LIGHTWEIGHT RESILIENT CONCRETE SUB-BASE LAYER WITH RECYCLED RUBBER FROM DISCARDED TYRES WITH REDUCED WALKING IMPACT NOISE

Abstract

A concrete sub-base layer with pretreated recycled rubber from discarded tyres (PFU), is described.

Claims

1. A concrete sub-base layer with recycled rubber from discarded tyres (PFU), said concrete comprising cement, aggregates comprising a mixture of aggregates comprising inert aggregates in an amount ranging from 0 to 10% by volume with respect to the total volume of the aggregates and aggregates from pretreated recycled rubber from discarded tyres in an amount ranging from 100 to 90% by volume with respect to the total volume of the aggregates; water and optionally polymeric additives; wherein said aggregates from pretreated recycled rubber from discarded tyres has a particle size lower than 20 mm, and wherein said concrete has: a compressive strength greater than 1 MPa, a density lower than 1,100 kg/m.sup.3, an elastic modulus lower than 5,000 MPa.

2. The concrete sub-base layer according to claim 1, wherein the aggregates comprise pretreated recycled rubber from discarded tyres (PFU).

3. The concrete sub-base layer according to claim 1, wherein the concrete mixture comprises from 35 to 50% by weight of cement, from 10 to 18% by weight of water, and from 30 to 50% by weight of aggregates, said percentage referring to the total weight of concrete.

4. The concrete sub-base layer according to claim 1, wherein the aggregates of pre-treated recycled rubber from discarded tyres have a particle size lower than 20 mm, and the rubber from discarded tyres is pre-treated by storage of PFU rubber in water for a time ranging from 7 days to 40 days, or by washing the PFU rubber with latex.

5. Use of a concrete sub-base layer with pretreated recycled rubber from discarded tyres, according to claim 1, for applications having reduced walking impact noise, in particular for flooring.

6. Use of a concrete sub-base layer according to claim 5, with a reduction in walking impact noise equal to or higher than Lw 17 dB.

7. Use of a concrete sub-base layer according to claim 6, in an element having a multilayer structure comprising said sub-base layer and a screed, wherein there is no resilient layer or pad between the sub-base layer and screed.

8. Use of recycled rubber from discarded tyres (PFU) with a particle size lower than 20 mm, preferably ranging from 1 to 10 mm, pre-treated by storage of PFU rubber in water for a time ranging from 7 days to 40 days, or by washing the PFU rubber with latex, as aggregate for a concrete sub-base layer.

9. A multilayer element comprising a sub-base layer according to claim 1, said sub-base layer forming a layer in direct contact with a screed.

10. The concrete sub-base layer according to claim 1, wherein said concrete has a compressive strength greater than 2 MPa at 28 days.

11. The concrete sub-base layer according to claim 1, wherein said concrete has a density lower than 1,100 kg/m.sup.3.

12. The concrete sub-base layer according to claim 1, wherein said concrete has an elastic modulus lower than 3,000 MPa.

13. The concrete sub-base layer according to claim 3, wherein the concrete mixture comprises 30 to 40% by weight of aggregates from pretreated recycled rubber (PFU).

14. The concrete sub-base layer according to claim 4, wherein the concrete wherein the aggregates of pre-treated recycled rubber from discarded tyres have a particle size ranging from 1 to 10 mm.

15. The concrete sub-base layer according to claim 4, wherein the concrete wherein the aggregates of pre-treated recycled rubber from discarded tyres have a particle size ranging from 2 to 5 mm.

16. The concrete sub-base layer according to claim 4, wherein the rubber from discarded tyres is pre-treated by storage of PFU rubber in water for a time ranging from 28 days to 40 days.

17. The concrete sub-base layer according to claim 4, wherein the rubber from discarded tyres is pre-treated by storage of PFU rubber in water for a time of about 30 days.

Description

EXAMPLE 1

[0066] A sub-base layer was prepared with the composition indicated as mixture 1 in Table 2 below.

TABLE-US-00002 TABLE 2 Mixture 1 Rubber Granule PFU G1 (3,8-5) [Kg/m.sup.3] 367 Cement CEM 42,5R II-A/LL [Kg/m.sup.3] 440 Additive (Creactive Quattro, an [Kg/m.sup.3] 2.2 acrylic superfluidifying additive) Additive (Esapon, a surfactant) [Kg/m.sup.3] 0.2 Water [Kg/m.sup.3] 165 Theoretical density [Kg/m.sup.3] 974
The rubber granule PFU G1 (3.8-5), forming the 100% of the aggregate of the concrete, is a rubber granule pre-treated as follows: the aggregate is crushed and sieved, with a particle size lower than 20 mm, and is stored in water for a time of about 30 days.

EXAMPLE 2

[0067] Two different stratigraphies of a horizontal partition that divides two areas (one overlying in which walking impact noise is generated and the other underlying in which said noise is detected), were compared from the viewpoint of walking impact noise reduction as described hereunder: [0068] Stratigraphy 1: floor (thickness 24 cm), sub-base layer object of the invention (density 1,000 kg/m.sup.3 according to the standard UNI EN 12390-7, thickness 14 cm), screed (density 1,600 kg/m.sup.3 UNI EN 12390-7, thickness 10 cm). [0069] Stratigraphy 2: stratigraphy equivalent to stratigraphy 1 consisting of floor (thickness 24 cm), traditional lightweight sub-base layer (with only natural inert aggregate) having the same density and thickness as the sub-base layer according to the invention and screed (density 1,600 kg/m.sup.3 UNI EN 12390-7, thickness 10 cm).

[0070] The compressive strength is measured according to the standard UNI EN 12390-3 and for the sub-base layer of stratigraphy 1 is equal to 2.3 MPa at 28 days.

[0071] The density is measured according to the standard UNI EN 12390-7, whereas the elastic modulus is measured according to the standard ASTM C215 and for the sub-base layer of stratigraphy 1 is equal to 3.6 GPa at 28 days.

[0072] The sound insulation performance to walking impact noise of the stratigraphies examined is evaluated by means of the calculation model (EN 12354) of impact sound pressure L.sub.n,W expressed in dB. This parameter, defined by DPCM 5/12/97, characterizes the capacity of a floor of reducing impact noise.

[0073] The impact noise level requirement (L.sub.n,W) therefore relates to the impact noise perceived within living environments and generated by different housing units. The lower the L.sub.n,W value, the better the performances of the floor will be. The same standard defines the maximum L.sub.n,W values allowed for residential buildings. The walking impact noise levels determined in the two stratigraphies were compared with these maximum L.sub.n,W values. Table 3 below indicates the results of the calculation of the impact sound pressure (L.sub.n,W) in the two stratigraphies examined, compared with the maximum limits allowed by standard regulations.

TABLE-US-00003 TABLE 3 Maximum L.sub.n,W L.sub.n,W allowed Stratigraphy 1 60.4 dB 63 dB Stratigraphy 2 72.6 dB 63 dB

[0074] The comparison shows that stratigraphy 1, object of the invention, satisfies the sound requirement even without a resilient layer (pad). Stratigraphy 2 having the same density and thickness obviously does not meet the requirements of law and has an absolutely insufficient performance of sound insulation against walking impact noise.