| WO2012069024A2 | 2012-05-31 |
| DE29724777U1 | 2003-12-11 | |||
| CN107098668A | 2017-08-29 |
HUISKES D M A ET AL: "Design and performance evaluation of ultra-lightweight geopolymer concrete", MATERIALS & DESIGN, ELSEVIER, AMSTERDAM, NL, vol. 89, 3 October 2015 (2015-10-03), pages 516 - 526, XP029303761, ISSN: 0264-1275, DOI: 10.1016/J.MATDES.2015.09.167
| CLAIMS 1. A method to manufacture a flooring element both for indoor and outdoor, characterized by a density greater than or equal to 1000 Kg/m3 and by a compressive strength greater than or equal to 4 MPa; said method being characterized in that it comprises : (a) a mixing step, during which a powdery mixture based on recycled foam glass powder is mixed with a basic solution with a pH greater than or equal to 10 and having a concentration of silicic acid salts greater than 2.5 M; during said mixing step, the weight ratio between the basic solution and the powdery mixture ranging from 0.3 to 0.6 to obtain a heterogeneous mixture; said powdery mixture comprising 50% by weight of recycled foam glass powder, from 0 to 10% by weight of inert material and from 0 to 50% by weight of a material chosen from aluminosilicates and recycled glass sand; (b) a firing/moulding step, during which the mixture resulting from the mixing step is poured into a mould having the shape of the element to be manufactured and heated at a temperature below 100°C and above 50°C. 2. The method according to claim 1, characterized in that said basic solution has a concentration of silicic acid salts ranging from 2.5 to 7.0 M. 3. The method according to claim 2, characterized in that said basic solution has a concentration of silicic acid salts ranging from 4.0 to 6.0 M. 4. The method according to one of the preceding claims, characterized in that said powdery mixture comprises, as inert material, ground rubber derived from used tyres without heavy metals . 5. The method according to one of the preceding claims, characterized in that said powdery mixture comprises microsilica and/or metakaolin. 6. The method according to one of the preceding claims, characterized in that said basic solution has a pH greater than or equal to 12. 7. The method according to one of the preceding claims, characterized in that said basic solution comprises NaOH and/or KOH. 8. A recycled-glass-based flooring element both for indoor and outdoor, characterized in that it is manufactured with the method according to the present invention and has a density greater than or equal to 1000 Kg/m3 and a compressive strength greater than or equal to 4 MPa. |
CROSS-REFERENCE TO RELATED APPLICATIONS
This patent application is related to Italian patent application No. 102018000009095 filed on 02/10/2018, the entire disclosure of which is incorporated herein by reference .
TECHNICAL FIELD
The present invention relates to a method to manufacture a recycled-glass-based flooring element, and to the flooring element thus manufactured.
BACKGROUND ART
The need to manufacture functional products with recycled material has been keenly felt for some time.
One of these materials is glass, which forms an important portion of waste. Although an effective used glass collection network has existed for some time, to date all the potentials of glass recycling have not yet been expressed.
Glass has a series of properties that make its recycling suitable in the manufacture of material for the building sector .
To date in the building sector it has only been possible to manufacture elements useful for wall insulation with recycled glass, while it has not yet been possible to manufacture a product based on recycled glass, with mechanical properties that allow it to be used in situations with high stress, such as, for example, flooring. In this regard, it must be underscored how the flooring elements are necessarily required to have low friability, low porosity, low water absorption levels and high strength. In particular, by flooring we mean a flooring suitable for vehicles, the element is required to have a density greater than or equal to 1600 Kg/m 3 .
Another requirement that has been present in the building sector for some time is that of being able to manufacture low cost building materials, without this in any way compromising the structural properties of these materials.
Therefore, the need was felt to manufacture flooring materials both for indoor and outdoor based on recycled glass, which were inexpensive and, at the same time, reliable from a structural viewpoint.
The inventor of the present invention has created a method to manufacture a flooring element that satisfies the above requirements .
DISCLOSURE OF INVENTION
The subject matter of the present invention is a method to manufacture a flooring element, characterized by a density greater than or equal to 1000 Kg/m 3 and by a compressive strength greater than or equal to 4 MPa; said method being characterized in that it comprises:
(a) a mixing step, during which a powdery mixture based on recycled foam glass powder is mixed with a basic solution with a pH greater than or equal to 10 and having a concentration of silicic acid salts greater than 2.5 M; during said mixing step, the weight ratio between the basic solution and the powdery mixture ranging from 0.3 to 0.6 to obtain a heterogeneous mixture; said powdery mixture comprising at least 50% by weight of recycled foam glass powder, from 0 to 10% by weight of inert material and from 0 to 50% by weight of a material chosen from aluminosilicates and recycled glass sand; and
(b) a firing/moulding step, during which the mixture resulting from the mixing step is poured into a mould having the shape of the element to be manufactured and heated at a temperature below 100°C and above 50°C.
