JPH06345509A - Sprayable mortar composition for repair - Google Patents

Abstract

PURPOSE: To improve cracking resistance, flexibility and durability by combining cement and a specific aggregate.

CONSTITUTION: To a mortar comprising 77-78 wt.% sand having ≤4 mm particle size (A) and 0.5-2.5 wt.% natural mineral material selected from limestone powder, micro rock powder, micro rock powder fibers or similar fibrous materials (B) based on the total dry weight of the dried mortar composition, an aggergate comprising the A and B components having a 15000-40000 N/mm² average static modulus of elasticity (E-modulus), all types of cement and water sufficient for dry-spraying constituting the rest of the weight part, and optionally silica fume, fly ash or fibrous reinforcing material are added as fillers. All the constituents are mixed in a dry state and packed in a spray nozzle of an optional spray dryer while adding air, subsequently water is mixed to adjust the water/binder weight ratio to 0.3-0.6 and sprayed to a substrate as a mortar at 12-100 mm applied depth.

COPYRIGHT: (C)1994,JPO

Description

Detailed Description of the Invention

[0001]

This invention relates to sprayable repair mortar compositions, and more particularly to such compositions for use on reinforced concrete.

[0002]

When reinforced concrete must be repaired, a layer of repair mortar, typically 30-35 mm thick, is applied by spraying. The repair mortar must be able to withstand dimensional changes in the matrix without being destroyed for a reasonable period of time. A measure of this ability is the characteristic crack length (Cha
racteristic crack length). If the prism of mortar composition is a center point loader (centre poin
When subjected to a strain test using a loading apparatus, the prism is strained as the load increases, and the surface opposite to the prism loading surface is a microcracked area that is a characteristic area for each composition under test. Is formed. Eventually these cracks combine to form a large crack and the prism breaks. The characteristic crack length is the fracture energy of a known composition (area under the bell curve of load against strain obtained from the above strain test), the static modulus (E-modulus) and composition of the composition. It can be obtained by the strength of the highest center tension of the object. The longer the characteristic crack length, the better the function of the material. The best materials have high breaking energy and long characteristic crack lengths.

It has been found according to the invention that it is possible to produce repair mortar compositions with very good properties, evidenced by a long characteristic crack length. The present invention therefore comprises cement and aggregate,
The aggregate has a static modulus of etasticit
y) To provide a mortar composition for concrete surface repair, which has 15,000-40,000 N / mm ² .

The static modulus of the aggregate to be used in the composition of the present invention (commonly known as "E-modulus")
Is usually “soft”, and the value of the aggregate of conventional spray mortar is 25,000 to 60,000 N / mm.
^It exceeds ² . E-modulus is generally measured using ultrasonic testing equipment; examples of such equipment are Steinkamp BP5 ultrasonic testing equipment (eg Dr. Steinkamp GmbH, Bremen, Germany). Made). The E-modulus is the average E-modulus of the aggregate; if it contains sufficient aggregate with a low E-modulus and results in the above average value, then the E-modulus has an upper limit of 4.0.
It may contain aggregate exceeding 00 N / mm ² . Depending on the place of application, all known types of cement can be used in conventional amounts, with Portland cement being preferred.

The "soft" E-modulus range of aggregates is achieved by the choice of aggregate used and its use in combination with natural mineral materials having a fibrous structure. The aggregate used is preferably sand, of which the proportion of sand with a high E-modulus is low. As a practical matter, sand with a particle size of up to 4 mm is selected. The sand mixture used preferably has an average modulus of 20,000-30,000 N / mm.
² and especially 25,000 N / mm ² or less. Generally preferred natural fiber-like mineral materials are limestone powder (which may be coarse), micro-rock powder, micro-rock powder fibers or similar fiber-like materials. Such materials are preferably present in the compositions of the present invention at 0.5 to 2.5% by weight of the total dry weight of the dry mortar composition.

The mortar composition according to the invention is preferably applied to the substrate by spraying, preferably by the dry spray method.

When sprayed onto a substrate as a repair mortar, the mortar composition of the present invention hardens to form a layer with high fracture energy and long characteristic crack lengths, which itself has high resilience. It exhibits good properties, high frost resistance and low elastic modulus. The elasticity can be evaluated by the crack performance. This is done using the same center point loader as described above as DIN 1048, part 1. In this case, the specific crack length is measured-the longer the crack length, the greater the flexibility and indeed the better the functioning of the mortar composition. Compared to known products which produce hard protective layers with a modulus of 30,000 N / mm ² or more, the composition of the present invention provides a protective layer with a modulus of 25,000 N / mm ² or less. Can be used. Thus, the compositions of the present invention may be used even when it is desired to produce a compliant overlayer that is insensitive to cracks. The improved ductility and low modulus of the mortar allow for reduced shrinkage reinforcement and even complete removal. Therefore, the layers need not be too thick and more adaptations can often be used.

It has been found that the combination of the fibrous material limestone powder and fine rock powder fibers with the above sands and cements gives particularly good results and is outstanding in the above crack test. A particularly good combination is when the weight percentages of limestone powder and fine rock powder fiber are each 1.
5 and 0.8-1.5. If no other components are present, the sand constitutes 77-78% and the cement + water (sufficient water for dry spray) constitutes the balance.
If other ingredients are desired, sand and cement levels may need to be adjusted, which is well within the skill of the art.

