【Daily Topic】【Civil Engineering Version 20160615】

A construction joint refers to the seam that forms between concrete poured in successive stages, due to design requirements or construction needs, during the concrete pouring process. A construction joint is not an actual \"joint\"; it is merely a junction surface that exists between concrete poured earlier and concrete poured later, as the former has been poured for longer than its initial setting time. This junction surface is what is referred to as a construction joint. 　　Method of leaving joints: The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: Horizontal joints should be left in columns and walls, while the concrete for beams and slabs should be poured in one go, without leaving any construction joints. 　　⑴ Construction joints should be placed on the top surface of the foundation, below the brackets of beams or crane beams, above crane beams, and below the column caps of slab-on-grade floors. 　　⑵ For large-section beams that are integrated with the floor slabs, construction joints should be placed 20 mm to 30 mm below the bottom surface of the slab. When there is a beam support under the slab, it is left below the beam support. 　　⑶ For one-way slabs, construction joints should be placed at any position parallel to the short side of the slab. 　　⑷ For floor slabs with primary and secondary beams, pouring should be carried out in the direction of the secondary beams, and construction joints should be placed within 1/3 of the span of the secondary beams. 　　⑸ Construction joints on the wall should be located within 1/3 of the span of the lintel above the door opening, or they can also be placed at the junction of vertical and horizontal walls. 　　⑹ The construction joint on the stairs should be located at 1/3 of the tread height. The concrete for the stairs should be poured continuously. In the case of multi-story staircases, if the upper floor has a cast-in-place floor slab that has not yet been poured, a construction joint can be left ； It should be positioned at the 1/3 middle section of the staircase, taking care that the joint surface is inclined perpendicular to the axis of the staircase. (The reason for the disputes during construction is that the old specifications required that stair construction joints be placed in the middle 1/3 of the stair section; traditional construction methods involved placing them at the top and bottom steps. When the joints are located in the middle of the stair, shear forces are theoretically lower. However, it is difficult to ensure the quality of these construction joints during construction, and when setting up the formwork a second time, it can lead to a short-term \"overhang\" in the already poured portion, which actually hinders the control of the quality of the structural elements.) ) ⑺ The construction joint in the wall of the water tank should be located on the vertical wall at a height of 200 mm to 500 mm above the surface of the bottom plate. 　　⑻ For two-way stressed floor slabs, mass concrete, arches, shells, silos, equipment foundations, multi-story rigid frames, and other complex structures, the locations of construction joints shall be determined in accordance with the design requirements. 　　Processing requirements: The connection method for construction joints shall meet the design specifications. When there are no specific requirements for the design, for plain concrete structures, connection bars with a diameter of not less than 16 mm should be embedded at the construction joints. The embedding depth and exposed length of the connecting rebar should both be no less than 30d of the rebar diameter, with a spacing of no more than 20 cm. When plain rebar is used, semi-circular standard hooks should be provided at both ends; hooks are not required when ribbed rebar is used. The treatment of concrete construction joints shall also meet the following requirements: 1. When the old concrete surface and the exposed rebar (embedded elements) are exposed to cold air, it is necessary to provide insulation to protect the old concrete within a range of 1.5 meters from the new and old concrete construction joints, as well as the exposed rebar (embedded elements) within a range of 1.0 meters. 　　2. When the concrete does not require heating for curing and will not freeze within the specified curing period, concrete can be poured directly on non-swellable foundations or existing concrete surfaces. 　　3. When concrete needs to be cured by heating, the temperature difference between the newly poured concrete and the adjacent hardened concrete or rock/soil medium shall not exceed 15°C; the temperature of the foundation surface in contact with the concrete shall not be lower than 2°C. 11.3.11 The temperature at which concrete curing begins shall be determined through thermal calculations in accordance with the construction plan, but it must not be lower than 5°C; for structures with thin cross-sections, it should not be lower than 10°C. 　　4. The cement mortar and weak layers on the surface of the poured concrete should be chiseled away; after roughening, the area of fresh concrete exposed should be no less than 75%. When chiseling the surface, the concrete strength shall meet the following requirements: 1) When chiseling manually, it shall be no less than 2.5 MPa. 　　2) When chiseling with mechanical tools such as air hammers, it should be no less than 10 MPa. 　　5. The chiseled concrete surface should be washed clean with water, but no water accumulation shall remain. Before pouring new concrete, it is advisable to apply a layer of pure cement paste on the surface of the old concrete for vertical construction joints; for horizontal construction joints, it is appropriate to lay a layer of cement mortar with a thickness of 10 mm to 20 mm and a mix ratio of 1:2, where the water-cement ratio is slightly lower than that of the concrete, or to lay a layer of concrete about 30 cm thick, using coarse aggregate that is 10% less in quantity compared to that used in the newly poured concrete. 　　6. When the construction joint is inclined, the old concrete should be poured or chiseled into a stepped shape.

