ABSTRACT
Colloidal Silica in Cement and Concrete . . . . . . . . 738
Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 738
What Is Cement and Concrete? . . . . . . . . . . . . 738
Hydration of Cement . . . . . . . . . . . . . . . . . . . . 738
Flaws in Cement . . . . . . . . . . . . . . . . . . . . . . . 740
Silica in Cement . . . . . . . . . . . . . . . . . . . . . . . . . . 740
Silica Fume . . . . . . . . . . . . . . . . . . . . . . . . . . . . 740
Colloidal Silica . . . . . . . . . . . . . . . . . . . . . . . . . 741
Colloidal Silica as Retention Aid in
Paper Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743
Fillers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743
Paper-Making . . . . . . . . . . . . . . . . . . . . . . . . . . . . 743
The Problem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 744
Retention, Retention Mechanisms
and Retention Aids . . . . . . . . . . . . . . . . . . . . . . . 744
Dual Retention Aid Systems . . . . . . . . . . . . . . . . 745
Colloidal Silica in
Lead-Acid Batteries . . . . . . . . . . . . . . . . . . . . . . . . 747
Gelling of Silica Sols . . . . . . . . . . . . . . . . . . . . . . 747
Types of Gels . . . . . . . . . . . . . . . . . . . . . . . . . . 747
Common Features in Gel Formation . . . . . . . . 748
The Central Mechanism in Gel Formation . . . 748
The First Role of Hydroxyl
Ions — As a Catalyst . . . . . . . . . . . . . . . . . 748
The Second Role of Hydroxyl
Ions — Charge Repulsion . . . . . . . . . . . . . 748
The Role of Neutral Salts — Screening
of Charge Repulsion . . . . . . . . . . . . . . . . . 748
Specific Salt Effects — Effect of Cations . . 749
Effect of Anions . . . . . . . . . . . . . . . . . . . . . . . . 749
The Salt Effect Is Proportional to the pH . . . . 749
The Effect of Temperature . . . . . . . . . . . . . . . 749
Differences between the Polymerization
and Collision Mechanisms of Gel Formation 749
Kinetics of Collision Gels . . . . . . . . . . . . . . . . 749
Colloidal Silica in Coatings . . . . . . . . . . . . . . . . . . . 751
Shop Primers for Steel Substrates . . . . . . . . . . . . 751
Inorganic Paints . . . . . . . . . . . . . . . . . . . . . . . . . . 752
Hard, Scratch-Resistant Thin Coatings . . . . . . . . 752
Colloidal Silica in Polymer Latices . . . . . . . . . . 753
Colloidal Silica and Ink Jet . . . . . . . . . . . . . . . . . 753
Colloidal Silica as Polishing
Agent for Electronic Products . . . . . . . . . . . . . . . . 754
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 755
Dilute silica sols were prepared and studied over 70 years
ago. Their uses as binders in catalyst preparation, as glazes
on ceramics, as coatings on concrete and plaster of Paris,
as agents for treating paper and textiles, and several
other applications were investigated [1]. These early
silica sols contained less than 10% by weight of silica,
were fairly unstable and did not have reproducible proper-
ties. Iler [2] predicted that colloidal silica would not be
accepted for wide commercial use before these short-
comings were remedied.
