GB2260281A

GB2260281A - Building material and method of producing the same

Info

Publication number: GB2260281A
Application number: GB9221380A
Authority: GB
Inventors: Wolfgang Moller; Rainer Kuhler
Original assignee: WILLICH F BERG BAUTECHNIK
Current assignee: WILLICH F BERG BAUTECHNIK
Priority date: 1991-10-12
Filing date: 1992-10-12
Publication date: 1993-04-14
Anticipated expiration: 2012-10-12
Also published as: GB2260281B; DE4133868A1; GB9221380D0; CZ310792A3

Abstract

In order to produce a structural material with resilient lightweight particles and which is then intended to be pumped at 4 bars and more, a method is used in which the particles are, prior to being admixed, sealed against penetration by liquid. They may be initially coated with a hydrophobing agent and then with water glass and are then dried. The sealing is intended to prevent water penetrating the pores of the balls. The particles are particularly expanded clay balls.

Description

2- 2 1) 1117 Il BUILDING MATERIAL AND METHOD OF PRODUCING THE SAME The

invention relates to a method of producing a building material having resilience and/or lightweight constituents which tend to absorb water and which are intended particularly for the roadside packing in underground mining work and which, after being mixed, is pumped at 4 to 6 bars, the resilient constituents being added in a layer-wise or even distribution. Furthermore, the invention relates to an expanded clay ball of moistly prepared and oven-fired clay or a ball of a similar lightweight material which is to be processed with water binding agents to produce lightweight cement products or structural members capable of controlled yielding.

Materials having a bulk density of about 1000 kp/M3 are termed lightweight structural materials. Unformed lightweight substances of granular inorganic material such as pumice, blast furnace slag, perlites, fly ash, sintering pumice, expanded clay and the like are admixed with the binders. It is also known for organic fibrous materials such as peat, straw, cork and the like to be added, these lightweight substances generally being used just as an additional structural material in walls or the like.

Such attempts have been made to use such lightweight structural materials and above all those with added expanded clay balls in underground mining, as roadside packing, in order thereby to impart a certain resilience to the roadside packing.. This resilience is desirable in order to avoid premature destruction of 'the structure. This structural material often has to be transported over considerable distances once it has been mixed together. It has been found that the resilient. and lightweight constituents absorb considerable quantities of water so that their pore volume is more or less lost. The resilient element embedded into the structural material is then no longer suitable for fulfilling its function, quite apart. from the fact that by virtue of the absorption of water, its lightweight is also lost.

Investigations have revealed that such constituents in the substances can absorb.50 or more % by weight of water when they "are subjected-to around 4 bars in a medium which contains a corresponding amount of water.

The invention is therefore based on the problem of guaranteeing the low weight and the resilience of corresponding constituents of light or resilient structural materials which have to be pumped at 4 and more bars.

According to the invention, this problem is resolved in that prior' to being admixed, the resilience and lightweight constituents are subjected to a preliminary treatment, their outer wall being sealed against penetration by liquid, above all water, without any substantial increase in their stability.

After sealing the surface of the resilient and lightweight constituents, the penetration of water is effectively prevented even under a pressure loading. Tests have shown that the water absorption of -resilient and lightweight constituents pre-treated in this way is less than 2% by weight. Compared with untreated resilient and lightweight constituents at over 50% by weight, this represents a marked reduction which cannot be overlooked where the efficacy of these constituents is concerned. As previously, these resilient and lightweight constituents are added to the binders and then transported and processed. Since the outside walls are essentially only insulated against moisture, i.e. above all water, as a result of this sealing, the brittleness of the resilieht-. constituent as a whole is retained so that - 3 under an appropriate pressure loading, the resilient element is still destroyed. Since water is unable to penetrate the individual component parts, not only are their function as a resilience constituent retained but also, the low weight so that appropriately pre-treated resilience and lightweight constituents can above all be advantageously used for lightweight structural substances, indeed regardless of whether they have to be added to an appropriate structural material in layers or are thoroughly mixed in a uniform manner.

Particularly in order not to increase the stability of the outer walls of the individual body or resilience and/or lightweight constituent part, the invention envisages a water-resistant seal of limited flexibility being applied. Furthermore, the seal does not represent more than a minimal coating because it is to a certain extent integrated into the outer walls of the individual body or is incorporated into such a body.

