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Clamp-firing system is a cost-effective technology used to produce burnt clay bricks in many West African countries including Ghana. However, this firing system generates between 7%- 15% of waste in a form of burnt broken bricks and with... more
Clamp-firing system is a cost-effective technology used to produce burnt clay bricks in many West African countries including Ghana. However, this firing system generates between 7%- 15% of waste in a form of burnt broken bricks and with time creates disposal problems. In this work, burnt clay broken bricks were sampled and pulverised to 75 microns and used as a partial replacement of cement between 10-40 wt. %. Two different sets of mortars were prepared, one from Portland cement as the binder whereas the other set using Portland cement-pulverised bricks as their binders. Compressive strength test was performed on the mortars after moisture exposure at 3, 7 and 28 days. Water absorption test was used to study the pore structure of the optimum mortar mix. The results of the Portland cement-pulverised bricks mortars were compared with the Portland cement mortars. The results of the study indicated that 30 wt.% of the pulverised brick used to replace Portland cement gave the optimum mortar mix. The pore structure of the cement-pulverised brick mortar mixture showed a significant reduction compared to the Portland cement mortars. Si and Al MAS NMR studies revealed that pore structure reduction was due to polymerisation of aluminosilicate hydrates. The study recommends the use of waste powdered burnt clay brick as a supplementary cementitious material and possible means to provide alternative solutions to the disposal of waste burnt broken bricks
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Abstract This study investigated pozzolan from the co-firing of clay and rice husk. Rice husk was used to replace clay at 1.0%, 1.5% and 2.0% and calcined at 800°C. Pozzolanic strength activity index (PSAI) was performed on the calcined... more
Abstract This study investigated pozzolan from the co-firing of clay and rice husk. Rice husk was used to replace clay at 1.0%, 1.5% and 2.0% and calcined at 800°C. Pozzolanic strength activity index (PSAI) was performed on the calcined powder materials in accordance with the ASTM C311 standard. The calcined material that obtained the highest PSAI was selected and used to optimize the calcined pozzolan added to Portland cement. The optimum mixture proportions were used for 29Si and 27Al MAS NMR as well as water sorptivity and shrinkage studies which involved autogeneous and drying shrinkages. The results of the study showed that calcined clay that contained 2.0% rice husk had the optimum PSAI whereas 30 wt.% replacement content was the optimum cement replacement. The 29Si and 27Al MAS NMR showed that the superior strength of the optimum mortar mix to the control was due to a stable monosulphate phase formed at the octahedral environment and the formation of extra calcium aluminosilicate phases in the mortar mix. The initial and secondary sorptivity values of the pozzolan were 0.0055 and 0.0022 mm/sec1/2 respectively, lower than the values of the control , which were 0.0299 and 0.0083 mm/sec1/2 respectively. The shrinkage performances of the Portland cement-pozzolan mix were much enhanced than the unblended mortar mix. The inclusion of the co-fired materials reduced the embodied carbon by approximately 29%. The use of the co-fired material could be a sustainable means to dispose of waste rice husk and also reduce embodied carbon.
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Management of solid waste continues to be a major developmental challenge for developing countries like Ghana. The current focus and attention have been on the collection and dumping of waste in urban communities where generation rate is... more
Management of solid waste continues to be a major developmental challenge for developing countries like Ghana. The current focus and attention have been on the collection and dumping of waste in urban communities where generation rate is high to the detriment of rural communities. In this study, a pilot waste management scheme was undertaken in Assin Kushea, a rural community in the Assin North Municipality, to determine the willingness of the community to sort their waste at source, the quantity of waste generated by the community, and the characteristics of the waste to inform the treatment or disposal options suitable for the community. The results of the study showed that the community generates approximately 20 to 40 kg waste per day which comprises about 77% biological municipal waste (BMW) and 23% of residual waste. Laboratory analysis of the waste showed that the moisture content of the waste was about 68%. The percentage volatile solid was about 85.45%, leaving an ash conte...
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Each year, nearly 40 billion tonnes of raw materials extracted from the Earth’s crust feed into the construction industry. The associated material flows dramatically contribute to anthropogenic CO2 emissions. Therefore, more sustainable... more
Each year, nearly 40 billion tonnes of raw materials extracted from the Earth’s crust feed into the construction industry. The associated material flows dramatically contribute to anthropogenic CO2 emissions. Therefore, more sustainable supply chains must be envisaged based on the use of locally available resources and the principles of circular economy. Drawing inspiration from vernacular architecture, innovative solutions for green construction based on sustainable exploitation of local resources can be posited. This strategy has also inspired the proposed practice of in situ resource utilization on planetary bodies such as the Moon and Mars.
