Precast Concrete 101

Prepared By: Ralph Verrastro, PE, Principal Engineer, Bridging Solutions, LLC E-mail: [email protected] Phone: 239-216-1370

Precast Concrete 101 Agenda • History • Advantages of Precast Concrete • Precast vs. Cast-in-Place Concrete • Precast vs. Prestressed Concrete • Wet Cast vs. Dry Cast Concrete • Utility/Drainage Products • Transportation Products • Structural Design Process • Shop Drawings • Manufacturing • Handling, Storage, Shipping & Installation • Case Study

Precast Concrete 101 History

• Ancient Romans – Aqueducts – Culverts – Tunnels • Liverpool England in 1905 – Precast panels for buildings • United States in 1950s – Many small companies – Many started with burial vaults (Wilbert) – Mergers and acquisitions prevalent today • Oldcastle (CRH in Ireland) • Hanson Pipe and Precast

Precast Concrete 101 Advantages of Precast Concrete

• Manufactured in a controlled environment • Quality is controlled and monitored • Weather is not a factor • Products may be cast and installed 24/7/365 • Less labor required compared to cast in place concrete • Structures are installed quickly on site

Precast Concrete 101 Advantages of Precast Concrete • Concrete is formed, poured and cured out of the critical path • Repeatability—easy to make many of the same products • Precaster can buy materials for multiple projects, quantity discounts can lower costs • Concrete is more durable due to controlled environment • Concrete strengths are higher than design requirements

Precast Concrete 101 Precast vs. Cast-in-Place Concrete • Which approach is most cost effective? Answer: It depends! • Here is an approach to consider if you are not sure: – Design and detail a CIP structure in contract plans – Provide design criteria for a precast option – Precaster’s specialty engineer designs precast elements – Precaster provides bidders cost for precast elements – Contractor determines which is more cost effective

Precast Concrete 101 Precast vs. Cast-in-Place Concrete Considerations • Crane size requirements • Site access requirements • Schedule – critical path • Dewatering requirements • Overhead wires/trees

Precast Concrete 101 PrecastPrecast vs.vs. CastCast--inin--PlacePlace ConcreteConcrete ConsiderationsConsiderations • Contractor availability/preferences • Precaster availability/proximity • Owner preferences • Engineer preferences • Cold weather (not in Florida!)

Precast Concrete 101 Precast vs. Prestressed Concrete • Concrete is strong in compression- weak in tension • Steel bars added to precast • Steel cables added to prestressed • Cables tensioned using jacks • Concrete is poured • Jacks released after concrete hardens • Bonded cables transfers forces to concrete • Compression force/stress adds tension and bending capacity

Precast Concrete 101 Precast vs. Prestressed Concrete

• National Precast Concrete Association (NPCA) is the industry association for these markets: – Utility – Underground – Drainage – Box culverts – Retaining walls • Precast/Prestressed Concrete Institute (PCI) is the industry association for these markets: – Buildings – Parking structures – Bridges

Precast Concrete 101 Wet Cast vs. Dry Cast Concrete

• Wet cast has a W/C ratio of 0.4 or greater • Dry cast has a W/C ratio of 0.3 to 0.36 or what is referred to zero slump concrete • Wet cast is cast and cured in forms for at least 24 hours • Dry cast may have the forms stripped very quickly

Precast Concrete 101 Wet Cast vs. Dry Cast Concrete

• Another term for dry casting is slip forming • Expensive machines are required for dry casting • Typical dry cast products are pipe, round manholes, block and hollow core slabs for buildings • The remainder of this presentation will focus on wet cast

Precast Concrete 101 Utility/Drainage Products

• Manholes • Catch Basins • Drop Inlets • Pump Stations • Grease Traps • Septic Tanks

Precast Concrete 101 Utility/Drainage Products

• Electrical Manholes • Pull Boxes • Light/Sign Pole Bases • Utility/Storage Sheds • Latrines

Precast Concrete 101 Transportation Products

• Box Culverts – Wingwalls – Toe Walls – Head Walls