Laboratory measurements on replaceable jack-up systems Marina Rodrigues 1 CDM Stravitec nv Reutenbeek 9-11 3090 Overijse Belgium Reinhilde Lanoye 2 CDM Stravitec nv Reutenbeek 9-11 3090 Overijse Belgium

ABSTRACT

Floating floor systems are part of state-of-the-art modern building technology. They are an efficient option to improve the acoustical performance of buildings and can be part of box-in-box systems installed in high-performance spaces. There are many types of high-performance floating floor types, one of which is a jack-up system that guarantees that the floor is decoupled from the structural floor. With these systems, once the concrete has cured, the isolated slab is raised off the structure to the required void depth using pre-cast boxes. These boxes allow for easy adjustment of the final floor height and, if the use of the room or load conditions change in the future, can also allow the replace- ment of the isolators inside them. Replaceable and inspectable acoustical floor systems are perceived as systems with lower sound in- sulation (airborne noise) than traditional floating floor or non-replaceable jack-up systems. To measure airborne sound reduction and impact noise isolation of replaceable jack-up systems and confirm factors that can influence its performance, CDM Stravitec invested in a testing campaign, where measurements were made considering many variables, such as: concrete floating slab thick- ness; bearings type, air void depth, steel lid installed on top of each box and insulation material installed in the air void. This paper will present the findings of the test campaign.

1. INTRODUCTION

A floating floor system can have three functions, or a combination thereof: airborne nose isolation, vibration isolation and impact noise isolation.

1 m.rodrigues@cdm-stravitec.com

2 r.lanoye@cdm-stravitec.com

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Stravifloor is the brand that represents CDM Stravitec product line of high-performance floating floors and Stravifloor Jackup-R is a jack-up floating floor system with reinforced steel boxes cast into concrete. Jack-up floating floor systems guarantee that the floor is decoupled from the structural floor (reducing the risk of acoustic bridging between the floating floor slab and the structural floor). With these systems, once the concrete has cured, the isolated slab is raised off the structure to the required void depth. Stravifloor Jackup-R boxes allow for easy adjustment of the final floor height as well as replacement of isolators, should the use of the room or load conditions change in the future. The isolators remain accessible and replaceable even after installation and concrete pour, allowing future inspection. However, replaceable and inspectable acoustical floor systems are perceived by the market as systems with lower sound insulation (airborne noise) than traditional floating floor or non- replaceable jack-up systems. To measure the acoustical performance (airborne sound reduction and impact noise isolation) of Stravifloor Jackup-R systems and define and confirm the parameters that can influence its perfor- mance, CDM Stravitec performed a test campaign (done on Belgian Building Research Institute, in- stitution recognized by application of the decree-law of the 30th of January 1947) that is described in this article. In this testing campaign, measurements were made considering the following variables: • Concrete floating slab thickness: 100 mm (4’’) and 150 mm (6’’) • With and without live load simulation • Bearings: natural rubber pads and springs • Air void depth • 50 mm (2”) steel lid installed on top of each box • With and without insulation material installed in the air void 2. TEST METHODOLOGY

2.1. Impact Sound Insulation of Floors Tests were carried out according NBN EN ISO 10140 Acoustics – Measurement of sound insulation in buildings and of building elements (ISO 10140-1:2021; ISO 10140-3:2021 and ISO 10140-5:2021) and NBN EN ISO 717-2:2021 Acoustics - Rating of sound insulation in buildings and of building elements (ISO 717-2:2020). Measurements were taken from 50 to 5000Hz and 100 to 3150Hz was the frequency range for rating in accordance with EN ISO 717-2. Test were carried out on the bare slab, a reinforced concrete slab of uniform thickness 140 mm (5.5”) over a surface of 260 cm x 442 cm (8.5-ft x 5.4-ft), with 210 mm (8-17/64’’) high elevated borders that simulate the surrounding walls of an actual floor slab. The test element was mounted according to the NBN EN ISO 10140-3, in a similar manner to the actual construction and tests were carried out on each system described on section 3. Limits of test chambers, due to flanking noise transmission, were measured and registered (L n,min ), being shown on section 4. The single-number values (given by the index “w”) and spectrum adaptation terms are described in the standard EN ISO 717-2:2020. As the standards ASTM E492 - 09 and the EN ISO 10140-3 give similar procedures for the measure- ment and determination of the normalised impact sound pressure level L n , the impact insulation class IIC was calculated based on the measured values from 100 Hz to 3150 Hz, rounded to the nearest decibel, according to the ASTM E989 - 21 procedures.