Other components suitable for use in the sprayable mortar of the present invention are well known in the art. These constituents are added in known proportions, depending on the place of use. For example, it is possible to add silica fume or fly ash as filler, or the known fibrous reinforcing agents. All components are dry mixed in a known manner and air is added to the spray nozzles of any dry atomizer (e.g. MEYCO Piccola, MEYCO UNICA marketed by Minadir Actien Gesellschaft in Winterthur, Switzerland). While filling, mix and spray water there. The amount of water varies depending on the conditions, but can be easily determined by a working technician under any conditions. Typical water / binder weight ratios for dry spraying operations (where the binder inherently contains materials such as silica fume or fly ash, where they are present) are 0.3-0.6, preferably It is 0.4-0.5. Accelerators are usually not used. The applied depth can vary from 12 to 100 mm.

The invention will be further described with reference to the following non-limiting examples, in which all parts are parts by weight.

[0011]

【Example】

 Example 1

[Table 1] ──────────────────────────────────── Component elastic modulus (N / mm ² ) Density (kg / m ³ ) Proportion (% by weight) ──────────────────────────────────── Cement 18,000 ( 17,000-21,000) 2000-2150 20.0 Sand 24,000 (23,000-83,000) 2670-3050 77.7 Limestone powder 24,000 2500 1.5 Fine rock powder 17,000 (transverse direction) 2500 0.8 Fiber 17,000 (longitudinal direction) ─────────── ────────────────────────── Spurable mortar 22,137 2131 100 ────────────────── ────────────────── Mix the various ingredients in a dry state and spray them with water at the usual water / binder ratio of 0.4. Add from nozzle. This ratio is also used in the examples below.

Examples 2 to 12 Further examples of suitable sprayable mortar mixtures are given in the table below. The proportions of the various constituents are weight percentages. In the table, "MSM" is fine rock powder, "MSMPF" is fine rock powder fiber, and "KTSM" is limestone powder. Limestone powder is a coarse (4 mm) material.

[0013]

Table 2 Examples Cement sand KSTM MSM MSM PF 2 20 77.7 1.5 0.8 0.8 3 20 75.5 3 1.5 4 20 72 5 5 3 5 15 74.5 10 0.5 6 15 75 10 7 20 77.7 1.5 0.8 8 20 20 77 2.5 2.5 0.5 9 20 69.2 10 0.8 0.8 10 20 77 1.5 1.5 11 20 77 3 12 12 20 77 3

Example 13 The compositions of Examples 1 and 10 were applied to RELEM 50-F.
Subject to the MC draft recommendation test. 42% by weight
Cement, 33% sand (0.15-1.20mm), 1
Similar to a commercially available repair mortar containing 7% sand (1.20-2.38 mm), 3.4% silica fume, 3.3% calcium oxide and the balance miscellaneous minor mixtures. Subject to the test method. The results are as follows:

Table 1 Example 1 435 mm Example 10 382 mm Commercial composition 262 mm

The cracking performance of the composition of the present invention is considerably superior to that of commercially available compositions.

The composition is sprayed onto the concrete surface. Subsequent softness tests demonstrate that the compositions of the present invention are superior in flexibility and durability as compared to commercially available compositions.

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[Procedure amendment]

[Submission date] July 8, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

[0013]

Table 2 Examples Cement sand KSTM MSM MSM PF 2 20 77.7 1.5 0.8 0.8 3 20 75.5 3 1.5 4 20 72 5 5 3 5 15 74.5 10 0.5 6 15 75 10 7 20 77.7 1.5 0.8 8 20 20 77 2.5 2.5 0.5 9 20 69.2 10 0.8 0.8 10 20 77 1.5 1.5 11 20 77 3 12 12 20 77 3

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

Example 13 The compositions of Examples 1 and 10 were prepared according to RILEM (Reunion I
nternationle des Laboratoires d'Essais et de Reche
rches sur les Materiaux et les Constructions) 5
0-Subject to the FMC draft recommended test. 42
Wt% cement, 33% sand (0.15-1.20mm),
Similar to a commercially available repair mortar containing 17% sand (1.20-2.38 mm), 3.4% silica fume, 3.3% calcium oxide and the balance miscellaneous minor mixtures. Subject to the test method. The results are as follows:

Table 1 Example 1 435 mm Example 10 382 mm Commercial composition 262 mm

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Laurent Wolfsee Switzerland 6340 bar, Crazy Mat 21

Claims (4)

[Claims] 1. A mortar composition for concrete surface repair, which comprises cement and aggregate, and the aggregate has an average static modulus of 15,000-40,000 N / mm ² . 2. The mortar composition according to claim 1, wherein the aggregate is a combination of sand and a natural mineral material, and the natural mineral material has a fibrous structure. 3. The mortar composition according to claim 1, wherein the natural mineral material is selected from limestone powder, fine rock powder and fine rock powder fibers. 4. A method for repairing concrete surface, which comprises spraying the mortar composition according to claim 1 by a dry spray method.