1. A construction joint is a seam that forms between concrete poured in stages due to design requirements or construction needs, as a result of pouring the concrete in separate phases； 2. The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: horizontal joints should be left in columns and walls, while the concrete for beams and slabs should be poured in one go, without leaving any construction joints ； 3. The connection method for construction joints shall meet the design requirements. When there are no specific requirements for the design, for plain concrete structures, connection bars with a diameter of not less than 16 mm should be embedded at the construction joints. The embedding depth and exposed length of the connecting rebar should both be no less than 30d of the rebar diameter, with a spacing of no more than 20 cm. When plain rebar is used, semi-circular standard hooks should be provided at both ends; hooks are not required when ribbed rebar is used.

Due to construction techniques or organizational reasons, concrete pouring cannot be carried out continuously; the joint formed between the already set and hardened concrete and the new concrete poured subsequently is known as a construction joint. Retention principle: The structure is subject to low shear forces and construction is convenient ； Treatment method: (After the strength of the poured concrete reaches 1.2 N/mm2,) remove the loose and weak layers on the surface → moisten with water and rinse → apply a layer of cement slurry or cement mortar → continue pouring.

Due to construction techniques or organizational reasons that prevent continuous concrete pouring, the interface formed between the already set and hardened concrete and the new concrete poured afterward is known as a construction joint. Retention principle: The structure is subject to low shear forces and construction is convenient ； Treatment method: (After the strength of the poured concrete reaches 1.2 N/mm2,) remove the loose and weak layers on the surface → moisten with water and rinse → apply a layer of cement slurry or cement mortar → continue pouring.

1. Construction joint: A joint left between different construction sections as required by the construction plan. A construction joint is not an actual \"joint\"; it is merely a junction surface that arises between the concrete poured later and the concrete poured earlier, as the latter curing time exceeds that of the former, and this junction surface is what is referred to as a construction joint. 2. What is the method for leaving construction joints? The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: horizontal joints should be used for columns, while vertical joints should be used for beams, slabs, and walls. (1) Construction joints should be placed on the top surface of the foundation, below the beams or the brackets of the crane beam, above the crane beam, and below the column caps of slab-on-grade floors. (2) For large-section beams that are integrated with the floor slab, construction joints should be placed 20 mm to 30 mm below the bottom surface of the slab. When there is a beam support under the slab, it is left below the beam support. (3) For one-way slabs with an aspect ratio greater than 2:1, construction joints should be placed at any position parallel to the shorter side of the slab; moreover, these joints must be vertical and cannot be formed as diagonal joints. (4) For floor slabs with primary and secondary beams, pouring should be carried out in the direction of the secondary beams, and construction joints should be placed within 1/3 of the span of the secondary beams. (5) Construction joints on the wall should be placed within 1/3 of the span of the lintel at the door opening, or they can also be located at the junction of vertical and horizontal walls. (6) The construction joint on the stairs should be located at 1/3 of the tread height. The concrete for the stairs should be poured continuously. In the case of multi-story staircases, if the upper floor has a cast-in-place floor slab that has not yet been poured, a construction joint can be left ； It should be positioned at the 1/3 middle section of the staircase, taking care that the joint surface is inclined perpendicular to the axis of the staircase. (The reason for the disputes during construction is that the old specifications required that stair construction joints be placed in the middle 1/3 of the stair section; traditional construction methods involved placing them at the top and bottom steps. When the joints are located in the middle of the stair, shear forces are theoretically lower. However, it is difficult to ensure the quality of these construction joints during construction, and when setting up the formwork a second time, it can lead to a short-term \"overhang\" in the already poured portion, which actually hinders the control of the quality of the structural elements.) ) (7) The construction joint in the pool wall should be located on the vertical wall at a height of 200 mm to 500 mm above the surface of the bottom slab. (8) For floor slabs subjected to bidirectional loads, mass concrete, arches, shells, silos, equipment foundations, multi-story rigid frames, and other complex structures, the locations of construction joints shall be determined in accordance with the design requirements.