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2.2. Airborne Sound Insulation of Floors Tests were carried out according NBN EN ISO 10140:2021 Acoustics - Measurement of sound insu- lation in buildings and of building elements (ISO 10140-1:2021 and ISO 10140-2:2021) and NBN EN ISO 717-1:2021 Acoustics - Rating of sound insulation in buildings and of building elements (ISO 717-1:2020). Measurements were taken from 50 to 5000Hz and 100 to 3150Hz was the frequency range for rating in accordance with EN ISO 717-1. Test were carried out on the bare slab with the size and characteristics and test elements mounted as described in the previous section. Limits of test chambers, due to flanking noise transmission, were measured and registered (R max ), being shown in section 4. A detailed description of the measurement method to determine the spectrum of the sound reduction improvement index of a lining on walls or floors, can be found in the EN ISO 10140-1 standard and the EN ISO 10140-2 standard. The sound reduction improvement index is defined as the difference between the sound reduction indices of the basic element with and without the lining for each one-third octave band:

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∆R = 𝑅 𝑤𝑖𝑡ℎ − 𝑅 𝑤𝑖𝑡ℎ𝑜𝑢𝑡

(1)

As the standards ASTM E90 - 09 and the EN ISO 10140-2 give similar procedures for the measure- ment and determination of the sound transmission loss TL (ASTM) and the sound reduction index R (ISO), the sound transmission class STC is calculated based on the measured values from 125 Hz to 4000 Hz, rounded to the nearest decibel, according to the ASTM E413 – 16. 3. TEST SETUPS

All floor systems tested contain 2x3 grid of 100mm (4’’) steel jack boxes with 1.5m (60’’) to 1.7 m (67’’) between the boxes in both directions. At the perimeter, the floating slab is completely decou- pled from the surrounding upstand in the concrete by means of a 20 mm (13/16’’) thick mineral wool strip. The differences between the different setups’ tests are described below.

Figure 1: Perimeter isolation and Stravifloor Jackup-R boxes installed + reinforcement.

3.1. Setup 1: Stravifloor Jackup-R with elastomers as resilient support & 100 mm (4’’) float- ing slab and 50 mm (2’’) air void

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1. 100 mm (4”) reinforced concrete floating slab 2. Reinforced steel box with Pad-H HR 50 [dim. 104x64x50 mm (4-3/32’’ x 2-33/66’’ x 2’’)] with approx. 7Hz of natural frequency 3. PE-foil 4. 50 mm (2”) air void 5. 140 mm (5.5”) reinforced concrete slab

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Figure 2: Setup 1 section.

3.2. Setup 2: Stravifloor Jackup-R with elastomers as resilient support & 100 mm (4’’) float- ing slab, 50 mm (2’’) air void and with live load (sandbags) The second test setup has the same buildup as setup 1 but considering a live load of 100 kg/m² (20.5 psf), simulated with the use of sandbags positioned on the area in between the boxes (never on the boxes themselves).

Figure 3: Live load of 100kg/m 2 (20.5 psf), simulated with the use of sandbags.

3.3. Setup 3: Stravifloor Jackup-R with elastomers as resilient support & 150 mm (6’’) float- ing slab, 50 mm (2’’) air void and with live load (sandbags)

1. 150 mm (6”) reinforced concrete floating slab 2. Reinforced steel box with Pad-X HR 50 X HR 50 [dim. 104x64x50 mm (4-3/32’’ x 2-33/66’’ x 2’’)] with approx. 8Hz of natural frequency 3. PE-foil 4. 50 mm (2”) air void 5. 140 mm (5.5”) reinforced concrete slab

Figure 4: Setup 3 section.

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100 mm (4’’) “jack-up boxes” were cast into the concrete during the initial 100mm pour., An extra 50 mm (2’’) concrete is poured in a second phase putting polystyrene on top of each box cap, to keep the boxes accessible [this 50 mm (2’’) polystyrene was removed prior to testing]. The tests consider a live load of 100 kg/m² (20.5 psf).

3.4. Setup 4: Stravifloor Jackup-R with springs as resilient support & 150 mm (6’’) floating slab, 50 mm (2’’) air void and with live load (sandbags)

1. 150 mm (6”) reinforced concrete floating slab 2. Reinforced steel box with 2x4kN/4.5Hz springs in the corner locations and 2x4kN/4.5Hz+2x1.35kN/4.5Hz in the center locations 3. PE-foil 4. 50 mm (2”) air void 5. 140 mm (5.5”) reinforced concrete slab

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Figure 5: Setup 4 section.

