There is a need for appropriate tools and techniques to undertake the vast task of sound repair, maintenance and rehabilitation of concrete infrastructure which is deemed to be deteriorating at unacceptable rates. Low economic growth predictions lead to limited budgets and a deferring of maintenance. The use of technology could be used to extend the useful life of concrete structures. Structural Health Monitoring Systems (SHMS) can be used to monitor structural integrity and the information obtained from these systems can be used in detecting overloading (on bridges for instance) and to alert asset managers of any due maintenance. Büyüköztürk (2007) argues that conventional methods of inspecting the condition of bridges are generally subjective and that this does not give a true reflection of the state of the structure. The objective of this study is to determine the economic value of using SHMS on South African bridges as opposed to conventional bridge inspection methods. The detailed study was conducted on railway bridges on the Transnet Freight Rail (TFR) Ermelo - Richards Bay coal route to assess the contribution that a commodities line such as this one makes to the South African economy. This study makes use of data from Transnet to establish economic value. It is recommended that the results and recommendations be used for a more detailed study into the value of SHMS to be extrapolated for use on other bridges (e.g. road bridges).

Globally, concrete is the most used construction material. Its embodied energy is relatively low, yet due to the vast quantities that are produced annually, it has substantial greenhouse gas (GHG) emissions associated with it. Of the concrete constituents, the manufacture of clinker - the basis of all conventional cements - contributes the most significant emissions. Therefore, to reduce the emissions associated with concrete manufacture, there has been extensive research into how clinker content can be reduced without compromising desired concrete properties. Existing methods for clinker reduction have, however, only allowed clinker replacement to a limited extent. This research investigated the more efficient use of clinker to minimise clinker content required to achieve desired mechanical and durability properties of concrete. The optimisation of powder (materials < 125 µm) packing, using filler materials with varying fineness, was identified to potentially increase clinker efficiency. The optimisation undertaken was the maximisation of powder packing density but without adversely affecting workability. The investigation entailed the application of analytical particle packing density models as well as experimental investigation. Two particle packing models, the Compaction Interaction Packing Model (CIPM) and the Modified Andreasen and Andersen Curve (MAAC) were applied. Various methods for determining the packing density of powder combinations were investigated which informed the use of the mixing energy test to provide experimental packing density data for the modelling procedures. The CIPM was used to optimise the powder phases of concrete as it incorporated the effect of surface forces on powder packing and the MAAC was used to complete the optimisation of fine and coarse aggregate materials. It was necessary to calibrate the CIPM through the selection of various model constants, based on the minimisation of the average error associated with predicted packing density. Despite the incorporation of surface force effects, the CIPM did not predict the trend in packing density observed for various experimental powder combinations with consistent accuracy. Combinations of cement with limestone of high and low fineness (relative to cement) were most accurately predicted but combinations with limestones of similar fineness to cement were less accurate. It was therefore apparent that the model inadequately accounted for the effects of varying particle size and the corresponding influence of surface forces on these particles. However, for practicality, model constants which minimised overall error were used to determine powder combinations enabling maximum packing density for use in optimised concrete mix design. Concrete mixes were designed in 2 phases. Initially water content was fixed, and limestone content was successively increased to 40 vol. % (Phase 1). Despite the formation of mixtures according to maximum packing density, the results showed that optimisation of packing density with a fixed water content was insufficient to reduce clinker content without adversely affecting compressive strength. However, workability was maintained without excessive superplasticiser (SP) dosage and oxygen permeability, water sorptivity and accelerated drying shrinkage were either improved or not adversely affected. This was attributed to the ability of fine fillers to prevent interconnectivity of the pore structure and the decreased volume of gel hydration products leading to reduced drying shrinkage. Compressive strength was tested for a binary (cement/limestone) and ternary (cement /limestone/fly ash (FA)) binder blend for Phase 2 in conjunction with a substantially reduced water content. Workability was adversely affected and both mixes required high SP doses, however, the FA blend required a relatively lower dose. Compressive strength was again decreased relative to the reference mix but when comparing Phase 1 and 2 mixes with predicted strength for equivalent w/c ratios, compressive strength was relatively unchanged, inferring little benefit of packing optimisation. However, binder efficiency indices (‘bi’) (between 5.3 and 6.9 kg/m3 /MPa) were reduced relative to data from previous investigations with similar strength class (between 10 to 20 kg/m3 /MPa), inferring increased binder performance. Powder packing optimisation thereby has the potential to enable clinker reduction, particularly for lower strength grade concrete, without adversely affecting compressive strength. Furthermore, the relatively unaffected durability indicators portray the beneficial effects of powder packing optimisation on increasing the impenetrability of concrete microstructure and it potential use in applications where durability is of importance. These findings also pointed to further possible reductions in the binder efficiency index below 5 kg/m3 /MPa if water content is further reduced (to maintain low water: cement ratio) and reactive SCMs are incorporated. However, further investigation and understanding of the fundamentals of powder packing is necessary to achieve a fully predictive process of low-clinker concrete mix design that can be universally applicable.