Joints left between different construction units as required by the construction organization. A construction joint is not an actual \"joint\"; it is merely a junction surface that arises between the concrete poured later and the concrete poured earlier, as the latter curing time exceeds that of the former, and this junction surface is what is referred to as a construction joint. How to leave construction joints? The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: horizontal joints should be used for columns, while vertical joints should be used for beams, slabs, and walls. (1) Construction joints should be placed on the top surface of the foundation, below the beams or the brackets of the crane beam, above the crane beam, and below the column caps of slab-on-grade floors. (2) For large-section beams that are integrated with the floor slabs, construction joints should be placed 20 mm to 30 mm below the bottom surface of the slab. When there is a beam support under the slab, it is left below the beam support. (3) For one-way slabs, construction joints should be placed at any position parallel to the short side of the slab. (4) For floor slabs with primary and secondary beams, pouring should be carried out in the direction of the secondary beams, and construction joints should be placed within 1/3 of the span of the secondary beams. (5) Construction joints on the wall should be located within 1/3 of the span of the lintel above the door opening, or they can also be placed at the junction of vertical and horizontal walls. (6) The construction joint on the stairs should be located at 1/3 of the tread height. (7) The construction joint in the pool wall should be located on the vertical wall at a height of 200 mm to 500 mm above the surface of the bottom slab. (8) For floor slabs subjected to bidirectional loads, mass concrete, arches, shells, tanks, equipment foundations, multi-story rigid frames, and other complex structures, the locations of construction joints shall be determined in accordance with the design requirements.

A construction joint refers to the seam that forms between concrete poured in successive stages, due to design requirements or construction needs, during the concrete pouring process. A construction joint is not an actual \"joint\"; it is merely a junction surface that exists between concrete poured earlier and concrete poured later, as the former has been poured for longer than its initial setting time. This junction surface is what is referred to as a construction joint. 　　Method of leaving joints: The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: Horizontal joints should be left in columns and walls, while the concrete for beams and slabs should be poured in one go, without leaving any construction joints. 　　⑴ Construction joints should be placed on the top surface of the foundation, below the brackets of beams or crane beams, above crane beams, and below the column caps of slab-on-grade floors. 　　⑵ For large-section beams that are integrated with the floor slabs, construction joints should be placed 20 mm to 30 mm below the bottom surface of the slab. When there is a beam support under the slab, it is left below the beam support. 　　⑶ For one-way slabs, construction joints should be placed at any position parallel to the short side of the slab. 　　⑷ For floor slabs with primary and secondary beams, pouring should be carried out in the direction of the secondary beams, and construction joints should be placed within 1/3 of the span of the secondary beams. 　　⑸ Construction joints on the wall should be located within 1/3 of the span of the lintel above the door opening, or they can also be placed at the junction of vertical and horizontal walls. 　　⑹ The construction joint on the stairs should be located at 1/3 of the tread height. The concrete for the stairs should be poured continuously. In the case of multi-story staircases, if the upper floor has a cast-in-place floor slab that has not yet been poured, a construction joint can be left ； It should be positioned at the 1/3 middle section of the staircase, taking care that the joint surface is inclined perpendicular to the axis of the staircase. (The reason for the disputes during construction is that the old specifications required that stair construction joints be placed in the middle 1/3 of the stair section; traditional construction methods involved placing them at the top and bottom steps. When the joints are located in the middle of the stair, shear forces are theoretically lower. However, it is difficult to ensure the quality of these construction joints during construction, and when setting up the formwork a second time, it can lead to a short-term \"overhang\" in the already poured portion, which actually hinders the control of the quality of the structural elements.) ) ⑺ The construction joint in the wall of the water tank should be located on the vertical wall at a height of 200 mm to 500 mm above the surface of the bottom plate. 　　