Hybrid ICP Base Bedding

Hybrid ICP Base Bedding

by “Paver Pete” Baloglou, Techo-Bloc

Traditional Interlocking Concrete Pavement (ICP) and Segmental Permeable Pavement (SPP) have had mutually exclusive installation systems until recently. A new “Hybrid” installation technique has emerged and is gaining recognition and acceptance. Combining SPP open-graded base and bedding with ICP sand-filled joints has several advantages in certain projects (disadvantages in others) and stepby-step differences that need clarification.

Hybrid ICP installs can consume less labor and equipment because little-to-no compaction effort is needed with opengraded material such as ASTM #57 and #8 stone. The materials are virtually self-consolidating and only require compaction effort (vibratory or static) for the creation of a smooth working surface. Also, open-graded base material can lead to OSHA Silica regulation compliance (less airborne fine particles).

Using #57 stone as a base for hybrid ICP helps minimize aggregate types on a project. For example, the same clean stone can be (and is commonly) used as a base and backfill for Segmental Retaining Walls (SRW). Volume use of #57 stone equals weight by volume savings on freight and tonnage rates.

The following is a step-by-step comparison of traditional and hybrid ICP:

Subgrade soil should be classified, amended, and compacted to 98% Standard Proctor Density (SPD). Excavation should mirror finished grade of pavement. These steps protect pavements from frost damage.

A woven geotextile should be used to separate base from subgrade and to bridge minor differential settlement.

A sub-base of ASTM #2’s and #3’s may be used, but its use should be closely scrutinized.

A base of ASTM #57 stone should conically distribute loads to ensure no rutting or failure. If desired, a biaxial geogrid layer(s) can be added, or additional base thickness applied if more load is present.

ASTM #57 isn’t freeze & thaw susceptible due to 30-35% void space, unlike ASTM C2940, but if the climate has a deep frost line, then additional grid and thickness may be needed. In vehicular traffic applications, a non-woven geotextile should be used between base and bedding. Fabrics prevent downward migration of the particles under the frequency of kinetic energy (traffic).

Bedding material is used to fix minor imperfections in base (+/- 3/8” over 10’) and paver thickness variation (+/- 1/8”) and provide drainage. It should also contribute to Vertical Interlock (a sand-filled, tight joint). The first three are accomplished in Hybrid ICP by #8 stone bedding. Vertical interlock is achieved through joint fill and consolidation via the top once pavers are laid.

Paving stones exceeding ASTM c936 standard from a reputable supplier with a written warranty should be used.

Edge restraints can be a hybrid-flexible product (with wedge-shaped stakes), precast units set in mortar and backfilled with tapered steel-reinforced concrete, or steel/fiber-reinforced concrete. The edge restraint must resist “creep” (the horizontal movement of the pavement) and encapsulate the bedding layer.

The joints are filled for traditional and hybrid installs the same way. Polymeric sand, water-swept epoxy-based sand, or ASTM c33 are all acceptable options.

Blindly choosing traditional or hybrid ICP, or, for that matter, a “standard/typical” cross-section of a SPP on any and every job is a bad idea. Look at proximity to foundation walls, soils, climate, etc. and choose the system that represents the best short-term and long-term advantages to the client. As SPP have gained in use and acceptance over the past years (doubling in growth annually) so will Hybrid ICP. Applying the technology on a smaller upcoming walkway, patio, pool deck, or driveway may help determine if the system suits your team and company standards.

For more information on Hybrid installations visit: https:// www.techo-bloc.com/hybrid-installation/

“Paver Pete” Baloglou is one of the industry’s leading experts on permeable pavement systems and is an accredited instructor on Porous Pavements for the American Institute of Architects/ American Society of Landscape Architects.

Pete is Techo-Bloc’s Director of Education and Information. With 19 years in the industry, he takes hardscape projects from inception to completion, manufacturing, and distribution… Pete knows how to build jobs. He is an ICPI and NCMA certified instructor and committee member. He’s made his mark in almost 40 states and five countries, and he’s a founding member of the Techo Bloc Showcase team!

With 20 plus years in the industry, he has authored numerous articles and has appeared as a leading hardscape expert on more than 25 national and local television and radio programs including “Hometime”, “Home Team” “Man Cave”.