In 1974 an article appeared in Science magazine with the dry-sounding title “Judgment Under Uncertainty: Heuristics and Biases” by a pair of psychologists who were not well known outside their discipline of decision theory. In it Amos Tversky and Daniel Kahneman introduced the world to Prospect Theory, which mapped out how humans actually behave when faced with decisions about gains and losses, in contrast to how economists assumed that people behave. Prospect Theory turned Economics on its head by demonstrating through a series of ingenious experiments that people are much more concerned with losses than they are with gains, and that framing a choice from one perspective or the other will result in decisions that are exactly the opposite of each other, even if the outcomes are monetarily the same. Prospect Theory led cognitive psychology in a new direction that began to uncover other human biases in thinking that are probably not learned but are part of our brain’s wiring.

Thinking fast and slow.

Markets and Hierarchies

Supplementary cementitious materials: New sources, characterization, and performance insights

Learning to see.

Russell Kenley and Olli Seppanen, Spon Press, London, 2009, 336 pp., ISBN 978 0 415 37050 9, £90 I found this book to be a very well‐researched and written summary of prevalent construction industr...

Location‐Based Management for Construction: Planning, Scheduling and Control

The influence of steel fibres on compressive and tensile strength of ultra high performance concrete: A review

New supplementary cementitious materials claimed to possess pozzolan properties emerge frequently. This development is driven both by economic and environmental pressures. Properties of new materials are compared with those of materials already well known, such as silica fume. Several test methods are standardized for making such comparisons, regulated by both European (EN) and American (ASTM) standards. Standardization indicates that procedures are secured to make comparisons valid and informative. In this article the sensitivity of accepted variations within each of the standard procedures are investigated to determine if the results are influenced by such variations. Various methods for testing pozzolanic properties are briefly discussed. Experimental work was carried out in compliance with the standard methods for testing silica fume, according to both EN and ASTM. Seventy two mixes are made and tested in the experimental series, combining two standard procedures, two types of sand, three cements and four flow agents (SP). The results show that determined values are highly influenced by variations accepted to be made within the standard procedures. Possible reasons for these variations are analyzed. Conclusions are made that even when complying with the standards, the results are heavily manipulable (intended or unintended). Also a shortcoming in EN regarding new materials, is detected. Suggestions are made on additional information required to be given together with the results when reporting pozzolanic properties according to standards in order to make results informative and reproducible. A limitation in EN towards testing nano-sized silica materials is detected. An adjustment is suggested, to make EN applicable correspondingly to ASTM, also for these materials.

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Inconsistencies in the pozzolanic strength activity index (SAI) for silica fume according to EN and ASTM

The paper address a pilot project in implementation of Last Planner initiated by the general contractor, Skanska, in a construction project of 6800 square metre made up of a kindergarten, junior high school and a sports and cultural centre. Excavation work started late autumn 2008 and the utility buildings are scheduled to be delivered to the owner in June 2010. The owner is the Municipality of Kristiansand. Action research is applied as research method, where academics take part in the change processes, together with professionals from the construction project and the general contractor’s head office. This paper concerns reflections from the ongoing construction process and is based on preliminary data. The first run is broadly in accordance with the Last Planner concept as outlined by Ballard. It is, however, identified a need to improve the system to link the output from the collective phase scheduling to production planning via the lookahead schedule and constraint analysis, which has been mis-conceptualised in the early phase of the project. The most successful part of the implementation study so far is several phase planning processes, in which the technical sub-contractors have been taking active part in the collective organised planning process. It is too early in the project to see if this also leads to improved PPC in production, but it is expected that it will. However, the same quality of coordination is missing for the architect and the subcontractor for site work. It is identified a number of empirical difficulties in the implementation the process. The largest challenge seems to be the relationship between the architect, the general contractor and the owner, as the pattern in the relationship appears to be dysfunctional in order to create best possible condition for cooperation, and which need to be further studied. Moreover is it identified proposals for further improvements in the Last Planner concept.

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Implementation of Last Planner in a Medium-Sized Construction Site

Rock aggregates constitute the enormous volume of inert construction material used around the globe. The petrologic description as igneous, sedimentary, and metamorphic types establishes the intrinsic formation pattern of the parent rock. The engineering properties of these rocks vary due to the differences in the transformation process (e.g. hydrothermal deposits) and weathering effect. The two most common mechanical tests used to investigate the performance of aggregates are the Los Angeles (LA) and micro-Deval (MD) tests. This study reviewed the geological parameters (including mineralogy, grain and crystal size, grain shape, and porosity) and the relationship to Los Angeles and micro-Deval tests. It was found that high content of primary minerals in rocks (e.g. quartz and feldspar) is a significant parameter for performance evaluation. Traces of secondary and accessory minerals also affect the performance of rocks, although in many cases it is based on the percentage. Furthermore, some studies showed that the effect of mineralogic composition on mechanical strength is not sufficient to draw final conclusions of mechanical performance; therefore, the impact of other textural characteristics should be considered. The disposition of grain size and crystal size (e.g. as result of lithification) showed that rocks composed of fine-grain textural composition of ≤ 1 mm enhanced fragmentation and wear resistance than medium and coarse grained (≥ 1 mm). The effect of grain shape was based on convex and concave shapes and flat and elongated apexes of tested samples. The equidimensional form descriptor of rocks somehow improved resistance to impact from LA than highly flat and elongated particles. Lastly, the distribution of pore space investigated by means of the saturation method mostly showed moderate (R = 0.50) to strong (R = 0.90) and positive correlations to LA and MD tests.

/pdf/review-of-the-relationship-between-aggregates-geology-and-3iajfv30mk.pdf

Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests

Ultra High Performance Concrete (UHPC) is a material that is attracting attention in the construction industry due to the high mechanical strength and durability, leading to structures having low maintenance requirements. The production of UHPC, however, has generally higher environmental impact than normal strength concrete due to the increased demand of cement required in the concrete mix. What is still not sufficiently investigated, is if the longer lifetime, slimmer construction and lower maintenance requirements lead to a net environmental benefit compared to standard concrete bridge design. This study utilizes life cycle assessment (LCA) to determine the lifetime impacts of two comparable highway crossing footbridges spanning 40 meters, designed respectively with UHPC and normal strength concrete. The results of the study show that UHPC is an effective material for reducing lifetime emissions from construction and maintenance of long lasting infrastructure, as the UHPC design outperforms the normal strength concrete bridge in most impact categories.

https://iopscience.iop.org/article/10.1088/1757-899X/245/5/052096/pdf

Rein Terje Thorstensen

Papers

The influence of steel fibres on compressive and tensile strength of ultra high performance concrete: A review

Inconsistencies in the pozzolanic strength activity index (SAI) for silica fume according to EN and ASTM

Implementation of Last Planner in a Medium-Sized Construction Site

Review of the relationship between aggregates geology and Los Angeles and micro-Deval tests

Determining the Environmental Benefits of Ultra High Performance Concrete as a Bridge Construction Material