NL2007738C2 - METHOD FOR CONTROLLED MANAGEMENT OF PURIFICATION OF YOUNG CONCRETE IN PRODUCTION SITUATIONS. - Google Patents

Abstract

Method for the production of a component of cement concrete with preferably reinforcement in a mould, preferably a thick walled massive structure outdoor, wherein a pipe is located into the mould and the from free concrete is poured over it such that said pipe is embedded into the concrete, preferably at least 20 centimetre below the concrete surface, and wherein through said pipe a heating or cooling liquid or gas like fluid is flown such that the concrete is from the inside and in a controlled manner heated or cooled by the fluid while the concrete cures to its final strength.

Description

Method for the controlled management of hardening of young concrete in production situations

The invention relates to a specific method for producing a concrete structure and the like.

When a concrete construction is made, a formwork is used that delimits a space in which the reinforcement is first placed and then the concrete mortar is poured. The formwork remains in position until the concrete is sufficiently cured and sufficiently self-supporting. Since the formwork is costly, the construction must be removed as quickly as possible so that the formwork can be reused.

The concrete is an initially form-free artificial stone-like material with mineral cement as a binder and mineral granulates such as sand and gravel which after curing offers a high compressive strength and possibly contains an internal reinforcement of, for example, steel bars.

During the hardening of concrete, the chemical reactions that take place release heat. Especially with thick-walled and mass constructions, such as for example a tunnel wall or pillar beam, internal areas occur where, when conventional cements according to EN 197-1 do not use cooling, the temperature can rise much too high, for example 65 to 80 degrees Celsius can reach. Too low concrete compressive strength, deferred sulphate attack, too high tensile stresses and hence cracking in the cured concrete can result.

With further curing, the speed of the chemical reaction decreases, causing the temperature to fall. However, then the strength and cohesion of the concrete are such that the hardening concrete already starts to shrink externally, so that internal tensile stresses arise.

In the case of large temperature differences between concrete core and concrete surface, these tensile stresses will rise high, as a result of which shrinkage cracks will easily arise. Shrinkage cracks and the aforementioned effects affect the functionality and durability of the structure.

Conversely, the form-free concrete must not be too cold during hardening, because otherwise the hardening will take up too much time. Reason why concrete is poured in cold weather conditions that is preheated in the concrete factory to a temperature between 15 and 20 degrees Celsius.

Some structures, such as tunnel elements, are made in 5 parts, for example first the bottom, then the upright walls and finally the roof. Thus, a following portion is made against an already hardened and cooled portion. Also because of this, cracks can easily occur and high internal tensile stresses and hence shrinkage cracks can arise, for example, in the area from the point of attachment towards the hardened and cooled part.

NL9500383 discloses a formwork which is equipped with a heat exchanger through which a cooling liquid circulates, so that during concrete hardening the concrete is alternately cooled and heated. For thick-walled constructions, external cooling is not the solution.

For thick-walled constructions, the use of internal cooling housings is known, through which cooling fluid circulates, with which the heat generated during hardening is discharged directly from the core to outside the construction in order to keep the temperature of the core sufficiently low.

JP2006008431A discloses placing a form-filled concrete in a water tank. Hollow pipes protrude through the hardening concrete so that the water from the tank can circulate through the hollow pipes. Thus, heat is dissipated from the core to the outside of the formwork while the water around the formwork heats up by mixing with heated water from the tubes. This state of the art requires placing the formwork filled with hardened concrete in a water tank and is therefore unsuitable for a thick-walled concrete construction. Thus, this state of the art is not relevant to our invention.

DE 3644532 Al discloses the creation of tunnel elements during tunnel drilling. A concrete is used which can be processed for more than two hours at a temperature of approximately 20 degrees Celsius, but which can no longer be processed within a few minutes at a temperature between 40 and 70 degrees Celsius. The flowing concrete is heated in the area of the sliding formwork in the concrete transport pipe by immediately introducing electrical energy to the temperature between 40 and 70 degrees Celsius. This state of the art relates to preheating the concrete even before it has been poured into the formwork. Thus, this state of the art is also not relevant to our invention.

The invention contemplates a further improvement of the controlled hardening of a thick-walled mass construction of concrete, also in situations where the construction is made into parts in which the concrete for a next concrete part is poured onto a previously made and already hardened concrete part . This concerns both constructions that are made in the work and / or the outside air, as well as constructions that are made in a factory where the processing conditions, including the environmental conditions, can often be better controlled.

The object of the invention is versatile and involves, among others, one or more of the following aspects: limiting the peak temperature during hardening so that delayed sulphate attack and strength reduction will not occur; reducing the risk of cracking and tensile stresses in the hardening concrete so that structures remain homogeneous and watertight; advance the moment of initial bonding of concrete mortar under cold weather conditions, as a result of which preheated concrete mortar will be required less quickly; accelerating the hardening of young concrete after the chemical hydration reaction is largely over and the hardening rate will naturally slow down by cooling the structure to 30 ambient temperatures; with all this, ensure a more durable, high-quality construction cross-section of concrete.

