EP #151: Most Concrete Durability Problems Start Here (Alkalinity Explained)

PRESENTED BY: GPRS Construction professionals know that utilities and concrete reinforcements can cause big problems when you’re on the job. GPRS helps you avoid them. We use ground penetrating radar to detect rebar, conduit, and post tension cables before you cut, core, or drill. And our concrete scans are 99.8% accurate… we guarantee it—helping you reduce hits, downtime, expenses, and keep your people safe.To keep your jobsite safer, visit https://www.concretelogicpodcast.com/GPRS SUMMARYConcrete strength gets all the attention.But what if the real driver of concrete performance isn’t strength at all?In this episode of the Concrete Logic Podcast, Bob Higgins returns to talk about alkalinity — the chemical environment inside concrete that may control moisture behavior, curing, permeability, and long-term durability.Bob explains why alkalinity is often confused with pH, why salts inside concrete can trap moisture that testing methods never see, and why modern cement chemistry may be quietly changing how concrete cures and performs.If you’ve ever wondered why concrete behaves differently today than it did decades ago, this conversation will make you think.WHAT YOU’LL LEARN· What alkalinity actually means in concrete chemistry · Why pH and alkalinity are not the same thing · The two alkaline salts that control moisture behavior in concrete · Why salts can trap moisture that RH tests can’t detect · How high alkalinity can lead to permeable, weaker surface concrete · The difference between porosity and permeability · Why precast heat curing can change long-term durability · Why compressive strength often fails as a durability indicator · How cement kiln dust may have increased alkalinity in modern cementCHAPTERS00:00 Introduction 02:20 What alkalinity means in concrete 03:10 Why salts control moisture behavior 07:40 Why RH probes can miss trapped moisture 10:20 Calcium hydroxide vs sodium hydroxide 14:00 Self-desiccation and modern cement chemistry 18:00 Where alkalinity in concrete comes from 23:30 Signs of high alkalinity in concrete 24:00 Why precast surfaces can be more permeable 26:00 Porosity vs permeability explained 29:00 Why compressive strength can mislead durability 31:20 Why sealers often fail long term 33:00 Alkali-silica reaction explained 35:00 Why alkalinity isn’t being studied enough 38:00 Why RH specifications often don’t make sense 39:00 Preview: additional forms of moisture in concrete GUESTBob HigginsChief Scientisthttps://www.concretelogicpodcast.com/guests/robert-higgins/ CONCRETE LOGIC ACADEMYIf you like what you’re learning on the podcast, the Concrete Logic Academy Unlimited Pro Membership is where it all comes together.We take the topics you hear on the show and turn them into structured courses—with real explanations, supporting material, and quizzes so you actually retain it.Most people in this industry learn by trial and error.This is how you get ahead without paying for mistakes.Many courses qualify for PDHs and CEUs.Start your free trial here: https://www.concretelogicpodcast.com/pro SUPPORT THE PODCASTIf the Concrete Logic Podcast has helped you learn something new or connect with someone in the industry, consider supporting the show.Donate here: https://www.concretelogicpodcast.com/supportLooking for great hunting or work gear: https://www.concretelogicpodcast.com/kuiuInterested in advertising or media services? https://www.concretelogicpodcast.com/partner-with-concrete-logic-podcast/ CREDITSProducers: Jodi Tandett, Concrete Logic MediaMusic by Mike Dunton https://www.mdunton.com/ WHERE TO FIND SETHWebsite: https://www.concretelogicpodcast.com LinkedIn: https://www.linkedin.com/in/sethtandett/ YouTube: https://www.youtube.com/@concretelogicpodcastUntil next time, let’s keep it concrete!