FR2830855A1 - Preparation of a light insulating concrete containing a cement coated cork or wood aggregate by preparing a milt of the coating element and spraying and mixing with the aggregate - Google Patents

Abstract

Preparation of a light insulating concrete containing a cement coated cork or wood aggregate, or a like particles of an element rendering them inert to external agents, consists of: (a) preparing a milt with the different coating elements by mixing them with a certain amount of water; (b) spraying this milt onto the cork or wood aggregate; (c) mixing this until the aggregate is coated; (d) drying the resulting coated aggregate. An Independent claim is also included for the light insulating concrete obtained.

Description

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 The present invention relates to a process for preparing a lightweight insulating concrete containing a cork or wood granulate or the like, and the lightweight insulating concrete obtained by said process.

 It is known that lightweight insulating concretes are cementitious matrix composite materials in which the conventionally used mineral aggregates, such as gravel or sand, are partially or completely replaced by light coated aggregates.

 Such lightweight insulating concretes offer advantages over conventional concretes, in addition to their lightness, they have qualities in thermal insulation of sound and sound insulation.

 The coated aggregates used must imperatively have certain criteria such as low chemical reactivity with respect to the environment and small dimensional variations as a function of the hygrothermal variations to which they are subjected.

 For this purpose, they are subjected to physical or chemical treatments such as mineralization which makes it possible to reduce the hygroscopy of the aggregates and their water absorption capacity, or the surface coating which makes it possible to isolate the cork, wood or the like and to make it inert vis-à-vis external agents.

 Among the coating techniques coating treatments are known using resins or paraffin, but also coating treatments using cement.

 These lightweight insulating concretes consisting of aggregates coated with cement are for example described in documents EP 0.517. 577 and FR 2.772. 745.

 The first describes a treatment process that involves dry coating silica wood granules to create a barrier that prohibits, at least temporarily, physico-chemical exchanges of wood with the external environment.

 In the second, which gives a better result, the coated wood granulate is obtained by mixing with water added with a plasticizer, then adding cement or silica fume, and optionally water until obtaining a non-pasty mixture, then drying.

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 The impregnation of the wood aggregate with the mixture of plasticizer and cement leads to the sealing of the pores of the wood, the paste penetrating the pores and the channels of the wood before solidifying.

 Clogging of the pores and the channels of the wood thus produced makes it possible to avoid the subsequent recovery of moisture. As a result, lightweight insulating concretes made from such a coated wood granulate have good stability qualities with respect to hygrothermal variations.

 The granulate thus prepared, however, has disadvantages, mainly of heterogeneity. In fact, the aggregates successively receive the various products that constitute the coating, such as cement, silica fume, plasticizer and water, and it has been found that not all aggregates are homogeneously charged, some being loaded more in cement compared to other loaded more plasticizer or others in silica fume. This heterogeneity of coating induces a weakening of the aggregates which know during handling a significant segregation. It follows that a lightweight insulating concrete made with such aggregates can age badly and lose its qualities of thermal and sound insulation.

 The object of the present invention is to overcome this drawback by proposing a process for the preparation of lightweight insulating concrete containing a cork or wood granule or similar encased in cement, and the light insulating concrete obtained, the coating of which is carried out in a manner homogeneous.

 The process for the preparation of a lightweight insulating concrete containing a cork or wood granulate or cement-coated analogue according to the invention is of the type consisting in coating particles of cork or wood or the like with an element capable of rendering them inert to external agents, and it is essentially characterized in that it consists in preparing a milt with the various coating elements by mixing them with a certain amount of water, then pouring said laitance by sprinkling on a cork granulate or wood or the like, then to knead the whole until a coating of said granulate, and finally to dry the resulting granulated sugared.

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 According to an additional characteristic of the process according to the invention, the wood granulate is dusted with cement or lime after kneading and before drying.

 Dusting cement or lime after the brewing operation and before that of drying, avoids agglomeration of the aggregate.

 According to an additional feature of the device according to the invention, the granulate consists of cork or wood grains or the like, while the products incorporated in the water to produce milt consist of a plasticizer, cement or lime and silica fume.

The cork or wood grains or the like used are preferably of a particle size of 0 to 4 mm, 0 to 8 mm, 0 to 16 mm or 4 to 16 mm depending on the intended use of the product. lightweight insulating concrete:

<Tb>
<tb> USE <SEP> GRANULOMETRY <SEP> (mm)
<tb> blocks <SEP> 0/8 <SEP> AND <SEP> 0/4
<tb> screeds <SEP> 0/16
<tb> walls <SEP> anti-noise <SEP> and <SEP> 4/16
<tb> other <SEP> cavernous <SEP> panels.
<Tb>

 According to a second variant of the process according to the invention, the aggregates consist of waste of cork or wood or the like, while the products incorporated in the water to produce milt consist of cement and / or lime, plasticizer and silica.

 Given the mixing of the ingredients, we can minimize the products other than cement or lime, resulting in a reduction in the cost price.

Example of proportions
220 kg of cement,
2.2 Kg of plasticizer
11 kg of silica
Lime, replacing or supplementing cement, will preferably be used in hot countries, given the time required for drying.

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 The lightweight insulating concrete obtained with a cork or wood granulate or the like prepared according to the process according to the invention has a better cohesion and therefore an increased resistance. In addition, there was less shrinkage and friability, and better workability.

 The coating obtained by the method according to the invention therefore has many advantages over the coating practiced so far.

 Thus, compression resistance tests were carried out, which consisted in placing lightweight insulating concrete blocks between the two plates of a hydraulic press and raising the pressure without jolting until said blocks broke, the latter being prepared for the first one based on conventionally coated granulate, and for the second based on cork granulate coated with the process according to the invention.

The measurements obtained are as follows:

<Tb>
<tb> Mixed <SEP>: <SEP> 2,53 <SEP> Mpa
<tb> Draggered <SEP>: <SEP> 3.10 <SEP> Mpa
<Tb>

The light insulating concrete according to the invention obviously has a greater compressive strength than a light insulating concrete prepared in the traditional way.

 The fire resistance of a light insulating concrete block according to the invention, also made from a cork granulate, has also been tested.

 The test consisted of subjecting the block to a temperature of 1500 C produced by the flame of a torch for 15 minutes. On the one hand, there was no smoke or gas evolution, and on the other hand that the material only slightly disintegrated at the point of contact with the flame.

 These characteristics, superior to that of a traditional mix, result essentially from the homogeneity obtained by the coating of the granulate.

 The thermal conductivity of such lightweight insulating concrete, which is 0.170 W / mK, has also been measured so that it has insulating qualities superior to those of traditional light insulating concretes.

Claims (4)

1) Process for the preparation of a lightweight insulating concrete containing a cork or wood granulate or similar encased in cement, of the type consisting in coating particles of cork, wood or the like with an element capable of rendering them inert external agents, characterized in that it consists in preparing a milt with the various coating elements by mixing them with a certain amount of water, then pouring said laitance by sprinkling on a cork granulate or wood or analogous, then to knead the whole until a coating of said granulate, and finally to dry the resulting granulated sugared.  2) Process according to claim 1, characterized in that one dusting with cement or lime the cork granulate or wood or the like after kneading and before drying.  3) Process according to claim 1 or claim 2, characterized in that the aggregate consists of cork or wood grains or the like, while the products incorporated in the water to achieve milt consist of a plasticizer, cement or lime and silica fume.  4) light insulating concrete characterized in that it is obtained by the method according to any one of the preceding claims.