Concrete Technology

Harza Engineering Company

Special Construction Methods

Special construction methods and materials Tunnel lining Horizontal slipform paving Canal lining Vertical slipform construction Roller-compacted concrete Controlled Low Strength Material

(CLSM) Pervious concrete

Concrete tunnel lining

Types Circular tunnels Horseshoe Shaped

Lining types Full-circle (Smaller diameters) Multiple placements (Large diameter)

Invert Sidewalls Crown

Placement methods

Invert and sidewalls Conveyors Pumping Invert slipform

Arch or crown section Pumping

Types of placement

Bulkhead sections dependent on length of form

Continuous placement Telescoping forms

Important items Rock cleanup and control of water Cleaning of construction joints Equipment capable of placing the

required concrete mixture Segregation during handling and

placement Proper consolidation (limited access)

- form and immersion vibrators Filling upper most reaches of the

crown

Horizontal slipform paving

Paving machines Slabs Curbs Barriers

All horizontal paving requires low slump concrete and good vibration

Consistent concrete is essential

Slope paving

Canal lining machine Slipform screed

Alternating panels

Vertical slipform construction

Jacking system on vertical rods Suitable for silos and shafts

Pervious concrete

Controlled Low Strength Material (CLSM)

CLSM is a self-compacted, cementitious material used primarily as a backfill in lieu of compacted fill. (ACI 229R)

Most current CLSM applications require unconfined compressive strengths of 300 psi or less. This strength requirement is necessary to allow for future excavation of CLSM.

Applications

Backfill Structural fills Insulating fills Pavement bases Conduit bedding Erosion control Void filling

Materials Cement Fly ash

Class C Class F

Fine aggregate ASTM C 33 Silty sand (up to 20% minus #200)

Coarse aggregate (occasionally) Air-entraining admixture

Mixture proportions

Slump range - 6 to 8 inches Cement content - 50 to 200 pcy Fly ash content - none to 2000 pcy Water contents - typically 325 to

580 pcy Air content as high as 20% Balance of mixture is aggregate