Behaviour of ground cupola furnace slag blended concrete at elevated temperature

Fires adversely affect the performance of concrete when expose to extreme temperatures. However, it is important to study the effects of elevated temperature on the concrete properties. Concrete often contains other cementitious materials such as ground granulated blast furnace slag (GGBFS) and this has been successfully used to improve its properties. Hence, little or no study has been carried out on the use of ground cupola furnace slag (GCFS) in concreting. Therefore, this paper investigates the behavior of concrete blended with GCFS at elevated temperatures. A total of 300 samples were prepared with four different GCFS contents. The test specimens were cured for 28-d and 56-d and subjected to elevated temperatures ranging from 200oC to 800oC up to 24 h. The slump, residual compressive and tensile strength tests were carried out on fresh and hardened concrete. The results showed that the compressive strength and splitting tensile strengths of concrete generally increased with increasing % GCFS content but decreased as temperature increases. At 28-d and 56-d, the strengths were observed to be maximum at 10% replacement when the temperature is 200oC compared to other mixes. It can be concluded that the strength drastically decreased at temperature above 200oC. An analysis of variance (ANOVA) was also carried out to determine the effect of the elevated temperature and percentage replacement of cement with GCFS on the 28-d and 56-d compressive strength of concrete. The results showed that temperature and % GCFS content had a statistically significant effect on the concrete performance. Based on Tukey’s honestly significant difference (HSD), the effect of GCFS was found to be statistically non-significant for 4% and 6% GCFS content at 28-d; and 2% and 4% GCFS content at 56-d. The effect of temperature was also found to be statistically non-significant for 600oC and 800oC at 28-d; and 27oC and 600oC; 200oC and 400oC at 56-d

Development of a construction quality assessment tool for houses in South Africa

Housing is a critical socio-economic driver in the vast majority of developing countries, including South Africa. It involves many aspects such as construction quality, affordability, geographic location, long-term financing, and the environment. A key research concern is the quantification of the construction quality of houses and how this may be used to assist in the delivery of better quality houses. This article is based on studies undertaken on housing construction sites in South Africa. A construction assessment tool is developed using principles similar to those used by CONQUAS in Singapore and Malaysia. The tool thus developed is capable of measuring the quality of ‘as-built’ construction elements of a house against national technical standards and specifications, within reasonable time and cost. Studies on the quality of houses were then conducted on 700 houses (two low-income projects and one middle-income project). The results showed that the two low-income projects had average quality scores of 58% and 64%, while the middle-income project scored 80%. Details of the sub-elements of the scores indicated the developmental needs of the contractors involved in the projects. Using the construction quality assessment tool, the government and other authorities can make better informed decisions when awarding contracts. If introduced and implemented correctly, the quality of the houses delivered across the entire housing spectrum can be measured and monitored, and improvement measures put in place. The data collected through this quality assessment tool will be invaluable for national authorities, regulators, and Statistics South Africa to evaluate and report if the housing stock being delivered is consistently improving. Risk assessment studies will assist the regulators in developing proper quality management strategies

Calibration of partial resistance factors for cold-formed steel in South Africa

Abstract: In 2011, the South African Loading Code (SANS 10160) was revised to align with international standards and benchmarked against the Eurocodes. The factors of safety were derived using a target level of reliability of (β = 3.0) as opposed to that used for the Eurocode (β=3.8). This target reliability was in line with the previous code provisions of SANS 10160 and ISO 2394. In this paper, a review of the load factors is made and it is shown that the current factors in the code produce a uniform level of reliability for different dead load ratios. The paper then looks at the development of the resistance factors for cold-formed steel for South Africa. The South African materials standard for cold-formed steel (SANS 10162-2) was adopted from the Australian-New Zealand (AS/NZS) standard and hence requires a calibration against the South African Loading Code. An investigation is made in the variation of the safety index with load ratio for different ratios of the mean resistance to the design resistance (�̅/�� = �̅/∅��) using the new load factors in SANS 10160. This is done for different dead, office live and wind loads for a given coefficient of variation. From the results, it is seen that the safety index is reasonably uniform with varying load ratio. For a given set of load factors and load combinations, the uniformity in the safety index will depend, amongst others, on the level of the target safety index and the coefficient of variation of the resistance member. The resistance factors φ for use in the cold-formed steel design are thus recommended

