Hot-weather and cold-weather concreting 1

[legner]

How do you handle hot-weather and cold-weather concreting requirements in your CD's? ACI 305R and 306R explicitly indicate they <b>cannot</b> be directly incorporated into project specifications.

 

[Ron]

The ACI documents are &quot;recommended practices&quot; and do not contain the appropriate mandatory language of CD's.&nbsp;&nbsp;The information contained in each (ACI 305/306) is good, relevant information that can be incorporated into the text of the CD's, not by reference, but by text inclusion with mandatory language at the appropriate locations.&nbsp;&nbsp;This requires a bit more initial work, but only necessary once and can then be tailored to the specific job.

 

[legner]

Ron:<br><br>That much is clear, but have you tried to write a specification based on ACI 305/306? It's not easy. For example, how do you define &quot;hot weather?&quot; Hot weather can mean 75 degrees (with low humidity and a drying wind).

 

[Ron]

In general, hot weather is defined (though incorrectly) only by temperature.&nbsp;&nbsp;You are correct in wanting to introduce humidity/wind considerations, but these can be done separately.&nbsp;&nbsp;The arbitrary rule for hot weather is about 90 F for the air temp.&nbsp;&nbsp;I practice mostly in the Southeast US where it hits 90 by late morning in July/August and we have seen our share of hot weather placement.&nbsp;&nbsp;Mostly no ill effects even when the air temp. exceeds 100 F.&nbsp;&nbsp;A lot of the problems come about when the CONCRETE temperature is significantly different than the AIR temp, whether hot or cold.&nbsp;&nbsp;In my experience, I have seen very little influence on the concrete as long as this temp. differential remains below about 25 degrees.<br><br>In my opinion it is not necessary to include every provision of 305 or 306 in your specification, but moreso to stress the general quality control of concrete production, delivery and placement using some tolerable constraints, i.e. inspect the batch plant, check the aggregate moisture control, check the procedural mix controls by the supplier, don't let the contractor control the concrete mix (i.e. adding water at the site indiscriminantly for placement convenience), observe and test delivery and placement, document batch and delivery times, water addition, temperatures, slump, slump loss, placement procedures, finishing, curing, sawcuts, etc.<br><br>A few fundamental practical considerations are that good concrete is made from good aggregates, good cement, good admixtures, and good water....bad concrete is all too often made from the same stuff!&nbsp;&nbsp;Ready mix suppliers (I'm not one, but occasionally they need defending)are less likely to compromise the quality of the concrete than the construction crews.&nbsp;&nbsp;In many years of failure investigations and concrete problem solving, more problems are caused by improper placement, finishing, and curing than by specifications or concrete production.<br><br>I will see if I can come up with a reasonably unedited spec for you that you might use as a guide.&nbsp;&nbsp;&nbsp;