2020Case5Sisk

Contents Lean Construction Ireland Annual Book of Cases 2020 23 Case 5 Pouring concrete Extensive time is generally lost in part because of the timing of trucks – that is, a full crew waiting for the next concrete truck to arrive. Sometimes this is unavoidable or at least beyond the control of the site team – the nature of concrete is that it must be “just in time” and queues at the batching plant or traffic can delay trucks. However, the direct observation record showed that a five-person crew could (notionally at least) be reduced to four or possibly three. In particular, it was noted that the concrete pump operator was 60% waiting/not working. The summary report on the Direct Observation exercise identified that up to 48%of the time spent on certain elements of the works were “waste”, primarily waiting, either for deliveries or waiting for materials from within site. The “Lean Project” approach had both a direct and measur- able impact, but perhaps more significant is our enhanced awareness of the extent of waste on our projects. The nature and dynamics of a construction project are different to a manufacturing environment, but the cold theoretical assess- ment of wasted effort (up to 48%) certainly gave the team a number of opportunities for immediate improvement, as well as pointing to longer-term potential. Clearly the full 48% can never be eliminated, but we made improvements: • The concrete frame was completed in 6 months, reflecting a one-month improvement on schedule. • The concrete frame contractor and Sisk had a very satisfactory commercial outcome from the concrete frame package which represented 21% of the overall project value. • The works were delivered to a high quality and with out any safety incidents. • As the first significant package on the project, the success and the manner of execution of the concrete package set the tone for the remainder of the project. There were a number of notable wins: i. Revising the design and construction sequence to construct the stair cores prior to the construction of the main frame had a double benefit. It gave the design team additional time to design the under-slab drainage whilst at the same time allowing significant flexibility to construction. Four work- fronts were open simultaneously with adequate laydown area available. Mobile cranes were required to construct the stair-cores, whereas the remainder of the structure could be constructed with more cost-efficient teleporters. Front- ending the stair-core construction allowed us to off-hire the mobile cranes early in the project, with resultant shared savings. ii. Rationalising the frame design and eliminating the downstand beam allowed us to use a lightweight system which could be erected in a bottom-up sequence so that the decking system could be erected whilst standing on the slab. This not only had a safety benefit, but also cost and schedule benefits. iii. Planning out the cycle times in detail in advance high- lighted both problems and opportunities; for example, al- tering the concrete mix design to a higher strength concrete with a super plasticiser. For a standard concrete slab pour of 80m3, we started pouring at 8am, had the concrete installed by 12 noon, and were finished power floating by 5pm. Figure 4. Example of Concrete Pour Breakdown Figure 5. Direct Observation Summary Report Extract Lean Initiative Improvements & Impact