Specifying Bonded Abrasive Polished Concrete for New Construction

Polished concrete is unique among flooring systems because it is manufactured entirely on site rather than in a factory. Unlike prefinished materials that arrive with consistent and predictable characteristics, polished concrete depends on the quality of the substrate, the skill of the installer, and the coordination of multiple trades working in the same space during construction. For builders and contractors specifying bonded abrasive polished concrete for new construction, understanding how the substrate is produced and how the polishing process works is essential to achieving a durable, aesthetically pleasing result. Before specifying the finishing process, it is important to ensure the underlying slab is sound. For more on preparing existing slabs for finishing, see Pour New Concrete Over Old Concrete Surface. This article draws on the Concrete Polishing Association of America (CPAA) specification framework and industry best practices to help specifiers navigate the key decisions involved in polished concrete specification for new build projects.

1. Understanding the Substrate Requirements for Polished Concrete

The finished appearance and performance of polished concrete depend fundamentally on the quality of the substrate. Any concrete slab can be put through a polishing process, but the substrate must be conducive to that process. Manufacturing a slab that polishes well begins with proper sub-grade preparation, reinforcement, and finishing techniques. The following subsections outline the critical factors.

Sub-Grade and Subsurface Requirements

For slab-on-grade installations, the sub-grade must be properly prepared to minimise the risk of cracking, which directly affects the visual continuity of the polished surface. Key subsurface requirements include:

• Preparation of the sub-grade to reduce cracking potential
• Vapour barrier installed according to ASTM E1745 and ASTM E1643
• Reinforcement designed to control shrinkage and structural loading
• Bulkheads and forms that create aesthetically pleasing construction joints
• Proper penetration finishing around pipes, columns, and other penetrations

Each of these elements contributes to a slab that can be polished to a high standard. Joints, in particular, must be planned carefully because they remain visible in the final polished floor.

Curing and Moisture Management

Curing is one of the most frequently underestimated factors in polished concrete specification. Improper curing leads to moisture loss that causes shadowing from uneven hydration, surface crazing, delamination, and cracking. Three curing methods are commonly used:

• Water curing
• Curing compounds
• Environmental condition control

Whichever method is chosen, the curing regime must prevent rapid moisture loss during the first seven to 28 days. The structural plans should include a graphic delineation showing the limits of the polished concrete areas so that the placing and finishing contractor pays extra attention to these zones during bidding and construction.

2. Mix Design and Placement Considerations for Polished Concrete Floors

The concrete mix design has a direct impact on how the slab responds to polishing. Variations in raw materials, admixtures, and finishing practices produce different results in colour, reflectivity, and durability. Specifiers must understand how each component affects the final finish.

Raw Materials and Admixtures

All raw materials including cement, water, and aggregates should come from the same batch and source throughout the project to avoid colour variations. Key considerations for each material type are summarised in the table below.

Air entrainment, while beneficial for exterior durability, is not recommended by ACI for interior hard-troweled surfaces intended for polishing. It can create micro-voids that appear in the finished surface. For more on batching and mixing equipment, see Concrete Construction Equipment Mixers Pumps and Batching Plant.

Placement and Finishing Practices

How the slab is placed and finished determines the quality of the surface that will be polished. The following practices are critical:

1. Smaller pours allow finishers to maintain attention to detail and prevent the concrete from setting before finishing is complete
2. Proper consolidation ensures a tight structure around aggregates, reducing the risk of delamination
3. Surface finishing must be performed by knowledgeable finishers to avoid over-watering, washing out cement fines around penetrations, and spalling
4. Flatness is measured by Floor Flatness (FF) numbers; the greater the FF, the less wavy the polished finish will appear
5. Joint placement must be planned to achieve aesthetically pleasing construction and control joints at appropriate spacing

The cast-in-place specification and the polishing specification must reference each other in the RELATED SECTIONS of each document. For more on forming and joint placement strategies, see Concrete Formwork Systems Types Design and Best Practices.

3. The Bonded Abrasive Polishing Process and Specification Approach

The CPAA defines three methods for producing a polished concrete surface: bonded abrasive, burnished, and hybrid polished concrete. Bonded abrasive polishing is the most widely specified method and forms the foundation of the polished concrete industry. However, writing an effective specification for bonded abrasive polishing requires a careful balance between prescriptive and performance-based requirements.

