EP #142 Concrete Moisture Myths Busted

Most people think moisture problems in concrete come from below the slab. Concrete Bob Higgins explains why that assumption keeps blowing up floors. In this episode, Bob Higgins breaks down how moisture actually moves through concrete, why liquid water and water vapor are not the same thing, and how alkalinity quietly does more damage than most people realize. We also get into why common moisture testing methods are misused, why surface damage matters more than deep readings, and how outdated standards keep throwing contractors under the bus. If you’ve ever wondered why floors fail even when the numbers “look fine,” this one connects the dots. What You’ll Learn · Why moisture in concrete is not just “moisture” · The difference between liquid water, water vapor, and chemically bound moisture · Why relative humidity testing is often misunderstood — and misapplied · How alkalinity concentrates at the surface and drives real damage · Why many moisture problems come from the top , not the soil · What self-desiccation is and why you can’t fix it once it happens · How material changes in cement quietly broke old assumptions · Why contractors keep getting blamed for problems they didn’t cause Chapters 00:00 – Why Moisture in Concrete Is Misunderstood 01:15 – The Different Forms of Moisture That Matter 03:30 – Why the Center of Concrete Often Doesn’t Dry 06:40 – The Problem With RH Probes and Surface Damage 10:30 – Why Cement Chemistry Changed the Rules 12:30 – What Alkalinity Really Is (and Why pH Misses the Point) 15:45 – Why New Cements Can Self-Desiccate 18:45 – Irreversible Damage From Heat and Chemistry 21:45 – Vapor Barriers, Curling, and Old Assumptions 24:30 – Why Most Moisture Comes From the Surface 28:45 – The Stack Effect Explained 31:30 – Why RH Numbers Don’t Match Real Failures 35:45 – What Needs to Change Going Forward 39:20 – Final Thoughts Guest Info Name: Bob Higgins Email: [email protected] Webpage: https://www.concretelogicpodcast.com/guests/robert-higgins/ Intelligent Concrete Concrete not behaving the way it should? At Intelligent Concrete, Dr. Jon Belkowitz and his team combine lab-level testing with real-world field experience to get to the root of performance issues, not just the symptoms. If you want data you can trust and answers you can use, learn more at https://www.concretelogicpodcast.com/intelligent-concrete Concrete Logic Academy Earn PDHs in the same straight-talk format as the podcast: https://www.concretelogicacademy.com Support the Podcast Support the show directly: https://www.concretelogicpodcast.com/donate KUIU helps support the podcast: https://www.concretelogicpodcast.com/kuiu Media, sponsorship, or content inquiries: [email protected] Credits Producer: Frank Stankunas, Jodi Tandett & Concrete Logic Media Music by Mike Dunton: https://www.mdunton.com/ Where to Find Seth Seth Tandett — concrete nerd and host of the Concrete Logic Podcast. LinkedIn: https://www.linkedin.com/in/seth-tandett/ YouTube: https://www.youtube.com/@concretelogicpodcast Podcast Website: https://www.concretelogicpodcast.com