ES2683082B1 - Non-structural concrete made with polyurethane pellet waste from the refrigerators recycling process. - Google Patents

Description

DESCRIPTION

Non-structural concrete made with polyurethane pellet waste from the refrigerators recycling process.

Sector of the technique

The present invention is part of the field of construction materials, specifically in the area of non-structural concrete prefabricated for a sustainable and eco-efficient construction.

BACKGROUND OF THE INVENTION

The lapilli, known as the picón in the Canary Islands, is an arid volcanic nature of extremely low density that is widely used in the Canary archipelago for the production of non-structural light concretes. One of the most outstanding uses of this concrete with lapilli aggregate is the manufacture of pieces of masonry in the form of blocks of picón used for the execution of partitions and vertical enclosures and in the form of vaults and caissons for the lightening of slabs. At present the extraction of picón is an activity that supposes a huge landscape and environmental deterioration that is aggravated in territories as sensitive as the insular ones. Consequently, the use of this aggregate in a generalized manner has been giving rise to its progressive exhaustion as a natural resource.

The interest of this invention arises from the need to look for sustainable solutions that allow the use of residual materials as a substitute for natural aggregate in the production of non-structural light concretes. For this reason, we propose the recovery of a waste consisting of polyurethane PELLET (PUR-pellet) from the recycling of electrical and electronic equipment (WEEE), using it as aggregate in the design of a non-structural and eco-efficient lightweight concrete, which contributes to the concrete an important improvement in its thermal insulation performance.

This approach contributes to the fulfillment of the objectives established in Spanish legislation (Royal Decree 208/2005, of 25 February, on electrical and electronic equipment and the management of its waste) and European (Directive 2002/96 / EC of the European Parliament and of the Board, of 27 January 2003, on waste electrical and electronic equipment) which establishes the search for recovery systems for the conservation, protection and improvement of the quality of the environment, and prudent and rational use of the natural resources.

The specialized literature includes several works that seek sustainable solutions that allow the use of other plastics of different origin and format as aggregate in the manufacture of concrete. Saikia, N., & de Brito, J. (2012) "Use of plastic as an aggregate in cement mortar and concrete preparation: A review. Construction and Building Materials, 34, 385-401 "and Siddique, R., Khatib, J., & Kaur, I. (2008)" Use of recycled plastic in concrete: a review, Waste Management (New York, NY), 28 (10), 1835-52 "perform a bibliographic review that includes more than 15 works concerning the use of different plastic waste as a component of concrete. The plastics used for this purpose are of different nature and origin: polyethylene terephthalate (PET) bottles, plastic containers (80% polyethylene and 20% polystyrene), polyvinyl chloride (PVC) pipes, recycled melanin, PET and polycarbonate blends from industrial waste and expanded polystyrene foam from the recycling of packaging among others.

In reference to lightweight non-structural concretes made with polyurethane, all the works contemplate the use of polyurethane foam obtained in situ or from rigid foam waste that is necessary to crush previously.

Verdolotti, L., Di Maio, E., Lavorgna, M., Iannace, S., & Nicolais, L. (2008) "Polyurethanecement-based foams: Characterization and potential uses." Journal of Applied Polymer Science, 107 (1) , 1-8 ' present the characterization of a material obtained with foamed polyurethane in situ with different dosages of cement and water.

Mounanga, P., Gbongbon, W., Poullain. P., & Turcry, P. (2008) "Proportioning and characterization of lightweight concrete mixtures made with rigid polyurethane foam wastes. Cement and Concrete Composites, 30 (9) " work with polyurethane foam from waste insulation panels of buildings replacing different proportions of limestones.

Gadea, J., Rodríguez, A., Campos, PL, Garabito, J., & Calderón, V. (2010) "Lightweight mortar made with recycled polyurethane foam. Cement and Concrete Composites, 32 (9), 672 677 ' use as arid polyurethane foam from the destruction of panels used in the automotive industry replacing percentages of river sand.

No reference has been found in which this polyurethane residue compressed in the form of PELLET is used for the production of light non-structural concretes. This residue of PUR-pellet is obtained after the treatment of refrigerating appliances recycling. This treatment is carried out in two phases. In a first phase some components of the refrigerators are extracted as cables, trays, lubricating oil and gases from the refrigeration circuit, and later in the second phase, the rest of the apparatus is crushed under an inert nitrogen atmosphere. Through this process, a mixture of waste of different nature is obtained, which is separated to receive, each one of them, its corresponding discharge or recovery treatment. Among them is a thick fraction of polyurethane that is subjected to a process of pelletizing by passing it through a perforated plate that makes it into pellets with a diameter of approximately 5 mm. The height of the pellet leaving the perforated plate is adjusted by the frequency of a cutter and oscillates, generally, between 5 and 8 mm. The pelletizing process described above facilitates the release, capture and storage of the gases contained in the foams initially present in the insulation of the refrigerator.

