Civil Engineering

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Analysis and Design of a Fully Submerged Underground Water Tank Using the Principle of Beam on Elastic Foundations
(2015) Ajagbe W.O; Ilugbo E.O; Labiran J.O; Ganiyu A.A.
The basic requirement in the design of reinforced water tank is to ensure it is crack free. This research studied the analysis and design of a fully submerged underground reinforced concrete water tank using the principle of beam on elastic foundations. To achieve this, a Microsoft Excel Spreadsheet Design and Analysis Program (MESDAPro) was generated for quick assessment of various moments of the tank, geometrical features and soil conditions for both full and empty conditions of the tank. It was observed that the wall moments, moment at base of wall and base slab moment decreases with increase in soil sub-grade modulus at constant capacity, height and breadth of the tank. However, wall moments, moment at base of wall and base slab moment increases with increase in height of the tank at constant value of sub-grade modulus, tank capacity and breadth. In all the examined cases, the moments obtained are higher when the tank is considered empty than when considered full
ANALYSIS OF PRE-CAST WAFFLE SLABS USING YIELD LINE AND RANKINE GRASHOFF THEORIES
(2012-09) AKINYELE, J. O.
Failure in pre-cast waffle slabs can be attributed to factors like analytical error, poor handling during transportation and placement which factors often lead to partial/total failure of slabs. The conventional method of analysing waffle slabs focuses on the ribs, while the slab portions at the top are avoided. This has led to under reinforcement and subsequent failure of the slab portions that are usually in direct contact with loads. In this study, a method that incorporates both the slab and rib portions in the analysis of pre-cast waffle slabs was therefore developed. Yield Line and Rankine Grashoff Theories (YLRGT) were combined for the analysis of pre-cast waffle slab. Six physical models of waffle slab were developed, each having five replicates, with the following dimensions: W1 (1353 x 430 x 58 mm), W2 (900 x 300 x 50 mm), W3 (1085 x 430 x 58 mm), W4 (407 x 364 x 50 mm), W5 (1312 x 300 x 58 mm) and W6 (860 x 360 x 50mm). Solid slabs of the same size and number designated S1, S2, S3, S4, S5 and S6 served as control. These models were validated using the slabs by testing for failure loads, deflections and crack width. Each slab was subjected to incremental load of 1.0 kN until failure occurred. Maximum bending moments were obtained for slab and rib portions using YLRGT, a finite element based method called ETABS was also used to analyse the slabs and results obtained were subjected to statistical analysis using ANOVA at p= 0.05. The YLRGT analysis of the various physical models (slab portion, transverse and longitudinal ribs) yielded the following bending moments: W1 (5526.0, 34.5, 918.3) Nm, W2 (1122.0, 279.2, 36.5) Nm, W3 (2880.0, 27.2, 619.9) Nm, W4 (590.0, 171.9, 160.9) Nm, W5 (947.0, 37.0, 4.4) Nm and W6 (1276.0, 90.4, 36.2) Nm respectively. The ETABS combined both slab and ribs giving W1 (4729.0) Nm, W2 (581.0) Nm, W3 (3338.0) Nm, W4 (733.0) Nm, W5 (851.0) Nm and W6 (686.0) Nm. Deflections at failure for waffle slab were smaller compared to solid slabs: (W1 = 1.19 and S1 =3.56) mm, (W2 = 3.64 and S2 =9.28) mm, (W3 = 3.90 and S3 =7.44) mm, (W5 = 8.17 and S5 =12.18) mm, (W6 = 3.29 and S6 =3.89) mm with the exception of W4 (6.60 mm) and S4 (6.44mm), where deflection of waffle slab was higher than that of solid slab. Mean deflection of S1 was significantly higher than W1, while S2 was significantly higher than W2. Average crack width for waffle (0.48 mm) and solid slabs (0.99 mm) were significantly different. High crack width in solid slab indicated lower shear strength. The Yield Line and Rankine Grashoff Theories have facilitated the accurate analysis of pre-cast waffle slabs by separating the slab and rib portions.
