FR2615620A1 - Method for "in situ" testing of the compression strength of cement conglomerates or the like and apparatus for implementing this method - Google Patents

Abstract

A method and a relevant apparatus are described for "in situ" testing of the compression strength of cement conglomerates or the like, in which the ageing of the conglomerate is accelerated by raising the values of temperature and humidity of the medium in which the ageing takes place. The method comprises sequentially: a phase of preparing at least one sample 6 obtained by pouring a predetermined quantity of cement conglomerate to be tested into a hollow mould; a phase of introducing the sample thus prepared into a container 12; a phase for adjusting the physicochemical parameters of the medium of the container, depending on the predetermined operational steps; a phase of extracting the sample from the container; a phase of removing the sample, which has been aged, from the hollow mould; a phase of placing the sample into a device 4 intended to measure its compression strength; a phase of actuating the device, which gives rise to the generation of signals dependent on the measured compression strength; a phase of processing and displaying the signals.

Description

 The present invention relates to a process for the "in situ" control of the compressive strength of conglomerates made of cement or the like and to an apparatus for carrying out the process.

 This apparatus can be particularly used in the building field to control the compressive strength, also called characteristic resistance "of cement conglomerates used for the construction of different types of structures.

For the effects of the provisions of the law valid in
Italy with regard to construction techniques, a cement conglomerate is indicated on the basis of its characteristic resistance to compression. This is defined as the value of the compressive strength below which we can expect to find 5% of the population of all measured resistance values; According to the provisions of Italian law, "characteristic resistance" means the resistance resulting from compression tests carried out 28 Days after casting, on samples in the form of cubes.

 Consequently, if one follows the traditional method in accordance with the Italian law in force, the control of the characteristic resistance of the cement conglomerate is only possible at the end of the twenty-eighth Day.

 This method therefore involves the risk that when the conglomerate has now hardened the results of the compression tests make it necessary to disqualify the product or else perform consolidation work and sometimes even demolition of the work.

 It is known that when it is a cement conglomerate the increase in temperature constitutes a factor capable of accelerating the hardening, provided that the product is kept in a humid environment.

In the sector, this knowledge is widely used in order to produce small-scale works and prefabricated elements which are caused to mature in heated environments with a high degree of humidity.

 As already said, according to traditional methodologies, the control of resistance currently requires relatively long times and these times obviously involve practical and economic disadvantages.

 The essential object of the present invention therefore consists in overcoming the drawbacks specified above with respect to the control method of known type, providing for the development of a method and of the respective apparatus for the "in situ" control of the resistance to the compression of cement conglomerates in a very short time, that is to say approximately 24 hours after casting, which are very functional and capable of giving very reliable results and, as regards the apparatus, of construction very simple, compact and low cost.

 This object and others are achieved by the method for controlling: resistance to conglomerates and by the apparatus for implementing the method forming the object of the invention, the main characteristics of which are illustrated in the claims which follow.

 Other characteristics and advantages of the invention will emerge more clearly from the detailed description made hereinafter of an example of execution of the method, .ett of a preferred embodiment of the apparatus, given simply non-limiting example with reference to the accompanying drawings relating to the apparatus, in which: - Figure 1 is a perspective view of the apparatus for the implementation of the process in question, some of which have been removed for better highlight some of them; - Figure 2 shows a side section of the apparatus for the implementation of the process in question, some parts have been removed to better highlight others.

 Referring to the appended drawings, the apparatus for checking the strength & compression of cement conglomerates according to the process forming the object of the present invention has been generally indicated at 1.

 The apparatus 1 essentially comprises an electric oven 2, a hydraulic distributor 3, a hydraulic press 4 and a control group 5.

 The electric oven 2 consists of a box-shaped container 12, provided at its upper part with a cover 11 articulated on one of its sides 13 and capable of allowing access to the interior of the oven 2.

 Inside the lower part of the oven 2 there is a heat exchange coil 9, above which two horizontal metal grids 7a and 7b are removably engaged to the interior walls of the container 12. The grids 7a and 7b superimposed relative to each other are intended to support samples 6 and they are suitably spaced from each other in a vertical direction, in order to allow the accommodation of several samples in the oven.

 The two grids 7a and 7b can oscillate because on one of their sides they are articulated at 19 to the container 12.

The heat exchange coil 9 is immersed in a layer of water 10 in order to create the desired conditions of temperature and humidity.

 The oven 2 is also associated with a transducer 18 intended to detect the temperature, which has not been described being known per se.

 Also the hydraulic part of the apparatus is not described here being carried out in a manner known per se. The hydraulic distributor 3 controls the press 4 to which it is connected by means of hydraulic pipes not shown.

 Above the press 4, the control group 5 is provided. This comprises a computer (not shown> with which are associated a printer 14, a display screen with light display 15, and control push-buttons 16.

 After having described the apparatus in question above all from a structural point of view, its operation appears as follows.

 When the casting is carried out, the quantity necessary for the preparation of two cubes 6 in two hollow molds 17 is removed from the cement conglomerate.

