Examination of production boards used in the manufacture of concrete blocks

Recently, the Andernach-based company, Assyx, has examined some used production boards delivered as samples by the French manufacturer of concrete products, Alkern located in Meximieux and the Icelandic manufacturer Steypustödin located in Reykjavik, respectively. In both cases, the boards sent as samples still were in immaculate condition even after having been used for many years.

1 Production boards of Alkern (3 boards)

On February 12, 2019, Alkern delivered three production boards, measuring 1400 x 1300 x 50 mm to Assyx for examination purposes.

An order for a total number of 4,650 boards had been placed on December 20, 2010, which had been supplied to Alkern (Meximieux/France) in June 2011. The rough lumber came from Finnforest (today‘s Metsä Wood) in the dimensions of 1392 x 1292 x 44 mm. In this case, it is a Kerto LVL Q-panel – a load-bearing and dimensionally stable laminated veneer lumber panel – which has been granted a national technical approval (abZ) in Germany.

The boards were delivered unpacked on a Euro pallet. After unstrapping, the boards were removed individually and inspected visually.

The surface of the boards was soiled as it is usual for production boards after seven to eight years in operation in the concrete block industry. Because of the soiling, it must be assumed that release agent was used in the production process, which is not uncommon either. Neither the surface nor the side faces of the three boards showed any visible damages. Information on the number of production cycles run is not available; it is also unknown which products had been manufactured on the boards.

In the first step, the three boards were weighed; afterwards the deflection under load was measured and then the thickness of the boards was measured in the delivered condition. In the next step, the coarse soiling was removed from the boards in a belt grinding machine process and thereafter the thickness was measured again at the previous measuring points.

The boards were cut into three parts by sawing, thus enabling the measurement of the wear over the entire surface. Afterwards, the Shore hardness and the wood moisture were determined and the bonding of the polyurethane with the wood surface was investigated. Two pieces of wood (without any adhesions of plastics) in the shape of rectangular cuboids were sawed out of the board in order to determine the density of the wood.

1.1 Analysis of the measurement results (Alkern)

The weight of the three boards ranged between 51.8 and 53.0 kg, with 52.6 kg on average.

According to Assyx, the weight of a new DuroBoardS of the same dimensions is 52.98 kg.

Determination of the modulus of elasticity: To simulate the transportation process in the manufacturing plant, strips were placed underneath the outer edges of the individual boards and then a weight of 780 kg was placed on the surface of the boards. The deflection was measured under load, calculating the resulting modulus of elasticity.

The individual boards showed a deflection of 2.56 mm, 2.85 mm, 2.42 mm, being 2.61 mm on average.

A modulus of elasticity of approx. 10,000 N/mm² is calculated from the determined deflection of the boards. This value corresponds to the value of a board in the condition supplied to the customer. Hence, it can be concluded that the boards evaluated did not lose their mechanical strength during their useful life so far and are suitable for continued use in the production.

The wood moisture of the three boards was measured on several spots. The result of the measurements amounts to approx. 15 % for all boards. For kiln-dried wood it ranges between approx. 8 to 12 % directly after drying and settles at approx. 15 to 18 % due to the equilibrium moisture content of wood. The measured values of 15 % on average are in the absolute normal range.

The determined Shore hardness (A) amounts to 68, using various measuring points distributed over all three boards; this corresponds to the value of a new board.

The thickness of the boards was measured at the edges at eight spots each, i.e. before and after cleaning.

A block of wood measuring 100 x 79.9 x 43.85 mm cut out of the board has a weight of approx. 165 g, corresponding to a wood density of 471 kg/m³, and thus being in the range of a well-dried LVL softwood. That implies that the polyurethane coating was complete all round and water did not ingress into the board.

The polyurethane is firmly bonding with the wooden core, enclosing the same completely. The plastics surface can only be removed by blunt force and with the aid of a broach, in doing so, wood sticks to the plastics and the wood fiber ruptures in lower layers. The bonding between wood and plastics is present over the entire surface.

1.2 Summary (Alkern)

The three boards delivered as samples by Alkern were in an immaculate condition at the time of the investigation. The plastics surface was completely intact and the dimensional accuracy of the boards corresponded to the condition on delivery.

Owing to the examination results it can be concluded that the production boards will remain appropriate for the manufacture of concrete block products with superior dimensional accuracy and will thus still be appropriate for use over a long period of time.