ANALYSIS OF PRE-CAST WAFFLE SLABS USING YIELD LINE AND RANKINE GASHOFF THEORIES
(2012-09) AKINYELE, J.o
Failure in pre-cast waffle slabs can be attributed to factors like analytical error, poor handling during transportation and placement which factors often lead to partial/total failure of slabs. The conventional method of analyzing waffle slabs focuses on the ribs, while the slab portions at the top are avoided. This has led to under reinforcement and subsequent failure of the slab portions that are usually in direct contact with loads. In this study, a method that incorporates both the slab and rib portions in the analysis of pre-cast waffle slabs was therefore developed. Yield Line and Rankine Grashoff Theories (YLRGT) were combined for the analysis of pre-cast waffle slab. Six physical models of waffle slab were developed, each having five replicates, with the following dimensions: W1 (1353 x 430 x 58 mm), W2 (900 x 300 x 50 mm), W3 (1085 x 430 x 58 mm), W4 (407 x 364 x 50 mm), W5 (1312 x 300 x 58 mm) and W6 (860 x 360 x 50mm). Solid slabs of the same size and number designated S1, S2, S3, S4, S5 and S6 served as control. These models were validated using the slabs by testing for failure loads, deflections and crack width. Each slab was subjected to incremental load of 1.0 kN until failure occurred. Maximum bending moments were obtained for slab and rib portions using YLRGT, a finite element based method called ETABS was also used to analyse the slabs and results obtained were subjected to statistical analysis using ANOVA at p= 0.05. The YLRGT analysis of the various physical models (slab portion, transverse and longitudinal ribs) yielded the following bending moments: W1 (5526.0, 34.5, 918.3) Nm, W2 (1122.0, 279.2, 36.5) Nm, W3 (2880.0, 27.2, 619.9) Nm, W4 (590.0, 171.9, 160.9) Nm, W5 (947.0, 37.0, 4.4) Nm and W6 (1276.0, 90.4, 36.2) Nm respectively. The ETABS combined both slab and ribs giving W1 (4729.0) Nm, W2 (581.0) Nm, W3 (3338.0) Nm, W4 (733.0) Nm, W5 (851.0) Nm and W6 (686.0) Nm. Deflections at failure for waffle slab were smaller compared to solid slabs: (W1 = 1.19 and S1 =3.56) mm, (W2 = 3.64 and S2 =9.28) mm, (W3 = 3.90 and S3 =7.44) mm, (W5 = 8.17 and S5 =12.18) mm, (W6 = 3.29 and S6 =3.89) mm with the exception of W4 (6.60 mm) and S4 (6.44mm), where deflection of waffle slab was higher than that of solid slab. Mean deflection of S1 was significantly higher than W1, while S2 was significantly higher than W2. Average crack width for waffle (0.48 mm) and solid slabs (0.99 mm) were significantly different. High crack width in solid slab indicated lower shear strength. The Yield Line and Rankine Grashoff Theories have facilitated the accurate analysis of pre-cast waffle slabs by separating the slab and rib portions.
ANALYSIS OF TRAFFIC FLOW ON SELECTED TWO-LANE HIGHWAYS IN IBADAN METROPOLIS
(2011-09) AKINTAYO, F.O.
