August 1981 Table of Contents

Features Failures During and After Construction

Several cases of construction failures, as well as some basic rules for preventing construction failures, are presented in this article in the hope of furthering the understanding and awareness needed to prevent such disasters. Read more

Features The Floor Tolerance Conundrum

Most specifications for surface tolerances are ambiguous and perhaps this is why there is no consensus on how to measure for compliance with tolerances. Read more

Features Expansion Joints in Post-Tensioned Parking Structures

Inspection of post-tensioned parking structures shows that expansion joints in parking floors are subject to a number of problems including inadequate sealing, spalled slab bearings and insufficient concrete cover over tendon anchors. Read more

Features Accelerated Strength Testing

The conventional way of determining strength potential of concrete is to cast cylinders which are moist-cured at 73 degrees F and tested 28 days after casting. Read more

Features Contractor-Made Test Cylinders

Using the contractor's own personnel to make concrete cylinders to be delivered to a laboratory for testing has advantages: It reduces the testing costs and ensures that someone will always be available to make test cylinders when needed. Read more

Features Concrete Pavement: an Answer to the Dwindling Petroleum Supply

Between 1975 and 1979 three industry associations published reports on energy as it related to pavements and pavement construction, taking into account energy used to produce and haul materials; energy requirements for mixing, transporting and paving equipment, and two of the three considered inherent energy in the materials. Read more

Features House Foundation Failure: Settling or Heaving?

House foundations or other parts of a home that are in contact with soil sometimes settle. Read more

Problem Clinic Positive Waterproofing for Roof

In concrete buildings I am designing it is important that exposed concrete decks over interior spaces be free of leaks. I need a tested and proven admixture or sealer to provide a permanently waterproof deck. The deck will be exposed concrete, subject to Read more

Problem Clinic Saw Pavements Promptly

What caused a crack to form early in our recent parking lot construction? We used air-entrained concrete estimated to attain 5500 psi compressive strength and placed it at a slump of 5 inches and finished it with a vibrating screed. The air temperature wa Read more

Problem Clinic Unbonded Topping

There is a floor in an old building which we intend to convert to a warehouse. There are some differences in floor surface elevation due to random cracking and settlement. We want to put in a new floor. Since increase in elevation would be no problem can Read more

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