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Cost estimation is particularly difficult, often leading to considerable deviations. For capital projects, especially transport infrastructure projects, deviations hover around an average of 28% of the estimated cost. There are several... more
Cost estimation is particularly difficult, often leading to considerable deviations. For capital projects, especially transport infrastructure projects, deviations hover around an average of 28% of the estimated cost. There are several factors that cause these deviations between the final accounts and the contract sum. How these factors combine to cause deviations between the contract sum and the final account in recent times has been of great concern to construction managers and researchers alike. This study sought to identify the significant factors that result in deviations between contract sums and the final accounts of capital projects. Using a sample size of 45, comprising contractors, consultants, and clients, the factors identified using Relative Important Indices were “price fluctuations,” “late material delivery,” “changes in the scope of work,” “fluctuations in the market demand,” and “changes in design.” Using Kendall’s coefficient of concordance, a coefficientpvalue of ...
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ABSTRACT
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Existing literature has shown that high grade kaolin can be processed into metakaolin to replace portions of Portland cement without compromising the properties of cement-based materials. However, , there is limited literature pertaining... more
Existing literature has shown that high grade kaolin can be processed into metakaolin to replace portions of Portland cement without compromising the properties of cement-based materials. However, , there is limited literature pertaining to the use of clays with low content of kaolinite as a pozzolanic materials, even though lower grade kaolin exists abundantly on the earth crust and in almost every country. This work analyzed clay obtained from Ghana. The clay material was calcined at temperatures ranging from 600C to 1000C. The raw clay characterization was determined based on geotechnical properties and the use of solid state Al Magic angle spinning nuclear magnetic resonance (MAS NMR). Strength activity index prescribed by the American Society for the Testing of Materials (ASTM) was used as a method of determining the appropriate temperature for clay calcination. Sorptivity analysis was determined as a way of checking the durability of cement and calcined clay mixtures. The resu...
The quest for a new-generation concrete, designed to be compatible with the need of mitigating the effect of greenhouse gas emissions on the climate, has prompted applied research to define a broad range of low-CO2 cement-based materials.... more
The quest for a new-generation concrete, designed to be compatible with the need of mitigating the effect of greenhouse gas emissions on the climate, has prompted applied research to define a broad range of low-CO2 cement-based materials. While minimizing CO2 emissions is a goal of the utmost importance, research into sustainable building materials must also tackle the issue of raw material depletion (including limestone, clay and aggregate deposits, as well as water resources) in favor of secondary raw materials. One possible solution is that of minimizing the impact of quarrying by a circular economy approach that envisages the reuse of waste from stone extraction and processing. It is estimated that 200 Mt waste are produced by the stone industry worldwide each year. This includes slurries obtained from the quarrying, cutting and polishing of marble, which can be used as a source of calcium carbonate, alternative to primary limestone. This contribution illustrates the use of wast...
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A thesis submitted in partial fulfilment of the requirements for the award of degree of Doctor of Philosophy in Materials Engineering, 2015
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This study investigated pozzolan from the co-firing of clay and rice husk. Rice husk was used to replace clay at 1.0%, 1.5% and 2.0% and calcined at 800°C. Pozzolanic strength activity index (PSAI) was performed on the calcined powder... more
This study investigated pozzolan from the co-firing of clay and rice husk. Rice husk was used to replace clay at 1.0%, 1.5% and 2.0% and calcined at 800°C. Pozzolanic strength activity index (PSAI) was performed on the calcined powder materials in accordance with the ASTM C311 standard. The calcined material that obtained the highest PSAI was selected and used to optimize the calcined pozzolan added to Portland cement. The optimum mixture proportions were used for 29Si and 27Al MAS NMR as well as water sorptivity and shrinkage studies which involved autogeneous and drying shrinkages. The results of the study showed that calcined clay that contained 2.0% rice husk had the optimum PSAI whereas 30 wt.% replacement content was the optimum cement replacement. The 29Si and 27Al MAS NMR showed that the superior strength of the optimum mortar mix to the control was due to a stable monosulphate phase formed at the octahedral environment and the formation of extra calcium aluminosilicate phas...
