A DEMOLISHING METHOD AND AN AGENT FOR THIS

Abstract: At breaking by means of burnt lime which is added together with water in order first to form a hard body which will then expand and break, an endothermic reaction and corresponding agents are used to brake the exothermic reaction of the burnt lime so that the added water does not start to boil and blows the agent out of the bore. An endothermic reaction is preferably chosen that does not start until water is added and/or a certain temperature is reached.

Description: A demolishing Tiethod and an agent for this In the last decades agents for demollshing/break- lnβc. rock, concrete and the like have been develoυed as alternatives ' to detonating exυlosives without the disadvantages accoτ anylng explosives that make these unsuitable in constructional activities in buildings and densely built-up areas. These new deτιolishing agents have a considerably slower effect eliminating sonic bangs, explosion gases * dust for¬ mation and minimize the required protective measures. Demolishing agents and associated methods used so far are aimed at adding burnt lime and reaction agents by means of a special υrocess in order to reduce the reaction time of the lime, thickeners- and water. The demolishing compound is then filled into prebored holes e.g. in rock or stone which break after some time. The chemical reactions are strongly temperature dependent in such a way that low temperatures give a long breaking time and high temperatures sive a short reaction and breaking time. Therefore dif¬ ferent composite materials have been υroduced for different temperature ranges. As examples of nrac- tical results it can be mentioned that a breaking time of 25 hours must today be calculated at an ambient temperature of 2-6°, at a temperature of between 18 and 22° a breaking time of 7 hours and, if the ambient temperature is as high as 28-32°, k hours. Apart from the fact that the relatively long breaking times are not desired and that eaki g agents must be carefully chosen all accordl-ner to temperature which is made still more difficult in that the temperature for the Ion-? times concerned may vary very much It is of course desirable for economical reasons to obtain a more ranld nrocess. β 4D However, it has so far been found to be difficult to achieve this i.a. due to the fact that when the reaction times are shortened the chemical reactions can take place at ' such a rate that the arising temperatures (the reactions are exothermic) amount to more than 100 before the compound has hardened which results in the water In the mixture being evaporated and the compound being blown out of the bores (blow-out) instead of hardening. It is the object of the invention to remove the above disadvantages and to obtain a more rapid breaking process as well as agents for this, said agents, moreover, being useful within a greater temperature range with minor variations of breaking t me. This object is accomplished in accordance with the Invention in that an endothermic reaction is arranged in parallell with the exothermic reactions to a certain extent, the expression endothermic being understood in a wide sense, i.e. a reaction is intended that can absorb.heat. This reaction need not be chemical but can also be a physical one. Nor is it necessary that the reaction goes in one direction, only, so that absorbed heat remains blocked but it is also possible that the absorbed heat can be given off again when the temperature decreases. It is also possible within the scope of the invention to use an endothermic reaction having a retarding effect on the working eτothermlc reac- tions of the demolishing agent. Endothermic reactions with threshold values are preferably used, i.e. below these temperatures no absorption of energy or brakinc: of temperature takes place. Of course these threshold temneratures need not be distinct temperatures but can consist of reaction gradients. The endothermic reaction can be accomplished by adding substances capable per se of reacting eπdo- ther.mlcally at dissolution in water or at melting, vaporizing, or which give an endothermic reaction only together with water. As water is added to all the agents found on the market the endothermic reaction need not necessarily have any threshold 5 value in this case as it is initiated and takes place in parallell with the exothermic reactions. By the parallel! arrangement of an endothermic reaction one can permit oneself to carry the exo¬ thermic reactions at such a great velocity that they 10 give themselves (controlled by the endothermic re¬ action) an enough high temperature in order that the reactions might take place rapidly. In this way fast breaking or demolishing processes are made possible also at lower plus temperatures at the 15 same time as it will be possible to use the same agent for higher temperatures. The endothermic * substances or agents added are only used in the. quantities required for the desired effect. How¬ ever, it is essential that the threshold value of 20 the endothermic reaction is below 100° or, alterna¬ tively, that the endothermic reaction has started so much already below 100°C that it prevents the temperature from rising above 100°C. It should especially be pointed out that the 25 risk of uncontrolled rapid reactions is greater at larger diameters of the holes In which the de¬ molishing compound is placed. This means in turn that it will be possible by the invention to use larger bore diameters which in turn gives greater 30 total breaking forces, and consqeuently the distances between the holes can be increased. It is also possible within the scope of the ^ invention that the additive responsible for the endothermic reaction is added only in connection 35 with the mixture of the demolishing agent with water. In an extreme case the water can be added only after the demollshi a. agent has been posi¬ tioned in its hole. Within the scope of the in¬ vention there is nothing preventing one from utl- lizing agents aiding in the formation of a solid body for the endothermic reaction. Within the scope of the Invention extremely rapid reaction processes within the demolishlnα: technique are possible. To permit gas or vapor possibly formed to leave rapidly the demolishing powder material can be sintered in one form or the other, e.g. in the form of tablets with sufficient grain density. As the tablet agent, in any case at the start, is permeable as a consequence of the spaces between the tablets, possible vapor or gases are prevented from creating blow-out tendencies. If the powder agent is made enough permeable for a sufficient time demolishing agents having an extremely rapid reaction can be used in this tech¬ nique at high temperatures, big hole diameters and small hole distances without any blow-out being obtained but resulting in blow-outs/breaking within some hour.

Claims: Patent Claims 1. A method at demolition and breaking by the aid of an agent that will in use first harden and then expand, c h a r a c t e r i z e d in that an endothermic reaction is used to adjust the reaction velocity, especially during the exothermic hardening phase. 2. The method of claim 1, c h a r a c t e r ¬ i z e d in that the endothermic reaction has a threshold value so that it will first start at temperatures above a definite temperature. 3. The method of claim 2, c h a r a c t e r ¬ i z e d in that the endothermic reaction starts in the temperature range 20-80°C, preferably 0-60°C. . The method of any one of the foregoing claims, c h a r a c t e r i z e d in that the endothermic reaction is initiated or made possible when water is added to the demolishing agent for use-, 5« A demolishing agent for carrying out the method of claim 1, c h a r a c t e r i z e d in that it comprises a substance or substances capable of creating an endothermic reaction. 6. The demolishing aa;ent of claim 5» c h a r a c- τ t e r i z e d in that it has a temperature threshold for the endothermic reaction so that no heat energy is absorbed below this threshold whereas absorption takes place above this threshold. 7. The demolishing agent of claim 5 or 6, c h a r ¬ a c t e r i z e d in that the endothermic organic or inorganic addition to the agent is dissolved or has Its melting point in the desired range of tempera¬ ture adjustment and that the heat absorption corre- -\ sponds to the melting heat or, alternatively, the dissolution heat. 8. The demolishing agent of any one of claims 5 - 6, c h a r a c t e r i z e d in that the endothermic additive in the demolishing agent reacts with water through hydration.

Inventors: JOHANSSON SVEN-ERIK, KAOWERT KAOWE, JOHANSSON, SVEN-ERIK, KAOWERT, KAOWE
Applicants: CEMENTA BYGGPRODUKTER AB
Application year: 1986
Main classification: E21C37
IPC codes: C04B41, E04G23, E21C37