Deployment of Lean Six Sigma and KAIZEN Techniques: A Case Study of the Concrete Production Plant for the 750 MW (5 * 150 MW) Kafue Gorge Lower Hydro Power Project

With the fourth industrial revolution on the verge of disruption, businesses and production companies around the world are trying to emulate the success of Toyota’s remarkable production system with a view of reducing waste and improving quality. Lean production has been the secret for Toyota to be as the most profitable automaker in the world. This paper presents a survey and re-views on how process improvement techniques such as the Lean Six Sigma (LSS) and KAIZEN may be implemented to realize reduced lead time in production processes and to attain the desired quality in concrete. The case study is based on the concrete production plant for the 750 MW (5 * 150 MW) Kafue Gorge Lower Hydro Power Project, which may be considered to have been one of the largest concrete batching plant with a total production capacity of 32 cubic meters. The analysis of the effectiveness and impact of the operation and management methods, i.e., LSS and KAIZEN techniques, were carried out over a period of approximately two years. Through literature review, evaluation of these philosophies was done by first defining waste in materials, time and work force at the concrete production plant. The KAIZEN, which is management techniques focusing on employees’ involve-ment to ensure continuous improvement and a high success rate of lean implementation at the plant, reduction and quality optimization of concrete but also provides applied management and economical improvements with assured reduced Takt-Time realization at the production plant.


Introduction
With the advent of the fourth industrial revolution, companies are striving to be leaders, relevant and competitive amidst the unprecedented change. Considering the fact that manufacturing and production are benchmarks of economic sustainability, (Allampallewar & Sathe, 2017) concludes that construction management and technology are key to the development in the construction industry.
Henceforth, in preparation for the fourth industrial revolution in the belt environment (Fletcher, 2016), integration of strategic approaches in manufacturing and production with methods and techniques that are constantly sharping market competitive advantages has become an obligation for every company to ensure survival and market share. New to the construction industry, Lean Six Sigma (LSS) and KAIZEN are the most effective methods to reduce defects and improve processes in construction. Lean manufacturing traces its origin from the Toyota Production System which defines the company's management methods and uniqueness. After World War II, Toyota faced very different business conditions making its market share very small in the post-war. With flexibility as their strength Toyota realized that making lead times short and integrating dynamism in production lines, assured higher quality, better customer responsiveness, better productivity, and better utilization of equipment and space are some of the rewards. During the 1940s and 50s, Toyota's True North was the elimination of wasted time and materials from every step of the production process from raw material to finished goods while addressing the need for fast flexible process that give customer what they want, when they want it, at the highest quality and affordable cost (Liker, 2004).
Six Sigma is a precise and highly effective implementation of proven quality principles and techniques in order to attain a close-to-ideal process. Sigma, σ, is a letter in the Greek alphabet used by statisticians to measure the variability in any process. First implemented by Motorola in the 1980s, Six Sigma is a quality improvement technique based on statistics with objectives of decreasing costs, optimizing processes and reducing the production time (Sarathkumar & Loganathan, 2016). The KAIZEN management originated in the Japanese management practices and is dedicated to the improvement of productivity, efficiency and quality. From  involves methods and techniques that are employed to make subtle improvements, which when applied to key processes will put a company on a journey towards increased revenue, reduced costs and improved collaboration. The KAIZEN management system is based on the continuous loss reduction by means of methods that do not rely on investments but on the improvement of the processes and the work force performance (Titu et al., 2010). With regards to Predictive and Run-to-Failure maintenance, the methodologies used when implementing the LSS and KAIZEN techniques can be used by companies to ensure continuity in production and also to harness the fourth Industrial Revolution for sustainability in reshaping the future of production and manufacturing (World Economic Forum, 2019).

Project Description
The demand for electricity in the Republic of Zambia has been increasing directly proportion to its economic development as can be seen from

Dam Design
The dam type for the KGL Project is Roller Compacted Concrete (RCC) Dam which, according to (Li, 2019), is formed by spreading the thin layer of the zero-slump concrete and rolling compaction by means of vibrating roller. Furthermore, in terms of consistency, RCC is very dry in nature just like soil during compaction and RCC mixtures are specified using the Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) instead of the Water-Cementing (w/c) ratio (Hazaree, 2007). The essential ingredients of RCC are coarse aggregate, fine aggregate, fly ash, cement and water. An advantage of RCC compared to Conventional Concrete (CVC) is the presence of fly ash that reduces O. A. Mhone, J. Jin American Journal of Industrial and Business Management the amount of cement, thereby reducing the material cost. In addition to that, with regards to crack formation due to heat of hydration in mass concrete dam structure, the phenomenon is mitigated by reduction in the quantity of cement used (Bank, 2003).