⑻ For two-way stressed floor slabs, mass concrete, arches, shells, silos, equipment foundations, multi-story rigid frames, and other complex structures, the locations of construction joints shall be determined in accordance with the design requirements. 　　Processing requirements: The connection method for construction joints shall meet the design specifications. When there are no specific requirements for the design, for plain concrete structures, connection bars with a diameter of not less than 16 mm should be embedded at the construction joints. The embedding depth and exposed length of the connecting rebar should both be no less than 30d of the rebar diameter, with a spacing of no more than 20 cm. When plain rebar is used, semi-circular standard hooks should be provided at both ends; hooks are not required when ribbed rebar is used. The treatment of concrete construction joints shall also meet the following requirements: 1. When the old concrete surface and the exposed rebar (embedded elements) are exposed to cold air, it is necessary to provide insulation to protect the old concrete within a range of 1.5 meters from the new and old concrete construction joints, as well as the exposed rebar (embedded elements) within a range of 1.0 meters. 　　2. When the concrete does not require heating for curing and will not freeze within the specified curing period, concrete can be poured directly on non-swellable foundations or existing concrete surfaces. 　　3. When concrete needs to be cured by heating, the temperature difference between the newly poured concrete and the adjacent hardened concrete or rock/soil medium shall not exceed 15°C; the temperature of the foundation surface in contact with the concrete shall not be lower than 2°C. 11.3.11 The temperature at which concrete curing begins shall be determined through thermal calculations in accordance with the construction plan, but it must not be lower than 5°C; for structures with thin cross-sections, it should not be lower than 10°C. 　　4. The cement mortar and weak layers on the surface of the poured concrete should be chiseled away; after roughening, the area of fresh concrete exposed should be no less than 75%. When chiseling the surface, the concrete strength shall meet the following requirements: 1) When chiseling manually, it shall be no less than 2.5 MPa. 　　2) When chiseling with mechanical tools such as air hammers, it should be no less than 10 MPa. 　　5. The chiseled concrete surface should be washed clean with water, but no water accumulation shall remain. Before pouring new concrete, it is advisable to apply a layer of pure cement paste on the surface of the old concrete for vertical construction joints; for horizontal construction joints, it is appropriate to lay a layer of cement mortar with a thickness of 10 mm to 20 mm and a mix ratio of 1:2, where the water-cement ratio is slightly lower than that of the concrete, or to lay a layer of concrete about 30 cm thick, using coarse aggregate that is 10% less in quantity compared to that used in the newly poured concrete. 　　6. When the construction joint is inclined, the old concrete should be poured or chiseled into a stepped shape.

A construction joint refers to the seam that forms between concrete poured in successive stages, due to design requirements or construction needs, during the concrete pouring process. A construction joint is not an actual \"joint\"; it is merely a junction surface that exists between concrete poured earlier and concrete poured later, as the former has been poured for longer than its initial setting time. This junction surface is what is referred to as a construction joint. 　　Method of leaving joints: The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: Horizontal joints should be left in columns and walls, while the concrete for beams and slabs should be poured in one go, without leaving any construction joints. 　　⑴ Construction joints should be placed on the top surface of the foundation, below the brackets of beams or crane beams, above crane beams, and below the column caps of slab-on-grade floors. 　　⑵ For large-section beams that are integrated with the floor slabs, construction joints should be placed 20 mm to 30 mm below the bottom surface of the slab. When there is a beam support under the slab, it is left below the beam support. 　　⑶ For one-way slabs, construction joints should be placed at any position parallel to the short side of the slab. 　　