GB2441526A - Reducing water ingress in building materials - Google Patents

Abstract

A building material comprises a water repellent material (such as aqueous siliconate) mixed with a cement bonded composite material, a cement formulation comprising calcium aluminate or a formulation comprising a cement clay matrix binder. The invention further provide a method of preventing weathering of mortar for a period in excess of 10 years, comprising manufacturing a mortar mixture having a water repellent in place of all or some of the water and the ratio by weight of water repellent to water in the mortar mixture being in the range 1-10 parts of water repellent to 99-90 parts of water.

Description

Reducing Water Ingress in Building Materials Such as Mortar,

CementfFibre Composite, Concrete and the Like.

This invention relates to building materials such as mortar, concrete, manufactured cement bonded composite materials such as cement fibre composites, mixtures and blended cement formulations such as Calcium Aluminate cements/portland cement, clay matrix binders and the like.

In conventional building techniques, where a damp course is required, a bituminous layer (or a layer of polythene or such other preparatory material) is provided. Such a * .* layer does, however, have serious failings; for example, the bituminous layer does not u** * * adhere to the structure above and below it and therefore an inherent weakness is built S.....

* into the construction and if significant lateral forces are applied the structure may collapse. * *. * S * * I. S. * * S *

* According to one aspect of the invention there is provided a mortar mixture characterized in that an aqueous siliconate is used in place of some or all of is the water and the ratio by weight of silicone solids to water in the mortar mixture is in the range of! to 10 parts of silicone solids to 99 to 90 parts of water.

A mortar mixture as defined above can be used as a damp-proof course (dpc) and has been found to be effective in such a use. The mortar adheres to the structure above and below, thereby providing strength to the structure and resistance to failure from lateral forces.

Furthermore, since the mortar relies on electrostatic repulsion rather than physical isolation, it provides an effective damp-proof course even if it becomes cracked.

The mortar can be used to provide render coats that actively repel moisture.

The mortar can be used to provide a damp course or a damp-proof screed, for

example, on a floor.

Other applications of the mortar are as a rendering or as a "plaster" on the inside of a damp house. * S.

" it was observed that very small air cells are introduced into the mortar as a result of S... * S S..

the aqueous siliconate and that the existence of these air cells does not surprisingly,

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* seriously reduce the strength of the mortar. With very small air cells and even distribution of the cells, the crushing strength may even exceed that of conventional * S. * . * * *.

mortar. *. S * . S * S.

Concentrations of silicone solids in water of 6 per cent by weight, 5 per cent by weight and 3.5 per cent by weight have all been tested and found to be satisfactory.

According to another aspect of the invention, a concrete is characterized in that it includes an aqueous siliconate resin.

The addition of aqueous siliconate results in less water than normal being required to bring the concrete to a working consistency. The use of less water strengthens the concrete. Thus there is scope, by the use of aqueous siliconate to provide a concrete with a higher crushing strength to weight ratio than conventional concrete.

Preferably, the air cells are smaller than 2.0 mm and advantageously smaller than I mm in diameter when cement aggregate or cement hydrocarbon, as an example only, expanded polystyrene are added to provide an air cell of an exact size is used.

According to another aspect of the invention a building material is characterized in that it includes low density beads distributed there through.

The building material may be concrete. * **

* ** The low density beads preferably have overall dimensions of less than 1 mm. The S... * S S...

beads may for example be made of polystyrene. It will be appreciated that "low" S.....

* density means a density that is several times lower than the mean density of the conventional building material. * .. * S S * ..

S * S S

* The technique can be applied to building materials other than concrete. In particular the technique may be employed in the baking of brick by the addition of hydrocarbon aerated compounds or other low density materials (not necessarily aerated) that can withstand high temperatures; this technique can also be applied to other building materials which have to be temperature cured or made by a similar process. The particles again preferably have overall dimensions of less than 1mm.

The technique may also be applied to metal sections e.g. steel.

The technique may also be applied to manufactured composites.

