GB2289892A

GB2289892A - Mortar compositions

Info

Publication number: GB2289892A
Application number: GB9510929A
Authority: GB
Inventors: Qiwei Yang
Original assignee: Sandoz AG
Current assignee: Sandoz AG
Priority date: 1994-06-03
Filing date: 1995-05-31
Publication date: 1995-12-06
Also published as: GB9510929D0

Abstract

A repair mortar composition for concrete surfaces comprises cement, aggregate and at least 5% by volume of non-porous granular crosslinked polymeric material, e.g. polyurethane. The preferred polymeric material is reinforced reaction injection-moulded (RRIM) particles in the size range 0.1 - 4mm. These repair mortars display good application and final properties.

Description

REPAIR MORTAR This invention relates to repair mortar compositions.

Repair mortars are essentially mixtures of cement and fine aggregate (usually sand) which are used to repair concrete surfaces. They are required to fill holes of reasonable size and to provide a strong, protective coating which will adhere firmly to the surface and which will be able to withstand deformation without peeling and cracking. In order to have these properties to a satisfactory degree, the repair mortar should have a relatively low modulus of elasticity or "E-modulus" (preferably below 25,000 MPa), together with an acceptable level of compressive strength. However, a reduction in elasticity modulus has generally meant a reduction in compressive strength.Some of these problems have been overcome by the incorporation into a mortar of polymeric material, usually an aqueous polymer latex, that is, a dispersion of film-forming polymer particles, or a redispersible polymer powder. This has produced a significant improvement in peel resistance and a significant reduction in the elasticity modulus but this has been achieved at the cost of reduced compressive strength. In addition, this is a relatively expensive solution.

It has now been found that the replacement of some of the aggregrate of a repair mortar by certain materials can lead to a significant enhancement of the properties. The invention therefore provides a repair mortar composition comprising cement and aggregate, wherein the aggregate comprises a non-porous granular crosslinked polymeric material to the extent of more than 5% by volume of the dry composition.

The non-porous, granular, crosslinked polymeric material may be any suitable material known to the art. By "non-porous" is meant that there has been no deliberate inclusion of porosity therein, for example by foaming agent, encapsulated fluid or leachable extender. It is known that there will almost always be a certain (low) level of porosity in these materials, and this is acceptable. It is preferred to have this level as low as possible. By "crosslinked" is meant that the material has been subjected to a crosslinking reaction with a suitable crosslinking agent.

It is preferable that the polymeric materials have some elastomeric qualities . A preferred material is polyurethane, especially reaction injection-moulded (RIM) material.

The best materials for the purposes of this invention are reinforced RIM (RRIM) materials which comprise reinforcing fibres. In addition to the excellent properties which they confer on the repair mortars according to the invention, RRIM materials are also relatively cheap, being often prepared from scrap material from, for example, the automotive industry. The mortars according to this invention thus also contribute to environmental preservation in their use of material which would otherwise be dumped or incinerated.

By "granular" is meant of the same order of size as the typical aggregate for a repair mortar, i.e. about 0.04 mm - 6 mm, preferably between 0.1 and 4 mm. The polymeric material is present to the extent of at least 5% by volume of the dry mortar composition. The other ingredients are present to such extent that a composition suitable as a repair mortar be given; the proportions will differ, depending on the nature of the ingredients, and the skilled person will readily be able to determine how much of each.

However, it is preferred that cement + aggregate (excluding polymeric material) should comprise from 40 to 98% by weight, preferably from 70 to 95% of the dry composition.

The cement should be present to the extent of from 10-70% (preferably from 20-50%) and the aggregate (excluding polymeric material) from 0-88% (preferably from 1778%), by weight of the dry composition. Preferably the polymeric material should be present to the extent of 80% by volume maximum of the dry composition. The preferred volume range for the preferred RRIM materials is from 10 to 50%.

The other components may be selected from any suitable materials known to the art.

The cement may be selected from any cement which is suitable for the use to which the mortar will be put, for example, Portland cement, slag cement and high alumina cement. The aggregate is generally sand but may also comprise other minerals. Other admixtures which confer properties appropriate to a particular end-use may be added by conventional means in art-recognised quantities, for example, water-reducing agents, airentraining agents and accelerators. Other materials such as reinforcing fibres of steel, glass or polymeric material may also be added.

