Mechanical properties of green concrete with Palm Nut Shell as low cost aggregate
- Authors: Agbenyeku, Emem-Obong Emmanuel , Okonta, Felix Ndubisi
- Date: 2014
- Subjects: Sustainable construction , Prestressed concrete construction , Concrete - Testing , Building materials , Palm Nut Shell
- Type: Article
- Identifier: uj:5077 , ISBN 9781614994657 , ISBN 9781614994664 , http://hdl.handle.net/10210/13648
- Description: The cost saving benefits of aggregate replacement in concrete works are well documented. The utilization of Supplementary Aggregate Materials (SAMs) in concrete engineering without compromising standards in concrete works remain very attractive to both infrastructure developers and design engineers. However, there is continual search for low cost beneficial substitute materials. The mechanical properties of green concrete produced from Palm Nut Shell (PNS) as coarse aggregate was investigated. The abundance of PNS (light weight waste product of palm oil production) in West Africa created the impetus for the study. Series of laboratory tests such as; Slump, Compaction factor, Density, Schmidt hammer and Compressive strength tests were conducted on specimens of 10, 20, 30, 40 and 50% replacements of dry weight of PNS as coarse aggregate and specimens of natural aggregate as control sample. The specimens were cured at relative humidity (RH) of 95-100% and temperature (T) of 22-25oC in a chamber for periods of 7, 14, 21 and 28 days. The results showed the PNS samples to have relatively medium to high workability ranging from 24-47 mm for slump height and values of 0.85 to 0.90 for compaction factors. A general strength development was observed across the different samples with the PNS sample reaching strength of 48.7 N/mm2 at 28 days curing. The 50% replacement specimens which mobilized UCS of 28.7 N/mm2 met the requirement for lightweight concrete however, 30% is the optimum for a partial aggregate replacement in green concrete as UCS of 39.2 N/mm2 was mobilized in 28 days. Thus PNS is a suitable concrete constituent and can be a major cost reduction factor especially in low cost rural projects with streamlined loading requirements.
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Performance of pozzolana as partial replacement for fine aggregate and cement in concrete
- Authors: Motau, Tshepo Canny
- Date: 2016
- Subjects: Aggregates (Building materials) - Specifications , Cement , Concrete - Testing
- Language: English
- Type: Masters (Thesis)
- Identifier: http://ujcontent.uj.ac.za8080/10210/373716 , http://hdl.handle.net/10210/225362 , uj:22760
- Description: Abstract: Improvement of the characteristics of cement, mortar and concrete is of interest to various researchers and practitioners in the field of construction materials engineering. This dissertation presents a study that investigated the potential of a natural pozzolana of volcanic origin from Kibangira: Rwanda to assess its effects on of paste, mortar and concrete. No previous research was done this material. The effect of pulverised natural pozzolana as partial cement replacement was assessed. In the case of concrete, the results obtained were compared to the results of companion specimens of concrete containing artificial pozzolana (Ulula fly ash) of the same percentage of cement replacement. In addition, the effect of the same natural pozzolana as partial sand replacement, on the properties of concrete, was assessed. Tests carried out on cement paste samples included setting time, heat of hydration behavior and rheology. Only mortar samples compressive strength were carried out on mortar samples. Tests carried out on concrete samples include workability, wet and dry density concrete, split tensile strength, compressive strength, oxygen permeability, sorptivity, sulphate solution exposure effects, modulus of elasticity and drying shrinkage. In conclusion, natural pozzolana from CIMERWA: Rwanda, Kibangira conformed to ASTM C 618:2000, therefore natural pozzolana can be used as cement replacement in concrete and was found to be suitable as partial replacement of sand in concrete. , M.Tech. (Civil Engineering)
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Potential South African standard sand for cement mortar testing and research
- Authors: Ekolu, Stephen
- Date: 2014
- Subjects: Concrete - Testing , Strength of materials , Sand - Specifications - South Africa , Mortar - Testing
- Type: Book chapter
- Identifier: uj:5037 , ISBN 9781614994664 , http://hdl.handle.net/10210/13557
