Verifi Concrete Quality Blog

Posts Tagged ‘batch’

Is it best to batch concrete above, below, or at the ordered slump?

by Verifi

Without Verifi, concrete producers often try to batch  ready mix concrete above the ordered slump, with the expectation that slump loss will occur during transit and the concrete will arrive near the ordered slump.  So, what are the implications of this policy?

Batch above Ordered Slump

In this first example, the concrete was batched about 2 inches above the ordered slump, lost this slump in transit, and arrived with the correct slump.

Concrete batched above ordered slump verifi

© Verifi LLC

(LP = leave plant, AS = arrive site, BP = begin pour)

However, this requires guesswork to estimate the time and amount of slump loss to the job.  Once this slump is determined, the batch operator must batch accordingly, which can be challenging.  If the slump at arrival is too low, the concrete will need to be adjusted.  If the slump is too high, as in the next example, the concrete is at risk of being rejected.

Concrete batched above ordered slump - verifi

© Verifi LLC

In summary, batching above ordered slump:

  • Requires guesswork about amount of slump loss in transit,

  • Requires the batchman to batch at the right slump manually,

  • Increases variability in slump at the site, and

  • May require manual slump adjustment by driver at the site.

Batch below Ordered Slump

Concrete producers may batch below the ordered slump, which requires the slump to be adjusted in the truck.  This adjustment is usually made manually be the driver and can occur at the site, as shown in the following example.

 Concrete batched below ordered slump verifi

© Verifi LLC

It can also occur at the plant, or both the plant and site, as shown in the next example.  Because the slump is adjusted manually, variability in slump is likely.

Concrete batched below ordered slump - verifi

© Verifi LLC

In summary, batching below the ordered slump:

  • Requires manual adjustment in the truck by the driver,

  • Results in poor documentation of water added on the truck,

  • Delays construction due to the need to adjust slump, and

  • Increases variability in slump at the site.

Batch at the Ordered Slump

Finally, it is possible to batch at the ordered slump.  Due to slump loss, the concrete is likely to arrive at the site below the ordered slump, necessitating the addition of water at the site.

 Concrete batched at ordered slump verifi

© Verifi LLC

In summary, batching at the ordered slump:

  • Requires manual adjustment of slump in the truck by the driver,

  • Results in poor documentation of water added on the truck,

  • Delays construction due to the need to adjust slump, and

  • Increases variability in slump at the site.

Water Additions

Regardless of whether it is added at the plant or site, water must be added to concrete to account for slump loss.  Although they can reduce slump loss, admixtures do not necessarily eliminate the need for water additions.

Given the above options, batching above the ordered slump is a logical choice for many producers.  More water is added at the batch plant, where it can be better controlled and documented, and the concrete is less likely to require adjustment at the site, which takes time.

However, the availability of Verifi changes this decision.

Automated Truck Water Additions with Verifi

Verifi automates the addition of water in transit to maintain an ordered slump.  With Verifi, batching above ordered slump is no longer necessary.  The need for driver adjustments of slump is eliminated.  Instead, producers can batch at or even below the ordered slump and Verifi will automatically add the necessary water to reach the ordered slump, up to the maximum water content for the load, as shown in the following example.  All water additions are recorded.  This has been show to be effective even in hot weather conditions, when slump loss is likely to be greater.

 water addition to concrete during delivery

© Verifi LLC

In summary, using Verifi to manage slump:

  • Results in time savings because concrete arrives on site ready to pour, with the right slump and water content,

  • Ensures all water additions are measured and documented,

  • Reduces variability in slump at the site, and

  • Eliminates driver involvement in adjusting the slump.

NOTE: All data in this article was recorded by Verifi.  However, to illustrate normal industry practice, Verifi was set to not manage loads in all but the last example.  In normal practice, Verifi is set to manage loads automatically by adding water or admixture to reach the ordered slump.



Verifi Feature: Batch Assistant

by Verifi

The Verifi Batch Assistant helps concrete producers determine the amount of water to “trim” (or reduce) from a mix design during batching. The amount of water trimmed can be added back in transit or at the site without exceeding the maximum water content for the mix.

Because the amount of water trimmed can change due to variations during batching, the decision on how much to trim is often made just before a truck is batched.  Without Verifi, producers had limited feedback on prior loads to determine the right amount to trim.

As seen in the example below, the Batch Assistant shows how closely prior loads were batched to the target slump.  It also shows the concrete temperature and Verifi’s proprietary calculation of the estimated amount of water needed to reach the target slump.  For example, the load batched at 11:12 AM was below target.  The water could then be increased on the next load at 11:36 AM, which was at the target slump.

Verifi recommends batching at or slightly below the target slump.  Verifi can then manage the slump in transit by adding water, admixture, or both to maintain slump until discharge.

In addition, Batch Assistant data is sortable by Mix Code because some mixes require more water to be trimmed than others.  For instance, a mix for a project with a long haul time would require more water trimmed, so that more water is available to be added in transit or at the jobsite.

The Verifi Batch Assistant helps concrete producers determine the amount of water to “trim” (or reduce) from a mix design during batching.

© Verifi LLC