In Namibia, the design and construction specification of concrete (for durability) follows the traditional method of prescribing parameters which over time are believed to produce durable concrete. These parameters include concrete exposure definition, cover, concrete strength, concreting materials and concreting methods. International research has shown that some of these parameters do not have a direct relationship with the durability of “As-built” concrete structures; rather that concrete structures can be designed and constructed to meet specific performance levels of the environment they are built in. In this case, testing of the concrete during design, construction and post-construction (to set acceptable limits and confirm adherence to the limits) becomes part of the process. This project was undertaken to look at how concrete practices (design and construction specification) followed in Namibia have impacted on the durability of concrete structures. To achieve the objective, the approach followed included; first assessing the prevailing concrete conditions (in different areas across Namibia), reviewing current concrete design and construction specifications used in the industry and finally assessing practitioner knowledge on performance-based concrete design and construction specification. Concrete infrastructure in four towns (Walvis Bay, Swakopmund, Arandis and Usakos) were inspected and deteriorations recorded. From these inspections, an evaluation of the causes of the deterioration was undertaken. A comparison was undertaken on the prevalence of different deterioration mechanisms in the four areas. Design standards, for durability, followed by structural engineers in Namibia were reviewed including specifications demanded by different infrastructure developing agencies. The limitations of these were highlighted. Interviews and observations were undertaken with structural engineering practitioners on knowledge of design for concrete durability. From the information collected, the comparison and assessment it was concluded that there is a need to revise the concrete design and construction specification to ensure concrete performs better against the most significant risk to concrete service life; damage due to reinforcement corrosion. Concrete specifications need to have measurable durability parameters which can be used for acceptance of concrete works besides compressive strength. The Namibia Port Authority (NAMPORT) has taken a step in this direction with the development of concrete construction specifications which have adopted the South African Durability Index method as part of the concrete acceptance criteria. Challenges encountered (by NAMPORT) include lack of testing equipment and a lack of knowledge by material testing engineers. With Namibia having the challenge of not having a national concrete construction standard, it is further recommended that major infrastructure developers (Namibia Water Authority, NAMWATER, and Roads Authority, RA) should lead in adoption of similar specifications to the NAMPORT ones. As most engineers in Namibia undertake works for either NAMWATER or RA, the industry will be more willing to undertake the training of engineers on the South African durability index method as it will make economic sense. The training is recommended to include training of laboratories offering material testing services in Namibia.

Concrete deteriorates due to, but not limited to the ingress of deleterious substances which react with the cement matrix, reinforcing bars corrosion, mechanical effects, physical effects, structural damages, poor construction practices. All these factors individually or combined, ultimately reduce the expected service lives of the concrete structures. The trends vary with different exposure conditions and geographical locations, and a reference guide is required in South African context. A total of twenty-four concrete structures were visually assessed by different University of Cape Town (UCT) scholars and findings were captured in project reports. The reports of these assessments were analysed in this research to identify the main causes of concrete deterioration and severity of damages in the three provinces considered in South Africa, whilst linking these to environmental exposure conditions and geographical location. It is important to elucidate that deterioration mechanisms and trends were drawn from the limited number of visual assessment reports, and the mechanisms assumed might not have been necessarily correct. The rating of the defects was done using the DER-U rating system, a method available for bridges and retaining walls. DER-U rating system was developed for buildings, exploiting the available rating system for bridges as there is no available established rating system for buildings, and the author considered it an important tool for the preliminary evaluation taking note of all limitations. However, reinforcing bars corrosion has been found to be the most prominent deterioration mechanism on structures assessed and severity was high on the structures located in the Western and Eastern Cape provinces, and was exacerbated by the inadequate cover provided on most structures. Furthermore, it was also noted that the severity of the damage increased with age of a structure. Although petrographic analysis as an additional investigation was required to ascertain Alkali-Silica Reaction (ASR), damage was observed in the Western Cape and Gauteng provinces. Even though the occurrence was low, it still required special attention as the effects are usually disastrous and very expensive to maintain the affected structures. Leaching was observed on all the bridge structures assessed though it was more prominent on the structures situated at the coast. Plastic and drying shrinkage cracks were observed on all structures in the Gauteng province and it has been noted from the literature that shrinkage cracks were exacerbated by very high seasonal temperatures in these provinces. Abrasion was high on all structures on the tidal zones and the elements of structures located in the water courses. The proposed in-situ and laboratory tests have been discussed in this report and they are recommended for full-scale condition assessments to complement the visual assessments in an endeavour to ascertain the mechanisms identified. Evidence of poor maintenance practices was observed in the Eastern Cape province where delamination and spalling were observed on freshly repainted structures. As a result, in South Africa there is undoubtedly, a constant need of developing and employing effective and efficient tools to ensure quality is not compromised. Design engineers must always take into cognisance the exposure conditions and ensure strict quality control measures during the construction phase. Maintenance engineers should take into consideration the location of the structure and deterioration mechanisms in the specific areas when determining the maintenance strategies. The clients should always employ knowledgeable design and maintenance engineers, to ensure durable structures are erected and correctly maintained.

