Cuidados na execução começam muito antes do lançamento do concreto nas fôrmas. Veja as principais dicas para essa etapa da obra.
Precautions with execution of works begins long before the concrete laying. Take a time to see the principal tips for this step at worksite.
Temperatura
Concretagem não combina com calor. Temperaturas acima de 35◦C aceleram a evaporação da água no concreto e prejudicam o processo de cura, com consequências sobre o desempenho da estrutura. Por isso, recomenda-se planejar a atividade para horários em que o sol está mais fraco, no começo ou no fim do dia. Muitas construtoras preferem as primeiras horas da manhã para evitar, também, problemas no fornecimento do concreto - à tarde, muitas concreteiras são prejudicadas por atrasos acumulados nas obras de seus clientes e não conseguem cumprir a agenda acordada anteriormente.
Temperatures
Concreting doesn`t match with high temperatures. Temperatures higher than 35◦C speed up the evaporation of the water which is inside the concrete, and prejudice the concrete curing, resulting in consequences on structure`s performance. That`s why, it is highly recommended to plan the concreting process when the sun is low, at the beginning or at the end of the day. Many construction companies prefer the first hours in the morning, in order to avoid, also, issues with the concrete supply - at afternoon many concrete suppliers companies are affected with accumulated lates with their client`s works and do not accomplish the previously agreed schedule.
Fôrmas, escoramento e armaduras
Antes da concretagem, o engenheiro deve conferir se as fôrmas, as armaduras e os escoramentos estão montados conforme o projeto, verificando se o posicionamento, o nivelamento e o prumo estão dentro das tolerâncias dimensionais. Deve-se certificar, ainda, da estanqueidade das juntas, para evitar o vazamento da nata do concreto, e da inexistência de sujeiras ou partes soltas nas superfícies internas.
Forms, shoring and reinforcement bars
Before concreting, the engineer must check if the forms, the reinforcement bars and the the shorings are set according to the design, checking if its location, leveling and plumbing are acceptable considering the dimensions tolerances. Also must be checked, the joints watertightness, in order to avoid the leak of the concrete fluids, and the lack of dirt or loose parts at its internal surfaces.
Forms, shoring and reinforcement bars
Before concreting, the engineer must check if the forms, the reinforcement bars and the the shorings are set according to the design, checking if its location, leveling and plumbing are acceptable considering the dimensions tolerances. Also must be checked, the joints watertightness, in order to avoid the leak of the concrete fluids, and the lack of dirt or loose parts at its internal surfaces.
Canteiro livre
O planejamento logístico dentro do canteiro está diretamente ligado à produtividade da concretagem. Deve-se cuidar para que o trajeto do caminhão-betoneira e do caminhão-lança seja feito sobre terreno firme e desimpedido, para evitar acidentes e proporcionar uma circulação contínua e sem esperas desnecessárias.
Worksite without obstructions
The logistics planning inside the worksite must be directly connected to the productivity of the concreting. Give special care to the path of the mixer truck and the truck bomb to be done in firm ground and without obstructions, in order to avoid accidents and provide a continuous movement, without unnecessary waits.
Worksite without obstructions
The logistics planning inside the worksite must be directly connected to the productivity of the concreting. Give special care to the path of the mixer truck and the truck bomb to be done in firm ground and without obstructions, in order to avoid accidents and provide a continuous movement, without unnecessary waits.
Aceitação do concreto
Na entrega do concreto, é preciso verificar se o caminhão-betoneira está lacrado e se o material está de acordo com as especificações do projeto. O responsável deve conferir, na nota fiscal, os dados referentes ao volume do concreto adquirido, à relação água-cimento, ao módulo de deformação, à dimensão máxima dos agregados, à classe de agressividade, à resistência à compressão (fck) e ao consumo de cimento por metro cúbico. Antes da descarga, também deve ser feito o ensaio e abatimento ou "Slump Test" ou de espalhamento no caso de concreto autoadensável, e eventual correção com água ou aditivo, quando solicitado.
