Construction labor-productivity assessment using six-sigma tools: a case of study = Evaluación de la productividad de la mano de obra en construcción usando herramientas six-sigma: un caso de estudio

In the construction sector labor-productivity growth just 1% on average the last two decades, which is very low compared to the 2,8% for the global economy or the 3,6% for the manufacturing sector. This shows that every year significant amounts of money and resources, both human and material, are lost due to inefficient processes in our industry. This issue gets worse due to the majority of construction companies do not have formal measuring systems a site level, what is necessary for the determination of productivity indicators. So the lack of measurement is the main problem involved in productivity improvement. In this scenario, a site labor-productivity case study is analyzed with the purpose of showing some productivity data and disclose some issues that occur when an incipient labor-productivity measurement processing based on Six-Sigma tools is implemented. The research is based on the cycle of beam and slab concreting work at three levels of a residential building superstructure. The measurements were performed for approximately four weeks, where 44 pours of pumped concrete were measured. The tools of the six-sigma approach provided a statistical structure that allowed to evaluate the concreting crew productivity in the case study. The results showed a work pace of 662.6 m² of concrete floor per week on average and, an averaged labor-productivity of 1.47 m³/mh with changes that responded to the natural process variability. Moreover, the process capability showed that concreting crew productivity variation did not meet the specification established for a typical 3s level, evidencing that a requirement above of 3s level is something difficult to fulfill in the construction sector since craft processes are in essence difficult to repeat with accuracy in a labor-intensive context .