Alkali Aggregate Reaction (AAR) is a deterioration mechanism which affects concrete structures all over the world. Different parts of the world employ various mitigation and control measures for AAR damage. Different tests are also performed worldwide to assess AAR. With the variety of AAR avoidance measures and AAR tests performed worldwide, it is necessary to have a thorough compilation and critical assessment of these AAR avoidance measures and AAR tests, which may be of assistance to engineers and other professionals who are involved in structural and material design of concrete structures or in the construction, quality control and condition monitoring and assessment of concrete structures. This dissertation aims to outline the types of AAR and the mechanisms associated with them, and to highlight case studies of AAR incidences around the world. This dissertation further aims to provide a comprehensive compilation and analysis of various AAR avoidance measures as well as AAR tests that are performed worldwide. Commonalities and differences will be highlighted between the different case studies, and critical analyses will be done on the AAR avoidance measures and AAR tests that will be discussed. There are three main types of AAR, distinguishable by the aggregate source. These are: AlkaliSilica Reaction (ASR), Alkali-Silicate Reaction and Alkali-Carbonate Rock Reaction (ACR). Since AAR is a type of internal chemical damage to concrete, it can be avoided by engineering design and by carefully selecting the concrete construction materials. In order for damaging AAR to occur in concrete, the following conditions need to be met: • Reactive silica in the aggregates should be present • Alkali, which is primarily from Portland cement, should be of a sufficient concentration • There should be sufficient moisture in the concrete • Portlandite should be in a sufficient concentration (this is specifically for ACR) To prevent the occurrence of AAR in concrete, one or more of the conditions above should be eliminated, except for the case of ASR in which one or more of the first three conditions should be eliminated. Since this dissertation mainly focuses on ASR, only the first three conditions will be considered as these are the only conditions for the occurrence of ASR. Various testing methods are employed all over the world to assess AAR. These tests include tests performed to assess whether certain aggregates are susceptible to AAR; tests to assess the performance of specific concrete mixes and thus determine if they are susceptible to AAR, and also tests performed to assess the occurrence and extent of AAR in existing concrete structures.

The main purpose of this research study is to test the applicability of the DER (Degree of defect, Extent and Relevancy of defect) rating system, used for road network infrastructures, to the support structures of a dry cooling tower in a power generation environment. The DER is a defect-based rating system developed locally by the Built Environment Division of the Council for Scientific and Industrial Research (CSIR) in Pretoria, South Africa. This study involved a visual inspection and the rating and analysis of defects of reinforced concrete (RC) structures in an Eskom power generation plant located in Grootvlei in Mpumalanga Province. Visual inspection and condition rating systems form part of an Asset Management System (AMS) that is used to ensure a safe operation and the economic benefit of the structure throughout its life cycle. For that reason, various organisations and roads authorities have developed condition-rating systems similar to the DER for visual assessment of their road network structures using a Bridge Management System (BMS) as a vehicle to achieve their operation and maintenance objectives. Other condition-rating systems have been identified and their applicability to structures in a power generation environment as compared to that of the DER was also tested. These condition-rating systems are: 1) The Overall Structural Condition Index (OSCI) - proposed by the Australasian Transport Research Forum (ATRF) for bridge condition assessment and prioritisation of maintenance activities and budget allocation. 2) The National Bridge Inspection Standard (NBIS) which establishes a uniform program for all state departments of transportation in the USA to regulate the minimum requirements for inspection types and procedures, inspection intervals, inspector qualifications, and inventory reporting, and 3) The Ontario Structure Inspection Manual (OSIM) which sets standards and provides uniform approaches for visual and detailed inspections and condition evaluation for all types of bridge structures in Ontario, Canada. Comparative rating analyses of the defects of the same RC structure in a power generation environment was conducted in order to establish the applicability of the DER in comparison with the other rating systems. The use of the DER, amongst other selected condition rating systems, was recommended with the suggestion that further improvement be undertaken so as to extend its usage within a power generation environment.