Certain examples of the invention will now be described with reference to the accompanying drawings, of which: A quantity of 3:1 sandlcement mixture (by volume) was thoroughly mixed in a mixer and the mixture was divided into two equal (measured on scale at 20kg) quantities. To the first quantity was added clean tap water and the mortar mixed to a working consistency. The measured quantity of water used was recorded. The prepared mortar was transferred into steel cube moulds, worked in and firmly trowelled over to form the standard I 00mm x 100mm x 100mm, i.e. 100mm3. The samples were marked as conventional mortar and set aside to set. * S.

Working consistency was chosen because any method involving complex dilutions, S... * .

measurements or titrations on site, is to be avoided. The average bricklayer will * S.....

* function at best when a technique he is used to is presented in a new situation. Thus, if the liquid aqueous siliconate is presented in a concentration which the bricklayer * .* :.: can pour into the sand and cement mixture instead of water to obtain a mortar whose working consistency "feels right", then the technology is likely to be applied correctly in practice.

The second measured sand/cement mixture was then put into the mixer once it had been washed and dried and the mixing procedure was repeated. In this case aqueous siliconate having about 3.5 per cent by weight of silicone solids was added in measured amounts until the same "working consistency" was achieved. It was noted that to achieve an equivalent working consistency less aqueous siliconate was required than clean tap water.

The prepared mortar was transferred into cubes as previously and the 100mm3 cubes prepared and set aside.

For practical reasons 5, 100mm3 cubes were prepared with siliconate mortar and 5 with conventional mortar as control. These cubes were left to set for two days and then removed from the mould and left to dry. Five days later the cubes were tested on an Avery-Denison machine. The results of the test were recorded and the results tabulated in Table 1.

Having concluded the breaking stress readings on the first batch of cubes, a further 3:1 sand/cement mixture (by volume using the same measuring apparatus) was * S. thoroughly mixed as before, and two sets of 5 x 100mm3 cubes were prepared. The *... * . *...

cubes as before were made by an experienced technician and allowed to set. As in the * *5*5** * previous experiment the cubes were tested seven days later. The results obtained were recorded and are reproduced, see Table II. * ** * . * * *5 *. S * S *

* Subsequently this procedure was adopted with a further twenty four cubes made over a period of 28 days (for practical reasons) and the cubes-were left in a constant temperature and humidity room for 28 days i.e. 4 weeks. These tests reflect the results in Tables I and II.

Graph 1 demonstrates the crushing strength results carried out on the Avery Davidson machine and was drawn from results tabulated in Tables I and II.

Graph I represents the breaking stress in N/mm2 is plotted on the y axis and the cube sample number shown on the x axis. The circled dots on the graph show the results of the tests on the siliconate mortar and the crosses show the results of the tests on the conventional mortar. A mean value for the breaking stress of the siliconate mortar is shown by the chain dotted line and a mean value for the breaking stress of the conventional mortar is shown by the solid line. As can be seen, the two mean values vary by one N/mm2 in 16.0. This variation is insignificant which means that for most practical purposes both mortars can be considered to have equal bonding properties.

In practice this means that architects can design structures using mortar of the invention to achieve the required damp proof course without building in a structural weakness.

* The deviation from the mean in these experiments is almost certainly due to the differential drying rate and, of course, to the impossibility of achieving a perfect sand **.S and cement mix. Some cubes will therefore have more cement than others, and the S SISS* * breaking stress will of course reflect this. For this reason the mean breaking stress ::; value is the only meaningful value to use.

The above results are considered approximate and in order to obtain a more exact indication of the effect of the siliconate on breaking stress many tests would have to be performed. Nonetheless, the results do indicate that a comparable breaking stress can be obtained with the mortar of the invention.

The aqueous siliconate also acts as a retarder and even after two days the centers of the I 00mm3 cubes remained soft to the touch, provided water is prevented from evaporating from the cubes.

Examination of the samples tested also shows that the aqueous siliconate acts as an aerating compound and creates extremely small air cells in the mortar. When these are evenly distributed and of extremely size, the crushing strength of the mortar can even be increased over that of conventional mortar (lower water content).