Traffic congestion is a common feature on highways in many cities of theworld, including Ibadan, Nigeria. Previous studies have shown that several mathematical traffic flow models developed to analyse congestion cannot be easily generalised or adapted to varying situations. In addition, validation errors of some models are as high as 60.0 %. In pursuit of the objective of minimising traffic congestion in parts of the Ibadan metropolis, headway simulation models were developed for the analysis of flow on some selected two-lane highways characterised by heavy traffic. Traffic survey was conducted on three purposively selected heavily-trafficked two-lane highways (Total Garden-Agodi Gate, J Allen-Oke Bola and Odo Ona-Apata) in the Ibadan metropolis. Headway modelling approach incorporating the prevailing mroadway, traffic and control conditions was developed. Field data were captured on the three roads with a camcorder between 7.00 a.m. and 6.00 p.m. for a period of six months as specified in the Highway Capacity Manual. Comparison of the modelling result and field headway data were carried out using Kolmogorov-Smirnov (KS) test (p = 0.05). A traffic flow simulator was developed to simulate the different congestion scenarios by varying the minimum and maximum headways. Capacity analysis and validation of the results were carried out using ANOVA methods. Average vehicular flow of 715 ± 3, 970 ± 5 and 1118 ± 9 vph per lane on Total Garden-Agodi Gate, J Allen-Oke Bola and Odo Ona-Apata roads respectively. Eighteen hyperbolic headway scenarios were produced and the highest coefficient of correlation (R2 = 0.92) was recorded at 90 percentile while 0.18, 0.36, 0.50, 0.71, 0.82, and 0.79 were obtained at 1, 10, 30, 50, 70, and 100 percentiles respectively. There was no significant difference between theoretical and field data using Kolmogorov- Smirnov (KS) test (p < 0.05). Also, a total number of 171 congestion scenarios were generated using the traffic flow simulator. Traffic flow varied between 204 and 2376 pcu per lane while headways varied between 1 and 18 seconds. The capacity analysis produced approximated maximum flow rates of 1850, 2865 and 2881 pcu in the two directions of travel for Total Garden-Agodi Gate, J Allen-Oke Bola and Odo Ona- Apata roads respectively. The capacity of Total Garden-Agodi Gate was within the recommended maximum value of 2800 pcu in the two directions of travel for two-lane highways. The results for J Allen-Oke Bola and Odo Ona-Apata roads showed that an additional lane will be required in each direction of travel. The validation of the models on the dualised J Allen-Oke Bola road showed that congestion can be reduced by about 55.0 %. A maximum validation error of 35.0 % was obtained. The traffic flow simulator developed successfully simulated the traffic situations on the selected highways. The analysis of the flow yielded results that could ameliorate traffic congestion on the selected two-lane highways in the Ibadan metropolis.
Appropriate Simulation Technique for Complete Single-Bolt Shear Connection Shear-Out Tensile Properties and Fracture Behavior Predictions (2
(2019) Adewole K.K.; Ajagbe W.O.
This paper presents the finite element (FE) predictions of the complete S235, S690, Q550D, Q690D and Q890D steel grades steel sheet single-bolt shear connections shear-out (SBSCSO) behavior (tensile properties and fracture behavior). This work reveals that the FE elastic–plastic simulations without the damage and fracture model generally employed in the literature for SBSCSO failure predictions cannot predict the post-ultimate-load damage behavior, fracture initiation by elements removal and sudden drops in load required for determining the SBSCSO displacement at fracture. Consequently, the FE simulation without the damage and fracture model cannot accurately predict the complete SBSCSO tensile properties and fracture behavior. In particular, the FE simulation without the damage and fracture model cannot predict the SBSCSO displacement at fracture required for the seismic and fracture-resistant designs needed for the prevention of the failure of single-bolt shear connections that exhibit the shear-out fracture under extreme loading. FE simulation with the elastic, plastic damage and fracture models represents the appropriate simulation technique for the complete SBSCSO tensile properties and fracture behavior predictions.
ASSESSMENT OF CARBON DIOXIDE EXTRACTION IN A SOLID WASTE MANAGEMENT FACILITY, AKURE, NIGERIA
(2016-09) ELEMILE, O. O.