Prescriptive versus Performance Specifications

A purely prescriptive specification that dictates every step of the process including equipment make and model, abrasive type, rotational speed, and forward pace will not work across different jobs. Each project has a unique substrate, set of site conditions, and logistical constraints. Contractors use equipment from different manufacturers and abrasives with different characteristics.

A purely performance specification, which only defines the measurable end result, is equally problematic because contractors can learn to manipulate the measurement methods. The most effective approach is a combination of both prescriptive and performance elements. This allows the specifier to define the expected finish while giving the contractor flexibility in how to achieve it within an approved framework.

The Proven Sequential Grit Process

Over the past 15 years, one system has repeatedly produced polished concrete surfaces with superior clarity, depth, and durability. The following prescriptive steps should be included in the specification:

1. Use bonded abrasives from a manufacturer with a proven track record of producing the best results the substrate will allow. The densifier does not create the polish; it is the mechanical interaction between the abrasives and the substrate that determines the finish quality
2. Follow a sequential grit process that does not skip grits and drops back one grit size when transitioning from metal bond to resin bond abrasives. If transitional abrasives are used, comparison testing in several areas of the slab must be performed to verify equivalent results
3. Fully refine each abrasive grit to its maximum potential as defined by the CPAA before moving to the next grit
4. Make sequential passes with each pass perpendicular to the previous pass to ensure uniform coverage
5. Thoroughly clean the floor after each grit, removing debris larger than what the next grit size will produce
6. Apply the densifier to the point of rejection and keep the surface saturated for 30 to 45 minutes. Reapply later in the process as needed based on porosity and environmental conditions
7. Apply semi-impregnating or impregnating protection as defined by the CPAA
8. Meet installer qualifications as defined in the CPAA 03 3543 specification

The specification must also state the visual degree of cut (cream or cement fines, salt and pepper or sand aggregate, or coarse aggregate exposure) and the degree of polish (flat ground, satin honed, semi-polished, or highly polished). Other visual characteristics to define include colour, decorative cuts, and joint fill. For more on precast systems and aggregate exposure, see Concrete Precast Elements Manufacturing Design and Construction of.

4. Coordination and Accountability for Successful Polished Concrete Installation

Unlike a factory-manufactured flooring product where one company controls every variable, a polished concrete floor on a construction site involves six or more independent companies in the manufacturing process, plus countless other trades working above and around the slab. This complexity means that specifications alone cannot guarantee success. Coordination and accountability are equally important.

Specification Writing and Submittal Requirements

Specifications must be customised for each project rather than copied from a previous job. The qualification section must require verifiable past performance on projects of similar size and scope. Submittals must include this qualification information, and the general contractor must actually check it. Too often, specifications state qualification requirements but do not require them as part of the submittal package, and even when they are submitted, the information is rarely verified.

General Contractor Responsibilities

The general contractor plays the central role in ensuring a successful polished concrete installation. Key responsibilities include:

• Coordinating all trades involved in the manufacturing process
• Ensuring specifications are followed and requirements are met
• Understanding the polished concrete contractor’s jobsite requirements
• Monitoring and qualifying finished work throughout the process
• Communicating the architect’s and owner’s expectations to all trades
• Enforcing substrate protection during construction

Protection of the substrate before polishing is a critical and often overlooked aspect. Requirements include diapering all equipment to prevent stains, prohibiting pipe cutting over the slab, protecting the surface during steel erection and drywall work, and never parking vehicles or lifts directly on the slab.

Scheduling and Trade Coordination

Polished concrete should ideally be installed after 28 days of curing, once the building is enclosed, and before interior wall construction. The earlier in the project the polishing occurs, the lower the cost and the lower the risk of damage. Key scheduling factors include:

• Adequate lighting must be available for the polishing process
• Power and water must be provided to the polishing contractor
• A dumpster must be supplied for dust and slurry disposal
• Sufficient square footage must be released to the polisher at one time
• Cast-in-place and polishing contracts should be bid separately to maintain clear communication

Managing Expectations

The architect and owner must have realistic expectations about what polished concrete can deliver. The floor will not be perfect. There will be imperfections inherent in all concrete. It will be consistently inconsistent. Variables such as wind, the angle of the sun, humidity, and temperature all affect the finished surface and are difficult to control. A decision to use polished concrete should be based on site visits to completed buildings of similar type, not on brochure images or internet photos.

When expectations are realistic, specifications are enforced, and all trades are held accountable, polished concrete delivers a floor that is aesthetically pleasing, highly durable, and extremely low maintenance. The key is recognising that a polished concrete installation is a group effort that goes beyond the specification document itself.