The principle of aerating either mortar or concrete with extremely small diameter holes, for example of not more than 1mm, filled with air or some other gas could add a new dimension to concrete technology. The crushing strength to weight ratio of the mortar concrete could be significantly improved by this means.

* Apart from the use of aqueous siliconate and other such compounds, other techniques may be advantageously employed to reduce the density of concrete. In particular S..

small beads of low density, for example polystyrene spheres of diameter of the order S.....

* of 1mm or less, may be employed as an additive in the concrete. Such beads may *: *: :* contain air or they may merely be low density materials. The advantage of such beads *:*. over a pure aerating technique is that whereas air cells can combine and thus grow to an undesirable size, for example as the concrete is mixed, the beads cannot.

In order to test the damp proofing characteristics of the aqueous siliconate, the following tests were carried out: A quantity of 3:1 sand/cement mixture (by volume) was thoroughly mixed and the mixture divided into two parts. To one part was added water to make conventional mortar and to the other part aqueous siliconate having 5 per cent by weight of silicone solids was added instead of water and this mortar was used in Tests 2 and 3 below.

In all the tests the bricks used were Hammill Multi Red Facing.

An aqueous siliconate suitable for use in the invention is the aqueous solution of potassium methyl siliconate, for example was sold by ICI as R333 Silicone Masonry Water Repellent. Such compounds have been used previously in the construction industry to add to brickwork, concrete, natural stone or other such materials once they have been fully formed as part of a structure: this is in contrast with embodiments of the present invention where the aqueous siliconate is mixed with the construction material in the course of its preparation.

* In the example of the invention described above, aqueous siliconate is added to the mortar. Other chemical compounds may be used in place of aqueous siliconate, a list being included. In addition to the patent application submitted by Abel & Imray in *.**** * 1982 further work was undertaken to test the concept independently and with this in ::; mind further tests were conducted to consolidate original experimental data.

Testing of water repellant additives.

The testing consisted of immersing brick constructions in water trays for 120 days over which time water transmission via various parameters was measured. The assembly is specified in Graph 1 and consists of assemblies with two Hammill multi red facing bricks, known for their manufactured consistency and picked for the experiments because they are known to transmit rising damp rapidly. These brick assemblies were placed in trays which contained about 25mm of water and were left in the trays for 120 days during which time the assemblies were periodically withdrawn, drained for about 5 minutes so that no free water dripped from the assembly and weighed. The variation in water absorption was calculated and plotted.

Graph 2 represents the water uptake of the reference assemblies: N.B. For convenience, the aqueous siliconate chemical DPC mixed into the 1:3 mortar, was referred to as Babic's mortar.

(a) when two dry bricks are separated by an absorbent paper tissue placed between the bricks, water is absorbed into the bottom brick across the paper tissue, to saturate the top brick. After about 20 days the water loss by * evaporation from the assembly is equal to the water absorption from the tray and there was no change in the weigh of the assembly thereafter. *..*

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* (b) when two dry bricks are separated by a physical damp proof course (DPC) *: ::* such as a piece of polythene, the immersed assembly quickly gains weight as *: * the bottom brick becomes saturated but because no water can pass through the DPC thereafter, there is no further change in the weight of the assembly and the graph is again a straight line.

(c) when two bricks separated by a paper tissue were pre-saturated and then places in the test trays, no substantial change was observed over the test period. The unexpected apparent drying out (N.B.), was discovered to be an unplanned draught which was isolated and blocked off from the test tray wherein the measurements settled down to the expected, i.e. no change in the weight of the assembly, demonstrating again that the water evaporating in the brick assembly was equal to the water absorption and the bricks remind saturated.

(d) when two saturated bricks were separated by a physical DPC the graph shows the top brick drying out demonstrating a loss in weight which settled to a steady state over the experimental period.

