13.2
Exemplo de projeto: juntas em pavimentos de concreto
As juntas de pavimento de concreto são essenciais para manter a integridade estrutural e a longevidade do pavimento, controlando onde e como o pavimen…
Propõe-se a extensão de um pavimento de concreto liso existente para construção com lajes de concreto, garantindo o mínimo de rachaduras no pavimento.
Um engenheiro de pavimento decide fornecer juntas de construção, expansão, isolamento e contração para controlar rachaduras no pavimento.
As juntas de construção são lacunas fornecidas entre a nova laje e uma laje existente para permitir quaisquer movimentos possíveis na nova laje. Barras de cavilha embutidas no concreto unem as lajes adjacentes.
As juntas de dilatação são vãos fornecidos entre as lajes adjacentes para permitir a expansão térmica do concreto.
Sua construção envolve a disposição das barras de cavilha em fileiras na direção transversal do pavimento e o despejo de concreto sobre as barras.
A lacuna deixada é então preenchida com cargas compressíveis e selantes.
As juntas de isolamento são fornecidas onde o pavimento encontra um bueiro. Uma junta de meia polegada de largura ao redor do bueiro, preenchida com um material compressível, forma a junta de isolamento.
Finalmente, a junta de contração é fornecida serrando uma ranhura no pavimento de concreto recentemente endurecido orientada perpendicularmente à direção do fluxo de tráfego.
Isso ajuda a localizar e controlar a formação de rachaduras durante a contração do concreto.
View the full transcript and gain access to JoVE Core videos
Q1: What are the main types of joints used in concrete pavement design?
Concrete pavements use four primary joint types: construction joints, which connect new and existing slabs; expansion joints, which accommodate thermal expansion; isolation joints, which separate pavement from fixed objects like manholes; and contraction joints, which are saw-cut grooves that control crack formation. Each joint type serves a specific function in managing pavement movement and preventing random cracking.
Q2: How do construction joints work in concrete pavement extensions?
Construction joints are gaps between new and existing concrete slabs that allow movement in the new slab during curing. Dowel bars embedded in the concrete tie adjacent slabs together, transferring loads while permitting controlled movement. This design prevents stress concentration at the interface between old and new pavement sections.
Q3: Why are expansion joints necessary in concrete pavements?
Expansion joints accommodate concrete's thermal expansion, preventing high compressive forces that can cause joint spalling or structural failure. These joints are created by arranging dowel bars in transverse rows and filling the gap with compressible fillers and sealants. This allows adjacent slabs to expand independently without damaging the pavement structure.
Q4: What is the purpose of contraction joints in concrete pavements?
Contraction joints are saw-cut grooves made perpendicular to traffic flow in recently hardened concrete. These joints create a weakened vertical plane that localizes and controls crack formation during concrete's contraction, directing cracks to predetermined locations rather than allowing random cracking across the slab.
Q5: How are isolation joints designed around pavement obstacles?
Isolation joints are provided where pavement encounters fixed objects like manholes. A half-inch wide joint filled with compressible material surrounds the obstacle, allowing the pavement and adjacent structures to move independently. This prevents stress transfer between the pavement and the fixed object.
Q6: What materials are used to fill concrete pavement joints?
Concrete pavement joints are filled with compressible fillers and sealants that accommodate movement while maintaining structural integrity. These materials allow adjacent concrete sections to expand and contract independently while preventing water infiltration and debris accumulation in the joint spaces, ensuring long-term pavement durability.
Q7: How do dowel bars function in concrete pavement joints?
Dowel bars are embedded in concrete to tie adjacent slabs together while facilitating controlled movement. In construction joints, they connect new and existing slabs; in expansion joints, they're arranged in transverse rows to transfer loads. This design maintains load transfer capacity while allowing thermal and contraction movements.