The bottom of the boxes was treated with a soft bottom of a high-dense EPDM (ethylene propylene diene monomer) compound [8/6 mm (5/16’’/15/64’’)– total thickness/thickness under the springs]. The tests consider a live load of 100 kg/m².

3.5. Setup 5: Stravifloor Jackup-R with elastomers as resilient support & 150 mm (6’’) float- ing slab, 50 mm (2’’) air void, with live load (sandbags) and steel lid

1. 150 mm (6”) reinforced concrete floating slab 2. 50 mm (1’’) steel lid 3. Reinforced steel box with Pad-X HR 50 [dim. 104x64x50 mm (4-3/32’’ x 2-33/66’’ x 2’’)] with ap- prox. 8Hz of natural frequency 4. PE-foil 5. 50 mm (2”) air void 6. 140 mm (5.5”) reinforced concrete slab

Figure 6: Setup 5 section.

The tests consider a live load of 100 kg/m² (20.5 psf). 50 mm (2’’) and a steel lid is added on top of each box after lifting of the floor (replacing the polystyrene cap used during second phase of concrete pouring).

3.6. Setup 6: Stravifloor Jackup-R with elastomers as resilient support & 150 mm (6’’) float- ing slab, 20 mm (13/16’’) air void and with live load (sandbags)

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1. 150 mm (6”) reinforced concrete floating slab 2. Reinforced steel box with Pad-X HR 50 [dim. 104x64x50 mm (4-3/32’’ x 2-33/66’’ x 2’’)] with approx. 8Hz of natural frequency 3. PE-foil 4. 20 mm (13/16”) air void 5. 140 mm (5.5”) reinforced concrete slab

Figure 7: Setup 6 section. The tests consider a live load of 100 kg/m² (20.5 psf).

3.7. Setup 7: Stravifloor Jackup-R with elastomers as resilient support & 150 mm (6’’) float- ing slab, 20 mm (13/16’’) insulation in a 50 mm (2’’) air void and with live load (sandbags)

1. 150 mm (6”) reinforced concrete floating slab 2. Reinforced steel box with Pad-X HR 50 [dim. 104x64x50 mm (4-3/32’’ x 2-33/66’’ x 2’’)] with approx. 8Hz of natu- ral frequency 3. PE-foil 4. 30 mm (1-3/16’’) air void 5. 20 mm (13/16”) insulation material 6. 140 mm (5.5”) reinforced concrete slab

Figure 8: Setup 7 section. The tests consider a live load of 100 kg/m² (20.5 psf).

Figure 9: Concrete floating floor after concrete has cured to the required strength and boxes open,

ready to jack-up.

4. RESULTS

Table 1: Impact noise isolation and airborne noise insulation global values, for the different setups tested.

Setup L nw (C i ) ∆L w (C i ,∆) IIC R (C,C tr ) STC

Bare slab 80 (-12) - 25 59 (-2,6) 58

1 36 (-4) 42 (-9) 74 75 (-3,-8) 74

2 38 (0) 39 (1) 69 76 (-3,-9) 73

3 38 (-5) 40 (-8) 69 79 (-3,-8) 78

4 37 (-5) 41 (-8) 71 77 (-3,-9) 75

5 37 (-5) 41 (8) 71 80 (-4,-10) 78

6 36 (-1) 40 (-10) 74 74 (-3,-9) 73

7 32 (-3) 45 (10) 77 80 (-3,-9) 80

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Figure 10: Impact sound insulation of the different setups and minimum L n possible to measure.

Ln (dB) 62,5 125 250 500 Frequency [Ez] 1000 ‘Setup 1 “Setup 2 Setup 3 Setup 4 Setup 5 Setup 6 Setup 7 -Lmin 2000 4000

Figure 11: Airborne sound insulation of the different setups and maximum R in possible to meas-

ure. 5. CONCLUSIONS

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Jack-up floating floors in general, and the Stravifloor Jackup-R system in particular, prove to score excellent marks in term of acoustical performance. Over the course of this test campaign, it became clear that adjustable floating floor systems are ideally suited for both airborne sound reduction and impact noise isolation, contrary to common market belief. Various parameters were introduced to thoroughly test each setup. The findings were meticulously recorded and led to the following results.

