The only ways to make concrete work more profitable are to improve productivity or reduce re-work. We all recognize that most contractors pay the same price for a cubic yard of concrete, so how can we place concrete faster and better than our competitors? Not a simple question. Today, a variety of outside elements can negatively influence your productivity. This article describes how to improve productivity. It comes down to maintaining a culture of continuous improvement.
Many factors in the construction industry make the need for improving productivity more important and difficult than ever. It is a very competitive market, schedules are getting shorter, and the buildings more complex. Then add in the decreasing number of skilled tradespeople and the demographic crisis facing the industry. Our workforce is aging and there is a lack of younger, skilled tradespeople to replace them, which will decrease productivity.
In terms of risk, the construction industry is moving toward contracts with more rigorous language about assignment of responsibilities, most of which is being pushed to the individual trades. Owners, construction managers, and general contractors pass responsibility down to the next level. And design professionals provide less information on their drawings than they once did — dimensions have all but disappeared, replaced with “field verification” on most drawings. So you are getting less information to perform more complex work in less time.
So how does a contractor perform the same amount of work with fewer people? Obviously, we must increase the productivity of each individual; make them more efficient. But that’s not so simple. Poor productivity is not because your staff is lazy or inexperienced. It is most often that they do not have the information they need. Becoming more efficient requires having the right people doing the right job with the right information. We must provide our people at the face of the work with the data and information in a way they can understand.
Over the last few years you’ve probably heard about a new type of software called building information modeling (BIM). Although this software was originally developed for use by design professionals, today construction contractors are BIM’s fastest growing consumers. This software represents the best new tool for improving site productivity and reducing risk. BIM offers a variety of ways to provide information that is clear and is easy to adapt and change as the project changes. Two-thirds of construction people are visual learners. In other words, show them something and they will likely understand it, describe it and they will have questions, make them go look for it and they will have lots of questions. With the power of visualization, BIM can improve document understanding. Let’s look at some examples.
Document clarification on a jobsite is one of the highest areas of lost productivity. Having to ask for missing dimensions and details slows a crew. When this happens during construction there is no choice but to shift crews to a different area of the jobsite or wait to get answers from the engineers. But the simple act of preparing BIM concrete lift drawings can address many of these critical questions before the sitework begins.
We recently worked on a major high school project to prepare a complete set of concrete drawings. By starting these drawings immediately after contract award, while site preparation was underway, BIM lift drawings were prepared and several hundred questions and requests for clarification were issued to the engineer. These questions included missing dimensions and beam pockets that were too deep for the wall or not aligned with the steel dimensions. The number of issues addressed on this job might seem extreme, but the BIM documentation brought many of these design issues, even minor dimensional questions, to light all at once. Many of these questions took only minutes to answer when identified ahead of time; during construction they could have cost the project many hours. Because we took these issues to the engineers before forming the foundations, the project proceeded flawlessly. Not only did productivity jump by more than 12%, but the foundations were weeks ahead of schedule.
Similarly, on a hospital project, we provided BIM concrete lift drawings to the rebar fabricator before construction. The fabricator knew the sequence of the pours and the steel required for each wall and pour so they could provide just-in-time delivery of the rebar. To further improve the process, the lift drawings were color coordinated with the steel shipments and the rebar was bundled by color, allowing field crews to match bundles with respective lifts.
Preparing lift drawings
Another huge productivity improvement with BIM concrete lift drawings is in how they are prepared. Trained BIM technicians prepare the drawings based on a marked-up key plan provided by the superintendent or the concrete foreman. Since the lift drawings are from a BIM template, the technician only needs to divide the foundation into parts indicated by the field crews. In the past the foreman or superintendent would hand-draw these lift drawings, which took their time away from managing the site.
The other big advantage to BIM is if the pour for a particular day had to be changed due to weather or other factors, hand drawings could not be easily changed. With BIM, the lift drawings can be changed in a matter of minutes and reissued to the field. Finally, because the BIM concrete lift drawing is centered around an internal database, the lift drawings can automatically provide quantities of concrete for each pour, square footage of formwork, manpower projections, and even schedule information. All of these improve the ability to track metrics for future work.
BIM used for slabs can produce similar advantages. The BIM documentation can provide critical information for curtain wall embeds, detect conflicts between embeds and other structures, and even expose critical rebar issues. On an eight-story university project, the slab lifts were being prepared. An observant superintendent noticed an area where a slab beam and column intersected. He was concerned that the rebar congestion would not allow concrete to flow into this area with proper consolidation. The three-dimensional BIM documentation proved that there was a problem.
This condition and the BIM model was taken to the structural engineer and was resolved before the rebar was even ordered. If this condition had been found in the field during installation, or even worse, during concrete placement, the cost for this one problem which occurred in more than 40 locations would have far exceeded the entire cost of the technician to develop the drawings for the concrete. On slabs, the reuse of formwork is critical for productivity. BIM allows you to link the schedule to the objects, in this case formwork, in the model. Now imagine being able to run simulations of forming, pouring, and stripping to optimize your formwork productivity and material use.
The last example of using BIM onsite and controlling quality concerns mobilizing concrete equipment. Imagine a pour more than 50 feet deep with a 3,000-cubic-yard continuous pour using multiple concrete pump trucks. Can you visualize where to stage the trucks for maximum efficiency?
The traditional method of swinging an arc will not work due to the depth of the pour and the limited reach of the equipment arm. BIM simulations were the answer. Each of the concrete pump trucks and their mobile arms were modeled. The exact reach of each truck into the excavation along with the safe location of the trucks with respect to the excavation was analyzed. This analysis showed that one corner of the slab could not be reached by any pump truck available, which meant that the tower crane with a bucket could concentrate on this area of the pour. None of the pump trucks had to move or be restaged and 12 hours of continuous pouring was a productivity success. And these models can be reused on future projects!
Results that matter
These are interesting examples, but BIM is not free so does it really save money? Proof of cost savings when you avoid problems is hard to document.
For instance, in the rebar example, what would the cost have been if the rebar had been placed or, worse yet, poured? It’s hard to know since the problem never happened. The contractor did an estimate and concluded that this one risk avoidance paid for the BIM modeling of concrete for the entire structure.
Another contractor took one year’s worth of concrete work and compared the productivity of concrete forming between jobs with BIM concrete lift drawings and without. He concluded that forming productivity on the BIM jobs was 12% to 15% higher. Of course, your results may vary. But the more you do it, the more efficient you will become. Using BIM can provide clear concise information, often all on one drawing. Clarifications can be addressed before starting work. Better information in the hands of your field crews will lead to higher quality and productivity.
Mike Whaley is the owner and founder of Turis Building Innovation Systems in Madison, Wis., where he works to increase construction efficiency through technology.