July 1981 Table of Contents

Features Rebound, Penetration Resistance and Pulse Velocity Tests for Testing in Place

It is sometimes necessary to estimate the strength of concrete in place for early form removal or to investigate the strength of concrete in place because of low cylinder test results. Read more

Features Pullout Testing of Concrete

Testing of field-cured cylinders to determine whether concrete strength is satisfactory for either removal of forms or application of post-tensioning has been required by many codes and specifications. Read more

Features Control Tests on Fresh Concrete

A true control test is one which gives results soon enough for the concrete producer to take correction action if results indicate that the concrete is outside specified limits. Read more

Features Getting the Most for Your Quality Control Dollar

Ultimately the owner pays for any activity intended to ensure high levels of quality in concrete work. Read more

Features What to Do When Cylinder Breaks Are Low

Procedures to be followed when low strength measurements occur can be programmed to minimize delays in construction without endangering either the safety of the structure or the interests of those involved in the construction. Read more

Features Petrographer: New Man on the Construction Team

Petrography once regarded as a somewhat esoteric laboratory discipline today increasingly is called upon to contribute to the concrete design and construction team. Read more

Problem Clinic Water-Cement Ratio

We repeatedly hear that the strength of concrete depends almost entirely on the water-cement ratio. Yet I cannot understand why two mixes, one containing four bags of portland cement per cubic yard and the other containing six bags per cubic yard, could h Read more

Problem Clinic Tolerances on Bar Straightness

Is there a standard tolerance on straight (not bent) deformed rebars? A recent shipment of 50-foot lengths of Number 18 bars has a slight fixed bend that is definitely an inelastic deformation; the bars are not just sprung. Do we have any justification fo Read more

Problem Clinic Thickened Edges and Curling

Curling is a big problem in our part of the country and we are concerned about ways to prevent it. Would thickened edges of the slab reduce or prevent curling, and if so, how much would they have to be thickened? Read more

Problem Clinic Spalling at Keyway

A warehouse floor has suffered spalling at joints that contain a metal keyway. What caused the spalling? Read more

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