To this end, an interconnected system of water / liquid-carrying pipes is placed in the formwork and is poured into the form-free concrete, so that those pipes are embedded in the concrete mortar and wherein a heating or cooling liquid or gaseous medium is allowed to flow through these pipes so that the concrete is heated from the inside or cooled by this medium.

In one embodiment alternately heating and cooling medium is passed through the concrete, via the same embedded pipes or separately embedded pipes, possibly with an interval during which no deliberately cooling or heating medium is passed through the pipe. For example, during and / or after the pouring of the form-free concrete, heating medium is first supplied to raise the temperature of the concrete from, for example, 5 to 20 degrees Celsius, after which it is waited for some time and then cooling medium is supplied to increase the rising temperature of lowering the concrete or not allowing it to rise further, after which, for example, heating medium is again supplied.

On the one hand, the medium can be allowed to flow through the pipe in the period that the concrete is not yet sufficiently hardened, for example to activate the concrete mortar in its bond early in its chemical reaction, or to prevent the concrete from becoming too hot, followed by recirculating, thereby stimulating the chemical reactions, for example to accelerate post-curing by supplying heat from the inside to the concrete mortar, or to reduce the risk of cracking by reducing the temperature difference in the mass cross-section, or between the already cured, cooled part and the just poured-in part of a concrete construction to be manufactured in parts.

In one embodiment, temperature sensors are used with which the temperature of the concrete is measured, on the basis of which measured values the flow of the medium through the pipe and the temperature (for example the inlet temperature, ie with which the medium enters the embedded pipe) of the medium is controlled. The temperature and flow of the medium are preferably computer-controlled and the sensors are connected to the same control unit. One or more temperature sensors are preferably embedded in the concrete, for example by placing such a sensor in the formwork, after which the form-free concrete is poured into the formwork so that the sensor is cast in the concrete. By embedding more than one sensor, a temperature gradient can be measured on the basis of which heating and cooling can be optimized.

The heating medium preferably has a temperature between approximately 20 and 40, more preferably between approximately 25 and 35 degrees Celsius. The cooling medium preferably has a temperature between about 5 and 15, such as about 10 degrees Celsius.

The pipe is preferably made of steel or polymer, such as tylene.

In one example there is a pump, a storage tank, a cooling and heating unit and a computer-controlled control unit outside the formwork. The computer runs a program and on this basis starts and stops the pump and the cooling and heating unit, the program making use of the signals supplied by the temperature sensors. The pump circulates the medium between the storage tank and the collapsed pipe. Depending on whether the concrete needs to be cooled or heated, the cooling or heating unit is switched on. In dependence on the temperature gradient determined with the sensors, possibly corrected to ambient temperature, the flow rate and the inlet temperature of the medium are automatically set via the program.

The computer could be included in a network, so that it is possible to log in remotely on the computer to enter control data or to request measurement data.

The invention may, for example, be embodied in a method for producing a component, such as a tunnel element, of reinforced concrete in parts by pouring parts together, for example the parts of bottom, upright walls and roof, the component having a wall thickness of at least about 50 or 80 centimeters and is produced in a formwork in which the reinforcement is placed prior to pouring the concrete. This is preferably carried out in which a separate pipe of steel 6 or polymer, such as tylene, is placed per part in the formwork, which pipe is poured into the form-free concrete, so that said pipe is embedded in the concrete and at a depth of at least approximately 10 or 15 or 20 centimeters below the concrete surface and allowing the concrete to cure until the part is sufficiently self-supporting, after which the formwork is removed, each subsequent part being made by pouring its concrete mortar against an already hardened and cooled and preferably demoulded part so that the fresh concrete mortar adheres to the already cured concrete, so that eventually an integral component is formed, and wherein, after the concrete mortar for the next part has been poured against the previous, possibly uncoffed, part, heating liquid medium with an elevated temperature, for example of approximately 30 degrees Celsius, flows through the pipe in the foregoing, o The cased part against which the concrete mortar for the next part has been poured, to heat the previous, cased part from the inside to ensure a temperature increase of at least 10 degrees Celsius, such as approximately 20 degrees Celsius during the curing period 20 until the concrete of the poured next part is sufficiently cured to be sufficiently self-supporting, whereafter this next part is optionally decomposed, while during the same curing period cooling liquid medium with a low temperature, for example of approximately 10 degrees Celsius is allowed to flow through the pipe in the next part to this following cooling part from the inside to dissipate the heat released during the hardening of the concrete mortar by the chemical reactions taking place, while preferably also temperature sensors collapsed during the concrete are collapsed, with which medium flows during the curing period during the curing period the t concrete temperature is internally measured, on the basis of which measured values the flow of the medium through the pipe and its inlet temperature are controlled by the control computer. Other temperatures for heating and cooling are also conceivable, for example to be determined on the basis of the composition of the concrete used.

