Fidelis Okafor - Academia.edu (original) (raw)

Papers by Fidelis Okafor

Research paper thumbnail of Potentials of Processed Termite as a Stabilizing Agent in Clay Soil

IOSR Journal of Mechanical and Civil Engineering, 2016

Expansive soil causes problem on civil engineering structures due to its tendency to swell when i... more Expansive soil causes problem on civil engineering structures due to its tendency to swell when it is in contact with water and shrinks when they dry out. Stabilization using chemical admixtures is the oldest and popular method of soil improvement. In this study, an investigation was conducted to explore the possibility of using termite dust as stabilizing admixture to improve clay soils. This investigation involves the determination of the swelling potential of clay soil in its natural state as well as when mixed with vary proportion of termite dust from (0 to 30%). The termite dust in this experimental work is obtained from termite mound (anthill), dried and ground followed by sieving through sieve no.36. Consistency limits, specific gravity, swelling properties were determined for the samples. Addition of termite dust decreases liquid limit, plasticity index, plastic limit. shrinkage limit, shrinkage index, specific gravity and activity. Also, the experimental results showed that the swelling percentage decreases and rate of swell increases with increasing percentage of termite dust in clay soils. The rates of swelling and swelling percentage of the stabilized specimens were also affected by curing in a positive direction such that the effectiveness of the stabilizer increases with increasing amount-of stabilizer. The CBR and UCS values obtained also increases with increased percentage of stabilizer. From the research findings, it can be deduced that termite dust at 25%-30% stabilization can be recommended for use in sub-grade pavement layer in road work.

Research paper thumbnail of Microstructural and compaction characteristics of tropical black clay soil subgrade modified with lead-zinc mine tailings

Journal of Environmental Management

Research paper thumbnail of Siltation in Reservoirs

In most recent times, both nation with sound technological background and those without are begin... more In most recent times, both nation with sound technological background and those without are beginning to show great concern on issues related to reservoir siltation, especially those nation with limited available water and those whose water sources are mainly from dams created reservoirs. This research work tries to highlight the implications of siltation on reservoir and consequently its eects on human resources. It is also intended to make known to the general public that though siltation cannot be totally eliminated, it can be controlled by employing some practices. This work goes further to make some recommendations towards minimization of reservoir siltation to a very manageable extent. Calls have been made to the government through various media to assist its populace in combating this nagging problem. It was concluded that sediment maximum accumulation is experienced in reservoir during the periods of maximum low.

Research paper thumbnail of Scheffe's models for optimization of tensile and flexural strength of recycled ceramic tile aggregate concrete

Research paper thumbnail of Modeling the Effect of Contact and Seepage Forces at Equilibrium on the Failure of Water Borehole

Nigerian Journal of Technology, 2015

Research paper thumbnail of Modelling the Effect of Contact and Seepage Forces at Equilibrium on the Failure of Water Borehole

There have been records of failures and quicksand c onditions in boreholes in recent times impedi... more There have been records of failures and quicksand c onditions in boreholes in recent times impeding the performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction problems, drilling inaccuracies, f problems, drilling inaccuracies, f problems, drilling inaccuracies, f problems, drilling inaccuracies, fitting and instal lation problems, some chemical effects within the a quifer medium itting and installation problems, some chemical eff ects within the aquifer medium itting and installation problems, some chemical eff ects within the aquifer medium itting and installation problems, some chemical eff ects...

Research paper thumbnail of Formulation of predictive model for the compressive strength of oyster shell powdercement concrete using Scheffe’s simplex lattice theory

Epitoanyag - Journal of Silicate Based and Composite Materials

Research paper thumbnail of Calibration of Four Nonlinear Failure Envelopes from Triaxial Test Data and Influence of Nonlinearity on Geotechnical Computations

It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity ... more It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate these nonlinear failure envelopes from triaxial test data. Currently only the power-type failure envelope has been studied with an established formal procedure for its determination from triaxial test data. In this paper, a simplified procedure is evolved for the development of four different types of nonlinear envelopes. These are of invaluable assistance in the evaluation of true factors of safety in problems of slope stability and correct computation of lateral earth pressure and bearing capacity. The use of the Mohr-Coulomb failure envelopes leads to an overestimation of the factors of safety and other geotechnical quantities.