2 Production boards of Steypustödin (5 boards)

On April 15, 2019, Steypustödin delivered five production boards, measuring 1400 x 1100 x 55 mm to Assyx for examination purposes.

An order for a total number of 1,250 boards had been placed and had been supplied to Steypustödin (Reykjavik/Iceland) on April, 2007. These were boards of the first generation, the Assyx DuroBoard; the wooden core consists of laminated veneer lumber (LVL) made of Brazilian pine wood.

The boards were delivered unpacked on a Euro pallet. After unstrapping, the boards were removed individually and inspected visually.

The surface of the boards was soiled, as it is usual for a production board after 12 years in operation in the concrete block industry. The production boards were used for the manufacture of concrete blocks in different shapes and sizes on an AMEthst 1300 manufacturing machine of AME, with release agent being used partially. Production was run here with a weight of up to 360 kg per batch. According to information given by Steypustödin, about 150 cycles were run per board in the past year, corresponding to projected 1,800 production cycles in the previous service life. Neither the surfaces nor the side faces of the five boards showed any extensive damages.

In the first step, three of the five boards were weighed, then the deflection under load was measured as well as the thickness of the boards in the delivered condition.Afterwards, coarse soiling was removed from the boards in a belt grinding process and thereafter the thickness was measured again at the previous measuring points.

For enabling measuring of the wear of the boards over the entire surface, the boards were cut into three parts by sawing and measured thereafter.

In the next step, the Shore hardness and the wood moisture were determined and the bonding of polyurethane with the wood surface was investigated. Two pieces of wood (without any adhesions of plastics) in the shape of rectangular cuboids were sawed out of the board in order to determine the density of the wood.

2.1 Analysis of the measurement results (Steypus.)

The weight of the three boards ranged between 60 and 63 kg, with 62 kg on average.

According to Assyx, the weight of a new DuroBoardS of the same dimensions is 61 kg.

Determination of the modulus of elasticity: To simulate the transportation process in the manufacturing plant, strips were placed underneath the outer edges of the individual boards and then a weight of 780 kg was placed on the surface of the boards. The deflection was measured under load, calculating the resulting modulus of elasticity. The individual boards showed a deflection of 1.2 mm, 0.9 mm, 1.1 mm, being 1.06 mm on average.

A modulus of elasticity calculated from the determined deflection of the boards significantly exceeds 10,000 N/mm². This value corresponds to the value of a board in the condition on delivery, here a modulus of elasticity of > 10,000 N/mm² is guaranteed by Assyx. Hence, it can be concluded that the boards evaluated have not lost any of their mechanical strength during their previous use and that they can still be used in production.

The three boards selected were used to measure the wood moisture on several spots. The result of the measurements ranges between 11 % and 14 % for all boards. In case of kiln-dried wood it ranges between approx. 8 to 12 % directly after drying and settles at 18 % due to the equilibrium moisture content of wood. The measured values of up to 14 % are in the absolute normal range.

The determined Shore hardness (A) amounts to approx. 68, using various measuring points distributed over all three boards. This corresponds to the value of a new board.

The thickness of the boards was measured at the edges at eight spots each, i.e. before and after cleaning.

The polyurethane is firmly bonding with the wooden core, enclosing the same completely. The plastics surface can only be removed by blunt force and with the aid of a broach, in doing so, wood sticks to the plastics and the wood fiber ruptures in lower layers. The bonding between wood and plastics is present over the entire surface.

A block of wood measuring 134.3 x 73.9 x 43.7 mm cut out of the board has a weight of approx. 280 g, corresponding to a wood density of 645 kg/m³, and thus being in the range of a well-dried LVL softwood. That implies that the polyurethane coating was complete all round and water did not ingress into the board.

2.2 Summary (Steypustödin)

The boards delivered as samples by Steypustödin also were in an immaculate condition at the time of investigation. The plastics surface was completely intact and the dimensional accuracy of the boards corresponded to the condition as supplied to the customer.

Owing to the examination results it can be concluded that the production boards will remain appropriate for the manufacture of concrete block products with superior dimensional accuracy and will thus still be appropriate for use over a long period of time.

CONTACT

Assyx GmbH & Co. KG

Zum Kögelsborn 6

56626 Andernach/Germany

+49 2632 9475-0

info@assyx.com:info@assyx.com%3C/a%3E">

www.assyx.com

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