Claims (15)

Method for producing a cement concrete component in a formwork, wherein a pipe is placed in the formwork that is poured into the form-free concrete, so that said pipe is embedded in the concrete, and wherein a heating or cooling liquid or gaseous medium flows so that the concrete is heated and cooled from the inside and controlled in a controlled manner by the medium while the concrete hardens to its final strength. 2. Method according to claim 1, with one or more of the following: a cement-reinforced concrete component is produced; the component is a thick-walled mass construction; is produced in the open air; the pipe is embedded at least 20 cm below the concrete surface. 20 Method according to claim 1 or 2, with one or more of the following: the medium flows, for example through a pump; During the process, the component is located outside of a liquid tank; the component is not submerged during the process; heating or cooling by the medium is carried out after the formwork has been filled with concrete to the predetermined extent and concrete pouring has thus been completed. 4. Method as claimed in any of the claims 1-3, wherein temperature sensors are used with which the temperature of the concrete is measured, on the basis of which measured values the flow of the medium through the pipe and the temperature of the medium in the pipe are controlled. The method of claim 4, wherein the temperature and flow of the medium are computer controlled by the control unit and the sensors are connected to the same control unit. 5 Method as claimed in claim 4 or 5, wherein the one or more temperature sensors are embedded in the concrete, for instance by placing such a sensor in the formwork after which the form-free concrete is poured into the formwork so that the sensor 10 is poured into the concrete. 7. Method as claimed in any of the claims 4-6, wherein more than one sensor is embedded and with these two or more sensors a temperature gradient is measured which is used by the control unit 15 for controlling the flow of the medium through the line and the temperature of the medium in the pipe. 8. Method as claimed in any of the foregoing claims, with a pump, a storage vessel, a cooling and heating unit and a computer-controlled control unit outside the formwork, which program runs and starts and stops the pump and the cooling and heating unit on that basis, the program possibly utilizing the signals supplied by the temperature sensors. 25 9. Method as claimed in any of the foregoing claims, wherein the moment of the initial bonding is allowed to flow through the medium during cold weather conditions through heating pipe during or after pouring concrete, preferably for at least four or ten or twenty hours. 10. Method as claimed in any of the foregoing claims, wherein for young concrete flowing through heating medium through the pipe after pouring concrete and after the chemical hydration reaction has largely, substantially or at least 80% passed and the hardening rate due to cooling of the structure will naturally slow down to ambient temperatures, the hardening of the young concrete will accelerate considerably. 11. Method as claimed in any of the foregoing claims, wherein during or after pouring the concrete the temperature of the concrete is raised from approximately 5 to approximately 20 degrees Celsius or by approximately 15 degrees Celsius by the medium flowing through the conduit. The method of any one of the preceding claims, wherein the inlet temperature of the heating medium is between about 20 and about 40, such as between about 25 and about 35, and / or of the cooling medium between about 5 and about 15, such as about 10 , degrees Celsius. A method according to any one of the preceding claims, wherein during and / or after the concrete pouring, heating medium and thereafter cooling medium and then optionally heating medium are allowed to flow through the pipe while the concrete hardens to its final strength. 20 A method according to any one of the preceding claims, wherein forced cooling or heating is carried out by allowing the medium to flow through the conduit for a minimum of four hours or ten hours or two days. 25 15. Method as claimed in any of the foregoing claims, for producing in parts a component, such as a tunnel element, of reinforced concrete by pouring parts together, for instance the parts of bottom, upright walls and roof, wherein the component has a wall thickness of at least about 50 or 80 centimeters and is produced in a formwork in which the reinforcement is poured prior to pouring the concrete, whereby a separate line of steel or polymer, such as tylene, is placed in the formwork for each part, which is cast in the form-free concrete, so that that pipe is embedded in the concrete and is at a depth of at least about 10 or 15 or 20 centimeters below the concrete surface and whereby the concrete is allowed to cure until the part is sufficiently self-supporting, after which the formwork is removed, each subsequent part is made by pouring its concrete mortar against a concrete that has already been hardened and cooled and preferably part so that the fresh concrete mortar adheres to the already cured concrete, so that eventually an integral component is formed, and wherein, after the concrete mortar for the next part has been poured against the previous, possibly uncovated, heating liquid medium with an elevated temperature, for example of approximately 30 degrees Celsius flows through the pipe in the preceding, molded part against which the concrete mortar for the next part is poured, to heat the preceding, molded part from the inside to ensure a temperature increase of at least 10 degrees Celsius, such as approximately 20 degrees Celsius during the curing period until the concrete of the poured-on next part is sufficiently hardened to be sufficiently self-supporting, after which this next part may possibly be removed, while during the same curing period 20 cooling liquid medium with a low temperature, for example of approximately 10 degrees Celsius late flow n through the conduit in the next part to cool this next part from the inside to dissipate the heat released during the hardening of the concrete mortar by the chemical reactions taking place, while preferably also during the pouring, temperature sensors are collapsed with which during the pouring flowing medium through the pipes during said curing period the temperature of the concrete is internally measured, on the basis of which measured values the flow of the medium through the pipe and its inlet temperature are controlled by the control computer.