Explanation of the invention

The invention relates to the manufacture of non-structural concretes by totally or partially replacing the aggregates with polyurethane PELLET (PUR-pellet). The polyurethane pellets are incorporated to obtain this concrete as they are after the treatment of the WEEE. Its granulometry is not modified nor is subsequent treatment carried out before its incorporation as a component of the concrete. The PUR-pellet obtained from WEEE has an approximately cylindrical shape with a diameter of about 5 mm and a height between 4 mm and 8 mm. The granulometric distribution is indicated in Table 1. Almost 95% of the PUR-pellet residue corresponds to the granulometric fraction 4/8.

Table 1. Gntmtfométrica distribution of i PUR-pellet and the picón

The density after oven drying of the particles (prd) was determined by the pycnometer method (UNE-EN 1097-6: 2014) which considers in its determination the volume of the particles, including the inaccessible and accessible water holes . The prd density of the PUR-pellet was 832 kg / m3. This density is much lower than the prd of the picón, with a value of 1,753 kg / m3. As a check, it is observed experimentally that at the time of introducing the PUR pellets in distilled water they float and sink when introduced in 2-propanol with a density of 787 kg / m3.

The manufacturing process for this new lightweight concrete consists of mixing cement and water with only PUR-pellet, or mixtures of PUR-pellet and other natural and / or artificial aggregates. To do this, mix it dry: cement, PUR-pellet and other aggregates, if necessary, in a planetary mixer for approximately 1 minute. After that time, the amount of water established in the water / cement ratio is added, and kneading is continued until homogeneity is observed in the fresh mixture.

From the tests and tests carried out, the following properties are deduced in lightweight concrete that incorporates PUR-pellet as aggregate in its composition:

- Low density of concrete made with PUR pellets. This supposes reduction of weight supposes an interest like pieces of masonry in the form of blocks and slabs nonstructural when diminishing the own overload of other prefabricated ones on the structures of the construction. The density values determined show that there is a linear correlation between the density of the concrete and the amount of cement used in its dosage. The values of the coefficient of determination (R2) are equal to or greater than 0.9, except for mixtures with 75% PUR that are 0.7. The density of concrete made with PUR ranges from approximately 1,000 to 1,150 kg / m3. For the same ratio a / c and quantity of cement, this density is 13% lower than those made with picón whose density varies between 1,100 and 1,500 kg / m3.

- Improvement of thermal insulation. The tests carried out show that the incorporation of polyurethane pellets waste allows to improve in the value of the thermal conductivity between 64% (100% PUR-pellet) and 38% (25% PUR-pellet) with respect to commercial concretes elaborated employee 100% lapilli (picon)

- Mechanical resistance. Compression strength values are obtained in a standardized cylindrical specimen of the order of 3.5 MPa or higher with concretes made with only PUR containing at least 400 kg of cement. This resistance value provides a reference to assess a possible application in the form of masonry pieces as the value obtained in the control sample of commercial concrete made with picon and used for the manufacture of blocks. With a substitution of 25% by weight of picon for PUR, concretes are obtained that reach the value of 3.5 MPa from cement dosages of 350 kg.

BRIEF DESCRIPTION OF THE DRAWINGS

Not applicable

PREFERRED EMBODIMENT OF THE INVENTION

In the elaboration of the test mixtures of this concrete, a cement was used with the addition of natural pozzolana CEM 1V / B (P) 32.5N and dosages grouped into two series whose composition varies according to the type, the proportion of aggregate and the amount of cement used in the mixture. For these tests, we worked with two water / cement ratios (a / c): 0.63 and 0.83, although this a / c ratio could be modified depending on the desired consistency.

Table 2. Dosing values, density (de28d) and compressive strength (Re ²⁸ d) at 28 days of the concretes made with PUR-pellet and mixtures of PUR-pellet and picon.

For mixtures with 100% PUR-pellet, an average thermal conductivity of A = 0.16 W / mK was obtained, increasing to a value of A = 0.27 W / mK for concrete with 25% in PUR- pellet and 75% in picón. These values of thermal conductivity are lower than those of commercial concrete mixtures containing only picón as aggregate (A = 0.44 W / m.K).

Concrete that incorporates PUR-pellet could be used in the manufacture of concrete masonry pieces. These pieces could comply with the thermal insulation of the building envelope using smaller thicknesses and therefore increasing the useful area of the house.

It could also be discharged in mass and used as insulating material executed in situ on horizontal elements or confining it in vertical elements so that it contributes to the constructive solution its insulating capacity with a reduced weight gain due to its low density.

Claims (2)

1. The partial or total replacement of concrete aggregate by polyurethane pellet (PUR-pellet) from the recycling treatment of refrigerating appliances in order to improve their performance. 2. The use of concretes made with partial or total incorporation of polyurethane pellets (PUR-pellets) from the recycling treatment of refrigeration appliances for the manufacture of masonry pieces and the implementation of construction solutions for their use in buildings.