ACI 330.1-03 Specification for Unreinforced Concrete Parking Lots (2003 or the newest version) is a guide specification for commercial paving. You can find this document on the American Concrete Institute Abstracts Portal.

Jointed Plain Concrete Pavement is the most economical and widely used concrete pavement currently.

Distributed steel, such as welded wire fabric, is not a recommended approach for controlling cracks. Crack control is best done with proper joint spacing (see below).

Synthetic macrofibers can help with crack performance, slowing deterioration after a crack forms. Synthetic macrofibers can also aid in controlling or minimizing plastic shrinkage cracks. Beyond these specific issues, jointed plain concrete pavements don’t include reinforcing.

Reinforcement for structural capacity is commonly covered with Continuously Reinforced Concrete Pavements (CRCP). These pavements are only used in a small number of states and are typically expensive to build.

From a design perspective, the biggest difference between road paving and commercial site paving is traffic. Truck and traffic volume and speed on roads is typically higher than what is common on commercial sites. The traffic flow on roads is frequently unidirectional, or channelized, and wheel paths are often well established. Design tools such as Pavement ME, which is an evolution of AASHTO design tools, can calculate traffic volumes and speeds encountered on roads. ACI 325.12R-02 Guide for Design of Jointed Concrete Pavements for Streets and Local Roads also provides guidance on lower-volume roads.

The pavement used on commercial projects, including warehouse/distribution and manufacturing facilities, generally has a lower overall volume of truck and general traffic. Speeds are significantly slower and traffic flow is rarely channelized into identifiable wheel paths. Design methods such as ACI 330R-08 Guide for the Design and Construction of Concrete Parking Lots and ACI 330.2R-17 Guide for the Design and Construction of Concrete Site Paving for Industrial and Trucking Facilities are well suited for commercial paving design.

From a construction perspective, road paving is frequently associated with larger projects. Equipment includes mainline paving machines and concrete for these projects is often produced on site. Commercial site paving can also involve equipment found on road projects and onsite concrete plants. More frequently, however, commercial site paving includes concrete delivered with mixer trucks from fixed location plants near the project. Roller Compacted Concrete (RCC) is an alternate concrete paving method suitable for both types of projects.

To recap, here are the typical differences between road paving and commercial site paving:

Cemex Paving and Infrastructure Engineers can help you with typical joint details on request.

Dowels are used for load transfer between concrete pavement slabs. They are typically round smooth steel bars. Dowels typically allow independent horizontal movement between slabs while vertical movement is uniform to facilitate load transfer. Dowels are generally not needed for pavements with a low volume of heavy traffic (trucks) moving at low speeds.

Low-volume traffic is generally considered 100 – 200 trucks per day or less, moving slower than 30 MPH.

Deformed steel tie-bars are typically used to keep concrete panels from moving under lateral pressures. They are frequently located between the two outer most panels on the perimeter of projects when no edge support exists.

Minimum dowel diameter (for round dowels) is recommended to be 1.25" with spacing recommendations as shown below. Source: ACI 330.2R-17 Design and Construction of Concrete Site Paving for Industrial and Trucking Facilities. Dowel lengths longer than 18” can be difficult to find.

The Water-Cement Ratio, or Water-Cementitious Ratio, describes the relationship between the amount of water and the amount of cementitious material (cement alone or cement plus Supplementary Cementitious Materials) by weight in a concrete mix. It is an indicator of the strength of a concrete mix. As shown in the table below, as the W/C ration increases, the compressive strength of the concrete decreases.

It typically isn’t necessary to specify a W/C ratio along with a required compressive strength for a concrete pavement. If, at any time, this becomes necessary, it is recommended that the specification be set at a maximum value. For example, Max. W/C = 0.5 would typically give compressive strengths of 4,000 psi or higher for non-air-entrained concrete and 3,000 psi or higher for air-entrained concrete.

Air is entrained (added to) in a concrete mix to aid in durability and freeze-thaw resistance. This is in addition to air already entrapped in a concrete mix during batching. Entrapped air consists of irregularly shaped bubbles and the amount varies based on maximum aggregate size. In contrast, entrained air consists of perfectly shaped round bubbles and is added by admixtures. Total recommended air content (entrapped plus entrained) is based on exposure conditions as shown in the table below. Source: ACI 330R-08 Guide for the Design and Construction of Concrete Parking Lots.

The amount of entrained air is the Recommended Total Air Content minus Typical Entrapped Air Content. Tolerance for total air in a mix is +/- 1.5%. It is suggested not to exceed the recommended air content for a given exposure condition as that may have a detrimental effect on compressive strength. See the Effect of Water on Compressive Strength graph above.

Supplementary Cementitious Materials (SCMs) are added to replace a percentage of straight cement in a concrete mix. These are typically used to help improve properties of the concrete as listed below. There are a variety of SCMs with Fly Ash and Ground Granulated Blast Furnace Slag (commonly called Slag) being the two most common. Fly Ash is a by-product of coal burning and Slag is a by-product of iron production. SCMs help:

• lower the heat of hydration
• increase set times
• increase long-term strength
• increase durability
• mitigate Alkali Silica Reaction (ASR) and sulfate attack
• lower costs
• reduce CO₂ emissions

At Cemex, we are actively engaged in developing several methods for reducing the carbon footprint of concrete. Methods of doing this include replacing some of the cement in concrete with SCMs, as discussed above and/or using a blended cement. Portland Limestone Cement (PLC) Type IL is a blended cement accepted by most Departments of Transportation and available in many markets across the USA. Cemex offers Vertua®, a lower-carbon concrete that we design to meet the carbon reduction goals of your project.

The CO₂ content of concrete is typically identified by its Global Warming Potential (GWP). The GWP is measured in kg CO₂-eq/cubic yard (or per cubic meter). The GWP number is obtained from an Environmental Product Declaration (EPD) for the particular concrete mix. EPDs are third-party verified documents and are specific to individual concrete mixes and plants. There are also online tools to help in the design process, as well as online resources to find EPDs for various materials.

Although there are some entities, such as the General Services Administration (GSA) that have identified GWP goals by number, currently most CO₂ goals are given in terms of reduction off a baseline concrete mix using 100% Ordinary Portland Cement (OPC). The initial reduction level for our CEMEX product is Vertua^® Classic Ready-Mix Concrete, which offers a CO₂ reduction of 30 – 49% off an industry standard concrete mix with 100% OPC.

There is a wide variety of available resources for concrete paving. Contact the Cemex Paving and Infrastructure Team with your questions and we will be glad to help you with resources to meet your needs.