Towards zero emissions and zero poverty in the Global South: a comparative analysis of South Africa, India and Mexico's approach to development and climate change mitigation

Among the foremost challenges of the 21st century are sustainable development and climate change mitigation. In light of these challenges, this thesis seeks to analyse and compare the extent to which development and climate change mitigation are aligned on a policy level in three countries in the global south, namely South Africa, India and Mexico. These three middle-income countries are plagued by high levels of poverty and large inequality gaps, and address the challenge of reducing GHG emissions in this context. The objectives of this study are fourfold: (1) an analysis of each country’s climate change policies mainly its Nationally Determined Contributions and climate response strategies and assesses to which extent development is addressed; (2) analysis of each country’s national development plans and the extent to which climate change mitigation is addressed; (3) based on the initial analysis, assessing the overall extent to which the development and climate policies are aligned; and (4) a comparative analysis of how each country performed in this regard. The study found that South Africa, India and Mexico are in pursuit of lower carbon development in the years to come. Targets for reducing their emissions in light of climate change considerations have been set and sectoral approaches to low carbon development are illustrated to varying degrees. South Africa was found to have done relatively well in integrating development and poverty alleviation into its national climate policy. The detailed analysis presented in the thesis found this at national scale, while a focus on co-benefits was particularly well integrated in Mexico’s and India’s climate policy. Thus the thesis shows that each country could learn or adopt some approaches to alignment from the other – and that there are several benefits associated with aligning development and climate policies. More research would need to be conducted at a finer scale to identify the trade-offs of certain mitigation actions and this information should be used in future national and sectoral development

Determination of land policy in Zimbabwe

A paper presented by a Minister of Lands & Agriculture on Zimbabwe's land policy during the aftermath of independence.This paper which focuses on the determinants of land policy will consist of two sections. The first section will attempt to desribe the background or context in which Zimbabwe’s land policy has evolved since independence in 1980. It will try to show that the formulation of a land policy1 has been more of a process rather than a political event. The ensuing policy has been a result of the interplay of several factors, such as the inherited natural resources, opposed political class interests and economic imperatives. It will be shown that, in trying to meet its political and economic objectives, the Government has had to grapple with several existing constraints, some of which were inherited as part of the previous socio-economic system, while others such as shortage of suitable agricultural land, climate and population were more or less naturally given. The evolving policy can, therefore, be regarded as a pragmatic and reconciliatory attempt to resolve contradictions and conflict in a transition of continuing social and economic struggle. The second section is a brief outline of the actual policy as it has evolved so far in Zimbabwe

Challenges in Implementing Innovative Building Technologies: Housing Case Studies in South Africa

Abstract : t South Africa has come a long way in addressing the housing backlog for the poor and has even taken further steps by providing a regulatory environment for energy efficient houses. The benefits of including energy efficiency are increasingly becoming realized, not only due to reduction in pollution but due to the additional electricity crisis affecting most South Africans. Many challenges, however, lie ahead with finding a balance between eradicating informal settlements and providing energy efficiency measures, taking into account the escalating cost of building materials. The South African regulatory environment provides for the implementation of innovative building technologies (IBT). However, the uptake of these IBTs to assist in fast delivery of houses and social infrastructure is very slow. The aim of this paper is to report on an investigation carried out on a few case studies where IBTs have been used in housing developments, by collating the data from the projects, analysing the challenges and making recommendations. The major challenge identified in the implementation of the IBTs is the construction cost. Cost analysis and comparisons are made in the paper, and it is apparent from the results that the construction costs of IBTs compare favourably with convectional construction. However, for single story units, the cost for implementing IBTs are not significantly reduced. On availability of more data, it is recommended that a more detailed life cycle cost be performed. In addition, a Housing Innovation Maturity Model is proposed in order to unify the understanding and interpretation of “innovation” in housing

Limiting structural damage on masonry structures due to foundation movement

Abstract: Over three million low-income houses have been built in the Republic of South Africa over the last two decades, many of which have experienced structural distress due to foundation movement or poor quality construction. The South African low-income housing sector employs a large number of entry-level ma- terial suppliers and building contractors, and this results in substantial variability of construction materials, technology and workmanship standards. Underpinning the foundation as a remedial solution to low-income houses is very expensive compared to the actual cost of the product (i.e. the house). Alternatively, it may be cost effective to demolish and rebuild the structure. In this paper, cost effective alternative to underpinning is explored using a proprietary type of reinforcement which is grouted to concrete blockwork. The reinforcement and grout act compositely with existing concrete blockwork, both to repair the cracks and to form deep rein- forced masonry beams. This paper covers the initial test programme to investigate and assess the suitability of different reinforcement systems to improve the structural strength and performance of concrete blockwork wall- ing systems. A series of tests were conducted on blockwork wall sections above window and door openings. The material specimens used for the investigation were sampled from a number of construction sites where the quality of the materials varied from site-to-site. The results of the tests showed strength enhancement of the blockwork and an improved ductility