In the presence of significant quantities of carbon dioxide (CO2) and elevated temperatures in the atmosphere due to climate change, cement-based materials are susceptible to carbonation. Blended cements are more prone to carbonation... more
In the presence of significant quantities of carbon dioxide (CO2) and elevated temperatures in the atmosphere due to climate change, cement-based materials are susceptible to carbonation. Blended cements are more prone to carbonation attack than Portland cement. There is a need to evaluate the carbonation resistance of blended cements in a carbonation-prone environment. This paper presents experimental findings obtained from an evaluation of carbonation resistance tests on Rice Husk Ash- (RHA-) blended cement. The blended cement was made by intergrinding of Portland Cement (PC) and RHA to make the test cement (PC-RHA). The RHA dosage in the PC-RHA was varied from 0 to 30% by mass of PC. Pozzolanicity, standard consistency, and setting time tests were conducted on PC-RHA. Mortar prisms measuring 160 mm × 40 mm x 40 mm were separately cast at a water/cement ratio ( w / c ) of 0.50 and 0.60 and cured in water for 2, 7, 14, 28, and 90 days. Compressive strength tests were conducted on t...
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Abstract In this study, waste clay bricks were collected, ground and used to replace Portland cement between 10 and 40 wt.%. The optimum cement replacement was obtained using compressive strength whereas the degree of hydration and heat... more
Abstract In this study, waste clay bricks were collected, ground and used to replace Portland cement between 10 and 40 wt.%. The optimum cement replacement was obtained using compressive strength whereas the degree of hydration and heat evolution characteristics investigated using the thermogravimetric analyzer and the isothermal calorimeter respectively. The compressive strength results indicated that the optimum Portland cement replacement with Ground Waste Clay Bricks (GWCB) was at 30 wt.%. This was due to the high degree of pozzolanic reaction in the GWCB-Portland cement system. The heat of hydration of the GWCB-cement system was also lower than the control system. The use of GWCB is recommended as a suitable pozzolan and their use as a pozzolanic material could be a way to redirect waste generated in clamp-fired brick factories in West Africa.
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Abstract Pozzolanic materials are well known to improve the mechanical and durability properties of cement based products including concrete, mortar and paste. This has therefore made pozzolans widely accepted for construction. In this... more
Abstract Pozzolanic materials are well known to improve the mechanical and durability properties of cement based products including concrete, mortar and paste. This has therefore made pozzolans widely accepted for construction. In this work pozzolans were produced from a mixture of clay and palm kernel shells. Thermal gravimetric analyzer (TGA) was used to determine the lime consumption pattern of the calcined clay pozzolan whereas the 29 Si and 27 Al solid state magic angle spinning nuclear magnetic resonance (MAS NMR) was used to determine the aluminate and the silicate phases of the hydrated product. The TGA results showed that the calcined pozzolan containing palm kernel shells had a higher lime consuming pattern than the calcined clay and Portland cement. The 27 Al MAS NMR showed that the calcined clay/palm kernel shell pozzolan produced stable monosulphate compounds at the octahedral environment. The 29 Si MAS NMR results also proved that additional calcium silicate hydrates were formed in the cement containing pozzolan than the Portland cement. The formation of stable monosulphates coupled with formation of additional silicate hydrates are the reasons for strength enhancement of the calcined materials than Portland cement.
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The Ghanaian concrete industry is really a booming industry due to many infrastructural developments and the surge in residential development. However, many developmental projects that utilize concrete do suffer from the negative impact... more
The Ghanaian concrete industry is really a booming industry due to many infrastructural developments and the surge in residential development. However, many developmental projects that utilize concrete do suffer from the negative impact of moisture rise including paint peeling-off, bacterial and fungi growth, and microcracks as well as unpleasant looks on buildings. Such negative outlook resulting from the effects of moisture rise affects the longevity of concrete and hence makes concrete less sustainable. This study seeks to develop materials that could minimize the rise of moisture or ions through concrete medium. The experimental works performed in this study included pozzolanic strength activity index, water sorptivity, and shrinkage test. Calcined clay produced from clay was used as pozzolan to replace Portland cement at 20%. The strength activity test showed that the cement containing the calcined material attained higher strength activity indices than the control. The thermal...
