Relationship between ultrasonic pulse velocity test result and concrete cube strength

This paper presents the findings of a study on the relationship between Ultrasonic Pulse Velocity (UPV) and Concrete Cube Strength; in three distinct stages. First, a preliminary investigation of the various properties of the materials used for the production of concrete was undertaken. This was followed by trial mix using a nominal mix of 1:2:4, water – cement, W/C, ratios of 0.4, 0.5 and 0.6; along with two different consolidation methods – manual and machine vibrated. Based on the result of trial mix, W/C ratio of 0.5 was used to prepare and cure 150mm x 150mm x 150mm concrete cubes. The third stage subjected the samples to UPV and destructive tests at the end of the following curing days: 1, 3, 7, 14, 21, 28, 56 and 90 days. Ultrasonic Pulse Velocity test result showed an inverse relationship (of -0.935) with the crushed concrete compressive strength. Correlation test, multiple regression analysis, graphs and visual inspection were used to analyze the results. The conclusion drawn is that there exists a relationship between UPV test results and compressive strength. It is expressed as follows: y = 151- 3.2x1; where y and x1 are compressive strength and UPV test results respectively. Hence it is recommended that the above formula can be used in converting the UPV test results to compressive strengthKeywords: Concrete, cube strength, non-destructive test, relationship, ultrasonic pulse velocit

Comparative reliability of ultrasonic pulse velocity and rebound hammer test methods in assessing compressive strength

This is an evaluation of the efficacy of the two most popular Non Destructive Testing (NDT) methods – Ultrasonic Pulse Velocity (UPV) and Rebound Hammer (RH) in assessing compressive strength of concrete. 150mmx150mmx150mm concrete cube samples were prepared, cured and subjected to UPV and RH tests at the end of : 1, 3, 7, 14, 21, 28, 56 and 90 days. The same samples were, then subjected to destructive (compressive strength) test. Correlation test, multiple regression analysis, graphs and visual inspection were used to analyze the data obtained. Results indicated increase in rebound hammer from 24 rebounds on the first day to 43 rebounds on the 90th day; while the result of UPV decreases from 43.10 Micro-Sec. on the first day, to 35.90 Micro-Sec. on the 90th day of curing. Regression Model which combines UPV with RH gave the following results: 10.93 N/mm2, 13.99 N/mm2, 25.23 N/mm2 29.72 N/mm2, 33.45 N/mm2, 33.32 N/mm2, 35.45 N/mm2 and 36.75N/mm2 for 1, 3, 14, 21, 28, 56 and 90 curing days, respectively. The conclusion drawn from the analysis, is that combination of rebound hammer and UPV methods is effective in assessing compressive strength of concrete. Hence it is recommended that for more accurate result, rebound hammer should be combined with UPV testing concrete, and that the following formula should be used = 45.80 + 0.88 X -1.31 X . 1 2Keywords: Concrete, Comparative study, compressive strength, rebound hammer, ultrasonic pulse velocit

An Evaluation of The Effects of Local Mix Design on the Compressive Strength of Concrete

This is a report on an evaluation of the effect of local mix design of concrete on its compressive strength. In order to accomplish this research work, field survey was first undertaken with a well-structured questionnaire. This questionnaire was administered to the respondents who are directly involved in concrete production. Oral interview was also carried out in order to confirm the information given by the respondents concerning batching, mix ratio, etc. A study of contract document was undertaken with emphasis on specification of contract, bill of quantity and structural design in order to study how mix design is carried out in construction industry. Based on the information obtained from the respondents on how concrete is designed and specified in contract document and how such information is used in the production of concrete on construction sites, an experimental programme was set up in order to assess the extent of deviation from the normal. In the experiment, six different mixes were used. A total number of one hundred and twenty (120) cubes were cast; twenty (20) cubes were cast for each of the design mix specified. The samples were cured and crushed after 1,3,7,14,21 and 28 days of curing so as to determine the compressive strength. The test result shows that, the compressive strength for both mass and reinforced concrete produced in the construction firm are 3.13N/mm2 and 6.00N/mm2 respectively at 28 days, which are lower than that produced using the standard mixes and that produced using the target mixes. It is concluded that there is a very wider deviation from the normal in the concrete produced on site and it affects the strength of concrete and therefore, durable and qualitative concrete cannot be achieved through such means (their mix design). It is recommended that professionals should be involved in the production and supervision of concrete works so as to take care of quality control and guard against irregularities