Carbon dioxide (CO2) emissions from solid wastes is a major contributor to the acceleration of global warming. In Nigeria, CO2 capture has been limited to the energy sector only. There is need to explore the reduction of CO2 emissions from solid wastes through appropriate technologies. This study, therefore was designed to assess CO2 extraction by adsorbents in a Municipal Solid Waste (MSW) management facility in Akure, Nigeria. An exploratory study design with an intervention component was adopted. For a year, wastes brought to the MSW facility from three locations viz: markets, residences and roadside, were characterised and quantified monthly. Chemical characteristics of the wastes were determined using standard methods. Carbon-dioxide emissions were estimated from the MSW composition using the Intergovernmental Panel on Climate Change tools. Air CO2 levels were monitored during the dry and wet seasons using a P-Sense Plus CO2 meter AZ-7755(PSPCM) and seasonal variations computed. A CO2 extractor which uses adsorbents consisting of Sawdust + Potassium Hydroxide (SKH), Sawdust + Sodium Hydroxide (SSH) and Sawdust + Calcium Hydroxide (SCH), all at ratio1:1, was designed and fabricated. The adsorbents were integrated into the equipment to capture CO2 from 5 kg samples of solid wastes burnt under controlled conditions with five replicates for each adsorbents during each test. The potential CO2 in the solid wastes was determined by ultimate analysis, while the concentration of CO2 adsorbed was obtained by finding the difference between the concentration of the CO2 at the inlet and outlet chambers of the extractor measured with the PSPCM. The effectiveness of the extractor combined with the adsorbents was determined by comparing the adsorbed CO2 with the potential CO2. Data were analysed using descriptive statistics and ANOVA at The mean monthly wastes generation from the three locations were 1,004,130.8+742,394.6 kg (biodegradable wastes), 1,322,831.0+810,634.9 kg (plastics) and 1,330,813.5+400,412.4 kg (paper). The mean values for the chemical constituents of these wastes for the three locations, residential, roadside and market respectively were Nitrogen 2.7+0.6, 2.1+0.8 and 3.4+0.7%; Phosphorus 0.10+0.03, 0.10+0.03 and 0.10+0.04% and Carbon 53.2+1.4, 53.1+1.8 and 53.1+1.5%, with no significant difference within the groups. The estimated CO2 emissions was 1.2 Gg/Yr. The ambient CO2 levels ranged between 438.0+7.2 and 630.0+124.5 ppm in the dry season, and 407.3+11.3 and 506.9+71.1 ppm for the wet season. The mean potential CO2 in the solid wastes was 160.0+ 42.0 ppm. The mean CO2 adsorbed were 99.0+24.0 ppm, 45.0+24.1 ppm and 30.0+13.0 ppm for SKH, SSH and SCH respectively. The effectiveness of SKH in the capture of CO2 was 61.9 % as against 20.8 % and 18.8 % by SSH and SCH, respectively. The selected adsorbents were effective in capturing carbon dioxide. Incorporation of Sawdust + Potassium Hydroxide improves the effectiveness of carbon dioxide extraction in the solid waste management facility.
Assessment of Fine Aggregates from Different Sources in Ibadan and Environs for Concrete Production
(2018) AGBEDE O.A.; AJAGBE W.O.
Assessment of natural sand being used as fine aggregate for concrete production in Ibadan and its environs was carried out. Ten sources (F1 – F10) were selected for the study; four (F5, F6, F7, F8) were river sand sources while six (F1, F2, F3, F4, F9, F10) were burrow pit sand sources. Samples from each source were subjected to sieve analysis, atterberg limit, bulk density, specific gravity, water absorption, sand equivalent, clay lumps and friable particles, amount of materials passing 75μm and organic impurities adopting ASTM standard procedures. Results revealed that sand from river sources met all the criteria for concrete production stated in ASTM standard while sand from burrow pits deviated from limits of the standard in some respects. F10 had water absorption of 2.6% which exceeded maximum 2% specified, F9 was not free from clay lumps and friable particles with a significant value of 6% as against 3% maximum specification. F1, F2, F3, F4, F9 and F10 have more amounts of materials passing the 75μm sieve ranging from 10.8% for F9 to 20.1% for F10 than maximum of 5% in standard specification while F1, F9 and F10 showed an indication of having organic impurities. It is recommended that performance test be conducted on concrete made from burrow pits sand before use for concrete production. The knowledge of this study can be used as a prospecting tool for selecting suitable sand for the production of quality concrete.
Assessment of the Impact of Road Dualisation on Adjacent Structures: A Case Study of Iwo-Road – Agodi Gate – Bashorun Road in the Ibadan Metropolis
(2019) Ajagbe W.O; Oladejo O.J; Omiwole D.D
Causes And Prevention Of Erosion In Urban Centres: A Case Of Okeotunu/Sanngo Area Of Ibadan City, Nigeria
(2004) Agbede O.A.; W. O. Ajagbe W.O
The causes of erosion in the study area, Okeitunu/ Sanngo, were investigated via the geology and soil properties of the area, the state of the existing road network and the drainage system, and the solid waste management practice in the local government area. It was revealed that both natural and man made activities contributed to the erosion of the area. Topographical nature of Okeitunu and the inadequate stream channel, in addition to bad environmental sanitation practices, unchecked vegetative removal and lack of enlightenment on the part of the inhabitants on erosion problems are the key factors causing the degradation of the Okeitunu environment. Stabilization of the steep slope, rehabilitation of the existing bare roads and damaged drainage will abate the wearing away of the soil. In addition, the populace needs to be enlightened to know what it takes to initiate or aggravate erosion.