Towards a rational design of composite-deck slabs subject to fatigue load

Abstract: The effect of dynamic loading, in particular fatigue loading, is a major consideration in the analysis and design of various engineering structures. An experimental investigation was conducted on the effect of fatigue loading on composite deck slabs. Composite deck slabs have been used extensively under static loading conditions but with limited use under vibration conditions. In this paper, the focus is on the composite Bond-Dek slab which is formed using a cold-formed steel profile. Composite action between the steel profile and the concrete slab is provided by rolled dimples or embossments that project from the sides of the steel profile. The experimental work involved testing the slabs for ultimate static strength and then subjecting the specimens to various cyclic fatigue load levels. As a result of the study, it appears justified that under static loading, debonding of the steel/concrete interface occurs prior to ultimate load, with failure occurring as a result of shear bond rupture. Fatigue test results have indicated that the composite deck slabs can further be used in structures subjected to fatigue loading. From the experiments, it was observed that the usual S-N curve representation was not appropriate for the results since there was an abrupt transition between the failure and no-failure points, and due to the limited test results. The results are thus represented in a modified Goodman Diagram which makes the rational design approach easier to interpret and implement. The limitation of the experimental test was the type of the steel profile, the loading conditions and the frequency of the applied load, which was limited to 4 Hz

Adaptation or adoption of Eurocode steel design : a comparison with South African standard

Abstract: The globalization of world’s economy combined with the information and communication revo- lution will, without doubt, impact the building and construction industry. For the South African construction industry to be competitive globally, the design engineer has to operate freely across the political and economic boundaries of the world. Contrary to the above, the South African Limit States Steel Design code for hot-rolled steel has not followed the route of European globalization and uniformity like the concrete design. The struc- tural Eurocodes have managed to achieve convergence of a consistent structural design practice in Europe. The aim of this paper is to provide an overview of current developments in hot-rolled structural steel design. These include the formulation of the design principles and a comparison of the load factors, load combination and material resistance factors. The comparison of the material resistance factors is based on reliability indices performed using Monte Carlo simulation. Although the results of the comparison do not show significant dif- ferences, the design formulations in Eurocode are complex, and difficult to follow for a practicing engineer, thus making it difficult to adopt the Eurocode. However, in order to reduce technical barriers to international trade for South African practicing engineers, it is proposed in the paper to adapt the Eurocode with certain simplifications for the South African environment. The proposal includes the use of the material resistance factors calibrated against the current load factors recommended in the South African Loading Code. The Euro- codes, in any case, do allow for countries to use the National Application Document, through “boxed” values

Assessment of the ternary coarse aggregates for economic production of sustainable and low-cost concrete

This paper study the effects of construction and agricultural wastes (CAW) as coarse aggregates in ternary blends on the properties of concrete. A concrete mix ratio of 1:2:4 by weight of cement, sand and granite was adopted with water-cement ratio of 0.50. Five different concrete mixes were prepared in this study; one natural aggregate concrete (NAC) and four concretes with 10%, 20%, 30% and 40% recycled aggregate and 40%, 30%, 20% and 10% palm kernel shell (PKS) contents in reverse order at constant 50% natural coarse aggregate (NCA). The results of slump tests showed an increase in workability as the percentage replacement level of RCA reduces and PKS respectively. The compressive strength of concrete mixes was observed to be less than the strength of lightweight concrete recommended by standards by 23.2%, 28.87%, 31.2%, 43.2% and 45.6% respectively. Based on the result of calculated thermal conductivity, it was observed that as the %RCA content reduces with increasing %PKS content significant amount of energy was saved. Also, an analysis of variance (ANOVA) was carried out to determine the effect of the % replacement and curing period on the compressive strength of concrete. It showed that % replacement had a statistically significant effect on the concrete performance. This type of concrete can be classified as lightweight concrete based on the strength and bulk density