Research paper thumbnail of Compressive strength and Scheffe’s optimization of mechanical properties of recycled ceramics tile aggregate concrete

Epitoanyag - Journal of Silicate Based and Composite Materials

Research paper thumbnail of Abandoned projects-implication on the strength of exposed steel and concrete in the Southern region of Nigeria

Nigerian Journal of Technology

This research is centered on the investigation of the implication of abandonment on the strength ... more This research is centered on the investigation of the implication of abandonment on the strength of exposed steel and concrete in an abandoned project; as most abandoned project are continued without due consideration to the current strength of the structural members, which may lead to eventual collapse, if the structural members have failed in strength. Six abandoned project sites were investigated: three in Port Harcourt, Rivers state and the other three in Lagos, Lagos state, Nigeria. Thus limiting the investigation to Southern region of Nigeria where the temperature ranges between 23°C and 32°C and precipitation/rainfall ranged between 36mm and 410mm.The Periods of the abandonment ranges from three to thirty-five years. All structural members were cast in-situ. Visual inspections were carried out on site, rebound hammer test was done, concrete samples were cored and steel reinforcement bars were cut from site. Laboratory test and analysis were carried on te cored samples as well as tensile test carried out on the steel samples. Data obtained from both field and laboratory analysis, were analyzed using Excel regression analysis and a model was obtained to help determine the estimated steel strength of exposed steel reinforcement bars after a period of abandonment in the region considered.

Research paper thumbnail of Models for predicting compressive strength and water absorption of laterite-quarry dust cement block using mixture experiment

Nigerian Journal of Technology

The use of laterite, quarry dust and recycle aggregates etc as replacement for sand in sandcrete ... more The use of laterite, quarry dust and recycle aggregates etc as replacement for sand in sandcrete block production is common trend in developing countries like Nigeria. Most resources and research efforts are committed towards conducting trial test with a view to coming up with mix production that will yield the desired property. This work presents a mathematical model for predicting the compressive strength and water absorption of laterite-quarry dust cement block using augmented Scheffe's simplex lattice design. The statistical models developed can predict the mix proportion that will yield the desired property. The models were tested for lack of fit and found to be adequate.

Research paper thumbnail of Review of the Synthesis of Nano-Sized Ash from Local Waste for Use as Admixture or Filler in Engineering Soil Stabilization and Concrete Production

The synthesis of local nano-sized ash materials from local waste burnt and completely pulverized ... more The synthesis of local nano-sized ash materials from local waste burnt and completely pulverized for use as admixtures or fillers in the stabilization or modification of weak engineering soil and the production of concrete is reviewed and the principles behind this all important aspect of nano technology X-rayed to give geotechnical engineers a clue and new turn in this area. These local waste materials as captured are palm bunch ash, coconut shell ash, palm kernel shell ash, bagasse ash, vehicle tyre ash, engine combustion ash, cigarette ash, fiber glass, pozzolan etc. Over the years, previous researches in the area of soil modification and stabilization of weak engineering soil have shown that remarkable improvement have been recorded in soil stabilization by using these ashes in their macro and micro scales. But in this era of nano technology and advent of nano-materials like nano copper, nano silica, nano carbon, nano aluminate, nano ferrite etc., resulting from chemical synthesis for various engineering uses, there is also the need to look into our readily available waste materials to nano-size the ashes making use of nano-sieves and nano filters and subjecting the collected powder to XRD test. These will lend to the research, parameters like wave length of X-ray (λ), full width of half maximum (β) and X-ray diffraction angle (θ). With these parameters, the average particle size of the powder under study would be determined using Debye-Scherrer’s formula as shown in Equation 1and establish the important fact that the powder belongs to nano-sized particle ranging between 0.1 to 999 nm as either 0-D, 1-D, 2-D or 3-D nanomaterial. In the same vein, the nano-sized particles are used as fillers in the production of concrete which is subjected to strength characteristic tests to establish the improvements on concrete properties. With this approach, local waste materials ash is used at the nano-scale to affect engineering soil for use and improve the strength properties of both soil and concrete.