Combined reusing of sorghum husk ash and recycled concrete aggregate for sustainable pervious concrete production
(2022) Tijani, M.A; Ajagbe W.O; Oluwole, A.A
The huge amounts of natural resources and high level of energy consumption in concrete production necessitate the use of agricultural and demolition wastes as alternative construction materials. The present study explores pervious concrete (PC) that includes sorghum husk ash (SHA) and recycled concrete aggregate (RCA) as alternatives to cement and natural aggregate (NA) in standard PC mixtures. PCs were prepared from mixtures derived from replacement levels 0%, 5%, 10%, 15%, 20% and 25% of cement with SHA and 0%, 20%, 40%, 60%, 80% and 100% of NA with RCA. The density, compressive strength and hydraulic properties (void ratio and hydraulic conductivity) of the samples were determined at 28-day using ACI standards. Sustainability efficiency of incorporating SHA and RCA on PC was also investigated using structural efficiency and carbon dioxide (CO2) emission. Their cost effectiveness was equally examined. Results revealed that densities of PC decreased with increase in SHA and RCA amount. Compressive strength and structural efficiency reduced with increase in SHA except at 5% where they were higher than the control. On the other hand, the incorporation of RCA decreased the compressive strength but improved the PC hydraulic properties. CO2 emission and production cost were found reduced with increase in SHA as well as RCA. The maximum reduction of CO2 emission (38.23%) and production cost (51.29%) were obtained when 25% SHA was combined with 100% RCA. The combined usage of SHA and RCA as raw materials in PC was found to be effective in boosting PC’s hydraulic properties at an appropriate compressive strength. The reduction of CO2 discharge and in production cost attributed to the construction materials demonstrates their impacts on mitigating global warming problems and lowering costs of PC production.
Comparative Study on the Design of Elevated Rectangular and Circular Concrete Water Tanks
(2012) AGBEDE O.A.; AJAGBE W.O.
Reinforced concrete overhead water tanks are used to store and supply safe drinking water. Design and cost estimation of overhead water tanks is a time consuming task, which requires a great deal of expertise. This study therefore examines the efficiency of Rectangular and Circular tanks. Tanks of 30m3, 90m3, 140m3 and 170m3 capacities were used in order to draw reasonable inferences on tank’s shape design effectiveness, relative cost implications of tank types and structural capacities. Limit state design criteria were used to generate Microsoft Excel Spreadsheet Design Program, named MESDePro for quick and reliable design. The basic tank’s construction materials- steel reinforcement, concrete and formwork were taken-off from the prepared structural drawings. Results of the material take-offs showed that, for each of the shapes, the amount of each structural materials increase as the tank capacity increases. Also Circular-shaped tank consumed lesser individual material as compared to Rectangular ones. Hence, this will give Circular-shaped tanks a more favoured selection over the rectangular shaped tanks.
Compressive Strength of Concrete Made from Aggregates of Different Sources
(2018) AGBEDE O.A.; AJAGBE W.O.
The use of substandard materials, particularly low quality concrete has been identified in literature as the leading cause of building collapse in Nigeria. The roadside artisans/bricklayers usually produce concrete for building construction without taking the aggregate source into consideration. This paper presents a comprehensive data on the compressive strength of concrete made from aggregates obtained from different sources in Ibadan, Nigeria. Experiments have been performed on 12 mixtures made up of fine aggregate from four sources and coarse aggregate from three different sources. The study utilize cement of the same strength (42.5R), coarse aggregate of the same size (10mm), the same water/cement ratio (0.6), and concrete mix (1:2:4) in order to determine the influence of aggregate source on concrete strength. Result revealed that only five mixtures had above the minimum cube compressive strength of 25N/mm2 recommended for the construction of the reinforced load-bearing building structural members. Three mixtures had above the cube compressive strength of 20N/mm2 recommended for use in plain concrete construction while the rest four mixtures had their cube strength between 19.3N/mm2 and 17.9N/mm2. Fine aggregate with higher compressive strength showed the lesser amount of deleterious materials. It was concluded that the compressive strength depend on aggregate source.