The repair mortars according to this invention have good application properties and can readily be applied to substrates by conventional methods. In addition, the mortars have good final properties. In particular, some compositions provide a highly desirable combination of high compressive strength and low modulus of elasticity which is not known to be achievable otherwise . The invention therefore also provides a repair mortar composition as hereinabove defined, having a modulus of elasticity of from 2,000-25,000 MPa, preferably from 5,000-15,000 MPa, and a 28 day compressive strength of from 10-60 MPa, preferably from 20-50 MPa.

The invention is further described with reference to the following examples in which all parts are expressed by weight.

Example 1 A repair mortar is made up by blending the following materials: portland cement 25 parts sand (SIA* standard) 60 parts RRIM granules (3-6mm) 15 parts water 12.5 parts (water/cement ratio 0.5) * Schweizerischer Ingenieur- und Architekten-Verein (Swiss society of Engineers and Architects); this is a well-known standard in the industry A commercial high-performance repair mortar has the following composition: portland cement 20 parts sand 77.7 parts mineral additives 2.3 parts water to a water/cement ratio of 0.4 Both compositions are tested for modulus of elasticity (E-modulus), density and 28 day compressive strength.The results are as follows: mortar according to commercial the invention mortar E-modulus 12500 22137 (MPa) density 1962 2131 (Kg/M3) compressive strength 30 32 (MPa) It can be seen that the mortar according to the invention has a similar density and compressive strength to the high-performance commercial composition, but has a substantially lower E-modulus. This gives the mortar according to the invention substantially better properties in use - it can withstand deformation without peeling and cracking.

Examples 2-7 A number of repair mortars are prepared by blending the following ingredients; Example No. 2 3 4 5 6 7 Composition [Weight %] Portland cement 25.00 25.00 49.00 30.00 25.00 29.50 Sand (SIA) 75.00 - - - 60.00 standard) Sand (DIN - 75.00 - - - 55.50 standard) Quartz sand (0.1 - 0.4 mm - - 49.80 - - Quartz sand (0.1 - 3.2 mm) - - - 69.25 - Polymer powder - - 1.20 0.75 - RRIM granules (1 - 3 mm) - - - - - 15.00 RRIM granules (3 - 6 mm) - - - - 15.00 Water 12.00 13.75 18.00 18.00 12.50 16.23 The polymer powder used is "Acronal" (trade mark) DS 6031 ex BASF and the RRIM materials are scrap from the automotive industry. Mixing is performed according to DIN 18 555.

The repair mortars are tested and the results are shown in the following table.

No. 2 3 4 5 6 7 fw 54 38 49 43 30 21 43.2 30A 39.2 34.4 24 16.8 d 2282 2185 1945 1961 1962 1856 E 28500 25900 21000 20104 12500 10600 Ae 40 46 39 39 29 32 fw = cubic strength (MPa), measured according to DIN 18 555 fc = cylinder strength (MPa) (= 0.8 x fw) d = density (KgIM3), measured according to DIN 18 555 E = Modulus of elasticity (MPa), measured according to DIN 1048 Ae = coefficient of E-modulus (MPa)05 (Kg/M3) l3) (according to S.H. Perry petal (see "Magazine of Concrete Research", 1991, 43, No. 154, Mar., 71-76)) The E-modulus values for the RRIM granule-containing mortars (Examples 6 and 7) are substantially lower than those of the materials which do not contain RRIM (Examples 2-5).

Claims

Claims:

1. A repair mortar composition comprising cement and aggregate, wherein the aggregate comprises a non-porous granular crosslinked polymeric material to the extent of more than 5% by volume of the dry composition.

2. A repair mortar composition according to claim 1, wherein the polymeric material has some elastomeric qualities.

3. A repair mortar composition according to claim 1 or claim 2, wherein the polymeric material is polyurethane.

4. A repair mortar composition according to any one of the preceding claims, wherein the polymeric material is a reaction injection moulded (RIM) material.

5. A repair mortar composition according to any one of the preceding claims, wherein the polymeric material is a reinforced reaction injection moulded material (RRIM).

6. A repair mortar composition according to any one of the preceding claims, wherein the particle size of the granular polymeric material lies in the range of from 0.04-6mm, preferably from 0.14mm.

7. A repair mortar composition according to any one of the preceding claims, wherein the polymeric material comprises 80% maximum by volume of the dry composition.

8. A repair mortar composition according to claim 5, wherein the polymeric material comprises from 10-50% by volume of the dry composition.

9. A repair mortar composition according to any one of the previous claims, having a modulus of elasticity of from 2,000-25,000 MPa, preferably from 5,000-15,000 MPa, and a 28 day compressive strength of from 10-60 MPa, preferably from 20-50 MPa.