Batching Site
Located a few kilometers off the central point between the Powerhouse and the Dam sites, the Crushing Site, Photo 1 & Figure 3, comprised of three batching plants, three ice plants, ammonia plant and two water chillers with specifications as summarized in Table 2 below.

Problem Statement
One of the main economic advantages of the speed of construction feature of RCC dams is that large volumes of (low or high paste) concrete can easily be placed with heavy equipment, thus shortening the construction period of RCC   dams. The cost of placing concrete is critically dependent on its workability which has been universally reckoned as one of the most important property of fresh concrete among consistency and moisture-density relationships (Hazaree, 2007). With the aim of ensuring continuity of placement of RCC, to prevent cold joint formation within a zone, it is imperative that the consistency in the rheology of fresh concrete is maintained to realize design qualities in the hardened structure, Photo 2. Henceforth, production management of concrete at the batching plant involves numerous techniques and measures to attain a desired workability of concrete with regards to the factors influencing the rheology of fresh concrete as shown in Figure 4.

Definition of Waste
With regards to the Lean Six Sigma and as defined by Toyota Way (Liker, 2004), the most common non-value-adding activities that are considered as wastes are Photo 2. Downstream of the Kafue gorge lower RCC dam.
Source: (Hazaree, 2007). 2) Waiting (time on hand): Workers merely serving to watch an automated machine or having to stand around waiting for the next processing step, tool, supply, part, etc., or just plain having no work because of stockouts, lot of processing delays, equipment downtime, and capacity bottlenecks.
3) Unnecessary transport or conveyance: carrying work in process (WIP) long distances, creating inefficient transport, or moving materials, parts, or finished goods into or out of storage or between processes. 4) Overprocessing: taking unnecessary steps to process products and services, ineffective process due to use of poor tools and product design, hence producing defects. Producing good quality products than necessary generates incipient waste.

Scope of Waste on Site
Defining and identifying non-value adding activities forms the basis for an appropriate evaluation of the plant operation optimization techniques. At the concrete batching plant, the true north was delivering good quality concrete on time to different sections on site, hence elimination of waste was focused in material use, work force coordination and process time (lead time reduction).

Analytical Methodology
The DMAIC methodology ensures the optimal integration of both the lean approach (focusing on the non-value and value adding activities) and the Six Sigma (tools and techniques to help identify, understand and reduce variations) to realize the combined advantages of the two techniques.

Using the DMAIC model to Improve Production Processes
Prior to the deployment of this approach, it is imperative to ensure that the current plant processes are correct and satisfactory with reference to design and production plant's true north, in our case: the automation of Discrete Control Systems, entering of the concrete placing orders into the concrete production management system and the monitoring system at the Control Centre was online with respect to Field Device Integration (FDT). With the aim of identifying variations in processes, the DMAIC (Define, Measure, Analyze, Improve, Control) model was used to implement lean six sigma improvements at the concrete production plant. The DMAIC model is a roadmap for process improvement that lean Teams should adhere to (Wisconsin, 2016).
• Define: Process analysis, define the problem and what is required to meet production targets. • Measure: Operational definitions, collect process data.
• Improve: Process flow, benchmarking, use of the KAIZEN.
• Control: Sustain improved standard operating procedures, Feedback Loop Analysis, use of KPIs.

Define, Measure & Analyze
During the define stage, it is imperative to know that process analysis is the foundation toward achieving process excellence, in addition to that, to deploy the measure and analyze techniques, the apprehension and review of basic statistical tools like Key Performance Indicators are some of the prerequisites not only to effectively implement analytical batch and process sizing, but also value stream and process mapping. In this case, the non-value adding activities, with reference to the definition of waste, comprise of: defects, overproduction and unnecessary transport or conveyance.

Defects and Overproduction
Quality control of concrete is a challenge for the fact that dynamism in the state of the aggregates in silos has a major impact on the workability of the concrete produced. Hence to ensure good characteristics in the hardened structure, which is only possible with adequate flow without segregation, it is important that the quality control team is capable to detect variations in the degree of quality of concrete by monitoring the water cement ratio (w/c) which is affected by aggregate gradation, admixture type and dosage, among others.
Initially, to validate and evaluate the quality of the concrete batch, a team of Laboratory technicians had to discharge a volume of concrete from the mixer truck as sample for them to test (vibe and slump tests), moderate and know the quality of every batch mixed before releasing the truck. In some cases, dry mortar (sand & cement) was added to the batch mix in order to attain the desired workability of concrete. NB: each batch was sampled before the next batch was O. A. Mhone, J. Jin mixed. With that method of quality optimization where a volume of concrete after sampling is discarded, Photo 3 & Photo 4, fostered the wastage of raw materials (cement, fly arch, morasses, ice and aggregates) from every batch of concrete produced, usually three cubic meters of CVC.
Hydration, the reaction between cement and water, involves exothermic processes. When cement, water, fly ash, aggregates and additives (molasses) are mixed heat of hydration is produced which rises as the hydration process progresses. Therefore, it is imperative to monitor the concrete temperature for the realization of desired workability in concrete. The mitigation and control of   Consider Figure 6 as an analogical depiction of the signing of delivery papers for mixer trucks carrying concrete batches. Proximity of the batching plant and the Laboratory station brooded non-value adding activities such as unnecessary transport or conveyance. For instance, for every changes and instruction to the mix proportions (sand, additives or any other) in the concrete production application software, Photo 7, a laboratory technician had to walk a distance close to hundred meters to confirm the parameter changes with the Batching Plant Operators at the control room located about ten meters high. With reference to

