Dear gravel turf friends,
as coordinator of the GREEN CONCRETE project I am very pleased about your interest. I am firmly convinced that your interest is worth because gravel turf is a promising technology and an absolutely up to date research area.
The challenge of our project is to fulfil the demands of a public thoroughfare (load bearing capacity) and to create a living space of high ecological value – enrichment for every cityscape.
The adaptability of plants seems almost incredible. However, successful construction of gravel turf expects:
In course of our European research project GREEN CONCRETE we will ascertain these aspects. Based on solid research results we will enable you to construct high-quality gravel turf, so your gravel turf meets your all expectations and pleases you in a long term.
With this in mind – Take heart to use plants!
Dear GREEN CONCRETE project team,
dear Sir or Madam,
with great interest I followed your project GREEN CONCRETE right from the start. The development of gravel turf – especially made of recycled construction materials - is a promising and forward looking technology.
In times of climate changes and accumulation of extreme weather occurrences like heat, drought and heavy rainfall-triggered (debris) flood events solutions and contributions from the sector of horticulture/landscape construction are needed.
Technologies which accomplish their functions (e.g. construction of parking lots) reliably, save recourses and allow natural cycles are in demand. Gravel turf is a technology which solves technical problems near-naturally and provides a socio-political contribution.
I compliment you on your European research project and look forward to the findings and the results. But the success of the project will only be given if horticultural/landscape construction enterprises and decision makers can be convinced of gravel turf. Professional training of future landscape gardeners offers the key to this success. Landscape gardeners must be able to design, construct and maintain gravel turf. The best promotion for horticultural/landscape construction enterprises and for the used technology is a successful project.
As president of the BGL I will back the GREEN CONCRETE team and wish success!
Yours Hanns-Jürgen Redeker
President of Bundesverbandes Garten-, Landschafts- und Sportplatzbau e.V.
The German-Italian-Austrian consortium of the GREEN CONCRETE project develops gravel turf consisting of natural gravel or recycled construction material. Based on established knowledge pending question concerning usability of recycled construction material, construction, material constitution and greening of gravel turf are investigated. Gravel turf will be further developed until market maturity.
Led by Prof. Dr. Florin Florineth ( University of Natural Resources and Applied Life Sciences, Vienna) the GREEN CONCRETE team consisting of 12 partners took up work in September 2006. First the applicability of many materials was tested. At the end of this phase 16 materials were destined for the construction of 184 investigation parking sites in total. The test sites were built at locations of the three research partners and at the public parking lot of the railway station “Goldrain” in South Tyrol.
After finalization of the construction work the comprehensive investigations begun. A distinction is made between two test groups – called ‘Basic Tests’ and ‘Special Tests’.
At present the project is in the phase of data collections and analysis. The unofficial results are auspicious!
The GREEN CONCRETE team strives to provide the positive cognitions of the project. We are looking forward to meet you at following events.
Seeping water quality of green parking lot consolidations
If we aim to use loadable green areas for seepage of precipitation, their infiltration capacity should be comparable to those plantable infiltration constructions.
Currently the Bayerische Landesanstalt für Weinbau und Gartenbau Veitshöchheim carries out giant lysimeter tests of six green surface consolidations and one drainage paving used as consolidation of parking lots (see figure 1 and table 1). Year-round the test sites are loaded three times per day. Furthermore the test sites are subjected to engine oil (5 ml oil two times per week) and street cleaning waste (6,7g once a week). Thus the test sites are contaminated by mineral oil hydrocarbons, persistent organic compounds and heavy metals like zinc, cadmium, lead, copper, chromium and nickel. After a triennial loading all green surface consolidations compared to the unloaded lawn test site showed no losses concerning the seeping water quality. Except raised lead and zinc concentrations of the seeping water of the drainage paving at the beginning phase there are no objections. The maximum values of heavy metal concentrations ( including very mobile heavy metals like cadmium, nickel and zinc) in the seeping water of almost all test variants are acceptable according to the edict “Bundesbodenschutz- und Altlastenverordnung (BBodSchV, 1999/2004)”. Also the motor oil contamination does not show negative effects on the water quality. Hence, a hazard of the groundwater can be excluded.
A reason for the filtering and purification capability of green surface consolidations may constitute in the longer resting time of the seeping water within the construction layers. This applies to individual simulated heavy rain events with intensities of up to 100 l/m² in 30 minutes and also to the annual water balance. At the end of a simulated heavy rainfall event the unloaded lawn reference test site already emitted 50 % of the total rain amount. The tested surface consolidations on the other hand released only 20 to 30 % of the simulated precipitation. Green surfaces with optimal construction for vegetation are able to handle 35 to 40 % of the annually accruing precipitation water. Drainage paving showed only 10 % seeping water reserve because of missing capillarity and lack of “green end-users”.
Figure 1: Seven at one blow: Six green surface consolidations and one covering with drainage paving are tested. Is loaded green a load for the environment?
Permeable surface consolidations
Conventional road constructions seal the surface to prevent water infiltration and hence loss of load bearing capacity. Precipitation is drained to seepage constructions. In contrary, permeable surface consolidation technologies shall soak as much water as possible. The reduction of surface runoff allows smaller dimensioned and less expensive seepage water systems. The retention of rainfall lowers runoff peaks and hence contributes to flood prevention. Unfortunately the runoff coefficient of the various permeable pavements is not known. It has to be tested and certified for every single permeable consolidation method or a runoff coefficient of only y = 0,6 according to RAS-EW may be assumed for water management planning.
Another positive effect of permeable surface consolidations is caused by the evaporation of the plant cover; humidity is increased, air temperature decreased and consequently the city’s microclimate benefits.
The applicability of different surface consolidation methods is defined by their load bearing capacity, drive- and walkability. Permeable surface consolidations are predominantly used for minor roads and squares as e.g. parking areas, walkways, bikeways and service roads.
According to the expected usage intensity and requirements for drive- and walkability gravel path, pavement with gravel or planted joints, interlocking concrete and plastic block pavers, gravel turf, and plastic-stabilized gravel path may be applied. Drainage concrete and asphalt are only rarely used for the above mentioned applications. Basically planted and unplanted consolidation methods are differentiated. According to the usage intensity planted consolidation methods shall be preferred. Similarly recycled construction materials, which are excluded from usage for the construction of major roads because of their commonly low frost resistance, shall be favoured for applications as e.g. gravel turf.
Prof. Gert Bischoff, Fachhochschule Erfurt
Figure 1: Interlocking concrete block pavers with low amount of joints.