Research paper thumbnail of Review of the Synthesis of Nano-Sized Ash From Local Waste for Use as Admixture or Filler in Engineering Soil Stabilization and Concrete Production

Research paper thumbnail of Waste Concrete as a Source of Aggregate for New Concrete

Three concrete mixes of widely differing water cement ratios were made using crushed waste concre... more Three concrete mixes of widely differing water cement ratios were made using crushed waste concrete as coarse aggregate. The properties investigated include the physical properties of the recycled aggregate, the compressive and flexural strengths of the concrete. The se properties were compared with those of similar concrete specim ens made with conventional natural aggregate. Also tested was the compressive strength of concrete cubes cut from the waste concrete. Results of the tests suggest that the strength of concrete made from recycled waste concrete aggregate is dependent on the strength of the original concrete from which the recycled aggregate is derived. It is concluded that recycled aggregate can be used to produce quality concrete when the strength of concrete required is not greater than the strength of the original concrete from which the recycled aggregate is derived.

Research paper thumbnail of Siltation in Reservoirs

In most recent times, both nation with sound technological background and those without are begin... more In most recent times, both nation with sound technological background and those without are beginning to show great concern on issues related to reservoir silta-tion, especially those nation with limited available water and those whose water sources are mainly from dams created reservoirs. This research work tries to highlight the implications of siltation on reservoir and consequently its effects on human resources. It is also intended to make known to the general public that though siltation cannot be totally eliminated, it can be controlled by employing some practices. This work goes further to make some recommendations towards minimization of reservoir siltation to a very manageable extent. Calls have been made to the government through various media to assist its populace in combating this nagging problem. It was concluded that sediment maximum accumulation is experienced in reservoir during the periods of maximum flow.

Research paper thumbnail of Performance of Recycled Asphalt Pavement as Coarse Aggregate in Concrete

Recycled asphalt pavement (RAP) is the reclaimed and reprocessed pavement material containing asp... more Recycled asphalt pavement (RAP) is the reclaimed and reprocessed pavement material containing asphalt and aggregate. Most RAP is recycled back into pavements, and as a result there is a general lack of data pertaining to the mechanical properties for RAP in other possible applications such as Portland cement concrete. In the present study, some mechanical properties of Portland cement concrete containing RAP as coarse aggregate were investigated in the laboratory. Six concrete mixes of widely differing water/cement ratios and mix proportions were made using RAP as coarse aggregate. The properties tested include the physical properties of the RAP aggregate, the compressive and flexural strengths of the concrete. These properties were compared with those of similar concretes made with natural gravel aggregate. Results of the tests suggest that the strength of concrete made from RAP is dependent on the bond strength of the “asphalt-mortar” (asphalt binder-sand-filler matrix) coatings o...

Research paper thumbnail of Modeling of the Effect of Critical Seepage Force on the Aquifer Soil Medium of a Borehole

There have been records of failures and quicksand conditions in boreholes in recent times impedin... more There have been records of failures and quicksand conditions in boreholes in recent times impeding the performance and operation of boreholes which may have resulted from various factors ranging from construction problems, drilling inaccuracies, fitting and installation problems, some chemical effects within the aquifer medium etc, but it has been ignored that the beneficial factor to the operation of water boreholes; seepage force could get to a considerable value that it becomes unsafe for the well operation thereby causing dislodgement of sand particles and sandstones from the wall of the borehole and the flow paths to the extent that sandstones experience boiling. The scouring of the particles collected at the wall of the transport pipe could damage the installations which is a huge financial loss to the owners of these facilities. Moreover, when soil particles flow, it makes the yield a poor one hence this research works to investigate the contribution of seepage force to the f...