⑷ For floor slabs with primary and secondary beams, pouring should be carried out in the direction of the secondary beams, and construction joints should be placed within 1/3 of the span of the secondary beams. 　　⑸ Construction joints on the wall should be located within 1/3 of the span of the lintel above the door opening, or they can also be placed at the junction of vertical and horizontal walls. 　　⑹ The construction joint on the stairs should be located at 1/3 of the tread height. The concrete for the stairs should be poured continuously. In the case of multi-story staircases, if the upper floor has a cast-in-place floor slab that has not yet been poured, a construction joint can be left ； It should be positioned at the 1/3 middle section of the staircase, taking care that the joint surface is inclined perpendicular to the axis of the staircase. (The reason for the disputes during construction is that the old specifications required that stair construction joints be placed in the middle 1/3 of the stair section; traditional construction methods involved placing them at the top and bottom steps. When the joints are located in the middle of the stair, shear forces are theoretically lower. However, it is difficult to ensure the quality of these construction joints during construction, and when setting up the formwork a second time, it can lead to a short-term \"overhang\" in the already poured portion, which actually hinders the control of the quality of the structural elements.) ) ⑺ The construction joint in the wall of the water tank should be located on the vertical wall at a height of 200 mm to 500 mm above the surface of the bottom plate. 　　⑻ For two-way stressed floor slabs, mass concrete, arches, shells, silos, equipment foundations, multi-story rigid frames, and other complex structures, the locations of construction joints shall be determined in accordance with the design requirements. 　　Processing requirements: The connection method for construction joints shall meet the design specifications. When there are no specific requirements for the design, for plain concrete structures, connection bars with a diameter of not less than 16 mm should be embedded at the construction joints. The embedding depth and exposed length of the connecting rebar should both be no less than 30d of the rebar diameter, with a spacing of no more than 20 cm. When plain rebar is used, semi-circular standard hooks should be provided at both ends; hooks are not required when ribbed rebar is used. The treatment of concrete construction joints shall also meet the following requirements: 1. When the old concrete surface and the exposed rebar (embedded elements) are exposed to cold air, it is necessary to provide insulation to protect the old concrete within a range of 1.5 meters from the new and old concrete construction joints, as well as the exposed rebar (embedded elements) within a range of 1.0 meters. 　　2. When the concrete does not require heating for curing and will not freeze within the specified curing period, concrete can be poured directly on non-swellable foundations or existing concrete surfaces. 　　3. When concrete needs to be cured by heating, the temperature difference between the newly poured concrete and the adjacent hardened concrete or rock/soil medium shall not exceed 15°C; the temperature of the foundation surface in contact with the concrete shall not be lower than 2°C. 11.3.11 The temperature at which concrete curing begins shall be determined through thermal calculations in accordance with the construction plan, but it must not be lower than 5°C; for structures with thin cross-sections, it should not be lower than 10°C. 　　4. The cement mortar and weak layers on the surface of the poured concrete should be chiseled away; after roughening, the area of fresh concrete exposed should be no less than 75%. When chiseling the surface, the concrete strength shall meet the following requirements: 1) When chiseling manually, it shall be no less than 2.5 MPa. 　　2) When chiseling with mechanical tools such as air hammers, it should be no less than 10 MPa. 　　5. The chiseled concrete surface should be washed clean with water, but no water accumulation shall remain. Before pouring new concrete, it is advisable to apply a layer of pure cement paste on the surface of the old concrete for vertical construction joints; for horizontal construction joints, it is appropriate to lay a layer of cement mortar with a thickness of 10 mm to 20 mm and a mix ratio of 1:2, where the water-cement ratio is slightly lower than that of the concrete, or to lay a layer of concrete about 30 cm thick, using coarse aggregate that is 10% less in quantity compared to that used in the newly poured concrete. 　　6. When the construction joint is inclined, the old concrete should be poured or chiseled into a stepped shape.

