vertical formwork striking

[oneintheeye]

Hi, looking into striking times of vertical formwork normally in water retaining applications. We typically use ggbs replacement mix. Apart from strength considerations what is minimum striking time used by others here? the ggbs will slow the strength gain and prolong the heat gain (although lower temps than non replacement mix). we have various 'guidance' here in UK and have advised site on times.

 

[civilperson]

What is ggbs replacement mix?

 

[oneintheeye]

ggbs is ground granulated blast furnace slag. its a cement replacement material used for cost and also as stated to reduce temperature rises in section. also has enviromental advantages.

 

[Ussuri]

Formwork striking times - criteria, prediction and methods of assesment (R136)
Author(s): T A Harrison
Date: 1995
ISBN (13 digit): 978-0-86017-431-8
ISBN: 0-86017-431-X
Pages: 72
Publisher: CIRIA/Thomas Telford

 

[uwrockguy]

Make sure you keep in mind what you are combining the GGBS with. As an example, cements in Canada and US are different in chemistry. US cements are low alkalis and Canadian cements are typically higher in alkalis. The net effect, higher alkali cements activate slag better than lower alkali cements. This will completely change the reaction rates. Haven't read the book listed by Ussuri, but keep the location of cements in mind when comparing to your situation.

 

[oneintheeye]

hi thanks for the replies, I am quite happy with how I would specify types etc. but control of cracking is reliant heavily on standard of workmanship on site so was asking really for minimum striking times used by others. We have had a number of instances where site have requested absolute min. striking for programming and if possible would like to reduce our times further.

 

[LittleWheels]

Is it worthwhile looking at concrete maturity monitoring?