Such an advantageous seal can be ascribed to the resilient and lightweight constituents especially if they comprise expanded clay balls are first treated with a hydrophobing agent and then with water glass and are finally dried. The hydrophobing agent substantially prevents penetration by water, the water glass in turn having the task of securing the hydrophobing agent while simultaneously providing an additional masking of the surface to prevent water penetrating it.

Not every water glass is sufficiently resistant to the water so the invention provides for the resilience and lightweight constituents to be coated and sealed with a dilute hydrophobing agent and then with potassium water glass. This advantageously prevents the water being washed off so that even under an appropriate pressure 4 loading, the water can still not penetrate the individual bodies. Processing is particularly favourable if the still warm expanded clay balls are already coated with hydrophobing agent and then with potassium water glass because then the readiness to absorb these auxiliary coating agents is optimum.

exDanded clav balls After the expansion of the these still retain a corresponding amount of heat, and this is a particularly favourable time for sealing.

In order to avoid shrinkage cracks in the water glass or potassium water glass on the surface of the bodies, the invention furthermore provides for the resilient and lightweight constituents, after being sealed, firstly to be gently pre-dried and then oven-dried. This gentTe heating or drying not only prevents shrinkage cracks but also prevents the individual constituents becoming baked together, so that the individual bodies are retained after the drying process.

The treatment with the potassium water glass is particularly advantageous, i.e. a particularly hard coating is achieved if the secondary drying stage is carried out in an oven for 15 to 30 minutes at 40 to 80C, preferably at 60C. For practical purposes, there is then a thorough hardening of the potassium water glass, resulting in optimum properties.

With the protective pre-drying, there is a warming of the individual resilient and lightweight constituents so that contact with the potassium water glass can then be very favourably performed, if relatively great temperature differences are present. This is the case when, after the hydrophobing agent has dried off, the potassium water glass is in accordance with the method of - 5 the invention added cold to the still warm resilient and lightweight constituents.

As mentioned, in order to achieve both minimal weight and also water resistance, the invention provides for the seal to be applied in such a way that it covers the pore walls. This means that the seal is so thin that the individual pores remain in recess form, in other words they are not filled in by the potassium water glass or the other sealing agent. The result is an accessory component substance which can be processed particularly well.

Expanded clay has already been stressed as a resilient.. and lightweight constituent which should be preferably used. Appropriate expanded clay balls can be processed particularly well. These expanded clay balls can then be further processed as such in a particularly favourable manner and can even be pumped at high pressure if the individual balls according to the invention carry a seal which largely prevents penetration by water. This seal gives the individual balls a shape or retains their shape so exactly that they can be used for all manner of applications without being changed. The seal is so applied that the porous surface is even retained so that it is possible to achieve optimum bonding of the individual balls into the structural substance. The binding agent is able to settle in the pores so that the necessary bonding into the overall substance is assured.

Both when in use as a lightweight structural material and also when used as a resilient element, it is advantageous if the individual balls remain as such which is possible according to individual balls are sealed independently from one another. By an appropriate construction and treatment of the individual balls, agglomeration and sticking together the invention since the 6 - can be prevented, so that each individual ball can be kept as an isolated element. Only upon bonding into the binding agent or into the structural material is there any bonding into the material as a whole.

In order to protect the i.ndividual expanded clay balls lastingly against water penetration, the- invention provides that the ba - lls may have an inner seal consisting of a hydrophobing agent, preferably Durosif' (Trade Mark) 74a and an outer seal consisting of potassium water glass.

The potassium water glass protects the Durosil and - the whole ball, without the weight of the ball being substantially increased as a result. By reason of the hydrophobing agent, i.e. in other words the Durosil, the water is:.constantly prevented from penetrating each ball. The potassium water glass also represents a protective coating for the individual ball without this having any adverse effect on the resilience of the individual ball or the expanded clay as a whole.

The necessary stability is imparted to this seal and at the same time particularly to the outer seal in that the seal, preferably the outer seal, is thoroughly hardened. This means that the individual bodies are in dried for 15 to 30 minutes at 40 to 80 Oc-- preferably around 60 0 C so that the potassium water glass hardens through in order to form the secure protective coating desired.