Graph 3 represents the water uptake of the Test Assemblies: Test Assemblies: (a) using two dry bricks with a physical DPC i.e. two bricks separated by a piece of polythene, shows rapid uptake of water in the bottom brick (within a few hours the bottom brick was entirely wet), to stabilize within 24 hours showing that no water passed through the physical DPC.

S.....

* (b) using Babic's Mortar dry brick assembly and placing into the water tray, *: ::* resulted in a rapid absorption of water into the lower brick, across the treated *: * mortar layer to wet the top brick, over the first few days of the experiment.

Over the next 28 days the top brick dried (the aqueous siliconate lattice was forming to become effective in preventing rising damp) out gradually. The weight of the assembly stabilized over the test period and the graph remained flat i.e. no additional water was passing through the mortar layer indicating that the chemical DPC was effective.

(c) when the Babic's Mortar assembly was saturated and placed into the tray there was a drying out of the top brick reflected in the loss of weight of the assembly, during the early part of the experiment. The graph flattened out and stabilized meaning that no water was passing through the chemical DPC.

(d) saturating the bricks with the physical DPC layer between the bricks prior to putting them into the tray resulted in the top brick drying out and the graph stabilizing out for the rest of the trial.

Graph 4 represents the water uptake of the 1: 3 portland cement and sand mortar: (a) The Babic's mortar dry assembly demonstrated a rapid uptake of water at a slightly higher level then the dry control. The flat part of the graph demonstrates that the there was no transfer of water across the chemical DPC and the steady state graph was lower than the polythene DPC, again due probably to the lower absorbancy of the bottom brick. * .*

(b) when the dry control assembly with the conventional mortar layer between * *. I the two bricks was placed in the tray, there was a rapid uptake of water I *S S IS * which continued across the mortar layer to wet the top brick. As the mortar *: ::* consolidates, water uptake across the mortar was reduced so that by about *:*. the 28th day virtually no water was being transmitted through the mortar layer to the upper brick.

(c) saturating the conventional mortar assembly initially retained water in the top brick because the rate of evaporation was equal to the rate of water transmission across the mortar between the two bricks but the top brick dried out after about 28 days providing similar results to conventional DPC.

(d) saturating the assembly with the Babic's mortar and placing into the water tray, was seen to be effective rapidly, achieving the drying out of the top brick more quickly than conventional mortar, indicating a lower transfer of water across the treated mortar layer. This assembly gave results very similar to the conventional polythene DPC.

Graph 5 represents test using 1: 6 portland cement: sand mortar: (a) the dry Babic's mortar assembly, produced an uptake of water to give substantially the same trace as a conventional DPC but was slightly wetter than conventional DPC.

(b) the dry control, conventional mortar using a dry assembly of bricks, indicates an uptake of water which dried slightly during the first 28 days, to give a constant trace to the end of the experiment.

(c) the control assembly in a saturated condition demonstrated a gradual drying out after about 25 days to provide a steady state towards the end of the experimental period.

*: * (d) the experimental chemical DPC in a saturated state demonstrated similar ."* behavior to the conventional DPC but was about 4% wetter and attained a S...

* : ..: similar final state to the saturated control. (e) * 0* * S * * SS

* * Graph 6 represents test using 1: 9 portland cement and sand mortar mix: In this, an experimental mortar mix, we wanted to test the concept in an extreme situation. Certainly such mortars have no value in standard construction practice and the use of such mortar for structural purposes is inconceivable but it nevertheless remained a useful indicator of the effectiveness of the siliconate molecule in this extremely porous and absorbent mortar: (a) initially the dry control demonstrated a large pick up of water which resulted in the top brick drying out by about the 20th day and thereafter leveled out (b) at about 30 days, meaning that the top brick attained an equilibrium of water absorption and evaporation. The assembly was drawing water from the tray to remain wet for the duration of the experiment.

(c) the saturated control showed a slight additional pickup of water transmitted from the tray to remain wet for the duration of the experiment again showing that the conventional 1:9 mortar mix transmitted water across the mortar layer.