Research paper thumbnail of Portland Cement/Quarry Dust Improvement of Olokoro Laterite for Road Base

Olokoro lateritic soil for use as base course material when stabilized with Portland cement using... more Olokoro lateritic soil for use as base course material when stabilized with Portland cement using quarry dust as admixture was studied. The soil used for the study was an A-2-6 soil base on AASHTO classification and GP (poorly graded) on USCS. The olokoro soil and constituent of the stabilization and admixture procedure were studied under varying proportions of both portland cement and quarry dust thus 0% as control on materials and 3%, 6%, and 9% for cement and 15%, 30%, 45% and 60% for quarry dust by weight of dry soil. The soil sample was subjected to soil classification test, compaction test, atterberg limit test, CBR test and unconfined compressive strength test. Results show that the gradation of soil is narrow from the particle size analysis. Liquid limit, plastic limit, plasticity index and maximum dry density (MDD) decreases with increase in quarry dust content in all the cement proportions used. Unconfined compressive strength increased with quarry dust content for all the...

Research paper thumbnail of The Performance of Cassava Flour as a Water -Reducing Admixture for Concrete

The performance of cassava flour as a water reducing admixture in concrete was investigated. Four... more The performance of cassava flour as a water reducing admixture in concrete was investigated. Four concrete mixes of widely differing water/cement ratios were made and each of the mixes contained three different dosage levels of cassava flour as admixtur e. The properties tested include workability of the fresh concrete, saturated density and compressive strength of the hardened concrete. These properties were compared with those of similar concrete mixes made without admixture. It was observed that cas sava flour has appreciable fluidifying action in the fresh concrete so that, under appropriate conditions, it either considerably improved the workability of the fresh concrete at normal water content or permitted a water reduction of at least 8% to be made while maintaining a given workability. Results of the tests also show that the 28 day compressive strength of concretes containing cassava flour admixture i s higher than those of control concretes and that the compressive strength...

Research paper thumbnail of Palm kernel shell as a lightweight aggregate for concrete

Cement and Concrete Research, 1988

These concrete mixes of widely differing water/cement ratios were made using palm kernel shell as... more These concrete mixes of widely differing water/cement ratios were made using palm kernel shell as course aggregate. The properties tested include the physical properties of the shell, the compressive, flexural and tensile splitting strengths of the concrete. These properties ...

Research paper thumbnail of Potentials of Processed Termite as a Stabilizing Agent in Clay Soil

IOSR Journal of Mechanical and Civil Engineering, 2016

Expansive soil causes problem on civil engineering structures due to its tendency to swell when i... more Expansive soil causes problem on civil engineering structures due to its tendency to swell when it is in contact with water and shrinks when they dry out. Stabilization using chemical admixtures is the oldest and popular method of soil improvement. In this study, an investigation was conducted to explore the possibility of using termite dust as stabilizing admixture to improve clay soils. This investigation involves the determination of the swelling potential of clay soil in its natural state as well as when mixed with vary proportion of termite dust from (0 to 30%). The termite dust in this experimental work is obtained from termite mound (anthill), dried and ground followed by sieving through sieve no.36. Consistency limits, specific gravity, swelling properties were determined for the samples. Addition of termite dust decreases liquid limit, plasticity index, plastic limit. shrinkage limit, shrinkage index, specific gravity and activity. Also, the experimental results showed that the swelling percentage decreases and rate of swell increases with increasing percentage of termite dust in clay soils. The rates of swelling and swelling percentage of the stabilized specimens were also affected by curing in a positive direction such that the effectiveness of the stabilizer increases with increasing amount-of stabilizer. The CBR and UCS values obtained also increases with increased percentage of stabilizer. From the research findings, it can be deduced that termite dust at 25%-30% stabilization can be recommended for use in sub-grade pavement layer in road work.

Research paper thumbnail of Microstructural and compaction characteristics of tropical black clay soil subgrade modified with lead-zinc mine tailings

Journal of Environmental Management

Research paper thumbnail of Siltation in Reservoirs

In most recent times, both nation with sound technological background and those without are begin... more In most recent times, both nation with sound technological background and those without are beginning to show great concern on issues related to reservoir siltation, especially those nation with limited available water and those whose water sources are mainly from dams created reservoirs. This research work tries to highlight the implications of siltation on reservoir and consequently its eects on human resources. It is also intended to make known to the general public that though siltation cannot be totally eliminated, it can be controlled by employing some practices. This work goes further to make some recommendations towards minimization of reservoir siltation to a very manageable extent. Calls have been made to the government through various media to assist its populace in combating this nagging problem. It was concluded that sediment maximum accumulation is experienced in reservoir during the periods of maximum low.

