Department of Structural and Construction Engineering

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    Alternative clay bricks inspired from termite mound biomimicry
    (Elsevier, 2022-06) Sanga, Reuben; Kilumile, Mernad; Mohamed, Fatma
    As the world is witnessing vast pollution during material production, construction and demolition processes of buildings there is a need to seek for alternative materials that will reduce the environmental impact. The present study borrows inspirations from termite’s technique to create a material for constructing a naturally cemented mound structure. The studied termite mound was built from a mix of soil particles and termites saliva containing mucopolysaccharides and cellulase enzyme that digests cellulose into beta-glucose or shorter polysaccharides and oligosaccharides. These polysaccharides are found to be a source of soil stabilization and gluing property. In the process to mimic termites’ activities clay bricks were produced from a mix of clay soil and cassava flour in a form of hot cassava paste as a source of polysaccharides at 1.5%, 3%, 4.5% and 6% weight of soil. Brick samples created presented an optimal value at 1.5% cassava flour with compressive strength higher than that of burnt clay bricks at 4.28 MPa.
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    Verification of Pavement Marking Degradation Models Using Eastern Tennessee Pavement Marking Retroreflectivity Data
    (IEEE, 2014) Onyango, Mbakisya A.; Malyuta, Daniel A.; Owino, Joseph; Chimba, Deo
    Pavement markings are lines/markings drawn on pavement surface to provide vital information to road users pertaining to lane restrictions and vehicle movements, which if adhered to, results into improved road users' safety. For the pavement markings to be useful they ought to be reflective. Pavement markings retroreflectivity is a measurement of how well the markings can be seen by road users, especially at night. Pavement marking retroreflectivity is measured in milli-candela per square meter per lux (mcd/m2/lux). Candela is a measurement of light intensity and lux is measurement of luminous light per square meter. The USA Federal Highway Administration (FHWA) in the Manual on Uniform Traffic Control Devices (MUTCD) recommends minimum retroreflectivity levels on different types of pavements. Pavement markings retroreflectivity degrade as a function of time, environmental condition and number traffic repetition after its application. There have been several studies that were conducted to establish trends and time it takes for pavement markings to stay above the threshold. Some of the studies published degradation models. This paper seeks to verify the published pavement marking degradation models using pavement retroreflectivity data collected from East Tennessee. The models selected for verification are published by Lee et. al., Aboud and Bowman , Sarasua et. al., and Sitzabee at. al. From these models, the model by Abboud and Bowman for white paint pavement markings had the highest R2; other models have published R2 values that are larger than what was obtained from this study. The model by Lee,
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    Analysis of Factors Affecting Pavement Markings and Pavement Marking Retroreflectivity in Tennessee Highways
    (University of Tennessee at Chattanooga, 2015) Malyuta, Daniel A.
    Pavement markings are lines drawn on a pavement surface to provide vital information to road users pertaining to lane restrictions and vehicle movements, which if adhered to, results in improved safety and smooth travelling to road users. Pavement markings’ visibility is quantified into a parameter called retroreflectivity, which is a measure of how well the markings can be seen by road users. The importance of the factors affecting pavement markings differs from one publication to another, which cause the effective management of pavement markings a difficult process. In addressing this concern, this thesis investigated factors affecting pavement markings and marking retroreflectivity in Tennessee highways using retroreflectivity data collected on asphalt highways. Quantifiable factors affecting pavement markings retroreflectivity are analyzed, and linear degradation models are developed using regression analysis. The analysis shows that age and traffic have significant impacts on pavement marking retroreflectivity degradation.
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    Review of Different Construction and Building Materials used before 21st Century in Africa Compared to the Present Situation after 21st Century
    (2013) Khalafalla, Mohamed; Malyuta, Daniel A.; Wu, Weidong
    Building materials are any materials which used for a construction purpose. Many of these materials are naturally occurring substances, such as clay, sand, wood and rocks. Also twigs and leaves have been used to construct buildings especially in many African developing countries up to date. Apart from naturally occurring materials, many manmade products are in use, some more and some less synthetic. The goal of this project is to investigate and to make the review of different materials used in building and construction of different civil engineering infrastructures before 21st Century, specifically in Africa continent. To review their general properties and effectiveness, to compare the previous and present situations on these materials, and to give out the overview of the expected building and construction materials which have to be considered in the future time.
