Construction professionals make hundreds of decisions a day. Navigating the complexities of running a business alone is hard enough. But to stay on top of industry advancements, evolving codes, new materials and the constant pressure to deliver structural integrity on tight schedules—we all need to rely from time to time on the advice from a colleague.

CFA not only serves as a critical technical authority for the cast-in-place concrete industry but also offers valuable resources like the CFA Member Connect Hotlines. This program provides CFA members with direct access to industry experts who can address their most pressing technical challenges and business inquiries. By leveraging these resources, professionals can move beyond simple compliance to understanding the “why” behind technical requirements and how their peers are dealing with similar issues. This member resource not only puts you in touch with industry experts and the CFA team, but the CFA also works with the engineering team at the American Concrete Institute to assist members in reviewing issues related to technical codes and standards.

This article shares the ten most common questions CFA’s Member Connect Hotline received in 2025 and a summary of the technical resources given. While these inquiries represent the technical questions we’ve been asked, our Member Connect 411 hotline connects members to businesses solutions too. Once you are done reading this list, check out the full CFA Member Connect Hotline program and database of inquiries.

10 Does a variance in the top-of-wall elevation warrant the rejection of a foundation?

ANSWER: Not typically. According to ACI 332,1 acceptable tolerances for the levelness of a foundation wall are ±0.75 in. Variations within this range are generally aesthetic or framing concerns rather than structural failures. They do not compromise the foundation’s

integrity.

Do not rush to demolition or costly rework. Instead, correct variations that fall within the allowable tolerance by grinding or patching the surface. This practical approach ensures a level bearing surface for floor systems without unnecessary delays or expenses.

9 How long should a contractor wait to strip new aluminum forms to prevent damage?

ANSWER: New forms lack a seasoned aluminum oxide layer and are highly susceptible to damage from the alkaline concrete mix. To prevent this, stripping should be delayed to allow sufficient concrete strength gain. This typically means waiting 24 to 48 hours, depending on ambient temperature and the mix design.

Prioritize equipment longevity over speed for the first few pours with a new set of forms. Avoid next-day stripping, especially in cold weather, to protect the delicate oxide layer and extend the life of your investment.

8 Why do test results show chloride ions when no calcium chloride was added to the mix?

ANSWER: While ASTM C12182 tests for water-soluble chlorides, their mere presence does not indicate a violation of a “no calcium chloride” specification. As long as the levels remain below the permissible limits set by ACI 318,3 the concrete is compliant.

It is key to provide documentation from the ready-mix supplier confirming that no calcium chloride was intentionally added to the mix and educate project stakeholders that trace chlorides are naturally occurring and unavoidable in most cases. The focus should be on compliance with the maximum specified threshold limits rather than the simple presence of chloride ions.

7 Are bent dowels required to connect a slab-on-grade to a foundation wall in non-seismic zones?

ANSWER: No. For projects in Seismic Design Category A, neither International Residential Code (IRC) 20184 nor ACI 3321 mandates a hard dowel connection. For lateral support, the friction and mechanical interlock between the slab and the foundation wall are often sufficient.

Another option is an engineered keyway or other interlocking mechanism at the joint between the slab and the wall to provide additional stability without requiring dowels. This approach satisfies structural stability requirements, provides the necessary lateral support and solves the problem of not being able to penetrate aluminum forms with dowels.

6 Do low seven-day concrete test breaks mean the concrete will fail to meet its 28-day design strength?

ANSWER: Not necessarily. Concrete strength gain is logarithmic, not linear, and is heavily influenced by the mix design and curing conditions. The CFA’s Cold Weather Research Report provides relevant data on this matter. For instance, Mix No. 9, a 5.5-sack Type I cement mix, achieved approximately 3200 PSI at seven days and ultimately reached 4290 PSI at 28 days. Similarly, Mix No. 10, with a water reducer, reached roughly 3500 PSI at seven days and finished at 4470 PSI. These examples show that even with variations in seven-day performance, a properly designed 4000 PSI mix has a high potential to meet or exceed its specified strength at 28 days, even under less-than-ideal curing temperatures.

Before assuming failure, verify the curing conditions of the test cylinders and maintain proper field curing for the in-place concrete. Wait for the definitive 28-day test results before considering more drastic measures like core sampling.

5 What causes hydrogen gas bubbles and “worm tracks” on concrete surfaces cast against aluminum?

ANSWER: This common issue stems from a chemical reaction. The high alkalinity (pH > 12) of fresh concrete reacts with elemental aluminum, producing hydrogen gas and sometimes creating bubbles and unsightly trails on the concrete surface. This surface reaction is particularly common with new or unseasoned forms. Additionally, the chemical bonding between aluminum and cementitious materials leads to concrete buildup on the forms, which is much stronger than physical adhesion.

One effective method is to pretreat the aluminum forms to create a protective layer of aluminum oxide. This can be achieved using proprietary seasoning products or lime slurry. The most effective method involves submerging the forms in a controlled environment with a specialized solution. Other methods include applying a resinous or powder coating to the aluminum forms, using highly reactive form release agents for the first few pours, and using a low-alkali concrete mix.

4 Does the presence of honeycombing require the removal and replacement of a foundation wall?

ANSWER: Rarely. Honeycombing is typically a surface issue caused by inadequate consolidation of the concrete. Per ACI 3321 and ACI 546R, repair is only strictly required if the reinforcement is exposed or if the depth of the void compromises the wall’s load-bearing capacity.

