In recent years, the issue of environmental impact of chemical products for construction has become increasingly relevant in every field of application. The mechanical excavation of tunnels with TBM is no exception. Considering the enormous amount of muck produced by the excavation with TBM, the impact of the chemicals used during the excavation on the environment and on the possibility of re-use of the excavated soil is a fundamental point for the success of the entire project.

The European legislation provides for the measurement of the quantity of some compounds within the excavated soil as discriminating for the reuse or disposal of the muck. If the measured values are higher than limit values, the soil must be disposed of as waste. The compounds considered in the evaluation, however, do not include the most commonly used products for the excavation of tunnels with TBM EPB: surfactants. The practice commonly applied in Italy in recent years involves several phases that lead to the evaluation of the maximum permissible quantities of product in the excavated soil, in order to be able to reuse it.

The first step is the evaluation of the toxicity of the chemical product as such, followed by the evaluation of the quantity of product necessary to give the soil the characteristics necessary for the excavation, then the assessment of the degradation time of the chemical in the soil, to evaluate after time from the excavation, the soil appears to have the characteristics of toxicity of the soil as it is. To meet the growing demand for foaming agents with low environmental impact, the Mapei research and development laboratory has developed the Polyfoamer ECO foaming agent line. Foaming agents formulated with raw materials of natural origin, with very low toxicity and high biodegradability. The use of Polyfoamer ECO products, allows to obtain optimal digging performance, reducing waiting times for the reuse of the toll due to the rapid degradation in the ground. The very low toxicity allows the use of the quantities necessary for excavation operations, without impacts on the environment surrounding the construction site and the area of reuse of the muck. The products of the Polyfoamer ECO line are successfully used in several projects in Italy and worldwide. Click here for the Mapei’s presentation at Sig conference during the Saie2018. Visit https://utt.mapei.com/. 44/18.