October 1984 Table of Contents

Features Selecting Repair Materials

The concrete repair contractor can choose from a wide array of specialty and conventional repair materials. This large selection gives the contractor greater opportunity to match material properties with job demands, but it can also increase his chance of selecting an inappropriate material. No matter how carefully a repair is made, using the wrong repair material will likely lead to early repair failure. Read more

Features Properties and Specifications for Epoxies Used in Concrete Repair

Epoxies are frequently used as repair materials because they bond well to almost all materials, cure rapidly, attain high strengths and exhibit good chemical resistance. Applications include use in bonding concrete (hardened to hardened, and hardened to fresh), and in patches, overlays and protective coatings. Epoxy compounds consist of resin, a curing agent or hardener and modifiers that make them suitable for specific end uses. Read more

Features Acrylic Concrete for Fast Repair

Unlike normal portland cement concrete, acrylic concrete contains no water and no portland cement. Aggregate is held together instead by an acrylic polymer. Read more

Features Latex-Modified Concrete and Mortar for Repair

Synthetic latexes are made by dispersing polymer particles in water to form a polymer emulsion. When these emulsions are added to portland cement concrete, the spheres of polymer will coalesce or come together to form a film that coats the aggregate particles and the hydrating cement grains and seals off voids. The resulting mixture develops higher strength, bonds better to existing concrete, has a higher resistance to chloride penetration and is more resistant to chemical attack than plain concrete. Read more

Features Nonshrink Hydraulic Cement Mortars and Grouts

Nonshrink hydraulic cements have been formulated with various job conditions and requirements in mind. The materials discussed in this article are based mainly on portland cement but they contain expansion-causing agents and sometimes other modifiers. Read more

Features High Density Polyethylene Sheet Stops Pool Leaks

What can be done when settlement causes a 200,000-gallon concrete pool to crack and leak? Read more

Features How to Double the Value of Your Concrete Dollar

Most of the people in construction are well aware that a 2x6 is much stronger than a 2x4. But how much stronger? The answer is simple. The bending strength of a beam increases with the square of the depth. Read more

Problem Clinic Wet Feet

I sometimes run into problems with water and mud while pouring footers and would like some guidelines. Can you pour concrete directly into water? Does the concrete just displace the water? How do contractors who build bridge piers set their forms? At the Read more

Problem Clinic Modern Concrete to Replace Yesterday's Wood

We have had an increasing number of requests to replace factory woodblock floors with concrete floors. There might actually be enough of this kind of business to keep us occupied full time. One thing that makes us hesitate is that we aren't sure about whe Read more

Problem Clinic Hardening Agents

We have been asked to comment on specifications that call for applying a fluosilicate hardener to concrete slabs at the time of construction. Some slabs are indoor and some outdoor, all part of an agricultural facility. Does such a hardener serve to both Read more

Problem Clinic Durability of Dry-Mix Shotcrete

Is it possible to entrain air in shotcrete when the dry-mix method is used? In 30 years experience I have never learned of a way to do it. I am interested in anything that can enhance the durability of shotcrete. Read more

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