JVAZCO pioneered polished concrete in the Philippines. Over the years, we’ve faced and solved a variety of challenges with flatwork: significant cracks, delamination, wavy surfaces, dusting, moisture issues, and embedded debris. These weren’t just problems for the owners—they were problems for us too. These challenges fueled our commitment to get involved right from the start, ensuring things are done right the first time. That’s how the Concrete Flatwork System was born, and the rest is history.
Since 2017, we’ve delivered over a million square meters of concrete flatwork using the right tools and equipment, tailored to projects of any size—big or small. Our results are driven by our investment in people: training over 40 skilled in-house concrete finishers. This stands in stark contrast to the typical “pakyawan” practice, which often prioritizes speed over quality, leading to higher risks. It’s also no secret that the ACI 302 Guide has been our playbook for years.
What is ACI 302?
ACI PRC-302.1-15, “Guide to Concrete Floor and Slab Construction”, was written and published in 2015 by the American Concrete Institute (ACI)—the leading global authority on consensus-based standards and technical resources for concrete. This 76-page guide outlines industry-accepted practices for producing high-quality concrete slabs on grade and suspended floors.
First Things First
The document opens with a truth bomb that might make even a seasoned professional furrow their brow:
“Even with the best floor designs and proper construction, it is unrealistic to expect completely crack- and curl-free floors.”
We hate to break it to you—this expectation must be aligned early among contractors, owners, and designers. Cracks and curling are not necessarily signs of poor design or shoddy craftsmanship. The reality is simple: concrete will always crack.
Among our flatwork team, there’s an old standing joke: concrete’s last name is “crack.” If it doesn’t crack, it’s probably not concrete. But here’s the silver lining: while cracks can’t be eliminated, they can be minimized. Curling, on the other hand? That’s a whole different beast.
We won’t dive into why concrete cracks or curls here—maybe in a follow-up article. For now, let’s focus on how ACI 302 has guided us in adopting best practices during construction to deliver exceptional results.
Assessing the Type of Floor
Floors for offices, churches, commercial spaces, institutional buildings, multi-unit residences, gymnasiums, industrial facilities, warehouses, television studios, and ice rinks require unique design considerations. As mentioned in our previous article, this is not a one-size-fits-all type of construction. This is why we have five (5) Concrete Flatwork System (CFS) categories designed based on floor classes and flatness and levelness requirements.
Figure 1: Concrete Flatwork System (CFS) Categories
ACI 302 identifies nine (9) classes of floors based on the anticipated type of traffic, use, special considerations, and final finish.
Figure 2: ACI 302 Classes of Floors
For instance, consider the floor design for a warehouse and distribution center. These facilities handle material-handling equipment (MHE), such as hard-wheeled forklifts, which demand a durable surface capable of withstanding heavy, repeated use.
As shown in Figure 3, a Class 6 floor incorporates a special metallic or mineral aggregate surface hardener, applied during construction to enhance abrasion resistance. Additionally, repeated and precise steel-troweling is required to achieve a smooth, robust surface that meets flatness and levelness criteria.
Flatness and Levelness Requirements
Flatness and levelness tolerances are determined based on floor usage requirements. Key considerations include:
- Anticipated Traffic: Type, frequency, and weight of MHE (e.g., forklifts, pallet jacks) influence requirements, especially distinguishing random from defined traffic.
- Racking System: Low, mid, or high racking systems require varying tolerances to prevent instability.
- Operational Needs: Some facilities use robotic automated guided vehicles (AGVs) that require extremely tight tolerances for navigation.
The floor must provide adequate flatness and levelness to ensure seamless operations, including MHE movement and static equipment stability. ACI 117 defines flatness and levelness as:
- Flatness (Ff): The degree of smoothness or bumpiness of the floor surface.
- Levelness (Fl): The degree to which the floor surface parallels the slope specified in project drawings.
Figure 3a: Flatness and Levelness Diagram
Figure 3b: Flatness and Levelness Tolerances (ASTM E1155)
Now, returning to the example of the floor design for a warehouse and distribution center, the design was carefully aligned with the flatness and levelness tolerances specified in ACI 117. The facility in question is designed to handle both static loads and dynamic loads. For static loads, the 8-meter push-back racking systems and mezzanine (raised floor) exert concentrated and distributed loads. Meanwhile, the dynamic loads of MHEs such as pallet trucks, counterbalance trucks, and reach trucks continuously traverses the floor. To ensure floor’s overall uniformity and that the surface delivers uninterrupted movement of MHE, the designer has specified Ff45 and Fl35. Therefore, the floor surface classification is a very flat floor (CFS 4).
Identifying the type of floor is a critical step in the design phase of construction. It is essential not to overlook this aspect, as the floor type directly impacts the construction methodology.
Design and Construction Variables
This section focuses on the design of slab-on-grade (SOG), defined by ACI as “a slab supported by ground, whose main purpose is to bear applied loads.” ACI 360 identifies four basic design choices for SOG construction:
- Unreinforced concrete slabs.
- Slabs reinforced to limit crack widths due to shrinkage, temperature restraint, and applied loads.
- Slabs reinforced to prevent cracking from shrinkage, temperature restraint, and applied loads.
- Structural slabs designed per ACI 318.
Both technical and human factors influence SOG design and construction:
- Technical Factors: Load requirements (dictating thickness, reinforcement, and strength), tolerances, joint types, material selection, mix design, and soil-support systems.
- Human Factors: Skilled workforce (particularly finishers), stakeholder coordination, timing of operations (e.g., finishing, curing, saw-cutting), and maintenance planning.
References:
ACI PRC-302.1-15 Guide to Concrete Floor and Slab Construction. (n.d.). https://www.concrete.org/store/productdetail.aspx?ItemID=302115&Language=English&Units=US_AND_METRIC
ACI PRC-117.1-14 Guide for Tolerance Compatibility in Concrete Construction. (n.d.). https://www.concrete.org/store/productdetail.aspx?ItemID=117114&Language=English&Units=US_AND_METRIC
ACI PRC-360-10 Guide to Design of Slabs-on-Ground. (n.d.). https://www.concrete.org/store/productdetail.aspx?ItemID=36010&Format=PROTECTED_PDF&Language=English&Units=US_AND_METRIC
ACI CODE-318-19(22): Building Code Requirements for Structural Concrete and Commentary (Reapproved 2022). (n.d.). https://www.concrete.org/store/productdetail.aspx?ItemID=318U19&Language=English&Units=US_Units
ASTM E1155-20 Standard test method for determining FF floor flatness and FL floor levelness numbers. (n.d.). https://www.astm.org/e1155-20.html