Acceptance of the concrete
When the concrete it's being delivered, it is needed to verify if the mixer truck are sealed and if the concrete is following the design specifications. The responsible must check, at the bill of sale, informations like the volume of the acquired concrete, the water / cement ratio, the deformation modulus, the aggregate maximum size, the aggresseviness class, the compressing resistance (fck) and the cement consumption per cubic meter. Before laying the concrete, another test must be done, the "slump test" or the spreading test in case of self-compacting concrete, and sometimes corrections with water or additive, when demanded.
Acceptance of the concrete
When the concrete it's being delivered, it is needed to verify if the mixer truck are sealed and if the concrete is following the design specifications. The responsible must check, at the bill of sale, informations like the volume of the acquired concrete, the water / cement ratio, the deformation modulus, the aggregate maximum size, the aggresseviness class, the compressing resistance (fck) and the cement consumption per cubic meter. Before laying the concrete, another test must be done, the "slump test" or the spreading test in case of self-compacting concrete, and sometimes corrections with water or additive, when demanded.
Rastreabilidade
É imprescindível garantir a rastreabilidade dos lotes do concreto aplicado na obra. Para isso servem os corpos de prova moldados com o material coletado de cada caminhão-betoneira. Cada exemplar deve adequadamente identificado e armazenado até o momento do ensaio de resistência à compressão. Além disso, durante a execução de estruturas com concretos mais consistentes, deve-se fazer o mapeamento da concretagem na planta da laje, associando cada setor ao seu respectivo caminhão-betoneira.
Traceability
It's indispensable to assure the traceability of the concrete lots used at worksite. For this purpose, the specimens are casted with the concrete collected on the mixer truck. Each element must be correctly identified and stored until the moment of the compressing resistance test. In addition, during the execution of the structures with more strong concretes, we must do the mapping of the concreting at the slab plant, linking each sector to it's related mixer truck.
Traceability
It's indispensable to assure the traceability of the concrete lots used at worksite. For this purpose, the specimens are casted with the concrete collected on the mixer truck. Each element must be correctly identified and stored until the moment of the compressing resistance test. In addition, during the execution of the structures with more strong concretes, we must do the mapping of the concreting at the slab plant, linking each sector to it's related mixer truck.
Lançamento do concreto
O concreto deve ser lançado o mais próximo possível de sua posição final na fôrma. Se ele for arrastado horizontalmente, pode tirar armaduras e espaçadores do lugar. Se for lançado de uma altura muito grande, pode danificar as fôrmas ou sofrer segregação. O material mais consistente deve ser adensado em camadas, durante e logo após o início da aplicação. A espessura da camada deve ser de aproximadamente 3/4 o comprimento da agulha do vibrador de imersão. Ao vibrar uma camada de concreto, o vibrador deve penetrar cerca de 10cm na camada anterior.
Laying of the concrete
The concrete laying must be done as close as possible to it's final location when the process are finished, If it is dragged horizontally, you may move the reinforcement bars and the spacers out of its correct locations. If the concrete was released in much higher heights, they can damage the forms or cause seggregations. The strongest material must be compacted by layers, during and short time after the start of the laying. The laying thickness must be around of three quarters of the vibrator's needle lengthen. When vibrating a concrete layer, the vibrator must penetrate 10cm inside the previous layer.
Laying of the concrete
The concrete laying must be done as close as possible to it's final location when the process are finished, If it is dragged horizontally, you may move the reinforcement bars and the spacers out of its correct locations. If the concrete was released in much higher heights, they can damage the forms or cause seggregations. The strongest material must be compacted by layers, during and short time after the start of the laying. The laying thickness must be around of three quarters of the vibrator's needle lengthen. When vibrating a concrete layer, the vibrator must penetrate 10cm inside the previous layer.
Fonte (Source):
Revista Téchne , edição n°. 229
Téchne magazine, edition n°. 229
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