O. M. Olofinnade

Forensic Investigation of Fire-affected Reinforced Concrete Buildings

This study focused on forensic investigation of fire-affected reinforced concrete buildings. Post-fire investigation was conducted on structural elements in three selected fire-affected concrete buildings, in order to ascertain their in situ residual strengths and also to provide data for use in future assessment of fire-affected buildings. The selected sites for investigation include a five-storey building at Alagbaka and a bungalow at Adegbola in Akure, and a ten-storey building in Benin, Nigeria. Rebound hammer and ultrasonic pulse velocity are two non-destructive tests apparatus used for this investigation. Average values of pulse velocity were fitted into an established model in order to estimate the probable temperature, which the buildings were subjected to. Tests were conducted on beams, columns and slabs in both the affected and the unaffected parts of the buildings. From the results, visual examination of the fire-affected buildings revealed changes in the colour of the concrete, delamination of plaster of slab and exposure of reinforcement for severe cases at various locations on the concrete members. In addition, there was notable reduction in the in situ strengths of the fire-affected structural members when compared with the unaffected members. It was deduced that concrete members subjected to temperatures above 600 0 C lost about 70 % of its strength.

Application of Waste Glass Powder as a Partial Cement Substitute towards more Sustainable Concrete Production

Use of waste materials in concrete is now a global trend for efficient waste management so as to achieve a sustainable green environment and with the added advantages of preserving the natural resources as well as producing a better performing concrete. This study examined the properties of concrete containing ground waste glass powder (GP) as partial replacement for cement. The waste glass was finely grounded into powder and the morphology imagery of the powder materials was carried out using scanning electron microscopy (SEM). Moreover, the chemical composition of the glass powdered material was determined using X-ray fluorescence (XRF). Laboratory tests were carried out to determine the strength activity index, workability, split tensile and compressive strength properties of the concrete with 0%, 15%, 18%, 21%, 24%, 27% and 30% partial replacement of cement with the ground waste glass powder. The results showed that the oxides composition of the glass powder meets the requirements for pozzolanic material, while the SEM morphology shows materials of amorphous flaky solid masses, and based on the 28-day strength activity index, concrete containing 21% cement replacement shows a higher strength index above therecommended 75%. It was also observed that workability of the concrete reduced with increase in percentage glass content while significant improvement of the compressive strength of the concrete was achieved at 21% cement replacement, after which a decrease in strength with increasing percentage glass content was observed. The revealed results were confirmed by the microstructural examination using SEM showing a denser concrete at 21% cement replacement but increase porosityas the glass content increases. However, a decrease in split tensile strength was observed with increasing glass content. The results clearly showed that it is possible to produce moderate strength sustainable concrete for structural application using 20% glass powder as cement replacement.

Dataset on ground radiometric survey in part of the Eastern Dahomey Basin, SW Nigeria

The dataset for this article contains the measured activity concentration of radionuclides and gamma-radiation dose rate obtained from the radiometric survey in Ota, Ado-Odo Local Government Area, Ogun State, Nigeria. The data were manually collected in fifty (50) locations using the Super SPEC RS-125 spectrometer for about three (3) weeks in January, 2017. The descriptive statistical analysis of the data were equally explored for possible statistical relationships. The field dataset is made available publicly for further extended analyses that can provide insights into the safety status of the study area from radiological health concerns. The dataset could also serve as a significant baseline radiometric data for future epidemiology researches and monitoring initiative in Ota and its environs.

Structural Properties of Concrete Containing Ground Waste Clay Brick Powder as Partial Substitute for Cement

With the increasing concerns on the impact of cement production on the environment and the need to protect the environment, the use of mineral additives as cementitious material to partially substitute cement is being considered as an effective option. One of such material is fired clay brick which can be sourced as generated waste from clay brick industry. This has an added advantage of reducing industrial waste and preserving the natural resources. The experimental objective of this study is to examine the possibility of utilizing clay brick waste as partial replacement for Portland cement in concrete. The clay brick was finely ground into powder size, and after grinding, the morphological characterization of the powder materials was carried out using scanning electron microscopy (SEM). Moreover, the chemical composition of the brick material was determined using X-ray fluorescence (XRF). Laboratory tests were carried out to determine the workability, split tensile and compressive strength properties of the concrete with 0%, 10%, 20%, 30% and 40% partial replacement of cement with ground clay brick (CB). From the test results, the chemical composition of the brick powder meets the standard requirements for pozzolanic material, with the SEM revealing an amorphous solid mass. The workability of the concrete reduces with increase in brick powder content. A significant improvement of the split tensile and compressive strength of the concrete was achieved at 10% cement replacement, after which a decrease in strength with increasing ground clay brick content was recorded. The use of ground clay brick of not more than 15% was recommended for concrete production.

Effect of Substitution of Crushed Waste Glass as Partial Replacement for Natural Fine and Coarse Aggregate in Concrete

Reusing of waste glass in concrete production is among the attractive option of achieving waste reduction and preserving the natural resources from further depletion thereby protecting the environment and achieving sustainability. This present study examines the possible reuse of waste glass crushed into fine and coarse aggregate sizes as partial substitute for natural fine and coarse aggregate in concrete. The variables in this study is both the fine and coarse aggregate while the cement and water-cement ratio were held constant. The crushed glass was varied from 0 – 100% in steps of 25% by weight to replace the both the natural fine and coarse aggregate in the same concrete mix. Concrete mixes were prepared using a mix proportion of 1:2:4 (cement: fine aggregate: coarse aggregate) at water-cement ratio of 0.5 targeting a design strength of 20 MPa. Tests were carried out on total number of 90 concrete cube specimens of size 150 x 150 x150 mm and 90concrete cylinder specimens of dimension 100 mm diameter by 200 mm height after 3, 7, 14, 28, 42 and 90 days of curing. Test results indicated that the compressive and split tensile strength of the hardened concrete decreases with increasing waste glass content compared with the control. However, concrete mix made with 25% waste glass content compared significantly well with the control and can be suitably adopted for production of light weight concrete.