Assess the depth of the honeycombing before reacting. For minor honeycomb areas (less than 0.5 in. deep), patching with a mortar mix of one-part portland cement to two-and-a-half parts sand is typically sufficient. For larger or deeper areas, the defective concrete should be chipped away to sound material and filled with a patching mortar. ACI 546R provides detailed guidance on patching procedures.

3 Must concrete placement be halted if form oil is sprayed onto the reinforcement?

ANSWER: No. This is a common point of contention, but the code is clear. ACI 332-20 Section 4.2.41 and its commentary explicitly state that common surface contaminants like form oil are not detrimental to bond strength. Deformed bars rely on mechanical interlock with the concrete, a mechanism that a light coating of oil does not negate. The bond mechanism relies primarily on the mechanical interlock provided by the deformations on the bar, and contaminants like form oil are removed by friction during the loading process.

Concerns about form oil likely stem from a conservative interpretation of older specifications, such as ACI 301-96, which required reinforcement to be free of materials deleterious to bond. However, updated research and codes, including ACI 332-20, provide clear evidence that form oil is not a deleterious material.

You can proceed with the concrete placement, as the presence of form oil on the reinforcement does not compromise the structural integrity or bond strength of the concrete-rebar system.

2 Is it acceptable to backfill a foundation wall without bracing?

ANSWER: Absolutely not. This is a non-negotiable safety and structural requirement. The International Residential Code (IRC) R404.1.7 requires that backfill should not be placed against a wall until it has sufficient strength and has been anchored to the floor above or sufficiently braced to prevent damage. This requirement ensures that the wall can resist the lateral forces exerted by the backfill.

There are cost-effective bracing methods that are commonly used, including temporary bracing systems like wood or steel braces, corner and offset bracing like backfilling to full height at corners to provide natural bracing, as well as counterforts or buttresses like thickened areas of walls cast integrally with the main wall which are particularly effective for long wall spans. Incorporate bracing into your standard workflow. The backfill material and method of placement significantly impact the pressure exerted on the wall. Using well-draining soils or granular fills can reduce lateral pressure. The fill should be placed in layers (lifts) of no more than two feet and compacted lightly to avoid excessive pressure.

1 Can concrete be placed safely when ambient temperatures drop below 20 degrees Fahrenheit without expensive prescriptive enclosures?

ANSWER: Yes. Both ACI 306R9 and CFA Cold Weather Research from 2004 demonstrate that the critical performance metrics are the internal concrete temperature and its maturity, not the ambient air temperature. Concrete can be successfully placed and cured in temperatures as low as 10 degrees Fahrenheit, provided that appropriate mix designs and minimal protection measures are used. The hydration process is exothermic, meaning it generates its own heat. This allows the concrete to continue gaining strength even in sub-freezing air.

Instead of adhering to overly restrictive local requirements, you can propose alternative methods that are supported by ACI 3069 and CFA research. These include using a mix design tailored for cold weather, such as one with Type III cement or accelerating admixtures, employing minimal protection for the first 24 to 48 hours to retain heat and prevent freezing, as well as monitoring in-place concrete temperatures using maturity meters to ensure that the concrete reaches 500 psi before freezing.

CONCLUSION

Technical challenges in foundation work often stem from misinterpretations of code intent or reliance on outdated practices. As these top inquiries show, the answers lie in a deep understanding of material science, specific code references and access to expert guidance.

The CFA’s Member Connect hotlines empower members to resolve disputes quickly, gain clarity on complex issues and keep projects moving efficiently. By leveraging this program, the database of past inquiries and the resources it provides, professionals can build with evidence-backed confidence and use construction methods that are safe, compliant and innovative.

As with any concrete mixture, it is essential to conduct trial batches to confirm the specific properties of the concrete. Final results can be affected by various factors, such as temperature, humidity, and the specific components used in the mixture. We recommend consulting a local concrete foundation professional for guidance.

Please note that no information provided herein should be interpreted as a warranty or guarantee, whether expressed or implied. This includes, but is not limited to, any implied warranty of fitness for a particular purpose.

SOURCES

1. ACI Committee 332. “Code Requirements for Residential Concrete (ACI 332-20) and Commentary.” Farmington Hills, Michigan: American Concrete Institute, July 6, 2020.
2. ASTM Subcommittee C09.69. ASTM C1218/C1218M-20 Standard Test Method for Water-Soluble Chloride in Mortar and Concrete. West Conshohocken, Pennsylvania: ASTM, 2020.
3. ACI Committee 318. ACI 318-25: Building Code for Structural Concrete—Code Requirements and Commentary. Farmington Hills, Michigan: American Concrete Institute, 2025.
4. International Code Council, Inc. 2018 International Residential Code. Country Club Hills, Illinois: International Code Council, 2017.
5. Concrete Foundations Association. “Cold Weather Research Report (2004).” Concrete Foundations Association of North America, 2004.
6. ACI Committee 546. “ACI 546R-14: Guide to Concrete Repair.” Farmington Hills, Michigan: American Concrete Institute, September 2014.
7. ACI Committee 301. 301-96: Specification for Structural Concrete Buildings. Farmington Hills, Michigan: American Concrete Institute, 2002.
8. International Code Council, Inc. 2015 International Residential Code: R404.1.7. Country Club Hills, Illinois: International Code Council, Inc., 2014.
9. ACI Committee 306. ACI 306R-16: Guide to Cold Weather Concreting. Farmington Hills, Michigan: American Concrete Institute, 2016.