Monitoring crack movement in polymer-based self-healing concrete through digital image correlation, acoustic emission analysis and SEM in-situ loading

A study was performed to assess the fitness of continuous monitoring methods to detect failure due to excessive strain on polymers bridging moving cracks in the context of self-healing concrete. Testing of several polymer precursors with distinct properties also allowed conclusions regarding the requirements for polymers in this application. Acoustic emission (AE) analysis was performed in parallel with digital image correlation (DIC) at the macro-scale. In addition, a micro-scale study was performed with tensile tests inside an SEM chamber. Detection of failure through AE analysis coupled with DIC was possible only in case of failure due to brittle fracture of a rigid foam after 9% strain, which generated high-energy acoustic events. Direct observation of interfaces with SEM insitu loading allowed determination of failure of a rigid foam due to cracking of the polymer matrix and detachment at the interface with the cementitious matrix, with an onset at 5% strain and complete detachment at 16% strain. For a flexible, continuous film of polymer, detachment occurred before 50% strain. Assuming adequate adhesion, polymers with high elongation (>100%) and modulus of elasticity much lower than 10 MPa are required if cracks subjected to a realistic amplitude of movement are targeted. (C) 2016 Elsevier Ltd. All rights reserved

Soil mobility of surface applied polyaromatic hydrocarbons in response to simulated rainfall

Polyaromatic hydrocarbons (PAHs) are emitted from a variety of sources and can accumulate on and within surface soil layers. To investigate the level of potential risk posed by surface contaminated soils, vertical soil column experiments were conducted to assess the mobility, when leached with simulated rainwater, of six selected PAHs (naphthalene, phenanthrene, fluoranthene, pyrene, benzo(e)pyrene and benzo(ghi)perylene) with contrasting hydrophobic characteristics and molecular weights/sizes. The only PAH found in the leachate within the experimental period of 26 days was naphthalene. The lack of migration of the other applied PAHs were consistent with their low mobilities within the soil columns which generally parallelled their log Koc values. Thus only 2.3% of fluoranthene, 1.8% of pyrene, 0.2% of benzo(e)pyrene and 0.4% of benzo(ghi)perylene were translocated below the surface layer. The PAH distributions in the soil columns followed decreasing power relationships with 90% reductions in the starting levels being shown to occur within a maximum average depth of 0.94 cm compared to an average starting depth of 0.5 cm. A simple predictive model identifies the extensive time periods, in excess of 10 years, required to mobilise 50% of the benzo(e)pyrene and benzo(ghi)perylene from the surface soil layer. Although this reduces to between 2 and 7 years for fluoranthene and pyrene, it is concluded that the possibility of surface applied PAHs reaching and contaminating a groundwater aquifer is unlikely

Etude d'une population microbienne du sol degradant l'acide 2,4-dichlorophenoxyacetique : diversite et sensibilite a d'autres molecules xenobiotiques

*INRA, Centre de Dijon (FRA) Diffusion du document : INRA, Centre de Dijon (FRA) Diplôme : DE

Impact des produits phytosanitaires sur la diversité spécifique et fonctionnelle de la microflore du sol

*INRA Laboratoire de microbiologie des sols BP 86510 21065 Dijon cedex (fra) Diffusion du document : INRA Laboratoire de microbiologie des sols BP 86510 21065 Dijon cedex (fra) Diplôme : Dr. d'Universit

Influence d'un biocide, le DNOC, sur la distribution au sein d'agrégats de sol et l'activité de micro-organismes dégradant le 2,4-D

National audienc

Perspectives and limitations in assessing side-effects of pesticides on the soil microflora

International audienc

Evaluation of side effect of DNOC on the soil microflora capacity to degrade 2,4-D

National audienc