Concrete and Masonry

The placement and finishing of concrete involves many different tasks that can be automated.  Automation is especially effective in the conveyance of concrete with such technologies as programmable concrete pumps, automated horizontal distributors, and conveyor systems.  Once the concrete is in place, a variety of technologies are available to perform vibrating, leveling, screeding, and finishing activities.  Cleaning and cutting of concrete can also be done using automated technologies.

Opportunities are available as well to automate masonry construction.  Mobile bricklaying and robotic masonry block installation machines provide accurate and efficient placement of masonry units that minimize common risks to worker safety and health while maintaining production.

Example Automated Technologies:

The following are examples of automated concrete and masonry technologies that are currently available for use:

Common Limiting Design Features

The following are examples of design features that often limit the use of automated concrete and masonry technologies during construction:

• Slope changes on slabs and roadways.

• Diagonal grade breaks.

• Warped crowns.

• Mid-slab protrusions and obstructions.

• Non-uniform distribution of floor slab protrusions and obstructions.

• Inconsistent masonry block size, shape, and pattern.

• Inconsistent reinforcing steel size and shape.

• Varying surface textures and features.

• A lack of clearance for access and operation of the technology.

Recommended Design Practices

The following are examples of suggested design practices that facilitate the use of automated concrete and masonry technologies during construction:

Concrete:

• Provide tighter specifications for grade, slope, and smoothness.

• Maintain long continuous paving with constant slope.

• Eliminate diagonal grade breaks, warped crowns, and perpendicular curvature.

• Eliminate mid-slab protrusions and obstructions.

• Keep utilities that penetrate concrete floor slabs grouped together; do not spread the utilities out.  If slab protrusions/obstructions cannot be grouped together, keep them as far apart as possible to allow for passage of equipment between them.

• Keep anchor bolts below the finish floor.

• Set concrete pours to be within machine widths.

• Specify concrete mix designs that allow for finishing by automated equipment.

• Design concrete placement phases to account for the capabilities and feasibility of concrete extruders.

Masonry:

• Maintain a common shape and size of masonry units throughout the project.

• Orient masonry blocks in the same direction and use a consistent pattern.

Reinforcing steel:

• Use repetitive rebar sizes, shapes, and lengths throughout the structure.

• Standardize rebar location within each structural element.

• Use smaller bars for easy fabrication.

• Use lap splices instead of mechanical or welded splices.

• Use standards conducive to the local rebar manufacturing facility.

General design practices:

• Limit the degree of architectural variability.

• Use round columns as opposed to square columns.

Expected Benefits

The following are examples of benefits that have been realized from the use of automated concrete and masonry technologies during construction:

• Increased quality of the concrete finished surfaces.

• Improved ability to meet tighter finish/flatness specifications.

• Shorter time required to place the concrete and masonry.

• Shorter time required to finish the concrete surfaces.

• Decreased exposure to worker safety and health hazards.

Example productivity improvements that have been realized:

Implementation Example

Automated Technology: Concrete Extruder

Project: Monterey Undercrossing and Stevens-Otty Frontage Road, Clackamas, OR

The project involved the construction of a freeway overpass.  Nearly 3,000 feet of MSE retaining wall rails were constructed during the two-year project duration, but not all of the railing was extruded.  The only railing that was extruded was railing attached to wall “H”.  Wall H is over 2,000 feet long and the extruder contractor completed the wall in two days.  Although wall H contained the longest stretch of railing, there were other opportunities to utilize an extruder.  Railing extending along another wall, wall “P”, and onto the bridge itself, was less than 300 feet in length and took the bridge contractor over three weeks to complete.  The railing along wall P and the bridge was not extruded, but could have been if designed differently.  The extruder contractor pointed out that the railing on wall H had a vertical back and curved face, allowing for optimal utilization of their extruder, while the wall P and bridge railing did not (Wall design details).  Also, there was a railing height difference along the length of the railing where it extended from wall P and onto the bridge.  Although attached, the height transition added to the overall cost of extruding.  Since the wall P and bridge railing was under 300 feet in length and required a change in shape configuration, the extruder contractor could not competitively compete against conventional construction methods.  Also, the railing on wall P and the bridge had two vertical faces, which magnifies any inconsistency and adds to the cost of using an extruder.  The extruder contractor added that having at least one curved face helps to reduce the visibility of inconsistencies to the human eye.