Strict Standards: Declaration of SubmissionKeywordEntryDAO::getByControlledVocabId() should be compatible with ControlledVocabEntryDAO::getByControlledVocabId($controlledVocabId, $rangeInfo = NULL, $filter = NULL) in /home/revistas/public_html/lib/pkp/classes/submission/SubmissionKeywordEntryDAO.inc.php on line 20
Warning: Cannot modify header information - headers already sent by (output started at /home/revistas/public_html/lib/pkp/classes/submission/SubmissionKeywordEntryDAO.inc.php:20) in /home/revistas/public_html/lib/pkp/classes/template/PKPTemplateManager.inc.php on line 836
Warning: Cannot modify header information - headers already sent by (output started at /home/revistas/public_html/lib/pkp/classes/submission/SubmissionKeywordEntryDAO.inc.php:20) in /home/revistas/public_html/lib/pkp/classes/template/PKPTemplateManager.inc.php on line 837
Is it possible to exceed the time limit specified by Brazilian Standard NBR 7212 for mixing and transporting concrete?
| Revista IBRACON de Estruturas e Materiais
Is it possible to exceed the time limit specified by Brazilian Standard NBR 7212 for mixing and transporting concrete?
Eduardo Polesello
Abrahão Bernardo Rohden
Denise Carpena Coitinho Dal Molin
Angela Borges Masuero
Resumo
Brazilian standard NBR 7212 sets a time limit of 150 minutes for a concrete load to be discharged in full. In practice, situations arise where mixer trucks have to hold their load for much longer periods. The main aim of this paper is to assess changes in the compressive strength of concrete that is used when the time limit for mixing and transport specified by standard NBR7212 is exceeded. To this end, concrete was mixed for a period of 6 hours, and a superplasticizer was added at intervals to restore slump to its initial value. Results show that compressive strength is not affected by the prolongued mixing in the conditions of this research.
