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SUMMARY
Concrete 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 cement

CHAPTERS
00:00 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

GUEST
Bob Higgins
Chief Scientist
https://www.concretelogicpodcast.com/guests/robert-higgins/

CONCRETE LOGIC ACADEMY
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CREDITS
Producers: Jodi Tandett, Concrete Logic Media

Music by Mike Dunton
https://www.mdunton.com/

WHERE TO FIND SETH
Website: https://www.concretelogicpodcast.com
LinkedIn: https://www.linkedin.com/in/sethtandett/
YouTube: https://www.youtube.com/@concretelogicpodcast

Until next time, let’s keep it concrete!

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