Economic Exploitation of Gravel in Place of Granite in Concrete Production

The paper investigated the application of gravel as partial economic replacement of granite in concrete production. Concrete was produced using granite/gravel combination in varying percentages of 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80 and 10/90. Concrete made from 100 % granite and 100 % gravel served controls while other constituents of concrete were kept constant. Two different mix ratios of 1:2:4 and 1:3:6 were employed. Sieve analysis was carried out on the aggregates, while slump and compaction factor tests were carried out on fresh concrete. Compressive strength tests were performed on hardened concrete. Specimens were produced using 150 mm cubes for compressive tests. The reliable percentage of granite/gravel combination from compressive strength view point 60/40 with a value of 21.15 N/mm2 for mix ratios 1:2:4 and 70/30 with 15.17 N/mm2 for 1:3:6 mix ratio at 28 days. Satisfying respectively the 20 N/mm2 and 15.17 N/mm2 minimum requirement of BS 8110: 1997.There were costs saving of 4 % per unit volume of concrete production for both 1:2:4 and 1:3:6 respectively. Empirical evidence from the regression analysis revealed that higher composition of gravel significantly improves the concrete consistency properties while greater proportions of granite do significantly enhance comprehensive strength.

Influence of Portland Cement Brands and Aggregates Sizes on the Compressive Strength of Normal Concrete

A good number of building failures have occurred in Nigeria which resulted in the loss of lives and a lot of these failures are attributed to the poor concrete practices used for the execution of these constructions. These have shown that the concrete technology adopted in Nigeria has some issues and requires urgent attention for development and improvement. This study explored methods of improving concrete practices so as to obtain better qualities structures. The research replicated some of the common concrete practices adopted by the construction industry in Nigeria to obtain the compressive strength of normal concrete. Two types of Portland cement brand, Type A and Type and three aggregate sizes (12.5mm, 19mm and 30mm) together with a mixed-size aggregate were utilized for the research. The concrete produced were tested for compressive strength and compared with test results from sites in Lagos Nigeria. The results showed how cement brands and aggregate sizes influence the compressive strength of normal concrete. The results also proved that the common poor quality concrete verified in Nigeria are not properly prepared.

Predicting Buildings Collapse due to Seismic Action in Lagos State

Buildings worldwide are one of the most essential assets of humans, and they serve as a major contributor to the sustainable development of any nation. The consequences of building collapse are colossal ranging from loss of lives, damage to properties and its attendant socio-economic implications, etc. This menace appears to be worst-off in developing countries like Nigeria where capacity to manage disaster is lacking. Recent incidence of seismic actions in hitherto geographically aseismic zone, has led to prediction of earthquake occurrence in the nearest future. This research attempts to compute the seismic hazard of buildings in Lagos State, a densely populated area of Southern Nigeria. Based on known seismic ground motion for South-Western Nigeria, a model is created that estimates the casualty and built area that would be affected by earthquakes with different seismic intensities. MATLAB software using Monte Carlo simulation to draw random data samples of built area, construction quality, probability of failure and occupancy level is used for the computational analysis. The result showed that existing construction quality is poor portending a high degree of damage during moderate intensity earthquake. A significant risk reduction is achievable for both the impending collapse and severe damage performance levels if the existing construction quality is improved.

The use of geological-based geophysical surveys for groundwater distribution in crystalline basement terrain, SW Nigeria

This research involves the subsurface geological characterization for groundwater potential assessment within the campus of the Polytechnic of Ibadan, southwestern Nigeria. The study is directed towards groundwater resources exploration, development and management in the campus. Five 2D resistivity imaging traverses were conducted using Wenner array in addition to five VES surveys using Schlumberger array that provide layering information and geoelectrical parameters. Three geologic layers delineated from the 2D resistivity inversion models include predominantly clayey sand/ sandy clay top soil (overburden), partly weathered or fractured basement and fresh basement. Their inverse model resistivity values ranges 6.68 – 98.6m , 68.0 – 929 m and  2252 m with bottom depths ranges 3.8 – 6.4 m and 6.4 – 10 m respectively. 1D model inversion from VES results also delineate three lithologies classifying both topsoil and some part of the partly weathered basement as overburden with resistivity and thickness range 483 – 1746.9 m , 1.1 – 1.8 m; partly weathered or fractured basement 60.3 – 93.5 m , 8.4 -12.9 m and fresh basement 984.6 – 2078.9 m . The saturated portion of the partly weathered or fractured basement at depth will favour groundwater exploration and development in this area, while the relatively shallow overburden thickness would serve as the protective layer and recharge for the fractures.

Data on the thermal properties of soil and its moisture content

The dataset contains thermal properties of soil such as thermal conductivity, thermal diffusivity, temperature and specific heat capacity in an agricultural farm within the University of Ibadan, Ibadan, Nigeria. The data were acquired in forty (40) sampling points using thermal analyzer called KD-2 Pro. Soil samples taken at these sampling points were analyzed in the laboratory for their moisture content following the standard reference of American Association of State Highway and Transport Officials (AASHTO) T265. The data were acquired within the first and second weeks in the month of April, 2012. Statistical analyses were performed on the data set to understand the data. The data is made available publicly because thermal properties of soils have significant role in understanding the water retention capacity of soil and could be helpful for proper irrigation water management.