Improve & Control
With developed capability to identify waste and major process constraints, plant O. A. Mhone, J. Jin LSS provides strategies like the 5S + 1 system that helps in benchmarking and consolidating solution selection matrix to be used during the improve stage (George, 2003). The main purpose of control is to uphold the deployed techniques and preserve the realized gains from improved processes. Basically, control involves the use of strategies and tools that consolidates implemented standard operating procedures, visual process control and communication plans.
The other concept that is very helpful in control activities is the setting of Key

Work Force
Reconsidered the number of batch plant operators with emphasis on delegation. In addition to that, the interaction and communication among civil engineers on site, quality control (Lab-tech) and plant operators was revised and coordinated as can be seen from Figure 7 depicting the LSS evolved information flow regarding the quality and quantity of concrete batch. As a way to uphold the improvements to plant processes and promotes a shared understanding of how each person is important to the batching plant's success (Go Lean Six Sigma, 2012), the use of Handheld Transceivers (HT) was consolidated by assigning a channel for each team operating at the plant, almost every employee had access to HTs, this built trust, sense of involvement, cooperation and responsibility among employees throughout all levels of the organization.

Lead Time
Integration of the quality assurance team together with batch plant operators in the control room, that is, from having two control room operator to three, with one representative from the quality assurance team who were able to relate the amperage of loaded concrete mixers and other quality indicators to workability of the concrete. Hence, workability had to be checked at the point of discharge from the mixer to the conveyor belt or mixer trucks. Evidently reducing the time to verify and confirm each produced batch adherence to the specification of fresh concrete.

Materials
Optimization in material use gave an added advantage in the mitigation of the cost of production. Some of the changes realized following the deployment of the LSS were as follows.
Wastage of concrete batch by disposal/site rejection: merging the batch plant operators and laboratory technicians by reducing the distance between batching plant and the location of the quality assurance team, we were able to reduce  Excess production of ice: Production of ice was reduced to fill up 50% the ice storage containers to ensure that enough room and space in the ice storage containers was left for fault troubleshooting, nullification and run-to-failure maintenance.
Delivery papers: As can be seen from Figure 8, paper use for delivery notes was reduced by 66.67%.

Concluding Remarks
As we embark on deployment of process and production improvement techniques and industrial value chain creation to ascertain the truth north for an organization, it is imperative to note that for these plant and organization changes to be profitable we have to ensure that there is the coalesce between the people and the processes. Takt-Time being the breathing rate or production rate of the plant, (Liker, 2004) states that Takt-Time is a concept that is to be used to design organized work or activities. Considering the Takt-Time establishment at the plant, it is everyone responsibility to understand the feedback reviews, once the work force starts looping in the same direction, that is having developed focus on the common "Takt-Time", all forms of waste activities in the organization will be eliminated and the lead time between receipt of site concrete placing orders to concrete batch production will be reduced.
Deployment of the LSS and KAIZEN methodologies creates a well nurtured platform for standardizing processes which in turn lays the groundwork for the successful implementation and integration of systems such as the ERP, MES and SAP. In addition to that, this also helps work force switch from being reactive to proactive with a prime directive of continually seeking out and eliminating waste and wasteful practices immediately transforming your operations. With a well reinforced team (Nkumbwa, 2009) to advocate for these process optimization techniques, formulation of KPIs for a production plant and realization of reduced costs in production becomes inevitable.
Although the speed of placement of RCC is of essence, it is imperative that the workability of concrete conforms to standard specifications, hence the symbiotic integration of plant operators and laboratory technicians at the Batching plant and on site. Placement of concrete at the KGL RCC Dam lasted approximately 20 months, that is, from the initial RCC placement (6 th June, 2018) to RCC Dam Completion (15 th April, 2020). Photos 8-12 shows some of the completed concreted works at the KGL Hydropower Station.