GB2368840A - Lime putty based grouting composition - Google Patents

Abstract

A mixture of lime putty (at least 75%), water (at least 20% by weight) and a polymeric gel forming material (at least 0.1%) provides an ideal mortar for supplying in cartridges and application by a gun. The polymeric material is suitably a polysaccharide or gum such as agar, alginates, carrageenan, furcellaran, guar, gum, gum arabic, gum tragacanth, karaya gum, locust bean gum, pectin, dextran, Gallen gum, rhamsan gum , welan gum, xanthan gum, succinoglycan, carboxymethylcellulose, methyl hydroxypropylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, propylene glycol alginate, hydroxypropyl guar or modified starches. Preferably, the formulation also includes sodium chloride, and a biocide such as sodium benzoate or sodium phenyl pentoxide.

Description

Conductive Grouting Mortar This invention concerns conductive grouting mortar.

Current electro-osmotic damp proofing systems consist of a series of anodes which are electrically connected to each other and are set in spaced apart holes drilled into masonry at various depths depending upon the wall thickness, e. g about 75mm in 100mm walls but up to 600mm in very thick stone walls. The anodes need to be held in place in order that they cannot be inadvertently removed by, for example, other trades people. More important is the requirement that there should be continuous electrical conductivity from each anode to the surrounding masonry over the full depth of the hole. In this respect, there is often concern that this may not be being reliably achieved under actual site conditions.

Traditionally the fixing in of these anodes has been achieved using a cementitious mix of Portland cement and water with or without aggregate. This is mixed, on site, to provide a thin slurry and injected by various methods into the holes in which the anodes have been placed. This slurry tends to settle and to block tubing used to inject it into the back of the holes. It is also common for such a slurry to drain away into gaps in loose stone infill in the middle of walls.

To overcome the problems of using cement slurries, a semi-dry mix of cementitious material and aggregate may alternatively be used, such a mix being rammed into the holes in which the anodes have been placed by means of a suitable size steel rod. This technique, however, requires that larger size holes are drilled, say up to 20mm diameter. This is time consuming and can be damaging to weak walls already affected by raising damp.

An object of this invention is to provide a premixed mortar material which could be supplied in cartridges (e. g mastic type cartridges) enabling easy application using a standard commercially available applicator, often known as a"gun", into relatively small diameter holes, typically 14mm, and up to the maximum depths required, e. g up to 600mm.

Portland cement, or any other hydraulic cement mixture, cannot be used for this purpose as the addition of water will cause the mixture to set. There is however a readily available material which sets by reaction with carbon dioxide in the air. This is calcium hydroxide commonly known as"lime", which is available commercially in a number of forms. A standard admixture of lime and water, referred to as"lime putty"is available from suppliers such as Masons Mortar of Edinburgh or Bleaklow Industries Limited of Bakewell, Derbyshire. It is a very stiff material that cannot easily be applied using a standard gun. However the addition of water to create a more fluid composition is not practical because separation of the additional water occurs upon storage.

According to the invention, a conductive grouting mortar is proposed which comprises a mixture of lime putty, a substantial amount of additional water and a polymeric material having a three dimensional structure capable of holding the water within the mixture and also beneficially improving the flow properties of the mixture so that it is typically of toothpaste like consistency.

The properties of this mixture are such that its setting action is quite slow. The natural viscosity of the material will hold the anodes in place in the holes prior to the development of the chemical carbonation process. As the water is removed, initially most likely by absorption into the masonry, the rate of reaction with atmospheric carbon dioxide can be expected to increase. Once the outer 5-10 mm has set the installation can be regarded as secure and effective.

The grout of the invention can be supplied in mastic cartridges (400cc) and injected into holes, typically of 14mm diameter using a standard skeleton gun. It is desirable to use an extension nozzle to ensure complete filling of each hole. Such a nozzle is a lOmmOD rigid plastic tube of any required length up to 600mm and sealed into the standard cartridge nozzle.

The polymeric material in the grout mixture of the invention may be selected from a variety of available polymeric gel forming materials of natural and synthetic origin. The material selected needs to be stable under the alkaline condition of the mixture and to provide good long-term stability of the lime/water mixture.

