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Heading: 1.1.1.1.1.1Mixing of concrete seems all wrong
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I must say i am not well versed in the mixing process from the plants into the delivery trucks, but from what i see being done in small mixers, the industry needs better guidelines for all, considering consistancy, strength and reliability.


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Jim Ryan


Didn't really understand your question but, the parameters set for mixing concrete has been going on for decades and it seems to be working. Regards
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ALEXANDER TONGEN


Mr Alexander, would you mlnd explaining in detal, what materials get loaded on mixing trucks from first to last---as in pozzolans first then aggregates--then water?

Thanks
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Jim Ryan


Hope you had a wonderful weekend. Usually once all aggregates and cementious is weighed up most admixtures are loaded first, approximately 85% of total water is loaded( head water)followed by loading of aggregates and cementious followed at times by certain admixtures which do better loading at the end of the load (adva 600), then the rest of the water 15 % (tailwater) goes in. Head and Tail water can be adjusted according to the individual mix and timing of aggregate versus cementious loading can be ajusted depending on the cement content of the mix to prevent excess balling. Regards Alex
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ALEXANDER TONGEN


Mr. Tongen;
Thank you and I hope your weekend was a great time for you and yours. As to the mixing of the trucks, it seems to be well thought out. However, I would ask why the cement is not added into the head water, right after the admixtures? Just from my perspective, the cement will have less chance of clumping--even though the plants likely mix it with the aggregate pretty well. I would also ask if using warm or hot water would cause the mix to set faster and if using cold water retards the mix? I would them ask if there are times when the head and tail waters are not added until the trucks are on site and if so, why?
Thanks again Mr.Tongen
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Jim Ryan


Hi Jim,
if dry batched - the cement must be after the aggregate otherwise you will get balls that will never break down.
if wet batched - you can mix the cement and the water first (typically called slurry batching) this is ok but required ribbon feeding the cement.
Hot water can speed up the setting, this is normally saved for cold environments. Cold water is used to lower the internal heat of the concrete once placed. it does work but only has a limited effect. if you need bigger reductions you could look at ice flake or cryogenically cooling the cement and aggregate. very expensive but depends on your needs.

hope this helps.
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Stewart Cameron
 
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