It has been proven that the presence of silicic acid salts plays an essential role in activation of the foam glass powder .
Experimental tests have shown that if the basic solution is created with a concentration of silicic acid salts outside the range defined above, the silicate ions present in this basic solution are in a concentration inappropriate to manufacture the final product with the desired properties.
Here and hereinafter by the term "foam glass" we mean a product obtained by heating a mixture of crushed or granulated recycled glass and a blowing agent (chemical foaming agent), such as carbon or limestone. Close to the melting point of the glass, the blowing agent releases a gas, producing a foaming effect in the glass. After cooling, the mixture hardens into a rigid material with gas-filled closed-cell pores comprising a large portion of its volume.
Preferably, the basic solution has a concentration of silicic acid salts ranging from 2.5 to 7.0 M.
Preferably, the basic solution has a concentration of silicic acid salts ranging from 4.0 to 6.0 M.
Preferably, the silicic acid salts are silicates.
Even more preferably, the aluminosilicates derive from electric arc steel mill slags.
Preferably, said inert materials comprise rubber deriving from used tyres, ground and without heavy metals. Preferably, said powdery mixture comprises microsilica and/or metakaolin .
Preferably, said basic solution has a pH greater than or equal to 12.
Preferably, said basic solution comprises NaOH and/or KOH.
Another subject matter of the present invention is a flooring element both for indoor and outdoor obtained with the method of the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments are set down below purely by way of non-limiting illustration .
Seven examples according to the present invention (Ex. 1 - Ex . 7) and three comparative examples (Ex. 8 - Ex. 10) have been provided .
EXAMPLE 1
A powdery mixture was created composed of: 50% by weight of recycled foam glass powder, 35% by weight of steel mill electric arc slags, 10% by weight of recycled glass and 5% by weight of microsilica.
In parallel, a basic solution with pH 13 was created, composed of 10% by volume of a 10M solution of NaOH and of 90% by volume of a sodium silicate solution with a density of 1.4 Kg/dm 3 . The resulting basic solution has a concentration of 5.0 M of silicic acid salts.
The powdery mixture and the basic solution were mixed together with a liquid/solid weight ratio of 0.45. This mixing step had duration of 15 minutes, the time required to obtain a macroscopically homogeneous heterogeneous mixture.
The mixture thus obtained was poured into a mould, which was subsequently placed in a static furnace where it was maintained for a time of 24h at a temperature of 75°C. It is important for the temperature not to reach 100°C in order to avoid evaporation of the water.
In this way a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 1760 Kg/m 3 .
EXAMPLE 2
A powdery mixture was created composed of: 50% by weight of foam glass powder deriving from recycled glass, 30% by weight of steel mill electric arc slags, 10% by weight of recycled glass and 10% by weight of metakaolin.
The basic solution used is the same described above for example 1.
The mixing procedure and the firing step were carried out according to the description in example 1.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 1657 Kg/m 3 .
EXAMPLE 3
A powdery mixture was created composed of: 50% by weight of foam glass powder deriving from recycled glass and 50% by weight of steel mill electric arc slags.
The basic solution used is the same described above for example 1.
The mixing procedure and the firing step were carried out according to the description in example 1.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 1920 Kg/m 3 .
EXAMPLE 4
A powdery mixture was created composed of: 50% by weight of foam glass powder deriving from recycled glass and 50% by weight of steel mill electric arc slags.
In parallel, a basic solution was created with pH 12 composed of a sodium silicate solution with a density of 1.35 Kg/dm 3 . The resulting basic solution has a concentration of 4.5 M of silicic acid salts.
The mixing procedure and the firing step were carried out according to the description in example 1.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 1906 Kg/m 3 .
EXAMPLE 5 A powdery mixture was created composed of: 60% by weight of foam glass, 30% by weight of steel mill electric arc slag (large grain size), 10% by weight of rubber granulate (fine grain size) .
The basic solution used is the same described above for example 1.
The mixing procedure and the firing step were carried out according to the description in example 1, the only difference being that the liquid/solid weight ratio is equal to 0.3.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 1200 Kg/m 3 .
EXAMPLE 6
A powdery mixture was created composed of: 60% by weight of foam glass, 35% by weight of steel mill electric arc slag (large grain size), 5% by weight of crumb rubber (fine grain size) .
The basic solution used is the same as described above for example 1.