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    Management of Pavement Network Maintenance and Rehabilitation Planning Using Shuffled Complex Evolution
    (2007) Mturi, Matiko S.; Shibayama, Tomoya
    This paper presents an approach for optimization of segment-linked maintenance and rehabilitation plan for a pavement network by using shuffled complex evolution. It extends the works of Nunuo and Agyei (2000) by improving the exploration-exploitation balance of the algorithm and by using a realistic pavement deterioration model to solve the problem of multiple maintenance and rehabilitation activities. An example to maximize the serviceability of the road network under a fixed budget and minimum serviceability level policy is also presented. The result of the optimization process using a part of Kanagawa prefecture road network showed very good results with reasonable computational times.
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    Proposal of Simple Pavement Deterioration Model by Using In-Service Survey Data
    (2007-07) Mturi, Matiko S.; Shibayama, Tomoya
    In this paper a nonlinear deterministic flexible pavement performance model is presented. The model uses the maintenance control index calculated from in-service condition survey data as its independent variable, and pavement characteristics of initial condition, structure and traffic loading as its dependent or explanatory variables. The parameters of the model are estimated using Kanagawa Prefecture Road Network condition survey data. The results of the model show that the model reproduces correctly the actual in-service pavement deterioration trend. This model is simple in its expression, uses a simple estimation method, and uses readily available data, consequently reducing the cost of model estimation. It therefore, suggests a promising avenue for improving the pavement performance prediction and consequently the pavement management system.
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    Pavement Rehabilitation Management: Performance Modeling and Rehabilitation Programming
    (2007-09) Mturi, Matiko S.
    Damage to the pavement begins from the first day of utilization; thus, timely and suitable maintenance rehabilitation are required to prevent substantial pavement damage and premature loss. Pavement management systems are used to developing efficient policies to monitor, maintain and rehabilitate deteriorating pavements. These systems consist of pavement inventory and condition information, pavement performance models, and pavement maintenanca and rehabilitation optimal programmes. This paper develops a pavement performance model, and the maintenance and rehabilitation optimal programme at a network level. The performance model is a non-linear empirical whose parameters are estimated from in-service pavement data. The shuffled complex evolution method is used to develop the optimum programming of the maintenance and rehabilitation at a network level. In both cases, the Kanagawa prefecture road network inventory and condition survey data were used.
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    Comparison of the Properties of Portland Cement and Portland Limestone Cement
    (2010) Mrema, Alex L.
    A study was made in one of the cement factories in Dar es Salaam, Tanzania, where Ordinary Portland Ce-ment (CEM I 42.5N) and Portland limestone cement (PLC) (CEM II/A-L/32.5R) are produced and conform-ing to the Tanzania Standard TZS 727 (Part1): 2002, which is equivalent to EN 197 published by the com-mittee for European normalization (CEN). A comparison was made between the two types of cements in terms of physical, chemical and mechanical properties. It was found out that they all complied with the standards, that there was no significant difference in their setting times and that the Portland cement had higher strengths than the PLC. Also it was observed that there was a slightly lower water demand for the same consistency when compared to OPC and hence there is an improvement of the cohesiveness of a con-crete mix when PLC is used. It was concluded, however, that the two cements are different and that using the two cements interchangeably as is done in Tanzania is wrong because they do not have equivalent strengths and therefore equivalent performance since the PLC is not optimized.
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    Properties of Concrete Made With Portland Limestone Cement Partly Replaced by Rice Husk Ash
    (2011-12) Mrema, Alex L.
    Research was conducted in Tanzania to investigate the properties of a concrete made by a replacement of 0%, 6%, 12% and 18% with RHA in Portland limestone Cement. What was investigated was the influence of the ash on the workability, strength development and water permeability of the concrete. The water/binder ratio was kept constant. The results obtained indicated that workability of the concrete decreases with an increase in ash content and suggests that there is an optimum replacement content which give maximum concrete strength. Beyond this optimum ash content, the strength of the concrete decreases. It was also found out that the permeability of the concrete decreased with an increase in RHA content and this confirmed earlier findings by some researchers that the introduction of RHA in concrete makes the concrete more durable. Other benefits of using RHA in concrete are increased resistance to chemical attack, reduced effects of alkali-silica reactivity, reduced shrinkage rates, increased insulation properties of concrete, reduced amount of plasticizers, and reduced potential for efflorescence. The other obvious advantage of using RHA apart from reduced environmental pollution is the reduction of carbon emission which is associated with the production of Portland cement. Any partial replacement with RHA in Portland cement implies reduced carbon emission which is the cause of global warming and which the world is fighting against.