5.1. Replaceable jack-up systems The holes created by replaceable jack-up boxes, barely affect the system’s overall performance. The addition of a 50 mm (2”) steel lid on top of each box after the floor was lifted, made hardly any difference in terms of impact noise isolation. Both with and without the steel lid, Stravifloor Jackup- R systems efficiently insulate impact noise and reduce airborne sound. The added advantage of being able to inspect and replace the bearings at all times out ways the marginal difference in acoustical performance.

5.2. With and without live load The resilient support should be designed according to the expected load. The bearings used in the jack-up floating floor system can’t be too stiff or too soft as this would create an underperforming acoustical system. Selection of the type of resilient support should also take into consideration the required loading of the floor and substrate to achieve the desired frequency response. The flexibility in terms of the type of bearing used, elastomers or springs, allows for a made to measure system with optimized acoustical performance. To mimic live loads, sandbags were placed in the area in between the boxes. In addition, when moving from a 100 mm (4”) thick slab to a 150 mm (6”) slab, the type of resilient support was adapted to the load conditions. High stiffness natural rubber elastomers were replaced by extreme stiffness natural rubber pads and in the case of the use of springs, the type and number of springs changed with the . steel houses installed at the corners of the floating slab. The boxes installed in the corners have smaller

R (dB) 100 90 80 70 60 30 40 30 31,25 125 250 500 Frequency (Hz) 1000 Setup 1 Setup 2 Setup 3 Setup 4 Setup $ Setup 6 Setup 7 -Rmax 2000 4000

influence area than the ones installed in the centre and by this reason they take less load. This leads us to the conclusion that when the support is designed according to the expected dead and live load, the impact noise insulation is better at low frequencies, which in turn can be explained by the lower resonance frequency of the bearings.

5.3. Flanking noise Taking into account the limits of the test chambers used during these tests, we can also conclude that the airborne sound insulation measured at high frequencies is limited by the transmission of flanking noise. Test data shows that when using elastomeric bearings supporting a 100 mm (4”) and a 150 mm (6”) concrete floating slab, a higher impact sound level (+2dB) is achieved for the 150 mm (6”) slab. This small difference is a consequence of the type of elastomeric pad used on both setups and its natural frequency. The 150 mm (6”) thick slab was tested with pads having a higher natural frequency than the ones used during the test on the 100 mm (4”) concrete floating slab.

5.3. Air void & insulation material During the test campaign the same floor setup was tested with different air void heights allowing us to conclude that the height of the air void mainly has an effect on the airborne sound insulation. After the introduction of mineral wool, the results improve significantly as the extra absorption material prevents a standing wave in the air void, which may cause noise breakthrough at high frequencies.

5.4. Pads or springs Stravifloor Jackup-R is available with either elastomeric or spring resilient supports. Comparisons between floor setups with steel springs and setups with elastomeric pads indicate that the selection of the type of bearing is directly related with the target natural frequency of the system. The required natural frequency can be one of the design requirements depending on the natural frequency of the structural elements or the excitation frequency. With both a concrete floating slab with elastomers and one with springs, a similar levels of impact noise insulation (IIC/Ln) and airborne noise insulation (STC/Rw) can be achieved. 6. REFERENCES

1. ASTM E413-16 – Classification for Rating Sound Insulation 2. ASTM E90 - 09 Standard Test Method for Laboratory Measurement of Airborne Sound Trans-

mission Loss of Building Partitions and Elements 3. ASTM E492: Standard Test Method for Laboratory Measurement of Impact Sound Transmission

Through Floor-Ceiling Assemblies Using the Tapping Machine 4. ASTM E989-21: Standard Classification for Determination of Single-Number Metrics for Impact

Noise 5. ISO 10140-1:2021, Acoustics - Laboratory measurement of sound insulation of building ele-

ments - Part 1: Application rules for specific products 6. ISO 10140-2:2021, Acoustics - Laboratory measurement of sound insulation of building elements

- Part 2: Measurement of airborne sound insulation 7. ISO 10140-3:2021, Acoustics - Laboratory measurement of sound insulation of building elements

- Part 3: Measurement of impact sound insulation 8. ISO 10140-5:2021, Acoustics - Laboratory measurement of sound insulation of building ele-

ments - Part 5: Requirements for test facilities and equipment 9. ISO 717-1:2013, Acoustics - Rating of sound insulation in buildings and of building elements -

Part 1: Airborne sound insulation

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10. ISO 717-2, Acoustics - Rating of sound insulation in buildings and of building elements - Part 2: Impact sound insulation

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