Source: BAM
Project period
01/07/2025 - 30/06/2027
Project type
Collaborative research project
Project status
Ongoing
Description
Earth-based building materials are sustainable, locally available, and fully recyclable. Because they harden solely through drying, however, they are sensitive to water. The research project analyzes whether ecological stabilization measures can sustainably improve the durability of weather-exposed rammed earth façades without creating a conflict with their recyclability.
Location
Bundesanstalt für Materialforschung und -prüfung
Unter den Eichen 87
12205 Berlin
Source: GOLEHM
Rammed earth is gaining importance in the context of the construction transition and is often used for design purposes because of its distinctive aesthetic. When used as an exterior façade, it must be weather-resistant. However, hydrophobic treatments should not significantly impair the sustainability, recyclability, or the thermal and visual properties of this construction method. The project investigates whether biopolymers can provide effective weather protection without compromising the beneficial properties of earth-based building materials.
Source: BAM
The objective of the research project is to develop an ecological hydrophobic treatment for rammed earth that allows its use in weather-exposed exterior applications. Research conducted within the framework of the WIR alliance contributes to modernizing rammed earth construction in Germany. A renaissance of this building material supports the construction transition and strengthens structurally weaker regions through the development of new value chains.
Source: BAM
For efficient material development and the dosing/application of hydrophobic agents, the interactions between clay minerals and biopolymers, as well as their behavior within the granular structure, must be analyzed. In the project, two rammed earth mixtures are combined with selected biopolymers. After characterizing the raw materials, the property profile is determined using test specimens. A sequential testing procedure allows for the rapid identification of promising mixtures.
Source: BAM
WIR! Bündnis GOLEHM: Initiative für Lehmbau und nachhaltige Kreislaufwirtschaft
https://www.golehm.de
Assoziierter Partner: ZRS Architekten Ingenieure, Berlin
ZRS – Architekten Ingenieure
Earthen construction materials are among the oldest building materials used by humankind and are currently experiencing a renaissance. As a regionally available, fully recyclable material requiring minimal processing effort, earth meets many of the requirements of sustainable construction. In addition, earth exhibits favorable hygrothermal properties and improves indoor climate conditions. This specific performance profile has led to growing demand for rammed earth walls for both interior and exterior applications.
Despite these advantages, a fundamental weakness remains: unlike hydraulic binders, earth hardens exclusively through drying. Under prolonged exposure to moisture, the material loses its strength, with damage ranging from superficial erosion to structural failure. This sensitivity to weathering significantly limits exterior applications and forms the starting point of the research project.
The aim of the project is the hydrophobic treatment of weather-exposed rammed earth walls. In order not to compromise the advantages of ecological earthen building materials, biopolymers are used, which often occur as by-products of agricultural or industrial processes. Initial studies have already shown promising results using biopolymers such as chitosan, locust bean gum, xanthan gum, and linseed oil in earth-based building materials.
Over a period of two years, suitable hydrophobic systems will be investigated in a results-open manner. Promising biopolymers will be selected, and their interactions with clay minerals as well as within the overall matrix will be characterized. Subsequently, biopolymers will be applied at different concentrations either as bulk hydrophobization additives or as surface coatings. The sequential testing program simulates various modes of water ingress and includes parameters such as water absorption, erosion resistance under dripping water, freeze–thaw resistance, and compressive strength as a function of moisture content. In addition, recyclability and visual appearance are assessed.
The sequential structure of the testing methodology is crucial: through stepwise selection, a very wide range of material–biopolymer combinations is systematically screened, unsuitable systems are discarded at an early stage, and resources are deliberately focused on the most promising approaches.
Initial preliminary investigations indicate that the composition of the rammed earth, the type of biopolymer, and the method of application can have a decisive influence on material–water interactions.
The research project does not regard biopolymer-treated rammed earth as a compromise between performance and sustainability but rather seeks to combine both. If it succeeds in developing an ecological and high-performance hydrophobic treatment, the construction industry will gain durable, weather-resistant building material that can be returned completely to the natural cycle at the end of its service life.
Project partner
WIR! Bündnis GOLEHM: Initiative für Lehmbau und nachhaltige Kreislaufwirtschaft
https://www.golehm.de
Assoziierter Partner: ZRS Architekten Ingenieure, Berlin
ZRS – Architekten Ingenieure
Funding
BMFTR-Bundesministerium für Forschung, Technologie und Raumfahrt (BMFTR), Förderinitiative „WIR! – Wandel durch Innovation in der Region“
Source: BMFTR