Central to the South African government’s vision of providing services to all is on-going maintenance of public infrastructure. Since 1994 the government focused on addressing backlogs in the provision of water services through new infrastructure investment; however it failed to make sufficient investment in the maintenance and renewal of this infrastructure (SAICE, 2006). Older infrastructure is not being renewed or refurbished as required and planned preventative maintenance on new infrastructure is inadequate (SAICE, 2006). This has been generally attributed to poor management strategies that are exacerbated by lack of skills in water services utilities and low levels of funding provisions (Mescht &amp; Jaarsveld, 2012; FFC, 2013). The continuing poor maintenance of water distribution networks has contributed to high leakage rates in South Africa (FFC, 2013; DBSA, 2012). To address challenges of maintenance of water distribution infrastructure a regulatory framework to guide municipalities is critical. The government approved the National Infrastructure Management Strategy (NIMS) in 2006 to support simultaneous infrastructure investment and maintenance (CIDB, 2008). One of the key thrusts of the strategy is the strengthening of the regulatory framework that governs planning and budgeting for maintenance. The literature survey of this study found that initiatives associated with the NIMS were very slow in gaining traction. The study reviews water services infrastructure management frameworks that are based on present legislative instruments and standards for two study areas; City of Capetown and City of Johannesburg. Challenges associated with effective management of water distribution infrastructure are assessed based on established infrastructure management policies, strategies and asset management plans for each entity. For each study area leakage control strategies are the key maintenance strategy outputs associated with the implementation of the management frameworks; therefore the study reviewed sector plans and annual reports to assess challenges associated with carrying out effective maintenance. The findings of the study show a correlation between the adoption of maintenance management strategies and the improvement of the performance of water distribution networks for both Cape Town and Johannesburg. The strategies are driven at the highest level of decision making in the municipalities as budgeting requirements are supported by the Integrated Development Plans of each study area. The maintenance allocations however remain below the international benchmark to enable the municipal entities to carry out satisfactory maintenance of their distribution infrastructure.

South Africa is considered a water-scarce country and this fact alone stresses the absolute need to preserve its water resources. As time goes by, the ageing of dams in South Africa is becoming an increasingly important factor to consider from a dam safety perspective. When considering concrete dams, Alkali Aggregate Reactions (AAR) which is the collective term referring to the potential chemical reactions between the cement and the coarse aggregate in the concrete, are a major cause of ageing. AAR causes internal swelling of concrete leading to stresses that eventually manifest on a macroscopic level as inter alia cracks, deformation and opening of horizontal construction joints. Although the effect of AAR expansion on arch dams is complex, certain behavioural phenomena have been identified as typical indicators of swelling concrete. These are well covered by literature. This thesis aims to compare the structural behaviour of concrete arch dams in South Africa that are subjected to swelling due to AAR. Three arch dams, namely Hartebeeskuil Dam, Poortjieskloof Dam and Thabina Dam (all located in different climatic regions), were identified and their behavioural patterns were investigated by using visual techniques along with the interpretation of instrumentation results. The typical instrumentation results that were used for interpretation purposes included geodetic surveying results, crack width gauge results, in situ stress measurement results and trivec measurement results. Poortjieskloof Dam, the oldest of the three dams, showed permanent upstream displacement trends of both flanks, but the centre of the arch showed a downstream displacement trend. Both flanks show swelling towards the abutments and rising crest levels are evident throughout the length of the dam wall. The dam wall was cracked quite severely on the downstream face and the horizontal joints showed clear separation. The most recent displacement trends suggest that the rate of AAR is decreasing. Hartebeeskuil Dam, the second oldest of the three dams, showed permanent upstream displacement trends throughout the length of the dam wall. Both flanks show swelling towards the abutments and crest levels at both flanks show some settlement. The central section of the arch show rising crest levels. The results of in situ stress measurements carried out in 1999 showed that the downstream section of the arch is experiencing tensile stresses while the upstream section of the arch is mostly experiencing compressive stresses. The cracking patterns on both the upstream and downstream faces seem to agree with these findings. The results generally seem to suggest that the AAR mainly occurs on the upstream side of the arch and that the effective arch has become thinner due to the tension zone on the downstream side. The most recent displacement trends suggest that the rate of AAR is not showing any signs of decreasing. Thabina Dam, the youngest of the three dams, showed permanent upstream trends of the right flank while the central region and left flank of the arch showed downstream trends. The flanks have moved permanently towards each other and the crest levels have increased throughout the length of the arch section. The most recent trends show increasing rates of strain especially in the vertical (z) and tangential (y) directions. More recently the entire arch has started showing upstream displacement trends. These may indicate the onset of a swelling mechanism in the concrete, most likely AAR, but extensive testing is required to prove this.

Thesis (M.S. in computer science)--Washington State University, December 2009. / Title from PDF title page (viewed on Jan. 20, 2010). "School of Electrical Engineering and Computer Science." Includes bibliographical references (p. 60-64).

Thesis PlanB (M.S.)--University of Wisconsin--Stout, 2007. / Includes bibliographical references.