Self-Compacting Mass Concrete

Self-Compacting Mass Concrete

Jabal Omar Development Project – Makkah

The Jabal Omar Development project calls for construction of a residential and commercial center in an area close to the Grand Mosque in Makkah. The development covers 230,000 square meters and is set to accommodate nearly 40,000 people in its 39 commercial and residential towers.

The development space has been divided into two areas; The Northern area, which includes fourteen 35 story buildings and a 6 story prayer building; The Southern area, with its own set of towers. Based on the complexity of the structural design, a transverse slab and drop beams of 1.5 – 4 meters thickness, the structure needs a heavily congested steel net element.

Project Requirements:

  • Target concrete strength (@ 28 days) = 52 MPa
  • Specified slump = 190 ± 40 mm
  • Mineral additives for strength, durability and pumpability
  • Maximum Heat Of Hydration = 70o C
  • Maximum Differential Temperature = 20o C

Challenges:

  • Produce mass concrete in compliance with the project’s concrete specifications:
    • Compressive strength of 52 PMaProduce a mix that would enhance the flowability and pumpability of the concreteControlled heat of hydration
  • The project’s location next to the Grand Mosque posed transportation and work area limitations. Work site required special preparations and extra precautions.
  • Difficulty of pumping conventional mass concrete due to high density of concrete mix.

Solutions:

  • Many trial mixes were conducted using different types and percentage of supplementary cementitious materials to reach the optimum mix that would meet the requirements of strength, slump and pumpability.
  • Supplimentary cementicious materials were used as a replacement to a percentage of the cement content to help reduce Heat of Hydration and enhance pumpability.
  • Special polycarboxylate based superplacticizer admixtures were used to achieve early strength and required flowability.
  • Thermocouple lugs and digital temperature recorders were installed in 3m x 3m containers during trial mix mock-ups to ensure achieving required controlled heat of hydration.
  • A special silo was installed at the factory’s batching plant to provide, and ensure the supply of, the large quantities of suplimentary cementicious materials the project’s mix requires.
  • The use of stationary pumps, due to their relative smaller size, in place of mobile pumps to reduce required work space.