preferred and merely illustrative embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

30% basaltic sand,

70% marine sand, and

100% Portland cement. Under this combination of percentages and components, a 14-day expansion of 1,215% has been obtained, with a DHI of 123. Thus, a potentially reactive and harmful expansion in accordance with ASTM C 1567.

EXAMPLE 13

In a thirteenth preferred embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

30% basaltic sand,

70% marine sand,

80% Portland cement,

10% fly ash, and

10% of pozzolana.

Under this combination of percentages and components, a 14-day expansion of 0.384% has been obtained, with a DRI of 102. Thus, a potentially reactive and harmful expansion in accordance with ASTM C 1567.

EXAMPLE 14

In a fourteenth preferred and merely illustrative embodiment, the mortar obtained from the invention It has been prepared with the following components and pcrcenrajes:

50% basaltic sand,

50% marine sand, and

100% Portland cement.

Under this combination of percentages and components, a 14-day expansion of 1.54% has been obtained, with a DRI of 149. Thus, a potentially reactive and harmful expansion in accordance with ASTM C 1567.

EXAMPLE 15

In a fifteenth preferred and merely illustrative embodiment, the mortar obtained from the invention has been prepared with the following components and percentages:

100% marine sand,

80% Portland cement, and

20% of pozzolana.

Under this combination of percentages and components, a 14-day expansion of 0.765% has been obtained, thus being a potentially reactive and harmful expansion in accordance with ASTM Standard c 1567.

Although, the expansions of some exemplary mixtures have been greater than 0.20%, those that they were in the range of 0.219% and 0.384%, have not demonstrated serious damage and consequently, it has been considered that the mitigation of the alkali-silica reaction with the cementitious combination is adequate against the high expansions and the observed damages in mortar specimens containing only cement (Examples 10, 11, 12 and 14).

Likewise, the use of the pozzolan to reduce the alkali-silica reaction should be emphasized since, the pozzolan used is the same material that is processed to obtain the basaltic sand, but that has been subjected to another additional grinding process to obtain it in powder form In this way, it is novel to use the same reactive material, but in a smaller size, which generates a reaction whose products do not affect mortar to a lesser extent, reducing its expansion significantly.

On the other hand, if Examples 8 and 15 are considered, it can be seen that pozzolan generates opposite effects on expansion, depending on the type of fine aggregate. This allows us to conclude that the use of pozzolana has given surprising results when combined with fine aggregates in an adequate proportion with other cementing elements, such as Portland cement and fly ash. This being the case, the alkali-silica reaction and its subsequent expansion are significantly reduced, avoiding thus the deterioration of the concrete and allowing a greater durability of the same.

That is, it can be noted that the pozzolan r.o decreases the alkali-silica reaction (5AS), but increases it, when used alone and with sea sand. Adeirás, er. The practice suggests nothing or teaches that the use of pozzolan to reduce RAS may be obvious. However, the inventors have surprisingly demonstrated, by means of the various embodiments, that pozzolan can generate the reverse effect, reduction instead of increase, when combined with basaltic sand and fly ash.

Although Examples 7-12 and 14-15 do not mention all the elements of the cementing formulation of the invention, they have been developed by way of example to support the investigations carried out by the inventors regarding the use of pozzolana and its importance to reduce the alkali-silica reaction and the expansion of concrete in order to avoid its premature deterioration.

In turn, in Figures 1 to 4, basaltic and marine sand particles can be observed. Basaltic sand (Figure 1) comes from a slightly greenish black volcanic igneous rock formed by matrix and plagioclase and mafic crystals; while the marine sand (Figure 2) corresponds to a mixture of monominerals with the presence of quartz and reactive volcanic rocks. Images corresponding to the thin section of the basalt sand rock are also observed (Figures 3 and 4). In its composition, about 15% of Palagonito was found, corresponding to a highly reactive volcanic glass. Figure 5 shows some materials used in the preparation of mortar mixtures. In Figures 5 A, 5 B, 5 C, 5 D and 5 E the sands are classified by size, material retained in meshes 4, 8, 16, 30, 50 and 100, respectively. Figure 5 F shows the cementing material. Figures 6 and 7 show the specimens corresponding to two mortar mixtures before being tested, in accordance with ASTM C 1260 and / or ASTM C 1567. In addition, the differences in Figures 8 and 9 are observed. existing both superficially and microscopically between the states of a mortar bar with low (Fig. 8 and 9) and high expansion (Fig. 10 and 11), respectively.

Claims

CLAIMS Having thus specifically described and determined the nature of the present invention and the manner in which it is to be carried out, it is claimed to claim as exclusive property and right:

1. A formulation of cementitious material for obtaining mortars with reduced alkali-silica reaction, being mortars comprising aggregates such as marine sands and basaltic sands, where the formulation comprises:

between 70% and 80% of Portland cement,

between 10% and 25% fly ash, and

between 5% and 15% of pozzolana,

2. A formulation of cementitious material according to claim 1, wherein it comprises:

70% Portland cement,

25% fly ash, and

5% of pozzolana.

3. A formulation of cementitious material according to claim 1, wherein it comprises: 70% Portland cement,

15% fly ash, and

15% of pozzolana.

4. A mortar comprising:

a) a fine aggregate comprising:

basaltic sand, and

b) a formulation of cementitious material comprising:

between 70% and 80% of Portland cement,

between 10% and 25% fly ash, and

between 5% and 15% of pozzolana,

5. A mortar according to claim 4, wherein it comprises:

a) basaltic sand, and

b) a formulation of cementitious material comprising:

70% Portland cement,

25% fly ash, and

5% of pozzolana.

6. A mortar according to claim 4, wherein it comprises: a) basaltic sand, and

b) a formulation of cementitious material comprising:

70% Portland cement,

20% fly ash, and

10% of pozzolana.

7. A mortar according to the claim wherein it comprises:

a) basaltic sand, and

b) a formulation of cementitious material comprises:

70% Portland cement,

15% fly ash, and

15% of pozzolana.

8. A mortar comprising:

a) a fine aggregate comprising:

between 30% and 50% basaltic sand, and

between 50% and 70% marine sand, and

b) a formulation of cementitious material comprising:

between 70% and 80% of Portland cement,

between 10% and 25% fly ash, and

between 5% and 15% of pozzolana, where the pozzolana is ground in a granulometric degree that passes through a 325 mesh.

9. A mortar according to claim 8, wherein it comprises:

a) a fine aggregate comprising:

30% basaltic sand, and

70% marine sand, and

b) a formulation of cementitious material comprising:

75% Portland cement,

15% fly ash, and

10% of pozzolana.

10. A mortar according to claim 8, wherein it comprises:

a) a fine aggregate comprising:

30% basaltic sand, and

70% marine sand, and

b) a formulation of cementitious material comprising:

80% Portland cement,

15% fly ash, and

5% of pozzolana.