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    Properties of Boards made from Rice Husk and Portland Cement as Binders and reinforced with Sisal Fibers
    (2013) Mrema, Alex L.
    A research study demonstrated that rice husks can be used to manufacture boards which can be used in low cost housing if bound by Portland limestone cement (CEM II/A-L/ 32.5R) and reinforced with sisal fibers to cater for their brittle behavior and that such boards can provide a substitute for wood panels. Boards made of rice husks and cement in the ratios of 1/3.3, 1/ 3.6 and 1/4 and with sisal fiber reinforcement contents of 0%, 0.4%, 0.5% and 0.8% were prepared and tested for their physical and mechanical properties. The results were compared with standard requirements for boards made with wood based fiber and particle panel materials according to DIN 1101 and ISO 2696 and BS EN 634-2. Results indicate that water absorption and thickness swelling decreased with an increase in fiber content and that there is an optimum rice husk/ cement ratio and fiber content that gives maximum flexural strength and that such boards could be used in low cost housing construction. The use of such boards could be seen as partially solving the problem of global warming and the problem of pollution associated with the disposal of rice husks in developing countries.
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    Feasibility of Lightweight Aggregate Concrete for Structural and Non-Structural Works in Tanzania
    (2013-09) Mrema, Alex L.
    There has been serious land degradation in Tanzania due to extensive exploitation of granite aggregates even in areas where there is plenty of natural lightweight aggregates. Many Engineers have resorted to using normal weight aggregates in construction not only due to the feeling that lightweight aggregates (LWA) are too weak for structural purposes but mainly due to lack of knowledge of the design procedures for lightweight aggregate concrete (LWAC). Structures made of normal weight aggregates have higher dead loads which demand reduced span lengths, deeper structural members, more reinforcement and increased foundation area when compared to those made of LWAC. In Tanzania there are major deposits of LWA in areas of previous volcanic eruptions namely Kilimanjaro, Mbeya and Arusha and these remain largely un-exploited. Research was done to investigate the feasibility of using scoria and pumice aggregates in structural lightweight concrete. The aggregates were obtained from Kilimanjaro and Mbeya respectively. A mix design for grade 20 concrete was performed for both aggregates. It was found out that it was possible to use the scoria aggregates for structural concrete but not the pumice without mineral additives or chemical admixtures. Using pumice aggregates without any additives, the strengths obtained were less than 17 MPa which is the minimum strength acceptable for structural LWAC. It was concluded that the use of scoria aggregates for structural LWAC was feasible and that the pumice aggregates could be used for non-structural LWAC. Further research is required to find alternative deposits of pumice with better strengths for use in structural LWAC as the strengths of these aggregates vary from place to place and even within the same locality. Structural and Construction Engineers in Tanzania are now in a position to design and use LWAC as the design procedures have now been elaborated. The use of light weight aggregates especially in areas where these deposits are present will reduce the current costs of transport of normal weight aggregates from long distances and this will also protect the environment.
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    Modeling Wood in Transverse Compression
    (1994) Pellicane, P. J.; Bodig, Jozsef; Mrema, Alex L.
    A plane-stress, finite element model has been developed to predict the stress distribution in wood members subject to perpendicular-to-grain compression. This model exploits linear-strain, isoparametric triangular elements used in sufficient number to achieve a convergent solution. Model verification was achieved through comparison of numerically obtained deformation predictions with corresponding experimental data obtained from actual test specimens. Twenty-seven specimens were instrumented to determine their deformations at numerous locations. Test materials were sampled from three logs (two engelmann spruce, one western hemlock). Specimens were fabricated with three widely different orthotropic ratios, three geometries (length/depth ratios), and three loading geometries (uniformly distributed load across the entire length, one-half length, and one-quarter length). In total, 377 experimental measurements on 27 specimens were compared to finite element predictions. The results showed that on average the model predicted local deformation to within 5%.
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    Behavior of Wood in Transverse Compression
    (1994) Pellicane, P. J.; Bodig, Jozsef; Mrema, Alex L.
