title: Nanostructured calcium silicate hydrate seeds accelerate concrete hardening: a combined assessment of benefits and risks.
abstract: Nanotechnology creates new possibilities to control and improve material properties for civil infrastructure. Special focus in this area is put on Portland cement and gypsum. Together their annual production is by far larger than for any other material worldwide. Nanomodification of these materials can be done during the few hours between dissolution and hardening, especially by nucleation of the re-crystallization with suitable colloids. Here we report first results in homogeneous seeding of the precipitation of calcium silicate hydrates within a real Portland cement composition. The occupational safety during the production phase and during mixing of concrete paste is addressed in detail by in vivo testing. We perform 5-day inhalation with 21-day recovery in rats and analyze organ-specific toxicity and 71 endpoints from bronchoalveolar lavage (BALF) and blood. In BALF parameters, no test-related changes were observed, indicating the generally low toxicity of the test material. Some mild lesions were observed in larynx level. In the lungs, all animals of the 50 mg/m³ concentration group revealed a minimal to mild increase in alveolar macrophages, which recovered back to control level.
authors.affiliation: BASF Construction Chemicals GmbH, Polymer Research, Mineralogy, Trostberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Bräu
authors.forename: Lan
authors.initials: L
authors.lastname: Ma-Hock
authors.forename: Christoph
authors.initials: C
authors.lastname: Hesse
authors.forename: Luc
authors.initials: L
authors.lastname: Nicoleau
authors.forename: Volker
authors.initials: V
authors.lastname: Strauss
authors.forename: Silke
authors.initials: S
authors.lastname: Treumann
authors.forename: Karin
authors.initials: K
authors.lastname: Wiench
authors.forename: Robert
authors.initials: R
authors.lastname: Landsiedel
authors.forename: Wendel
authors.initials: W
authors.lastname: Wohlleben
mesh_terms: D000280:Administration, Inhalation; D000395:Air Pollutants, Occupational / Q000737:chemistry / Q000633:toxicity*; D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D017610:Calcium Compounds / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity*; D003252:Construction Materials / Q000032:analysis / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D005858:Germany; D006801:Humans; D007830:Larynx / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D008168:Lung / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D008297:Male; D008422:Materials Testing; D008679:Metaplasia; D049329:Nanostructures / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity* / Q000648:ultrastructure; D010316:Particle Size; D051381:Rats; D017208:Rats, Wistar; D018570:Risk Assessment; D017640:Silicates / Q000008:administration & dosage / Q000737:chemistry / Q000633:toxicity*
chemical_list: D000395:Air Pollutants, Occupational; D017610:Calcium Compounds; D017640:Silicates; C031293:calcium silicate