An investigation into the prospects of green building practice in Nigeria

Green Building (GB) is a concept that gains currency as an important mitigating measure against the negative side effects of developmental activities. This is a report on investigation carried out on the prospects of GB practice in Nigeria. This research work entails review of related literature to establish the concept of GB, problems militating against the practice of GB and method of constructing GB. A total of 50 structured questionnaires were distributed, out of which 40 were received. Practice of GB in Nigeria, factors hindering the practice and benefits of GB were investigated. Based on Likert scale ranking, results show that GB is currently not practiced and the need for it exist. Also, lack of awareness is the most prominent factor hindering the construction of GB, followed by 'Lack of enabling environment in the form of policy or legislation that will encourage prospective clients to use GB and 'Economic situation of the country'. Health and productivity gain is identified as the most important benefit of green building, followed by 'preservation of natural resources while taking care of their health' and 'attraction and retention of employee'. It was recommended that public enlightenment should be done by Non Governmental Organizations, government and professional bodies, the practice of Green building should be encouraged by the government, request for construction environmental management plan from contractors as part of tender documents and the government should liaise with the industry's stakeholders to establish a construction bank that will empower the people

Comparative study of the properties of ordinary portland cement concrete and binary concrete containing Metakaolin made from Kankara Kaolin in Nigeria

The study explored metakaolin as alternative material to cement. It compares the properties of Ordinary Portland Cement (OPC) concrete and binary concrete containing metakaolin as partial replacement of OPC. Two set of concrete samples; one with 10% Metakaolin (MK) replacing OPC by weight, and the other without MK (100% OPC) as control, were produced. The samples were tested for compressive and tensile strengths at 7, 14, 28 and 90 days. The result revealed that the slump of the binary concrete was 26% lower than the control. However, the compressive and tensile strengths of binary concrete were higher than those of control by 10.8% and 11.9% at 28days, and by 21.6% and 34.5% at 90 days, respectively. Therefore, the MK produced from Kankara Kaolin can be used as Pozzolan to improve the strengths of concrete.Keywords: Pozzolana, binary concrete, OPC concrete, metakaoli

Characteristics of concrete produced with periwinkle and palm kernel shells as aggregates

We assess the suitability of palm kernel shell (PKS) and periwinkle shell (PS) as partial or full replacement of fine and coarse aggregates respectively, in concrete production. First, the physical properties of PKS and PS were determined. Then concrete was produced using varying percentage replacements of 0%, 25%, 50% and 100% of fine and coarse aggregates, with PKS and PS respectively. The samples were cured for 7, 14, and 28 days. Tests to determine its compressive strength, tensile strength, abrasion resistance and water absorption capacity we conducted. Results showed that the compressive strength and tensile strength of the samples with 25% of its aggregate replaced with PKS and PS are very close to the values of the control samples but there was huge difference when the samples of 50% and 100% replacement were compared with the control sample. However the concrete samples produced with 50% and 100% replacement levels, showed more resistance to abrasion when compared with the control sample. It was concluded that the compressive strength of concrete produced with partial or full replacement of fine and coarse aggregates with PKS and PS, has inverse relationship with the quantity of PKS and PS. It is recommended that maximum of 25% replacement level of PKS and PS as fine and coarse aggregates respectively can be used in concrete production.Keywords: Aggregates, Concrete, Palm Kernel, Periwinkle, Properties, Shel

Evaluation of the effect of volcanic ash on the properties of concrete

Effect of volcanic ash on the properties of concrete was assessed in the study. Preliminary tests were carried out on the different properties of materials used. The concrete samples were prepared using 0%, 5%, 10%, and 15% volcanic ash replacements and nominal mix of 1:2:4 with a 0.5 w/c ratio. Concrete sample specimen was subjected to workability test. Thereafter, Cube mould of size 100mm x 100mm x100mm and cylinder mould of size 200mm x 100mm were used to cast a total of 405 concrete samples, 162 cubes were used to assess compressive strength test while 162 cylinders were used to determine the tensile strength by the split tensile method. The specimens were cured and tested at 7, 14, 21, 28, 56 and 90 days. The results show setting time and soundness test of Miango volcanic ash satisfied the necessary requirements. Also, increase in compressive strength and split tensile strength of about 7.99% and 6.14% respectively, for concrete samples with 10% volcanic ash replacements after 28days of curing. It was concluded that Miango volcanic ash retards the setting time of concrete and enhances the properties of concrete. Hence it was recommended that it should be used to produce a strong and dense concrete and serve as an admixture.Keywords: Concrete, compressive strength, volcanic ash, partial replacement, workabilit