The mixing procedure and the firing step were carried out according to the description in example 1, the only difference being that the liquid/solid weight ratio is equal to 0.3.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively. The product has a density of 1100 Kg/m 3 .
EXAMPLE 7
A powdery mixture was created composed of: 50% by weight of recycled foam glass powder, 40% by weight of steel mill electric arc slag, 10% by weight of metakaolin.
In parallel, a basic solution with pH 13 was created, composed of 10% by volume of a 10M solution of NaOH and of 90% by volume of a sodium silicate solution with a density of 1.4 Kg/dm 3 . The resulting basic solution has a concentration of 8.0 M of silicic acid salts.
The mixing procedure and the firing step were carried out according to the description in example 1, the only difference being that the liquid/solid weight ratio is equal to 0.35.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 1720 Kg/m 3 .
EXAMPLE 8
A powdery mixture was created composed of: 80% by weight of foam glass powder deriving from recycled glass and 20% by weight of steel mill electric arc slag.
The basic solution used is the same described above for example 1.
The mixing procedure and the firing step were carried out according to the description in example 1, the only difference being that the liquid/solid weight ratio is equal to 0.25. The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
The product has a density of 780 Kg/m 3 .
EXAMPLE 9
A powdery mixture was created composed of: 80% by weight of foam glass powder deriving from recycled glass and 20% by weight of steel mill electric arc slag.
The basic solution used is the same described above for example 1.
The mixing procedure and the firing step were carried out according to the description in example 1, the only difference being that the liquid/solid weight ratio is equal to 0.8.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
In this case the product was not formed, remaining in a semi liquid state.
EXAMPLE 10
A powdery mixture was created composed of: 50% by weight of recycled foam glass powder, 40% by weight of steel mill electric arc slag, 10% by weight of metakaolin.
In parallel, a basic solution was created with pH 13 composed of 10% by volume of a 10M solution of NaOH and of 90% by volume of a sodium silicate solution with a density of 1.4 Kg/dm 3 . The resulting basic solution has a concentration of 1.5 M of silicic acid salts.
The mixing procedure and the firing step were carried out according to the description in example 1, the only difference being that the liquid/solid weight ratio is equal to 0.35.
The same mould of example 1 was used and, therefore, a product in the shape of a cobblestone was manufactured, with a height of 7.5 cm and with upper and lower square bases with sides of 8 cm and 6 cm respectively.
In this case the resulting product was extremely friable and dissolved in contact with water.
Materials used
The recycled foam glass used is marketed with the name SAVELPOR 50 by the company SASIL SRL .
The steel mill electric arc slag used is marketed with the name GRANELLA by the company PITTINI.
The microsilica used is marketed with the name MICROSIL 90 by the company AZICHEM.
The metakaolin used is marketed with the name METASIL by the company STIKLOPORAS.
The rubber used is rubber granules and powder obtained from the recycling of tyres manufactured by the company RPNtyres .
The sodium silicate solution used is marketed by the company INGESSIL SRL.
The solution of NaOH is marketed by the company SIGMA-ALDRICH . PROPERTIES OF THE ELEMENTS MANUFACTURED
Mechanical and water absorption tests were carried out on the elements manufactured in the examples above, in order to verify their possible uses in indoor and outdoor flooring. The water absorption values are correlated to porosity and, therefore, to the fragility of the element.
The mechanical tests carried out concerned "compressive strength (MPa) " and were conducted according to the standard UNI EN 12390-3:2009.
The water absorption tests were carried out according to the standard UNI EN ISO 10545-3:2018. Tables I and II indicate the results of the above tests on the elements obtained with the method according to the present invention .
The description above shows how the method of the present invention, although being extremely cost-effective, is able to manufacture a product with technical properties such as to be applied to manufacture both indoor and outdoor floorings.
As can be seen from the values indicated in Tables I and II, the composition of the powdery mixture necessarily influences the properties of the element manufactured in terms of breaking load and water absorption and, consequently, the type of application of the element to be manufactured. For example, if the element is to be used to produce flooring suitable for vehicles, a powdery mixture with a composition able to guarantee higher breaking load values and lower water absorption values will be used.
The results relating to example 7 show that, although the concentration of silicic acid salts greater than 7 still leads to the manufacture of a product according to the invention, its properties do not offer advantages that justify the cost deriving from such a high concentration of these silicic acid salts .
The cost-effectiveness of the method resides mainly in the use of recycled glass and in the use of low temperatures in the firing step.
Finally, it must be underscored how the method of the present invention has an important ecological value, as it offers the possibility of recycling a potentially very large amount of glass in an effective way, and at the same time, of replacing a material, the production and processing of which would necessarily have an environmental impact.