Compressive Strength of Concrete Using Sorghum Husk Ash and Calcium Chloride
(2020) Tijani M.A.; Ajagbe W.O.; Ayininuola G.M.; Dahunsi B.I.O.; Agbde O.A.
This paper investigated the effects of Sorghum Husk Ash (SHA) and Calcium Chloride (CaCl2) on the compressive strength of concrete. Concrete specimens were prepared by partial replacement of cement with SHA (5, 10, 15, 20 and 25% by weight) and addition of 1% CaCl2 by weight of binder; using a constant mix proportion (1:2:4) and water-to-binder ratio (0.6) for all mixtures. The properties evaluated were slump, density and compressive strength. The result indicated that addition of SHA reduced the slump (concrete turn out to be stiffer) and density of concrete. The 28 day compressive strengths result showed that 0%SHA/1%CaCl2 have the maximum strength of 28.11 N/mm2 followed by 5%SHA/1%CaCl2 (26.45 N/mm2), 10% (25.01 N/mm2), 0%SHA/0%CaCl2 (23.11 N/mm2), 15%SHA/1%CaCl2 (22.45 N/mm2), 20%SHA/1%CaCl2 (20.90 N/mm2) and 25%SHA/1%CaCl2 (18.13 N/mm2). This suggests that the best addition of SHA as fractional replacement for cement in CaCl2 concrete is in the range 0 - 20% since their compressive strength results were above 20 N/mm2 target strength. Incorporation of 1%CaCl2 together with 5 and 10%SHA would yield a concrete of greater compressive strength than standard concrete grade 20.
Construction and building materials
(2012) AGBEDE O.A.; AJAGBE W.O.
This study researches into solid waste management in South-West Nigeria in relation to pollution control using a an North as a case study. The generation pattern storage, collection and transportation, and the final disposal of solid waste ocean government are all discussed. Data used for this study were collected by the use of structured questionnaires and oral interviews. Analysis of the data revealed that all the functional elements of solid waste management system in the local government and the city of lbadan in general as practiced by existing institution - Ibadan Solid Waste Management Authority, are engulfed with fundamental problems which apparently have been the reason why institutions are unsuccessful in the efficient management of solid waste and control of environmental pollution. The various problems are identified, analyzed and discussed, pragmatic means of solving the problems, such as the encouragement of waste recycling; the active provision
Determination of appropriate mix ratios for concrete grades using Nigerian Portland-limestone grades 32.5 and 42.5
(2015) Agbede O.A; Ajagbe W.O
The construction of buildings by incompetent craftsmen and the use of low quality building materials, including low quality concrete have been identified in the literature as two of the major reasons for the incessant collapse of building in Nigeria. The roadside craftsmen/artisans usually/generally construct buildings using 1:2:4 cement-fine aggregate-large aggregate mix ratio irrespective of the cement strength class. In this paper, the investigation conducted to determine the appropriate concrete mix ratios required to produce Class 20/25 and Class 25/30 concretes commonly used for design of building structural members using the Portland-limestone cement grades 32.5 and 42.5 that are available in the Nigerian open market is presented. Investigation revealed that the cube compressive strength of 1:2:4 concrete produced with Portland-limestone cement grade 32.5 is less than the minimum 25MPa required for concrete Class 20/25 and a richer 1:1.5:3 concrete produced with Portland-limestone cement grade 32.5 may be needed to produce concrete Class 20/25. Investigation also revealed that Portland limestone cement grade 32.5 may not be suitable for the production of concrete class 25/30 with cube compressive strength of 30MPa as the cube compressive strength of 1:1:2 concrete produced with Portland-limestone cement grade 32.5 may not attain 30MPa. Concrete strength classes 20/25 and class 25/30 can be produced with Portland-limestone cement grade 42.5 using
Development of model to predict the compressive strength of concrete using schmidt hammer
(2016) Ajagbe W. O||Adebisi W.||Ukya, T. J.; Adebisi W.; Ukya, T. J.