Protective effect of Ziziphus mauritiana leaf extract on carbon tetrachloride-induced liver injury

Protective effect of ethanol extract of Ziziphus mauritiana leaf was studied on carbon tetrachlorideinduced liver damage. Pretreatment of rats with 200 and 300 mg/kg body wt of Z. mauritiana leaf extract protected rats against carbon tetrachloride liver injury by significantly lowering aspartate aminotransaminase (AST), alanine aminotransamine (ALT), alkaline phosphatase (ALP), total bilirubin (TB), and lipid peroxide levels compared to control. The extract at both doses also significantly restored depleted levels of glutathione and vitamin E compared to control. Reduction in lipid peroxidation, restoration of glutathione and vitamin E levels indicate strong antioxidant property of the leaf. Phytochemical screening of the leaf extract of Z. mauritiana indicates probable presence of flavonoids, phenolic compounds, tannins and saponins

Properties of concrete at elevated temperatures using selected brands of ordinary Portland Cement

In recent times, there has been a serious controversy as to whether the different brands of OPC commonly used in Nigeria can attain adequate strength and even the Standard Organization of Nigeria (SON) attributed the incidences of building collapse in the country to this assumption. This has prompted researchers to investigate the properties of concrete produced with various brands of the cement produced in the country. This study therefore evaluates the properties of concrete made with different Nigerian brands of OPC exposed to an elevated temperature. Four brands of Ordinary Portland Cement commonly available in Nigeria were used in this project to produce different concrete specimens which were labeled A, B, C and D. a total of seventy two (72) specimens of size 100mm x 100mm x 100mm cubes were produced using a nominal mix of 1:2:4 and W/C ratio of 0.55. After curing the concrete specimens produced in water for 28days, 36 of the specimens were exposed to an elevated temperature of 800oC, 1000oC and 1200oC for 3hrs while the remaining 36 were used as control. Thereafter, compressive strength of the concrete specimens was determined. The average compressive strength obtained for concrete specimen made with cement brand A, B, C and D exposed to 800oC were 6.27N/mm2, 5.08N/mm2, 5N/mm2 and 6.4N/mm2 respectively while at 1000oC the compressive strength values were 3.03N/mm2, 1.97N/mm2, 2.57N/mm2, and 3.27N/mm2 respectively. At 1200oC, all the concrete specimens melted. Result obtained shows that concrete specimen produced with cement brand D has better compressive strengths when compared to A, B and C. It is concluded that cement D showed higher compressive strength after its exposure to elevated temperature. It is therefore recommends that cement D be used in areas where concrete is likely to be exposed to high elevated temperature.Keywords: Brands of Cement, Elevated Temperature, Properties, Compressive Strengt

Comparative Study of the Compressive Strength of Cement Laterite Brick Produced with Rice Husk Ash and Wood Ash as Partial Replacement Of Cement

The paper presents an outcome of experimental comparative study on the compressive strength of laterite brick made with rice husk ash and wood ash as partial replacement of cement. First, Rice Husk Ash (RHA) and Wood Ash (WA) were prepared and subjected to the following tests: specific gravity, density and bulk density. This was followed by the production of three types of bricks viz cement laterite-bricks(control), cement-laterite bricks produced using RHA as partial replacement of cement and another brick made with WA as partial replacement of cement. Replacement levels range from 0 - 30% at 10% intervals. The samples were cured by water sprinkling, before testing them for compressive strength at 7, 14, 21 and 28 curing days. Result of the tests showed that the specific gravity of RHA and WA are 2.20 and 2.13 respectively. The Absorption capacity of all the samples is in the range of 4.5 – 9.1%which is within the allowable value of 25% set by the Nigerian Industrial Standard. Compressive strength for 10 % replacements range from 0.75N/mm2 for 7days to 3.7N/mm2 for 28 days for RHA, as against 2.6 N/mm2 for 7days to 5.3N/mm2 for 28days curing for WA. This shows that bricks produced using WA are relatively higher in strength than those made with RHA. Though it is concluded that RHA and WA, can be used as partial replacements of cement in the production of laterite brick. Also, laterite brick produced with 20% and 30% partial replacements of cement with RHA and WA, respectively,, have, satisfied the minimum requirement as contained in BS 6073, and are recommendable.Keywords: Cement, compressive strength, rice husk ash, laterite brick, partial replacement levels, wood ash