(d) adding the aqueous siliconate to the 1: 9 cement sand mortar mix in the dry assembly resulted in the rapid uptake of water in the lower brick to allow only a small transfer across the chemical DPC into the top brick, which then dried out to achieve a steady state that resulted in the assembly being about 1% wetter than the conventional DPC assembly.

* :* (e) The Babic's mortar saturated assembly allowed the top brick in the water * : * tray to dry out during the first 20 days to give a stable graph indicating that the mortar layer was acting as a DPC even though the trace did not fall to a * value of 0 and was therefore not as effective as the polythene DPC. ** * * * * * 0s

Conclusions.

Most usefully these experiments indicate that the 1:9 mortar mix with the chemical additive prevents the upward passage of water across the modified mortar layer. The conventional 1:9 mortar mix does not prevent the upward passage of water across the mortar layer and therefore the brick assembly remained wet.

In applications using the chemical additive where saturated assemblies were placed in the water trays, it was found that the assemblies dried out at about the same rate as the assemblies with physical DPC, to prevent the upward passage of water across the mortar layer, during the experimental time scale.

In applications using dry brick assemblies that were then placed into the water trays it was found that the conventional and the experimental mortars prevented the passage of water across the mortar layer during the experimental time scale.

Clearly conventional mortars fail during prolonged use so that long term tests were required to asses the long term effectiveness of conventional mortar mixtures as compared with identical mortar mixes to which was added the aqueous siliconate chemical DPC.

* Our fmdings were submitted to the UK Agrement Board and a Report No 500, * December 23rd 1982, presents their findings in some detail.

* ***** * * Integral water repellent additives. * ** * S S * **

* : * There are very many commercially available water repellent additives that the construction industry uses but for the sake of simplicity, we categorize the available preparations into basic groups. Water repellents act by a variety of means but all are directed at reducing the water ingress into the substance of the material. When mixed with cement fibre composites, mortars, concretes and the like, the admix is spread throughout the matrix of the material to achieve its effect at each site the additive is precipitated. Once cured the water repellent additives are effective for the duration of the given additive's lifespan.

The many currently available water repellent additives supplied by the UK admix manufacturers provided for integral cement composites, can be classified into two basic groups: I. Chemical formulations that form electrostatic mesh constructs, which repel water to reduce the diffusion coefficients.

2. Compositions that block the pores within the formed material to configure physical barriers.

Available integral water proofing formulations: * *. I. Silicone resins * . I * S. *::::* 2. Fluoropolymers 3. Lignosuiphates and sterates 4. Soaps and fatty acid composites 5. Acrylic preparations * 6. Colloid silicates 7. Styrene Butadiene Rubbers 8. Oil based emulsions 9. Inorganic additives 10. Other e.g. (air removal additives such as antifoaming agents) More specifically, examples of additives used: I. Silicon resin formulations, modifications and innovations such as siliconates, silanes, siloxanes emulsions as supplied by eg. WAKER Gmbh 2. Fluoropolymers as provided by the DuPONT Group.

3. Lignosulphates and sterates as provided by DEGUSSA Gmbh.

4. Soaps and fatty acid composites such as Brunolene SP, as supplied by the WYKAMOL Group.

5. Acrylic polymers such as mixtures of vinyl chloride, ethylene, vinyl esters, and proactive colloids and co-polymers, supplied by WYKAMOL Group.

6. Colloids of for example the SEKA 1 range, provided by BSF Construction Chemicals, UK.

7. The many SBR formulations as provided by for example, FOSROC UK.

8. Linseed oil composites.

9. Inorganic solid additives that increase the density by blocking up the pores *:*::* of the material to reduce porosity and permeability.

10. Many other formulations mixtures and preparations are sold by the damp proof industry. Research continues and bitumen based water soluble emulsions are being experimented with. The antifoaming or defoaming - * agents prevent the formation of air bubbles within the matrix and thus *: * remove the spaces via which water ingress could occur. Many preparations exist but as an example only the COGNIS Foamaster PDI is useful.