The invention is characterised particularly in that a method has been provided with which it is for the first time possible also so to pretreat expanded clay balls and like resilient and lightweight constituents that th.ey can then be pumped even at a high pressure without losing their function in the process. Instead, it is possible at no substantial 1 - 7 expense so to pre-treat expanded clay balls that their "inner space" is sufficiently sealed and secured that the pores remain therein so that both the light weight and also the destructibility are retained. In particular, balls of expanded clay which have been previously produced by a firing process can be sealed almost continuously and simultaneously so that they are retained in the sealed condition and can also be subjected to further processing at once. Their water absorption is negligible since it is around 1%, the possible premise being that only the outwardly open pores absorb water, which means that the interior remains virtually unaffected by penetrating water even if a pressure loading is present. The protective gentle drying prevents any damage to the seal so that a lasting protection is guaranteed.

Further details and advantages of the object of the invention will emerge from the ensuing description of the associated drawings which show a preferred embodiment together with the necessary details and component parts. In the drawings:

Fig. 1 shows a section through a non-sealed ball, Fig. 2 is a plan view of the ball shown in Fig. 1, but with a seal, Fig. 3 shows a cross-section through the sealed ball and Fig. 4 shows a detail of the ball according to Fig. 3, with externally disposed pores.

Fig. 1 shows a resilient - and/or lightweight constituent, i.e. in this case a ball (1) consisting of expanded clay, the drawing showing this in cross-section. From the drawing, it is apparent that due to the preceding firing process, more or less large pores (3, 4) are more or less distributed through the clay (2) of the ball as a whole. These pores (3, 4) ensure that the ball (1) as a whole is of relatively low weight while on the other hand, - 8 if an appropriate pressure is applied, it can still suffer destruction. This intentional destruction, for example in the case of the dam material used in underground mining for roadside packing, is particularly protective because a reduction in volume takes place so that the compressed concrete or other structural material, not shown here, also undergoes a volume reduction without the material being immediately destroyed.

Fig. 2 shows the ball (1) in a perspective view, it being indicated that a seal (5, 6) has been applied externally which according to Fig. 3 comprises an inner seal and an outer seal (5). Here, the individual layers of the seals (5, 6) are shown as being particularly thick for the sake of clarity. In reality, the seal (5, 6) is so thin that it cannot even be perceived by the naked eye.

The hydrophobing seal (6) lies directly on the surface of the ball (1). The seal (5) consisting of potassium water glass on the other hand forms the outer covering coating, the illustration of this being greatly enlarged. What is clear is that now the inner pores (3, 4) are also unaffected by pressurised water, so that the ball (1) as a whole can completely fulfil the function envisaged for it. An attempt has been made in Fig. 3 to illustrate that the seal (5, 6) adapts to whatever may be the surface (8) of the ball (1).

By way of further clarification, Fig. 4 shows a detail from such a ball (1), it being apparent that the pores (2, 3) in the interior of the ball (1) are empty, i.e. are only filled with air, whereas the pores (4') which are in the region of the surface (8) are provided with the seal (5, 6) over their entire pore wall (7). This is. intended to illustrate that the seal (5, 6) is so thin that the pores (4') are retained as such even if the seal (5, 6) has been applied to the ball (1) in the manner proposed by the invention.

All the said features, even those which can only be derived from the drawings, may be regarded individually and in combination as features of the invention.

E X A M P L E S The results of some sealing experiments are shown hereinafter summarised in tabular form. Tests 1 and 2 were carried out with sodium silicate, the appropriate pre-treated expanded clay balls only being dipped in the water once. Here it may appear that relatively low water absorption is experienced, but in view of the field of application, this is far from reality because during pumping, pressures of situations.

4 bars and above prevail in such For this reason, tests 3 to 9 were carried out with sodium silicate, potassium water glass and Durosil, in each case individually. The correspondingly pre-treated expanded clay balls were then immersed under pressure (4 bars). Here, it is demonstrated that in spite of the pre- treatment, 15 to more than 30% by weight of water were absorbed by the expanded clay balls so that these tests have to be described as unsatisfactory.

In principle, the same also applies to tests 10 to 12, but in this case Durosil was applied in a single or double layer. Here, too, the water constituents absorbed are still too high, but it is already clear that in accordance with test 12, with a corresponding oven drying, i.e. in other words drying under suitable conditions, the water absorption does drop.

- Optimum values are achieved with a double sealing using Durosil and potassium water glass, if an appropriate treatment follows, i.e. a protective and then controlled drying. Then even with immersion under high pressure, a water absorption of only about 1% by weight is achieved and this can be regarded as negligible.

