How to Avoid Water Leakage Arising From Improper Pour Strip Concreting?

During the engineering construction, there are five reasons may cause the basement leakage including improper metal waterstop setting, improper pour strip concreting, improper waterproof material protection, poor through-wall pipe area sealing and improper outdoor grade waterproof closure height. Here, we’d like to discuss the water leakage arising from improper pour strip concreting.

Pour strip construction lasts a long period and involves many links. Combined with improper detail treatment, all these reasons eventually lead to water leakage. According to our analysis, pour strip leakage may arise from the following reasons.

  • Limited construction period leads to pour strip casting too early.
  • The waterstops on both sides of the pour strip are not firmly fixed, resulting in displacement and inconsistent concrete thickness for the first time.
  • The pour strip first casting is finished and left open. The reinforcement deforms due to repeated tramples, and even combines with pipelines and wire box inside the strip to form a seepage channel.
  • High density reinforcements make it is hard to erect formwork on both sides of the pour strip. In addition, improper blocking method and mortar leakage also lead to uncompacted concrete.
  • Reinforcements in the pour strip are badly corroded. The ash in the seam of the floor has not been thoroughly cleaned, and the existing concrete on both sides has not been roughened.
  • The grade of the expansive concrete used in the pour strip is not improved and the amount of micro-expansive agent is insufficient. Moreover, the slump of the concrete is not strictly controlled, the vibration is not performed carefully, and the existing and new concretes are not firmly combined.
  • During the curing period, the pour strip is not covered in time with less watering times, and the formwork is demolished in advance before the specified curing period expires.

Pour strip leakage

Improper pour strip arrangement

All reasons mentioned above will lead to serious water leakage. We must take the following measures to address the water leakage.

Before carrying out construction on both sides of the pour strip, the drawings shall be optimized to avoid the arrangement of wiring tube and cable box in the pour strip forming a water channel.

  • Before pouring concrete on both sides of the pour strip, wooden mold open seams blocking is employed to minimize the loss of cement slurry. Cleaning ports shall be reserved intermittently in the pour strip.
  • Before pouring concrete in the pour strip, remove the loose stones on both sides until the solid layer and strive to level it off; remove the rusted surface on the reinforcements or metal waterstops, and clean up the garbage and ash with an air compressor or a high-pressure water gun.
  • The concrete for the pour strip shall be expansive concrete whose strength grade shall be 0.5 to 1 grade higher than that of the existing concrete. In addition, it shall be mixed with expansive agent accounting for 14% to 15% by cement weight, and the slump shall be controlled within 160 mm to 180 mm.
  • When the concrete is poured on both sides, protective measures must be taken. Cover the top area to prevent the occurrence of garbage, reinforcement pollution and trampling deformation in the pour strip.
  • The lower formwork of the cast-in-place slab in the pour strip shall not be removed prematurely. When removing, the pillars in the strip and on both sides shall be reserved and aligned up and down layer by layer to prevent water leakage arising from deformation cracks.
  • The pouring period of the post strip: The general cycle of concrete construction is 6 weeks. If there are no design requirements, the second pouring on both sides of the concrete shall be conducted two months after the first pouring.

Proper pour strip arrangement

Pour strip construction layout

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