A construction joint refers to the seam that forms between concrete poured in successive stages, due to design requirements or construction needs, during the concrete pouring process. A construction joint is not an actual \"joint\"; it is merely a junction surface that exists between concrete poured earlier and concrete poured later, as the former has been poured for longer than its initial setting time. This junction surface is what is referred to as a construction joint. Method of leaving joints: The location of construction joints should be chosen in areas where the structure is subject to less shear force and where construction is easier; moreover, the following rules must be followed: Horizontal joints should be left in columns and walls, while the concrete for beams and slabs should be poured in one go, without leaving any construction joints. 　　⑴ Construction joints should be placed on the top surface of the foundation, below the brackets of beams or crane beams, above crane beams, and below the column caps of slab-on-grade floors. 　　⑵ For large-section beams that are integrated with the floor slabs, construction joints should be placed 20 mm to 30 mm below the bottom surface of the slab. When there is a beam support under the slab, it is left below the beam support. 　　⑶ For one-way slabs, construction joints should be placed at any position parallel to the short side of the slab. 　　⑷ For floor slabs with primary and secondary beams, pouring should be carried out in the direction of the secondary beams, and construction joints should be placed within 1/3 of the span of the secondary beams. 　　⑸ Construction joints on the wall should be located within 1/3 of the span of the lintel above the door opening, or they can also be placed at the junction of vertical and horizontal walls. 　　⑹ The construction joint on the stairs should be located at 1/3 of the tread height. The concrete for the stairs should be poured continuously. In the case of multi-story staircases, if the upper floor has a cast-in-place floor slab that has not yet been poured, a construction joint can be left ； It should be positioned at the 1/3 middle section of the staircase, taking care that the joint surface is inclined perpendicular to the axis of the staircase. (The reason for the disputes during construction is that the old specifications required that stair construction joints be placed in the middle 1/3 of the stair section; traditional construction methods involved placing them at the top and bottom steps. When the joints are located in the middle of the stair, shear forces are theoretically lower. However, it is difficult to ensure the quality of these construction joints during construction, and when setting up the formwork a second time, it can lead to a short-term \"overhang\" in the already poured portion, which actually hinders the control of the quality of the structural elements.) ) ⑺ The construction joint in the wall of the water tank should be located on the vertical wall at a height of 200 mm to 500 mm above the surface of the bottom plate. 　　⑻ For two-way stressed floor slabs, mass concrete, arches, shells, silos, equipment foundations, multi-story rigid frames, and other complex structures, the locations of construction joints shall be determined in accordance with the design requirements. 　　Processing requirements: The connection method for construction joints shall meet the design specifications. When there are no specific requirements for the design, for plain concrete structures, connection bars with a diameter of not less than 16 mm should be embedded at the construction joints. The embedding depth and exposed length of the connecting rebar should both be no less than 30d of the rebar diameter, with a spacing of no more than 20 cm. When plain rebar is used, semi-circular standard hooks should be provided at both ends; hooks are not required when ribbed rebar is used. The treatment of concrete construction joints shall also meet the following requirements: 1. When the old concrete surface and the exposed rebar (embedded elements) are exposed to cold air, it is necessary to provide insulation to protect the old concrete within a range of 1.5 meters from the new and old concrete construction joints, as well as the exposed rebar (embedded elements) within a range of 1.0 meters. 　　2. When the concrete does not require heating for curing and will not freeze within the specified curing period, concrete can be poured directly on non-swellable foundations or existing concrete surfaces. 　　3. When concrete needs to be cured by heating, the temperature difference between the newly poured concrete and the adjacent hardened concrete or rock/soil medium shall not exceed 15°C; the temperature of the foundation surface in contact with the concrete shall not be lower than 2°C. 11.3.11 The temperature at which concrete curing begins shall be determined through thermal calculations in accordance with the construction plan, but it must not be lower than 5°C; for structures with thin cross-sections, it should not be lower than 10°C. 　　4. The cement mortar and weak layers on the surface of the poured concrete should be chiseled away; after roughening, the area of fresh concrete exposed should be no less than 75%. When chiseling the surface, the concrete strength shall meet the following requirements: 1) When chiseling manually, it shall be no less than 2.5 MPa. 　　2) When chiseling with mechanical tools such as air hammers, it should be no less than 10 MPa. 　　5. The chiseled concrete surface should be washed clean with water, but no water accumulation shall remain. Before pouring new concrete, it is advisable to apply a layer of pure cement paste on the surface of the old concrete for vertical construction joints; for horizontal construction joints, it is appropriate to lay a layer of cement mortar with a thickness of 10 mm to 20 mm and a mix ratio of 1:2, where the water-cement ratio is slightly lower than that of the concrete, or to lay a layer of concrete about 30 cm thick, using coarse aggregate that is 10% less in quantity compared to that used in the newly poured concrete. 　　6. When the construction joint is inclined, the old concrete should be poured or chiseled into a stepped shape.