Browsing by Author "Malherbe, Jan Stephanus"
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- ItemSelf-compacting concrete versus normal compacting concrete : a techno-economic analysis(Stellenbosch : Stellenbosch University, 2015-12) Malherbe, Jan Stephanus; Wium, J. A.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.ENGLISH ABSTRACT: Self-compacting concrete (SCC) also referred to, as self-consolidating concrete, is a relatively new concrete technology used in the construction industry. It is able to flow under its own weight and compact into every corner of the formwork, purely by means of its own weight. According to the University of Johannesburg, engineers can expect a strong demand for their services over the next four years and construction projects might start experiencing even higher pressure on their schedules. This will force the industry to look at possible time saving technologies. It is therefore useful to investigate possible construction methods that might accelerate project schedules and to understand their financial impact. It is also important to see if it will be worthwhile for the South African construction industry to follow the international trend for SCC application. The primary objective of this study was to construct an accurate cost implication model to quantify the impact of the decision to implement self-compacting concrete on a South African construction project. This was done by constructing a static costing model and by performing a sensitivity analysis and a Monte Carlo analysis on the static results of the relevant Key Performance Indicators (KPI’s). As a secondary aim, the study examined the labour requirements at a typical South African construction project. This was done to enable a project leader to easily implement self-compacting concrete technology without facing the perceived challenges concerning job creation policies in South Africa. The technical information regarding the material properties of SCC is well researched and guidelines for implementing the material in a project already exist. The knowledge gap about the detailed cost impact of using SCC on a South African construction project still exists. Interviews with industry representatives showed a good, but fragmented, knowledge of SCC in the South African industry. The factors that influence the cost of using SCC and how these factors influence the construction cost are known, but the size of the influence on the different cost constituents are still uncertain. The labour requirements set out by the National Development Plan (NDP) and the Expanded Public Works Programme (EPWP) for labour-intensive construction was also identified as a perceived obstacle for SCC implementation. A modelling and calculation methodology was proposed in this research to quantify the financial impact of using SCC on a South African construction project. This methodology was tested and found to be useful when applied to a case study. The case study was a six span bridge constructed near George in the Western Cape. The results obtained are of particular value to the client and contractor in a project team. The cost quantification results are presented in terms of cost KPI’s that can be used for interpreting the influence of SCC on the construction cost. For this case study it was found that the construction cost would increase by 17.4% if SCC had been used. This is mainly due to the increased material and formwork cost. The higher cement content of SCC raises the material unit price and the increased formwork strength requirements, needed to accommodate hydrostatic pressures, manifests as an increased expense. A Monte Carlo analysis yielded a 90% confidence that the total cost difference would be between 14.0% and 20.9% (R294 800 and R438 200) on a total amount of R2 098 700. The labour requirements set by the EPWP and the NDP for labour-intensive infrastructure projects was shown to have a limited influence on the decision to implement SCC. The labour reduction resulting from the use of SCC implementation is small. The labour reduction should not prevent the implementation of a new technology. The main risks applicable to this case study are the lack of SCC expertise and the possibility of formwork failure or leakage that can result in total concrete material loss during concrete placement. The cost comparison should be done prior to the construction phase in order to manage and lower the cost difference by identifying the most efficient way to focus cost reduction strategies. A project dashboard with all the graphical results and the KPI summary, can be used to summarise the effect of implementing SCC at a South African construction project if the proposed calculation method is used. The information contained on the dashboard can then be altered to suit the needs of a specific decision maker. The heuristic modelling, especially the Monte Carlo analysis, should be tailored to cover only the information that has inherent uncertainty for a specific project. To minimise the cost increase, the incorporation of cement extenders should be considered. SCC expertise and a formwork specialist should be included in the project team during the project inception phase. Further research should be done to enhance the knowledge about the SCC cost implication, opportunities of SCC in the South African market as well as the implementation intensity and success of SCC in South Africa.