As always with admixtures, the user must assess the available additives to confirm that the proposed application is suitable for the purpose for which it is intended. The additive must be examined for compatibility of all constituents within the proposed composite.

When adding an integral water repellent to high alumina cement the exclusion of water from the spaces formed during conversion provides an advantageous property to the finished material. The crystal structure of high alumina cement undergoes conversion to form the thermodynamically stable final form. In the process of converting from the metastable crystal forms of CAH io and C2AFI8 to the cubic C3AH6 crystal form, there is a reduction in the volume of the crystal formed so that additional spaces are created within the substance of the composite. These spaces increase the porosity of the material so that more water can penetrate the material.

The water freezes during freeze thaw cycles to damage the material so that some compositions fail in prolonged wet conditions. There is no information on what happens in wet situations during the reversion of molecules from the metastable crystalline phase into the ionic state in solution and how excess water effects the chemistry of CAC. The molecules forming the metastable crystals must revert into the ionic state before they can recombine to form the thermodynamically stable final *:*::* crystal fonn. Provided water is prevented from contaminating the finished product the *. range of uses for calcium aluniinate cements could be extended. I...

I

* .S*.I * . We greatly look forward to long term results with water repellent additives admixed * : :* with high alumina cement. Samples of high alumina cement and more specifically * Lafarge Cement Fondu, demonstrate that provided the fmished product is not exposed to water, that the product formulations retains their properties and that there is no degradation of the cement matrix during the experimental time scale. It seems to us that adding selected integral water repellents during production of high alumina composites materials, will reduce water ingress and extend the life of such composites. The fmal thermodynamically stable cubic crystal structure of high alumina cement, remains stable provided water is prevented from contaminating the finished product. The range of uses for such cements could be extended provided water ingress is prevented.

YEAR FOLLOW UP

OF BABIC'S MORTAR In addition to the patent application submitted by Abel & Imray, Improvements in or relating to building materials such as mortar, concrete, cement fibre composites manufactured or cast and the like, is enclosed adding further data following long term follow up observations on structures built in 1982.

Many new applications were tried and tested and in particular the technology was extended to fibre cement composite materials. Exclusion of water in cement aggregate fibre composites imparts very advantageous properties to the manufactured material. * S. * . S * S.

*. . . Excluding water from the substance of materials prevents the spalling damage seen in wet construction materials, to prolong the life of the material by at least twice the * 5I5S0 * S expected lifetime service provided by conventional materials. Materials that are not *: *: :* wetted by the elements do not degrade as quickly as materials that are soaked by rain * : * etc. The freeze thaw cycle does less damage to materials that have integral water repellant materials mixed into their substance during manufacture.

Following the release of the above results, Oxford Construction undertook over the years, a number of contracts which were judged to be ideal for the further practical long term testing of the liquid dpc concept. We chose a number of non-critical applications, for this technology and built low level garden walls applying Babic's Mortar at the dpc level, instead of conventional dpcs.

1 Photograph/Drawing Composite.

Shows a conventional bituminous dpc and the spalling-that occurs inbricks due to damp conditions below the dpc level over the given timescale.

2 Photograph/Drawing Composite.

The most surprising finding is the fact that the conventional mortar appears to be ageing much more rapidly than the dpc layer. As can be seen, the Babic's Mortar layer B, shows no sign of weathering when compared to the conventional mortar A, on the upper layers on the same structure. The pointing tool impression, left by the *:*::* bricklayer closing off the surface layer, is clearly seen in the dpc mortar layer B. The surface tension forces draw out of the mix fine particles that remain on the surface. *...

The upper layers show that the indentation has all but disappeared. Given that the * ..*** * * wall was built by the same craftsman, from the same material composition and the *: *::* pointing technique was identical, one can only conclude, that the addition of aqueous siliconate imparts better weathering properties to mortar. This finding was examined very closely because such a property could have important implications to the construction industry. No obvious reduction in the cementing property is observable at this time. Photograph/Drawing Composite 2, a close up examination of a section of the experimental wall taken in 1993.

