September 28, 2023
1. Quality problems and phenomena
Concrete segregation; The strength of concrete is insufficient.
2. Cause analysis
1) There are problems with concrete raw materials and mix ratio, or insufficient mixing time.
2) No strings are used when injecting concrete, or the distance between the strings and the concrete surface is too large, and sometimes the concrete is directly poured into the hole at the opening, resulting in the segregation of mortar and aggregate.
3) When there is water in the hole, pour concrete without draining the water. When the concrete should be injected underwater, the dry casting method is used, which results in serious segregation of pile concrete.
4) When pouring concrete, the water leakage of the wall is not blocked, resulting in more water on the surface of the concrete, and the water is not removed to continue pouring concrete, or the use of bucket drainage, and the result is discharged together with cement slurry, resulting in poor concrete consolidation.
5) When local drainage is needed, when a pile concrete is injected at the same time or before the concrete is not initially set, the nearby pile hole digging work does not stop, continue to dig the hole pumping, and the amount of water pumped is large, the result is that the underground flow will take away the cement slurry in the hole pile concrete, and the concrete is in a granular state, only the stone can not see the cement slurry.
3. Preventive measures
1) Qualified raw materials must be used, and the mix ratio of concrete must be prepared by a laboratory with corresponding qualifications or a compression test to ensure that the strength of concrete meets the design requirements.
2) When using the dry casting method, the string drum must be used, and the distance between the string drum mouth and the concrete surface is less than 2m.
3) When the rise rate of water level in the hole exceeds 1.5m/min, the underwater concrete injection method can be used to inject pile concrete.
4) When the precipitation is used to dig holes, the nearby digging construction should be stopped when the concrete is injected or before the concrete is initially set.
5) If the concrete strength of the pile body fails to meet the design requirements, the pile can be replenished.