Research paper thumbnail of Scheffe's models for optimization of tensile and flexural strength of recycled ceramic tile aggregate concrete

Research paper thumbnail of Modeling the Effect of Contact and Seepage Forces at Equilibrium on the Failure of Water Borehole

Nigerian Journal of Technology, 2015

Research paper thumbnail of Modelling the Effect of Contact and Seepage Forces at Equilibrium on the Failure of Water Borehole

There have been records of failures and quicksand c onditions in boreholes in recent times impedi... more There have been records of failures and quicksand c onditions in boreholes in recent times impeding the performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction performance and operation of boreholes which may ha ve resulted from various factors ranging from const ruction problems, drilling inaccuracies, f problems, drilling inaccuracies, f problems, drilling inaccuracies, f problems, drilling inaccuracies, fitting and instal lation problems, some chemical effects within the a quifer medium itting and installation problems, some chemical eff ects within the aquifer medium itting and installation problems, some chemical eff ects within the aquifer medium itting and installation problems, some chemical eff ects...

Research paper thumbnail of Formulation of predictive model for the compressive strength of oyster shell powdercement concrete using Scheffe’s simplex lattice theory

Epitoanyag - Journal of Silicate Based and Composite Materials

Research paper thumbnail of Calibration of Four Nonlinear Failure Envelopes from Triaxial Test Data and Influence of Nonlinearity on Geotechnical Computations

It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity ... more It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate these nonlinear failure envelopes from triaxial test data. Currently only the power-type failure envelope has been studied with an established formal procedure for its determination from triaxial test data. In this paper, a simplified procedure is evolved for the development of four different types of nonlinear envelopes. These are of invaluable assistance in the evaluation of true factors of safety in problems of slope stability and correct computation of lateral earth pressure and bearing capacity. The use of the Mohr-Coulomb failure envelopes leads to an overestimation of the factors of safety and other geotechnical quantities.

Research paper thumbnail of Compressive strength and Scheffe’s optimization of mechanical properties of recycled ceramics tile aggregate concrete

Epitoanyag - Journal of Silicate Based and Composite Materials

Research paper thumbnail of Abandoned projects-implication on the strength of exposed steel and concrete in the Southern region of Nigeria

Nigerian Journal of Technology

This research is centered on the investigation of the implication of abandonment on the strength ... more This research is centered on the investigation of the implication of abandonment on the strength of exposed steel and concrete in an abandoned project; as most abandoned project are continued without due consideration to the current strength of the structural members, which may lead to eventual collapse, if the structural members have failed in strength. Six abandoned project sites were investigated: three in Port Harcourt, Rivers state and the other three in Lagos, Lagos state, Nigeria. Thus limiting the investigation to Southern region of Nigeria where the temperature ranges between 23°C and 32°C and precipitation/rainfall ranged between 36mm and 410mm.The Periods of the abandonment ranges from three to thirty-five years. All structural members were cast in-situ. Visual inspections were carried out on site, rebound hammer test was done, concrete samples were cored and steel reinforcement bars were cut from site. Laboratory test and analysis were carried on te cored samples as well as tensile test carried out on the steel samples. Data obtained from both field and laboratory analysis, were analyzed using Excel regression analysis and a model was obtained to help determine the estimated steel strength of exposed steel reinforcement bars after a period of abandonment in the region considered.

Research paper thumbnail of Models for predicting compressive strength and water absorption of laterite-quarry dust cement block using mixture experiment

Nigerian Journal of Technology

The use of laterite, quarry dust and recycle aggregates etc as replacement for sand in sandcrete ... more The use of laterite, quarry dust and recycle aggregates etc as replacement for sand in sandcrete block production is common trend in developing countries like Nigeria. Most resources and research efforts are committed towards conducting trial test with a view to coming up with mix production that will yield the desired property. This work presents a mathematical model for predicting the compressive strength and water absorption of laterite-quarry dust cement block using augmented Scheffe's simplex lattice design. The statistical models developed can predict the mix proportion that will yield the desired property. The models were tested for lack of fit and found to be adequate.