The use of Babic's Mortar as a screed was disappointing in situations where the finished screed was covered by an impermeable membrane that trapped water vapor.

The 3D molecular mosaic formed by the siliconate molecules was permeable to water vapour. The mortar is partially permeable to water vapour and is said to "breath".

Experiments with plastic covered areas condensed the vapor to soak the floor.

The use of the mortar as render, was promising. Addition of water repellent integral additives into mortar mixes is seen to retard water ingress into the substance of the material. As can be seen, the water sprayed on the junction between conventional mortar and treated mortar, demonstrates that the untreated mortar absorbs water to be wetted whilst the treated mortar repels water. The impinging water spray is seen to form water droplets on the surface of the render.

The long term tests give a clear indication that the application of mortar dpc is viable and has considerable advantages over the conventional dpc technology. * ** * . * * .. S... * .

25YEAR *.SS.* * .

FOLLOW UP STUDY

:; OF WATER REPELLANT ADDITIVES TO MORTARS Assessment of the structure built to test long term the effects of introducing water repellent in mortar, fme aggregate concrete mixes and concretes is proving the original concept exceptionally useful. The mortar is showing surprising resistance to weathering.

3 Photograph/Drawing Composite, the mortar layer which was treated with a water repellent and demonstrated that virtually no weathering of the surface of such layers occurred. This exceptional result is substantially better than expected given that some diffusivity exists within the molecular mosaic of the water repellent molecule. This diffusivity is seen in render applications, to allow some vapor to pass through the water repellent barrier to evaporate from the surface. For this reason the molecular mosaic formed by the additive makes this particular molecular structure unsuitable for positive pressure uses but the availability of several water repellent water soluble integral additives that have been developed by the industry shows promise that the use of such additives call play an important role in the construction industry and other applications.

The use of water repellent additives into mortars and other cement based mixes provides industry with a means whereby the active component prevents the material so treated from becoming saturated with water. The advantage of this in the winter months in temperatures that are below freezing is that water within the matrix is * .S present in such small quantities that it cannot damage the superficial layers to spall the *.*.

surface layer of the material. In this case no damage to surface layer of materials I.....

* treated with water repellents occurs and the integrity of the surface layers is maintained. * S. * * * * .. * S * SI * I.

In situations where cement bonded materials are wet and the water within the material freezes, spalling, occurs. This is a process where to varying degrees the material is weakened and breaks away from the main body of the material because the force exerted by the expanding freezing water breaks the cement bond adhering the particles of the cement or concrete or the composite materials in question. The spalled sections increase the surface area of the exposed section and its porosity provides an even more absorbent material that is damaged at ever increasing rate by subsequent thaw/freeze cycles.

The addition of water repellent additives reduces the rate of wetting and the rate of spalling to an insignificant degree so much so that the twenty five year examination shows no noticeable degradation of the surface layers of the treated mortar in this experiment.

In the above Photograph/Drawing Composite 3, of the experimental structure which is a metre high garden wall built of poor quality porous general purpose bricks, built to provide a boundary well for the North side of the property in question and exposed to the elements from all sides, it can be clearly seen that the treated mortar layers have stood the test of time very well as compared to the similar mortar without the water repellent additive. The mortar layers above the experimental mortar course are seen * to have weathered to an extent where all the surface layers have been abraded by the elements. The coarser aggregate contents of the mortar are clearly seen and the lichen populations are developing in many areas of these layers. The presence of lichen * indicates an increase in porosity and water retention to a level whereby the mortar can ::; contain enough water to sustain living organisms.

The case for additives is clear because there is no reason for the experimental mortars to suddenly fail. It is expected that the additive will perform their design function for as long as the water repellent additive remains functional and thereafter, the mortar will degrade in a similar way to conventional mortar. The treated mortar will therefore have a lifespan for the duration of the water repellent additive in its active form and thereafter for a similar period to conventional mortar. The total lifespan of materials to which was added water repellent compounds will at least double the expected lifespan of produced materials and thereby exceed all current standards requirement for building practice.

l'his specification specifies a development that extends the life span of construction and other materials which have extended life-spans i.e. the manufactured materials so made last much longer in use.

