Concrete Pumping Techniques and Fresh Concrete Properties for Construction

Concrete Pumping

• Reduces installation time
  • Suitable for embedding large areas without the need for concrete joints
  • Ready-mixed concrete is usually used
  • The system consists of:

• Hopper in which concrete is discharged
• Piston pump or pressure pump
• Tubes through which concrete is pumped

Pumped concrete must have certain qualities:

• Continuous grain size. Maximum aggregate size less than one quarter of the pipe diameter if metal, and one third if plastic
• Crushed aggregate is prohibited
• Soft or fluid consistency
• Maximize all control techniques and procedures

Fresh Concrete Properties

Docility and Workability

Docility means the ability of concrete to be placed and compacted with the available means, so the reinforcement is surrounded and the formwork is completely filled without producing voids.

Docility depends on:

• Amount of mixing water
• Particle size of the aggregates. Docility will be greater with a higher sand content
• Docility is higher with rounded aggregates
• Docility increases with cement content and cement fineness
• Increasing plasticizer dosage improves workability

Consistency

Consistency describes how easily fresh concrete deforms. It depends on many factors, especially the amount of mixing water, the maximum aggregate size, particle size and shape of aggregates, and the presence of admixtures or additions.

Fluid consistency should not be used; soft consistency is recommended and should be compacted by vibration.

Workability

Workability is the amount of useful internal work required to produce full compaction. Its purpose is to remove the air trapped inside the concrete.

Homogeneity

Homogeneity means the various components and qualities of concrete are uniformly distributed throughout the mass, so that two samples taken from different parts of the same mix yield virtually identical results.

Homogeneity is achieved with good mixing and, to maintain it, requires appropriate transport and placement. It can be lost by segregation or settling. Both increase with higher mixing water content, larger maximum aggregate size, vibration or shock during transportation, and placing by free fall.