Research paper thumbnail of Review of the Synthesis of Nano-Sized Ash from Local Waste for Use as Admixture or Filler in Engineering Soil Stabilization and Concrete Production

The synthesis of local nano-sized ash materials from local waste burnt and completely pulverized ... more The synthesis of local nano-sized ash materials from local waste burnt and completely pulverized for use as admixtures or fillers in the stabilization or modification of weak engineering soil and the production of concrete is reviewed and the principles behind this all important aspect of nano technology X-rayed to give geotechnical engineers a clue and new turn in this area. These local waste materials as captured are palm bunch ash, coconut shell ash, palm kernel shell ash, bagasse ash, vehicle tyre ash, engine combustion ash, cigarette ash, fiber glass, pozzolan etc. Over the years, previous researches in the area of soil modification and stabilization of weak engineering soil have shown that remarkable improvement have been recorded in soil stabilization by using these ashes in their macro and micro scales. But in this era of nano technology and advent of nano-materials like nano copper, nano silica, nano carbon, nano aluminate, nano ferrite etc., resulting from chemical synthesis for various engineering uses, there is also the need to look into our readily available waste materials to nano-size the ashes making use of nano-sieves and nano filters and subjecting the collected powder to XRD test. These will lend to the research, parameters like wave length of X-ray (λ), full width of half maximum (β) and X-ray diffraction angle (θ). With these parameters, the average particle size of the powder under study would be determined using Debye-Scherrer’s formula as shown in Equation 1and establish the important fact that the powder belongs to nano-sized particle ranging between 0.1 to 999 nm as either 0-D, 1-D, 2-D or 3-D nanomaterial. In the same vein, the nano-sized particles are used as fillers in the production of concrete which is subjected to strength characteristic tests to establish the improvements on concrete properties. With this approach, local waste materials ash is used at the nano-scale to affect engineering soil for use and improve the strength properties of both soil and concrete.

Research paper thumbnail of Review of the Synthesis of Nano-Sized Ash From Local Waste for Use as Admixture or Filler in Engineering Soil Stabilization and Concrete Production

Research paper thumbnail of Waste Concrete as a Source of Aggregate for New Concrete

Three concrete mixes of widely differing water cement ratios were made using crushed waste concre... more Three concrete mixes of widely differing water cement ratios were made using crushed waste concrete as coarse aggregate. The properties investigated include the physical properties of the recycled aggregate, the compressive and flexural strengths of the concrete. The se properties were compared with those of similar concrete specim ens made with conventional natural aggregate. Also tested was the compressive strength of concrete cubes cut from the waste concrete. Results of the tests suggest that the strength of concrete made from recycled waste concrete aggregate is dependent on the strength of the original concrete from which the recycled aggregate is derived. It is concluded that recycled aggregate can be used to produce quality concrete when the strength of concrete required is not greater than the strength of the original concrete from which the recycled aggregate is derived.

Research paper thumbnail of Siltation in Reservoirs

In most recent times, both nation with sound technological background and those without are begin... more In most recent times, both nation with sound technological background and those without are beginning to show great concern on issues related to reservoir silta-tion, especially those nation with limited available water and those whose water sources are mainly from dams created reservoirs. This research work tries to highlight the implications of siltation on reservoir and consequently its effects on human resources. It is also intended to make known to the general public that though siltation cannot be totally eliminated, it can be controlled by employing some practices. This work goes further to make some recommendations towards minimization of reservoir siltation to a very manageable extent. Calls have been made to the government through various media to assist its populace in combating this nagging problem. It was concluded that sediment maximum accumulation is experienced in reservoir during the periods of maximum flow.

