Editor’s Note: This is part one of a two-part article. Look for the second installment in the July issue.
Every load of ready-mixed concrete comes with a delivery ticket full of useful information, if you know how to crack the secret code. Critical information includes identifying the mix, batch, and cumulative volume; help on checking yield; admixtures; and the amount of water that can be added within specs. The ticket also tells the batch time, which is important for predicting slump loss and setting time, and there is a lot of important cost information that will help you figure out what the concrete is worth (if you are delivering it) or how much you will have to pay (if you are receiving it).
Besides of all of this, if and when something hits the fan on your concrete project, the tickets are likely to be introduced as evidence, marked “Exhibits A, B, and C.” But despite this practical and economic value, concrete delivery tickets “just don’t get no respect.” When I needed some fresh tickets for an upcoming presentation, I visited the nearest construction site and found three of them blowing away in the wind!
The right mix
If you have ever placed concrete only to find out that you put the wrong mix in the wrong place, you already know how important it is to check the mix ID on the ticket. Look for the customer and jobsite info, special delivery instructions (back gate, east entrance) and the mix ID. Most producers have an ID code such as “4012” for non-air-entrained 4000 psi (@ 28 days) with #1 and #2 stone, or perhaps “4012AE” for a similar air-entrained mix. Special features such as fibers will often be in the mix designation as well.
Of course the busiest time onsite is when you are trying to get a pour started, which is when the concrete is being delivered. But if you don’t have the time to read the ticket to make sure that you are about to place the right mix, you have to ask yourself, “Do you have time later to deal with having placed the wrong mix?” If you only have one mix on the project, and your producer is shipping to you only, this may not be a big deal. But if you have a footing mix, slab-on-ground mix, column mix, and elevated-slab mix, and if your job is big enough that any of these can be placed on a given day, it pays to check the ticket.
The ticket also shows the volume of concrete in this load, and the total volume of the same mix shipped for this order today. It is important to know that these are calculated volumes, not measured volumes (more on yield later). This total cumulative volume is essential for managing your concrete order. Given the unevenness of subgrade, variable slab thickness, deformation of forms, settlement of shoring, and variable air content and yield of the concrete, it is tough to predict the exact volume of concrete to order. One common routine is to give the concrete producer an estimated total volume (say 100 cubic yards) and a hold value (maybe 96 cubic yards). But the trick is to make your final order before that last truck arrives. At the end of any given load, say 80 or 88 cubic yards, you can check the ticket, discover total yardage placed, estimate the volume to complete (maybe add ½ yard), and call in your final order.