    A finite element analysis program exists to evaluate the stress distribution in wood members subjected to perpendicular-to-grain (transverse) compression. In this study, the program was used to perform parameter studies to evaluate the effects of key variables on the distribution of stresses and the maximum stress concentrations in wood subjected to transverse compression. These variables included: specimen geometry (length/depth), loading geometry (loaded length/specimen length), and material properties (ratio of moduli of elasticity of the wood in the direction of loading/perpendicular to loading). The results showed that a complex state of stress exists in members even when the load is distributed over the entire specimen surface. In particular, numerically-determined stresses nearly 3.5 times the nominal stress were found for certain combinations of input parameters. In addition, an empirically-derived equation is presented that estimates the magnitude of maximum stress concentration as a function of the three parameters investigated. The equation was developed with the use of multiple regression techniques and had a correlation coefficient of 0.958.
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    Earth Building in Tanzania – Use of Soil Stabilized Bricks and Blocks
    (2005-06) Mrema, Alex L.
    This paper presents experimental results of investigations done on the use of stabilized earth (soil) for the manufacture of bricks and blocks. The soil used was clayey sand of low plasticity. Two types of stabilizers were used to make stabilized bricks and these were cement and a combination of cement and lime. Different stabilizer proportions were employed. Results of tests carried on these bricks at 28 days indicate an optimum mix proportion of 7% cement if cement is used alone and an optimum mix proportion of 5% each if a combination of lime and cement is used as a stabilizer. With these stabilizer contents we obtain bricks of strengths of at least 2.5N/mm2 with acceptable functional capabilities in a wall for low cost housing. To make bricks comparable in strength with those made of cement and sand with a minimum strength of at least 3.5N/mm2 for load bearing walls as suggested in the Tanzania Standard, TZS 283:1986, the optimum mix proportion was found to be 8.5% cement and 7% each if cement and lime is used in combination. It is suggested that further research on the effectiveness of the various other stabilizers like bitumen, gypsum, ash/sand, and cow dung is required for the different types of soils commonly found in Tanzania.
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    Assessment of Strength Compliance with Standards for Tanzania Eucalyptus Wood Poles Treated with Copper-Chromium-Arsenic Compounds
    (2007-07) Mrema, Alex L.
    Samples of copper-chromium arsenic compounds (CCA) treated Eucalyptus poles for power transmission were sampled from a lot following Militmy Standard MlL-STD 105D, Single sampling, Tightened Inspection, Acceptable Quality Level (A QL) of 4 as provided for in the South African Standard SABS 754: 1994 from lots containing 151-500 poles. Samples were randomly selected from a lot. Maximum fiber stresses were evaluated taking into account the actual taper in each pole. The cantilever loading test was peiformed on the samples following SABS 754:1994. It was found out that the average taper for the poles was smaller than that assumed in the standard due to the dijJerent pole growth characteristics and environment in Tanzania and that the average modulus of elasticity obtained for the poles was lower than the average assumed in SABS 754: 1994. The poles also showed excessive deflections at working loads. It is recommended to the Tanzania Bureau of Standards that although SABS 754: 1994 ;s meant to be used for eucalyptus poles grown ill Southern Africa south of the Sahara that are treated with creosote or CCA there is a need to review it to take into aCCOl/nt the actual characteristics of the poles grown in Tanzania where they are normally grown in highland areas with higher rainfall and colder climates.
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    Cement Bonded Wood Wool Boards from Podocarpus Spp. For Low Cost Housing
    (2006) Mrema, Alex L.
    This paper gives results of a preliminary study on the properties of cement bonded woodwool boards manufactured as composites by using wood wool (excelsior) from podocarpus spp. wood species and ordinary Portland cement. Two main parameters were varied during the investigation and these were the width of the wood wool and the cement to wood wool ratio. Results show that the optimum mix proportion is three parts of cement to two parts of wood wool by weight and that a smaller excelsior width gives higher board strengths. The results from tests on flexural strength, compressive strength and tensile strength far exceeded the requirements of the German Standard DIN 1101:1989. Results of water absorption and swelling were, however, higher than those specified in the standard but this was attributed to insufficient pressure on the boards during manufacture an anomaly which can be corrected. The potential uses of the boards are in basements, floor units, permanent shuttering, partitioning, sound insulation in walls, ceilings and floors, roofs, sound barriers and thermal insulation. Further research is required to investigate the use of different wood species and different mineral binders.