 The cement conglomerate to be checked is thrown into the hollow molds 17 which are then placed in the furnace 2, the first on the lower grid 7a while the grid 7b is held in the raised position, and the second on the upper grid 7b.

 It should be emphasized that the lower part of the oven 2 must be previously partially filled with a quantity of water 10 sufficient to create, at operating temperatures, the required relative humidity (equal to approximately 100%).

 The oven 2 is then hermetically closed by known means (not shown). At this point the oven 2 is actuated by acting on the push buttons 16 and the optimal thermal cycle is controlled by means of the control group 5 which supplies the coil 9 suitably.

 The phase of adjusting the physico-chemical parameters of the container medium comprises the following stages: - a first preheating stage in which the temperature is brought from the ambient value to a value of approximately 20-35KC in a time interval 2 to 4 hours; - a second step of raising the temperature to values of around 65-80 C in a time interval of 1 to 4 hours; - a third step of maturing said cement conglomerate at a temperature between 65C and 80'C for a time interval of 4 to 8 hours; - a fourth step of decreasing the temperature to values of around 20-35 C in a time interval of 1 to 4 hours; - a fifth stabilization step at a temperature of around 20-35 C for a time interval of 2 to 4 hours.

 The duration of the parameter adjustment phase described above is less than 24 hours.

 The value of the ambient humidity is kept constant during the parameter adjustment phase and is equal to approximately 80-100 h of relative humidity.

 During the various stages of the thermal cycle, the light display panel 15 displays the instantaneous temperature, the time which has passed and the time which is missing; at the end of the cycle, it informs the operator, by means of a light signal, that the cubes 6 have reached maturity. The cubes 6 will then be removed manually which will be placed in their respective hollow molds 17 and placed below the press 4. The latter will then be actuated by means of the control push buttons 16. The value of the corresponding compressive strength will appear on exit from printer 14.

 The printer 14 can also be used suitably to trace the course of the temperature inside the oven 2, during the various stages of the thermal cycle.

 The apparatus can advantageously be mounted on a suitable means of transport capable of facilitating its transfer to the employment areas.

 Obviously the apparatus for carrying out the process of the invention may take, during its practical implementation, forms and configurations different from that illustrated above without departing from the protective framework of the 'invention.

 In addition, all the details may be replaced by technically equivalent elements and the shapes, dimensions and materials used may be of any kind and size as required. Also the chemical-physical parameters may be modified, so that they can meet the various requirements, always within the limits of the inventive concept characterizing the present invention.

Claims (5)

R E V E N D I C A T I O N S  1. Process for the "in situ" control of the compressive strength of cement conglomerates or the like, in which the maturation of the cement conglomerate is accelerated by the increase in the values of the temperature and of the humidity of the medium in which said maturation takes place, characterized in that it comprises the following operating phases: - a first phase of preparation of at least one sample, obtained casting a predetermined quantity of cement conglomerate to be checked in a hollow mold; - a subsequent phase of introduction of said sample thus prepared into a container; - a subsequent adjustment phase, according to predetermined operational steps, of the physicochemical parameters of the medium of said container; - a subsequent phase of extraction of the sample from said container; - a subsequent phase of removal of the sample, which has reached maturation, of said hollow mold; - a subsequent phase of placing the sample in a device capable of measuring the compressive strength of said sample; - a subsequent actuation phase of said device, which will cause the generation of signals as a function of the resistance to compression measured; - a subsequent processing and display phase of said signals.  2. Method according to claim 1, characterized in that said parameter adjustment phase has a duration of less than 24 hours and that said parameters include at least temperature and humidity.  3. Method according to claim 1, characterized in that said phase of adjusting the physicochemical parameters of the medium of said container comprises the following steps: - a first preheating step in which the temperature is brought from the ambient value to a value d '' about 20-35 C in a time interval of 2 to 4 hours; - a second step of raising the temperature to values of around 65-80 C in a time interval of 1 to 4 hours; - A third step of maturing said cement conglomerate at a temperature between 65 <C and 80 C for a time interval of 4 to 8 hours; - a fourth step of decreasing the temperature to values of around 20-35 C in a time interval of 1 to 4 hours; - a fifth stabilization step & a temperature of approximately 20-35 ° C during a time interval of 2 to 4 hours, the value of the ambient humidity being kept constant during said phase of adjusting said parameters and equal to approximately 80 -100% relative humidity.  4. Apparatus for implementing the method according to the preceding claims, characterized in that it comprises: - at least one maturing container (12) the interior medium of which has adjustable physicochemical parameters; - a transducer (18) intended to measure the temperature inside said container and to emit a signal as a function of the detected value; - a device (15) for viewing the data detected by said transducer; - a mechanical press (4> intended to load said samples (6) to predetermined values; - at least one transducer intended to measure the pressure exerted by said mechanical press and to emit a signal which is a function of the detected value; a computer associated with said transducers and capable of instantly supplying the value of the compressive strength of the cement conglomerate and of regulating the value of the temperature in said container (12).  5. Apparatus according to claim 4, characterized in that said container (12) consists of an electric oven (2) provided with a heat exchange coil (9) immersed in a layer of water (10).