Clearly the number of applications of this basic concept are numerous and it remains to be seen to how many different applications this concept can be put to. As an example only the addition of water repellent additives to the matrixes of mortars, concretes mixtures and composites is huge and can as an example only, be applied to cement bonded materials such as roofing tiles, cladding composites and mixtures of many kinds including additives that contain cellulose, ceramic, natural, synthetic fibre * S. * S S * " in composites etc. *. * S a..

S

a.*S S. * The impregnation of timber with selected water repellent materials that are used in construction materials can have a beneficial effect on cellulose materials and indeed * *5 there are examples of cellulose materials such as straw, that have retained their properties for thousands of years provided they are kept dry.

Extending the lifespan of manufactured materials has important commercial implications for the cement bonded industry.

1 Photograph/Drawing Composite A. Conventional bituminous type dpc.

B. Undamaged brick layer above the dpe membrane.

C. Badly spalling brick below the dpe.

Year Follow-up 2 Photograph/Drawing Composite A. Conventional mortar demonstrates loss of surface layer.

B. The experimental mortar demonstrates NO loss of surface layer and still retains tooling marks.

C. The brick below the dpc layer is spalling.

Year Follow-up.

3 PhotographfDrawing Composite. * ** ** * * **

A. Weathered conventional mortar. Pieces of mortar falling off. No surface layer left.

B. Aqu. Si!. additive experimental mortar. The surface layer remains unchanged with NO deterioration of any kind in the mortar layer. Note the integrity of the surface *: *: :* layer and the original tooling marks.

C. Brick below the dpc layer is badly spalled but the pieces bonded to the experimental mortar remain bonded.

Claims (12)

S 2'S CLAIMS

1. A building material comprising cement, characterised in that a water repellent is mixed with the cement, the building material being selected from cement bonded composite materials, calcium aluminate containing cement formulations and compositions comprising cement clay matrix binders.

2. A building material according to claim 1, wherein the water repellent is selected from aqueous siliconate, silicone resin, fluoropolymer, lignosuiphate, lignostearate, soap, fatty acid composite, acrylic preparation, colloidal silicate, styrene butadiene rubber, oil based emulsion, inorganic additive, antifoam agent and bitumen based water soluble emulsions.

3. A building material according to claim I or 2, wherein the water repellent comprises aqueous siliconate, the aqueous siliconate being used in place of some or all of the water which is mixed with the cement, the ratio by weight of silicone solids to water in the cement mixture is in the range 1-10 parts of silicone solids to 99-90 parts of water.

4. A building material according to any preceding claim, comprising a cement fibre composite.

5. A building material according to any preceding claim, comprising a calcium aluminate cement/portland cement blended cement fonnulation.

6. A building material according to any preceding claim, comprising high alumina cement.

7. A method of making a building material, comprising mixing cement with a water repellent material, the building material comprising cement bonded composite material, calcium alumiriate containing cement formulations and a formulation having a cement clay matrix binder.

8. A method of preventing weathering of mortar for a period in excess of 10 years, comprising manufacturing a mortar mixture having a water repellent in place of all or some of the water and the ratio by weight of water repellent to water in the mortar mixture being in the range 1-10 parts of water repellent to 99-90 parts of water.

9. A method according to claim 8, wherein the water repellent is selected from aqueous siliconate, silicone resin, fluoropolymer, lignosuiphate, lignostearate, soap, fatty acid composite, acrylic preparation, colloidal silicate, styrene butadiene rubber, oil based emulsion, inorganic additive, antifoam agent and bitumen based water soluble emulsions.

10. A method according to claim 8 or 9, wherein the water repellent is aqueous siliconate.

11. A method according to any of claims 8 to 10, wherein the mortar is used to build at least part of a brick wall.

12. A method according to any of claims 8 to 11, wherein the mortar is used to provide a damp course in a wall.