Of interest here is test no. 14 which illustrates that with a treatment with just potassium water glass and otherwise the same treatment, a water absorption level of around 18% by weight is still observed. Therefore, this Table illustrates very clearly that it is important to have a controlled pre-treatment of the expanded clay balls or other resilience and/or lightweight constituents of a structural material.

1 Summary of th._seal..itig tests -.9 -. E.

Sealing fluid Sealing methodl Mass increase Immersion test Immersion time Water absorption by weight) (mi n) by weight) 1. NaWg 40/42 E, H, 0 OF1,1 5 1.0 2. NaWg 40142 E. H. 0 OFN 1440 8.0 3. NaWg 48/50 E, H, 0 35.41 UD 10 15.36 4. NaWg 40.42 E, [1, 0 24.55 UD 10 28.22 5. NaWg 28/30 E, H, 0 12.20 UD 10 30.72 6. Durosil 74a(I:5) E. H. 0 3.54 UD 10 21.41 7. Durosil 74a(I:4) E, H, 0 3.55 OD 10 27.93 8. Durosil 74a(1:3) E. H. 0 3.63 UD 10 30.70 9. Durosil 74a(1:2) E H, 0 3.88 UO to 28.30 10. Durosi 1 74a(1:5) D H, R UD 10 28.24 11. Durosil 74a(I:5) E H, R UD 10 22.50 12. Durosil 74a(l:S) D, H, 0 UD 10 18.15 13. KaW9 28/30 D H, 0 UD 10 1.48 14. KaWg 28130 E 11, 0 UD 10 17.10 NaW9 m Sodium E = Single seal OFN = Immersed close to the surfac e silicate 0 = Double seal UD = Immersed under pressure (4 bars) Ka14g = Potassium H = Pre-drying silicate 0 = oven drying R = long-term drying 1 1 9 a 12 P a t.e n t

Claims

C 1 a i m s

A method of producing a building material having resilient land/or lightweight constituents which tend to absorb water and which are intended particularly for the roadside packing in underground mining work and which, after being mixed, is pumped at 4 to 6 bars, the resilient constituents -being added in a layer-wise or even distribution, wherein -prior to being admixed, the resilient and lightweight constituents are subjected to a preliminary treatment, their outer wall being sealed against penetration by liquid, above all water, without any substantial increase in their stability.
2. A method according to Claim 1, wherein a water-resistdnt limited-flexibility seal is applied.
3. A method according to Claim 1, wherein the resilient and lightweight constituents, preferably expanded clay balls., are initially coated with a hydrophobing agent and then water glass, after which they are finally dried.
4. A method according to Claim 1 or Claim 3, wherein the resilient and lightweight constituents are coated and sealed with a dilute hydrophobing agent and then with potassium water glass.
5. A method according to Claim 1 to Claim 4, Wherein after sealing the resilient and lightweight constituents are first gently pre-dried and then dried in an oven.
6. A method according to Claim 5, wherein the secondary drying is carried out in the oven for 15 to 30 minutes at 40 to WC and preferably at WC.
7
8.

A method according to Claim 4, wherein after the hydrophobing agent has dried the potassium water glass is added cold to the still warm resilience and lightweight constituents.

A method according to Claim 1 wherein the seal i ng is applied to cover the walls of the pores.
9. Expanded clay balls of moistly prepared and oven-fired clay or balls of a similar lightweight structural material which is to be processed with water binding agents to produce lightweight cement products or structural members capable of controlled yielding, wherein the individual balls have a seal which substantially prevents penetration by water.
10.

Expanded clay balls wherein the individual balls provided with the seal another.
according are independently to Claim 9, of one Expanded clay balls according to Claim 9, wherein the balls have an inner seal of a hydrophobing agent, preferably Durosil 74a and an outer seal of potassium water glass (KaWg).
12. Expanded clay balls according to Claim 9 and Claim 11, characterised in that the seal and preferably the outer seal ---isthoroughly hardened.
- 11+. - A method of producing a balled resilient or lightweight building material constituent comprising sealing the outer wall against penetration with a sealent not substantially increasing the strength of the building material.
14. A method of producing a building material substantially as described herein.
15.

A resilient or lightweight building material comprising crushable balls of porous material each ball having a seal substantially preventing water penetration.
16. A resilient or lightweight building material substantially as described herein.