In Nigeria and in the world at large, there are recorded cases of building and structural collapse and this is been on the increase. This implies that there is a drastic reduction in the quality assurance of construction processes and stages. Many factors: availability of compression machine and its proximity to the construction site, the technical know how in the operation of the machine, the difficulties associated with conveying concrete cubes from construction sites to the laboratory for testing, the time required for this, and the epilepsy in the power supply needed for the operation of the machine among other factors militate against the assurance of quality control. Therefore, this study considered the possibility of developing a model to predict the compressive strength of concrete using Schmidt hammer. In an attempt to develop a model to predict the compressive strength of different mix proportions, a mix proportion was carried out by the used of the mixture module of the Design Expert 10.0. Three hundred and twenty numbers of 100mm cubes of concrete were cast from the proportioned mixes with a constant water cement ratio of 0.6 and tested at day 7, 14, 21, 28 and 56 by Schmidt hammer and then by the compression strength machine. The data obtained were modeled to forecast the compressive strength of concrete with the used of Response Surface Methodology (RSM). The model was validated using different sets of concrete cubes at day 7, 14, 21, 28 and 56. The resulting two-factor interaction- 2FI model with a confidence level of about 95 % obtained is given as y = 0.40490x1 + 3.29201x2 - 0.030370x1x2- 24.21467.Where, y = compressive strength, x1 = age and x2 = rebound number. The results obtained from the validation of the model revealed that the application of the model in the prediction of compressive strength of concrete has an average of 95.2 % accuracy with very high conservative value and 4.7% deviation from the compression machine’s results. Thus, the application of Schmidt hammer in the prediction of compressive strength is effective and conservative and the results from the model can be employed in the design satisfactorily and the model can be employed in the assurance of quality control in construction sites.
Effect of aggregate type on properties of pervious concreteutajeet
(2019) AGBEDE O.A.; AJAGBE W.O.
Pervious concrete (PC) is a cheap and effective drainage system for reducing storm-water runoff in urban centers. This research aim to investigate the influence of different type of aggregate on PC properties. Three PC mixtures were prepared with different aggregate types [Granite, Gravel and Recycled Concrete Aggregate (RCA)]. Physical and strength characteristics of the aggregates were analyzed. Density, porosity, permeability as well as compressive strength of PC made with these aggregates were measured. Results showed that PC made from RCA has the highest porosity and permeability due to the porous nature of adhered mortar on RCA. However, highest density and compressive strength was obtained from granite PC followed by gravel and then RCA PC. The study concluded that aggregate type has significant influence on PC properties.
EFFECT OF CRUDE OIL CONTAMINATED SAND ON THE ENGINEERING PROPERTIES OF CONCRETE
(2013-01) AJAGBE, W. O.