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    A Kinetic Study of Anaerobic Biodegradation of Food and Fruit Residues during Biogas Generation Using Initial Rate Method
    (Scientific Research, 2013) William, Wanasolo; Manyele, Samwel V.; Makunza, John K.
    A kinetic study of biogas production from Urban Solid Waste (USW) generated in Dar es Salaam city (Tanzania) is presented. An experimental bioreactor simulating mesophilic conditions of most USW landfills was developed. The goal of the study was to generate the kinetic order of reaction with respect to biodegradable organic waste and use it to model biogas production from food residues mixed with fruit waste. Anaerobic biodegradation was employed under temperature range of 28˚C - 38˚C. The main controls were leachate recirculation and pH adjustments to minimize acid inhibitory effects and accelerate waste biodegradation. The experimental setup was comprised of three sets of bioreactors. A biodegradation rate law in differential form was proposed and the numerical values of kinetic order and rate constant were determined using initial rate method as 0.994 and 0.3093 mol0.006·day−1, respectively. Results obtained were con-sistent with that found in literature and model predictions were in reasonable agreement with experimental data.
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    Infrastructural Development in Africa by Use of Suitable Construction Approaches
    (2013) Msinjili, Nsesheye S.; Makunza, John K.; Akindahunsi, Akindehinde A.
    The construction sector generally shows a great contribution to socio-economic development in Africa, and has particularly enhanced the continent’s employment sector over the last few years. The African concrete construction sector is quite different when compared to its European and/or American counterparts. Modern infrastructural development exists in many urban cities in Africa, but this is at variance with rural areas, which tend to have little or no basic amenities such as sound road networks, solid and affordable shelter, and potable water. A large percentage of the construction activities are observed through the informal construction sector which mainly constitutes of cheap labour. This paper gives a basic introduction into the necessities for infrastructural development in Africa with focus on the construction sector. The paper addresses the practised construction activities based on the informal construction sector as well as suggests sustainable construction approaches sufficient for the African rural communities to benefit from the available economy. A better understanding of this sector is required which can help improve the existing methods of construction rather than adopt the construction techniques observed from the developed countries.
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    Analyses of Deteriorating Old Masonry Buildings; Characterisation of Materials for Establishment of their Compatible Repairs
    (2015) Makunza, John K.; Kumaran, Senthil G.
    Most of the Governmental and religious building structures in Rungwe district are masonry structures built during the German East Africa period. These structures are deteriorating despite of various efforts on their repair intervention using modern cements and paints. This paper studies the types of mineral binders used, composition and physical characteristics of these in-situ mortar materials for the purpose of deciding on their appropriate compatible repair materials. Field observations and investigations, laboratory materials testing and review of the literature showed that the in-situ mortar materials constituted of sub-hydraulic lime mineral binders to natural sand (1:3) mortars. Currently there are no producers of hydraulic lime in Africa and a limited production worldwide. Mix design and analysis of locally available hydrated lime plus pozzolana natural sand (1:3) mortar material have shown compatibility in chemical and major physical properties and characteristics with the substrate in-situ hardened sub-hydraulic masonry mortars. Therefore use of these repair mortars is recommended for compatible repairs to these masonry structures and as a regional alternative to cement based materials for low rise masonry structures.
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    Regression Modeling and Analysis of Factor-Interactive Effect on Anaerobic Biodegradation Process for Biogas Generation
    (2014) William, Wanasolo; Manyele, Samwel V.; Makunza, John K.
    In this study, regression modeling and analysis of factor-interactive effect on anaerobic biodegradation process (ABP) of food residues mixed with fruit-waste is presented. An experimental anaerobic digester simulating mesophilic conditions of most urban solid waste dumpsites was developed. The goal was to carry out regression modeling on anaerobic biodegradation process for biogas generation. The main-and interactive-effects of initial-pH, ash-loading and leachate-level were investigated. Response surface methodology with miscellaneous 3-level factorial design was employed. A second-order polynomial regression equation was generated that predicted biogas generation rate (BGR). Results indicated that within the experimental range of factors applied there was a single factor significant effect of initial-pH and ash-loading on ABP while leachate-level single effect was observed to be insignificant (α < 0.05). The two factor interactive-effects of initial-pH/ash-loading and leachate-level/ash-loading were found to be significant while that of initial-pH/leachate-level interactions was not significant. Verification tests yielded maximum BGR values that were in good agreement with predicted values thereby validating the regression model.