Episode Details

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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/





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