Research paper thumbnail of Performance of Recycled Asphalt Pavement as Coarse Aggregate in Concrete

Recycled asphalt pavement (RAP) is the reclaimed and reprocessed pavement material containing asp... more Recycled asphalt pavement (RAP) is the reclaimed and reprocessed pavement material containing asphalt and aggregate. Most RAP is recycled back into pavements, and as a result there is a general lack of data pertaining to the mechanical properties for RAP in other possible applications such as Portland cement concrete. In the present study, some mechanical properties of Portland cement concrete containing RAP as coarse aggregate were investigated in the laboratory. Six concrete mixes of widely differing water/cement ratios and mix proportions were made using RAP as coarse aggregate. The properties tested include the physical properties of the RAP aggregate, the compressive and flexural strengths of the concrete. These properties were compared with those of similar concretes made with natural gravel aggregate. Results of the tests suggest that the strength of concrete made from RAP is dependent on the bond strength of the “asphalt-mortar” (asphalt binder-sand-filler matrix) coatings o...

Research paper thumbnail of Modeling of the Effect of Critical Seepage Force on the Aquifer Soil Medium of a Borehole

There have been records of failures and quicksand conditions in boreholes in recent times impedin... more There have been records of failures and quicksand conditions in boreholes in recent times impeding the performance and operation of boreholes which may have resulted from various factors ranging from construction problems, drilling inaccuracies, fitting and installation problems, some chemical effects within the aquifer medium etc, but it has been ignored that the beneficial factor to the operation of water boreholes; seepage force could get to a considerable value that it becomes unsafe for the well operation thereby causing dislodgement of sand particles and sandstones from the wall of the borehole and the flow paths to the extent that sandstones experience boiling. The scouring of the particles collected at the wall of the transport pipe could damage the installations which is a huge financial loss to the owners of these facilities. Moreover, when soil particles flow, it makes the yield a poor one hence this research works to investigate the contribution of seepage force to the f...

Research paper thumbnail of Portland Cement/Quarry Dust Improvement of Olokoro Laterite for Road Base

Olokoro lateritic soil for use as base course material when stabilized with Portland cement using... more Olokoro lateritic soil for use as base course material when stabilized with Portland cement using quarry dust as admixture was studied. The soil used for the study was an A-2-6 soil base on AASHTO classification and GP (poorly graded) on USCS. The olokoro soil and constituent of the stabilization and admixture procedure were studied under varying proportions of both portland cement and quarry dust thus 0% as control on materials and 3%, 6%, and 9% for cement and 15%, 30%, 45% and 60% for quarry dust by weight of dry soil. The soil sample was subjected to soil classification test, compaction test, atterberg limit test, CBR test and unconfined compressive strength test. Results show that the gradation of soil is narrow from the particle size analysis. Liquid limit, plastic limit, plasticity index and maximum dry density (MDD) decreases with increase in quarry dust content in all the cement proportions used. Unconfined compressive strength increased with quarry dust content for all the...

Research paper thumbnail of The Performance of Cassava Flour as a Water -Reducing Admixture for Concrete

The performance of cassava flour as a water reducing admixture in concrete was investigated. Four... more The performance of cassava flour as a water reducing admixture in concrete was investigated. Four concrete mixes of widely differing water/cement ratios were made and each of the mixes contained three different dosage levels of cassava flour as admixtur e. The properties tested include workability of the fresh concrete, saturated density and compressive strength of the hardened concrete. These properties were compared with those of similar concrete mixes made without admixture. It was observed that cas sava flour has appreciable fluidifying action in the fresh concrete so that, under appropriate conditions, it either considerably improved the workability of the fresh concrete at normal water content or permitted a water reduction of at least 8% to be made while maintaining a given workability. Results of the tests also show that the 28 day compressive strength of concretes containing cassava flour admixture i s higher than those of control concretes and that the compressive strength...

Research paper thumbnail of Palm kernel shell as a lightweight aggregate for concrete

Cement and Concrete Research, 1988

These concrete mixes of widely differing water/cement ratios were made using palm kernel shell as... more These concrete mixes of widely differing water/cement ratios were made using palm kernel shell as course aggregate. The properties tested include the physical properties of the shell, the compressive, flexural and tensile splitting strengths of the concrete. These properties ...