A considerable fraction of sand in Niger Delta Area of Nigeria is contaminated with crude oil. The contaminated sand is largely utilised by local contractors for the production of concrete. However, there is need to establish its suitability in concreting. Previous works have centered on hardened uncontaminated concrete in crude oil environment but not on concrete made with Crude Oil Contaminated Sand (COCS). This research was designed to evaluate the effect of COCS on some engineering properties of fresh and hardened COCS concrete. Levels of crude oil contamination were determined using gravimetry method of Total Petroleum Hydrocarbon (TPH) test on nine sand samples randomly collected from some oil spill sites in Rivers State. Based on the test results, seven types of artificially contaminated sand were prepared with crude oil levels of 0.0, 2.5, 5.0, 10.0, 15.0, 20.0 and 25.0%. Workability (slump, compacting factor and flow), compressive strength, linear shrinkage, water absorption, and fire resistance were determined using concrete cubes, flexural strength using concrete beams, and surface resistivity using concrete cylinders in accordance with standard methods. Data obtained were analysed using ANOVA at p = 0.05. Eight models were developed using historic response surface methodology to predict the engineering properties of COCS concrete at water-cement ratio (w/c) of 0.5. Also, COCS concrete design mixes with contamination level and w/c ratio suitable for reinforced concrete were formulated. The TPH varied from 8.6 ± 0.2 to 14.1 ± 1.3%. The workability of concrete was improved by the presence of COCS. Slump, compacting factor and flow of the fresh concrete increased with increase in contamination from 30.0 to 200.0 mm, 0.5 to 0.9 and 15.0 to 85.0%, respectively. Compressive strength, flexural strength, linear shrinkage and water absorption of the hardened concrete reduced with levels of contamination from 31.5 ± 2.3 to 3.5 ± 0.0 N/mm2, 5.9 ± 0.8 to 0.1 ± 0.0 N/mm2, 0.1 ± 0.0 to 0.0 cm and 0.2 to 0.0 kg respectively. At a temperature of 200.0˚C, the percentage strength reduction increased from 18.4 to 94.8% for 2.5 to 25.0% contamination. Surface resistivity ranged from 25.1 ± 0.2 to 32.3 ± 0.2 kΩ-cm. The compressive and flexural strengths of COCS concrete were reduced by more than 50.0% at crude oil contamination level greater than 10.0%. The water absorption and surface resistivity values indicated that COCS concrete exhibited greater resistance to water and chloride penetration respectively, it shrank less when compared with the uncontaminated concrete, but exhibited poor fire resistance. Coefficient of determination, R2, of the models developed ranged from 0.823 to 0.999. Concrete design mix ratio of 1part of cement to1.6 part of COCS (10.0% crude oil) to 2.4 part of coarse aggregate was found to be appropriate at 0.45 w/c. This mix gave minimum compressive strength of 21.0 N/mm2 which is acceptable for reinforced concrete structures. Concretes produced with sand contaminated with less than ten percent crude oil were found suitable for use in low strength structures. Mix re-design using lower w/c improved the strength of the concrete.
Effect of crude oil impacted sand on the properties of concrete.
(2012) Ajagbe W.O.; Agbede O.A.; Dahunsi B.I.O
This study investigates the effect of Crude Oil Impacted Sand (COIS) on some engineering properties of fresh and hardened concrete. Total Petroleum Hydrocarbon (TPH) test was carried out on samples from the study area to determine the level of crude oil contamination. Based on the test results, six levels (2.5%, 5%, 10%, 15%, 20% and 25%) of artificial contaminated sand were prepared and engineering properties including slump, compacting-factor, flow-table, compressive-strength, flexural-strength, water-absorption, linear-shrinkage, surface-resistivity, and fire resistance were determined using standard methods. Predictive models were developed and concrete mixes were designed using COIS for reinforced concrete stuctures. TPH of the soil samples varied from 8.6 to 14.1%. The slump, compacting factor, flow-table, and surface-resistivity of the COIS concrete increased with levels of contamination. Compressive-strength, flexural-strength, shrinkage, water absorption and fire-resistance of the COIS concrete reduced with increased level of contamination. Coefficient of determination, R2, of the models ranged from 0.823 to 0.998. Mix ratio of 1: 1.6 : 2.4 of cement : COIS: coarse aggregate was found to be appropriate at 0.45 w/c. The Crude Oil Impacted Sand concrete with not more than 10% contamination is suitable for use in low strength structures
Effect of the portland-limestone cement grades on the compressive strength of hollow sandcrete blocks
(2014) Agbede O.A.; Ajagbe W.O.
The commercial sandcrete block makers in Nigeria use the same cement-sand mix ratio for sandcrete blocks production irrespective of the cement grade. Investigation revealed that the compressive strengths of hollow sandcrete blocks produced with Portland-limestone cement grade 42.5 are higher than the sandcrete blocks produced with cement grade 32.5. The use of stronger sandcrete blocks produced with cement grade 42.5 will ensure the construction of stronger buildings and other sandcrete blocks-based infrastructures and reduce the incessant failure of building and other sandcrete blocks-based infrastructures in Nigeria at no additional cost as both cement grades cost the same amount in Nigeria. It is recommended that the Standards Organisation of Nigeria should create grassroots awareness on the different cement grades in Nigeria and specify that Portland-limestone cement grade 42.5 be used for sandcrete blocks production.