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Cost estimation is particularly difficult, often leading to considerable deviations. For capital projects, especially transport infrastructure projects, deviations hover around an average of 28% of the estimated cost. There are several... more
Cost estimation is particularly difficult, often leading to considerable deviations. For capital projects, especially transport infrastructure projects, deviations hover around an average of 28% of the estimated cost. There are several factors that cause these deviations between the final accounts and the contract sum. How these factors combine to cause deviations between the contract sum and the final account in recent times has been of great concern to construction managers and researchers alike. This study sought to identify the significant factors that result in deviations between contract sums and the final accounts of capital projects. Using a sample size of 45, comprising contractors, consultants, and clients, the factors identified using Relative Important Indices were " price fluctuations, " " late material delivery, " " changes in the scope of work, " " fluctuations in the market demand, " and " changes in design. " Using K...
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Thesis submitted to the Department of Minerals Engineering, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Philosophy, 2009
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Crushed Ghanaian limestone (L) powder was analysed for its physical, chemical and microstructural properties for the formulation of mortar for masonry. Ordinary Portland Cement (OPC) was replaced by 10-40% limestone powder for paste and... more
Crushed Ghanaian limestone (L) powder was analysed for its physical, chemical and microstructural properties for the formulation of mortar for masonry. Ordinary Portland Cement (OPC) was replaced by 10-40% limestone powder for paste and mortar formulation. Mechanical properties that included compressive strength, water demand and setting times (initial and final) were determined and analysed. The mechanical properties were determined in accordance with ASTM standards. The test results indicated that crushed limestone powder contained about 88.7% CaO in calcite form. A 10-30% and 35-40% limestone content in conjunction with OPC was suitable to produce ASTM type M and S mortars respectively. Formulated OPC-L paste showed a high water demand, a delayed initial setting time and an accelerated final setting time than the plain OPC paste.
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The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making... more
The performance of Portland cement in concrete or mortar formation is very well influenced by chemical compositions among other factors. Many engineers usually have little information on the chemical compositions of cement in making decisions for the choice of commercially available Portland cement in Ghana. This work analyzed five different brands of Portland cement in Ghana, namely, Ghacem ordinary Portland cement (OPC) and Portland limestone cement (PLC), CSIR-BRRI Pozzomix, Dangote OPC, and Diamond PLC. The chemical compositions were analyzed with X-Ray Fluorescence (XRF) spectrometer. Student’st-test was used to test the significance of the variation in chemical composition between standard literature values and each of the commercial cement brands. Analysis of variance (ANOVA) was also used to establish the extent of variations between chemical compositions and brand name of the all commercial Portland cement brands. Student’st-test results showed that there were no significan...
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Greener technologies and sustainable developments are currently among the main tools used by many industries in shaping the world for a better future. The construction industry that is known to have numerous negative impact on... more
Greener technologies and sustainable developments are currently among the main tools used by many industries in shaping the world for a better future. The construction industry that is known to have numerous negative impact on sustainability is now wide awake on sustainable measures which can aid in reducing its negative impact. In this work, green cement was produced from pyroprocessed clay (PC) at 800°C and mixed together with Portland cement. This paper presents both laboratory tests and some field applications of green cement application. Laboratory tests performed included setting times, compressive strength, and shrinkage. Field applications of the green cement are shown. Results from the work showed that well-proportioned greener cement gained strengths between 11% and 30% more than Portland cement at standard curing period of 3, 7, 14, and 28 days. However, in real statistical terms, there was no difference between Portland cement and green cement strength performance. Shrin...
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Heat treated low-grade kaolin clays are now considered as a suitable pozzolanic material to metakaolins. However their suitability as a good pozzolanic material depends on the geochemistry and structure of the clay which is usually... more
Heat treated low-grade kaolin clays are now considered as a suitable pozzolanic material to metakaolins. However their suitability as a good pozzolanic material depends on the geochemistry and structure of the clay which is usually influenced by the geographical environment. This study investigated a low-grade kaolin clay from Nyamebekyere in the Ashanti Region of Ghana. The influence of the calcined material on the early and late strength development of Portland cement was analyzed. The early 3- and 7-day strength as well as the late 28-day strength of Portland cement replaced with 20% by weight of the calcined material yielded the optimum strength values. Further analysis using Solid State Magic Angle Spinning Nuclear Magnetic Resonance (Ss MAS NMR) probed into the Aluminium (Al) environment to detect the presence and nature of Al hydrates using the optimum mixture proportion. The Ss MAS NMR results showed that the strength enhancement of the optimum mixture was due to the growth ...