The polymeric material may be a polysaccharide or gum or a derivative of these materials that can be obtained from botanical sources or by an industrial fermentation process. Commercially available polysaccharides and derivatives are: from marine plants-agar, alginates, carrageenan, furcellaran; from terrestrial plants-gar gum, gum arabic, gum tragacanth, karaya gum, locust bean gum, pectin; from micro-organisms-dextran, gellan gum, rhamsan gum, welan gum, xanthan gum, succinoglycan, microfibrous cellulose (Cellulon); polysaccharide derivatives-carboxymethylcellulose, methyl hydroxypropylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, propylene glycol alginate, hydroxypropyl guar, modified starches.

A preferred polymer for use in the grout mixture of the invention is Welan gum, a fermentation polysaccharide. This is stable in the presence of calcium ions and under high pH conditions.

Since the grout mixture of the invention is likely to be stored for long periods before use, a broad spectrum biocide is preferably included in the mixture to control development of mould and bacteria that would affect appearance, create a smell and possibly affect the gel forming agent.

The biocide selected will need to be stable and effective at the high pH and high calcium ion concentration of the grout. Suitable biocides may be sodium benzoate or sodium 2-phenyl phenoxide, but others may also prove suitable.

The damp proofing system for which the grout of the invention has been devised depends on electrical conductivity and this is ensured by using a material (i. e lime) which is typical of mortars used for the original construction of older buildings. Additionally a very small quantity of salt (sodium chloride) may be included along with the polymer material. However this latter is not strictly necessary to achieve the required conductivity.

A specific practical example of a grouting mortar in accordance with the invention and its manner of preparation in a small batch production is as follows: Ingredients: Weight % by Weight Lime Putty 6.8 KG 77.13 Welan Gum (KELCO-CRETE KIC376) 14gm 0.16 Sodium chloride 2gm 0.02 Water 2. 0kg (i. e 2 litres) 22.69 The Welan Gum is available from Kelco Biopolymers, a division of Monsanto Company, with sales offices in Tadworth (Surrey), San Diego, Hamburg, Paris, Singapore and Tokyo.

Firstly the sodium chloride (2gm) is added to the 2 litres of clean water and mixed with a high speed stirrer. Then approximately 2gm portions of the Welan gum are successively added thereto. When each portion has fully dispersed further 2gm amounts are added up to 14gm in all. The mixture is then stirred for 10 minutes.

500ml of this Welan gum dispersion is added to the 6.8kg of lime putty and stirred at slow speed using a spiral mixer (approx. 1-300rpm). When this is fully incorporated further 500ml lots of Welan gum dispersion is added until the entire amount is used.

During the final stage of the mixing process a broad-spectrum biocide is added. Mixing is complete when the mixture is of smooth consistency with no free water visible.

The mixture is then loaded into plastic 400cc cartridges. These should be stored in frost-free conditions. The storage life is probably up to six months.

Claims (10)

1. Claims 1. A conductive grouting mortar comprising a mixture which includes lime putty, water and a polymeric gel forming material.
2. 2. A mortar according to claim 1 wherein the mixture contains at least 20% by weight water.
3. 3. A mortar according to claim 1 or 2 wherein the mixture contains at least 75% by weight lime putty.
4. 4. A mortar according to claim 1,2 or 3 wherein the mixture contains at least 0. 1% by weight of polymeric gel forming material.
5. 5. A mortar according to any preceding claim and further including sodium chloride.
6. 6. A mortar according to any preceding claim and further including a biocide.
7. 7. A mortar according to claim 8 wherein the biocide comprises sodium benzoate or sodium phenyl pentoxide.
8. 8. A conductive grouting mortar consisting of only lime putty, water, sodium chloride and a polymeric gel forming material.
9. 9. A mortar according to any preceding claim wherein the polymeric material comprises a polysaccharide or a gum or a derivative of either of these materials, or a mixture of any of these.
10. 10. A mortar according to any preceding claim wherein the polymeric material consists of or includes any of the following: agar, alginates, carrageenan, furcellaran, guar gum, gum arabic, gum tragacanth, karaya gum, locust bean gum, pectin, dextran, Gallen gum, rhamsan gum, welan gum, xanthan gum, succinoglycan, micro fibrous cellulose (Cellulon), carboxymethylcellulose, methyl hydroxypropylcellulose, hydroxypropylcellulose, hydroxyethylcellulose, propylene glycol alginate, hydroxypropyl guar, modified starches.