Measuring Thermal Conductivity of Renewable Construction Materials
Olive mill pomace is a by-product of olive oil production, and it is often incinerated to generate renewable energy. The ash by-product of combustion is then often used as a fertilizer (Figure 1) However, more ash is produced than is needed as fertilizer, leaving the remainder as waste which must be disposed of.
Figure 1. L: Olive mill pomace (Source: Olive Bar Ltd). R: Incinerator ash (Source: BBC). Olive mill pomace is often incinerated, producing an ash by-product. Incinerator bottom ash aggregate is a thermal insulator, and can modify the thermal conductivity of construction materials when used in a composite
Researchers have been finding ways to create value-added products from the waste pomace ash. Combustion ash from the petroleum industry is widely used to create composite construction materials and incinerator bottom ash is often processed into an aggregate which is then used in construction applications such as road sub base material and filler materials.
Depending on the application, thermal conductivity can be an important parameter when selecting a construction material. In some cases, such as in the interior of heat-exchangers, thermal conductors are desirable. In other cases, such as building wall materials, a thermal insulator would be a more cost-effective selection. C-Therm’s TCi thermal conductivity instrument employing the patented Modified Transient Plane Source (MTPS) technique enables quick and easy characterization of construction materials.
Recently, scientists from the Universidad de Jaén in Jaén, Spain published work in Waste Management on the use of olive pomace ash in kiln-fired ash-clay composite bricks, resulting in the identification of optimal blends of clay and ash to maintain industry standards for mechanical strength while reducing density. This results in a construction material which meets standards for strength while also being more fuel-efficient to transport.
Figure 3. Effect of olive mill pomace ash addition on thermal conductivity of clay bricks. Adding the olive mill pomace ash results in a substantial decrease in thermal conductivity, resulting in a material with a higher R-value while still meeting international standards for building material strength.
The researchers also analyzed their bricks for thermal conductivity using a C-Therm TCi instrument. They found that the bricks have substantially reduced thermal conductivity relative to a clay control, as can be seen in the figure. A reduction of 14.4% in thermal conductivity relative to the control was observed for a 10 wt % addition of ash, and for a 20 wt % addition of ash, a 16.8% reduction in thermal conductivity relative to the control was observed, showing that the composite materials not only maintain strength and are more fuel-efficient to transport, they also are better insulators, which makes this composite material more attractive than conventional clay bricks for building construction.
Those who wish to read the full paper, which also includes density and mechanical strength analyses and details on experimental procedures, can find a link to it here.