Browsing by Author "Ballim, Yunus"

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Curing and the durabilty of concrete
(2016-06-08) Ballim, Yunus;
This thesis presents the details and results of an investigation into the effects of early age curing on the durability of concrete The two main objectives of the investigation were: to develop simple test methods, applied at relatively early ages, for measuring the effects of early-age moist curing on the advance of hydration in the cover zone of concrete; to quantify the effect of early age curing on the durability performance of concretes of various strength grades and made with different binder types. [Abbreviated Abstract. Open document to view full version]
The effects of supplementary cementing materials in modifying the heat of hydration of concrete
(2008-09-23) Ballim, Yunus; Graham, Peter C.
Minimising the risk of thermally induced cracking in mass concrete structures through suitable materials selection and processing
(Springer, 2018) Ballim, Yunus
The hydration of cement is an exothermic reaction which generates around 300 kJ/kg of cement hydrated. In mass concrete structures such as dams and large foundations, this heat of hydration causes a significant rise in temperature in the internal sections of the concrete. If thermal gradients between the internal sections and the near-surface zone of the concrete element are sufficiently large, the thermal stress can cause cracking of the concrete. This cracking may cause functional or structural problems in the operation of the structure. In order to minimise the potential for such cracking, it is necessary to minimise the rate and amount of heat that is evolved, particularly during the early period of the hydration process. This can be achieved by design engineers and concrete technologists through judicious selection and processing of concrete-making materials. This paper presents the observations and results obtained over a number of years from adiabatic testing of concretes, computational modelling of temperature development in large concrete structures and direct temperature measurements in actual structures, with a view to understanding the effects of concrete-making materials on temperature development in concrete. The paper considers the effects of different types of rock aggregates, different types of Portland cement, fineness of grinding of the cement, the addition of supplementary cementitious materials and variations in the concrete starting temperature on temperature development in a large concrete element over time. The results indicate that using a coarser ground cement, adding significant amounts of supplementary cementitious materials and cooling the concrete mixture before placing has a more significant effect in reducing the risk of cracking than varying the aggregate type of the Portland cement type.
Opening Address to the 2nd International Conference on Concrete Repair, Rehabilitation and Retrofitting. Cape Town 24 November 2008.
(2004-11-24) Ballim, Yunus
Most people, whether consciously or unconsciously, are attracted to what I shall call, the “great human narrative” of transformation through journey. We find the narrative attractive because it appears prominently - as a leitmotif - in much of the way in which we construct our religious and cultural understandings of ourselves. The journey narrative speaks strongly to our sense of identity - both as belonging to a group (tribe, nation, human, etc) but also as individual (adult, academic, gardener, etc). We recognise these identities as having been formed through difficult intellectual, spiritual and often, physical journey. Importantly, we think of the personal as well as the shared journey as a process towards a better understanding of complexity – towards a more enlightened view of the world and our place in it.