Concrete workability affects construction productivity. If the concrete does not have the appropriate workability for a given application, it can lead to delays in construction. This session will discuss the challenges in controlling workability and how it can be manipulated to help improve construction productivity. This session will include presentations from multiple perspectives: Specifier, Designer, Producer, Admixture manufacturer and Contractor. This session will be of interest to researchers, owners, consultants, contractors, and manufacturers.
Learning Objectives:
(1) How workability that is too high for an application can actually slow down placement;
(2) How improved workability through proper aggregate gradation increase placement;
(3) How on-board slump sensors and automated slump management can improve placement rates;
(4) How focusing on proper metrics during delivery of concrete can help focus support on the right challenges to improve placement rates.
Workability of Concrete: Can There be Too Much of a Good Thing?
Presented By: Jacob Borgerson
Affiliation: Wiss, Janney, Elstner Associates, Inc.
Description: The workability of concrete is critical for the successful placement and finishing of concrete. In some instances, constructors and designers want highly mobile concrete that can spread throughout the formwork without the use of internal vibration for consolidation. These type of concrete mixtures typically utilize conventional concrete constituents, but adjusts the proportions to achieve a highly flowable and non-segregating concrete. This presentation will discuss the factors that influence the workability of concrete and potential concerns to consider when deciding to utilize highly mobile concrete. In addition, attendees will be introduced to various quality procedures that can be implemented during the concrete placement and when their use is appropriate. Case studies will be used to illustrate the concepts presented. This presentation will benefit engineers, architects, testing laboratories, contractors, ready-mix suppliers, owners, and anyone who has sat in a job site trailer to discuss the workability of concrete.
Field Evaluation of the Tarantula Curve and the Box Test to Assess/Predict the Workability of Concrete Paving Mixtures
Presented By: Jagan Gudimettla
Affiliation: FHWA - ATI
Description: The Tarantula curve and the Box Test are a recent concept and test method to asses / predict the workability characteristics (workability, finishability, edge-slump and constructability) of slip-formed paving concrete. Both are good (and complementary) tools for contractors to use during the concrete mixture design process for designing mixtures that are workable. This paper shows the Tarantula curve and the Box Test field data from 20 mainline paving projects (from across the United States) collected by the FHWA Mobile Concrete Technology Center as part of its new-technology implementation work. Specifically, data /observations from 6 of the 20 projects will be presented in detail to showcase the effectiveness of the Tarantula Curve and the Box Test in predicting field constructability issues. The paper also shows how the Box test data at multiple intervals of time can be used to assess the workability window from two additional paving projects. The data presented in this paper is not from a controlled study/experiment in a laboratory but observations from the field and relies significantly on photos.
How On-Board Sensor Can Help Improve Productivity
Presented By: Pierre Siccardi
Affiliation: Command Alkon
Description: Productivity and profitability refer to the ratio of either good or money respectively between output and input needed to produce something. They are both influenced by the time it takes to produce the goods and by the quality and added value of the final product. In terms of concrete delivery, this is obviously very much affected by the concrete delivery cycle, and to a larger extend by the whole construction cycle; both will be analyzed and discussed. This presentation is mainly centered around time saving and problems prevention. Therefore, it will delve into daily hiccups of the concrete industry like mixing, QC testing, retempering, waiting, rejection, waste management, pump blockage, end of poor adjustment, etc. but also on how these are influenced using on-board sensors in the ready-mix and construction industries. It should become clear to the audience that the benefits are not only a question of individual sensor but also how they interact, from the truck scale to the network of systems, and thus in the end, it is the whole monitoring system that provide the real value.
Slump or Slump Flow Versus Yards per Hour: What Really Matters?
Presented By: Tarek Khan
Affiliation: Master Builders Solutions
Description: This presentation will highlight the potential for tension between prescriptive limits on concrete workability and the concrete production and construction team’s productivity. Common metrics that are useful to quantify a producer's operational performance will be discussed. For example, concrete producers measure “yards delivered per hour” and contractors measure “yards placed per hour”. It will also discuss how these important metrics can be influenced to optimize the speed of construction, benefiting the producer, the contractor and ultimately the owner.
Ready to Pour? Aligning Producers and Contractors to Streamline Placement
Presented By: Nathan Tregger
Affiliation: Verifi LLC
Description: Placing ready-mix concrete at the job site requires teamwork between the producers and contractors. Congestion at the job site, mismatched slump target expectations and site-readiness (i.e. formwork) are major factors that influence the productivity at the site. This presentation will enlighten different underlying challenges that can be mitigated or eliminated through use of in-transit management systems, where the slump is adjusted automatically on the mixer truck. Combined with the ability to track the location, these trucks can help identify and vastly improve productivity at the site. Case studies will be discussed.