- Description: Mortars are used extensively in accelerated methods of testing the physical properties of cementitious materials. Mortar strength is invariably used to determine cement strength grade of cements and for general evaluation of material behavior, as typically employed in research and testing. Presently, the South African (SA) cement industry imports standard from Europe for cement testing purposes. This study was conducted to formulate South African standard sand that could be used to conduct mortar strength tests for compliance to specifications and for general research purposes. Two formulations of local South African silica sands, referenced as SA513S and SA413S, were developed to suit standard gradings. The formulated South African standard sands (SASS) where tested in comparison with European standard sand (ENSS) of EN196-1 and American graded standard sand (GSS) of ASTM C- 778. Following the formulation and grading of SASS, mortar mixtures of 1:3:0.5 cement to sand to water were cast in 50 mm cubes and tested for compressive strength for ages up to 90 days. Two types of cements were employed in the tests, the ordinary Portland cement CEM 1 42.5N and pozzolanic cement CEM V 32.5N. Comparison of the 28-day compressive strength results between the four SS types showed an excellent agreement, giving standard deviations of 1.96 and 2.51 for CEM I and CEM V. The flow results for the standard sand types varied, with EN196-1 giving the highest mortar flow followed by GSS sand and SA413S. The GSS and SA513S gave precisely the same flow results.
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The strength relationship between the cube and cylinder
- Authors: Sun, Ryan W. , Fanourakis, George C.
- Date: 2016
- Subjects: Concrete - Testing , Strength of materials
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/217507 , uj:21648 , Citation: Sun, R.W. & Fanourakis, G.C. 2016. The strength relationship between the cube and cylinder.
- Description: Abstract: Concrete laboratory tests compressive strengths differ in a laboratory depending on whether the shape of the concrete specimen is either a cube or a cylinder. General assumption has defined the cylinder to possesses, approximately 80 % of the cube strength. The validity of this approximation needs to be assessed; as several studies have shown this approximation to be invalid. This investigation assessed the effect of compressive strength and curing age of concrete on the Cylinder–Cube Strength Relationship (CCSR) of South African Concretes. Cubes and cylinders were cast for 7, 28 and 56 day curing ages from 36 concrete mixes varying in strength, aggregate type and cement type. Concrete strength did not influence the CCSR, but rather, the CCSR was influenced by the curing age (r = 0.998). The general CCSR values were 83.66 %, 84.88 % and 86.96 % (on average) for 7, 28 and 56 day concrete, respectively. The overall average CCSR, calculated considering results across all curing ages, was 85.17 %. This research shows that 80 % is not an accurate representative value of the average CCSR for typical concretes varying in composition. In addition, this study also acknowledged that the CCSR cannot simply be represented by a single value. This research does however propose that if there should be a value that provides a better guideline to what can generally be expected, should accuracy not be a requirement, an average CCSR of 85 % should be adopted, as opposed to 80 %.
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Validation of concrete elastic modulus estimation methods
- Authors: Sun, Ryan Wok
- Date: 2015
- Subjects: Elastic analysis (Engineering) , Concrete - Testing , Reinforced concrete construction , Concrete products , Strength of materials
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/56194 , uj:16341
- Description: Abstract: The modulus of elasticity (E) is an important property of concrete that needs to be quantified when designing complex structures. The methods to best quantify this property are empirical within the laboratory, but outside the laboratory, designers may depend on estimation models. There exists numerous estimation models at the designer’s disposal but the accuracy and reliability of those models have not been comprehensively and comparatively assessed. The actual E values of 108 specimens, whose properties differed in aggregate type, cement type, concrete strength and curing age, were measured. The actual E values were compared to the predictions made by 23 estimation models. The accuracy of each model was analysed statistically to conclusively determine which of the models was most accurate. The Noguchi et al (2009) model was found to be the most accurate and consistently so, rendering an overall coefficient of variation of 15.94%. The CEB-FIP (1970) model was found to be the least accurate, resulting with an overall coefficient of variation of 31.81%. In addition to the primary objective, this study included the analysis of the degree of influence of aggregate percentage content, compressive strength, curing age and concrete density on the actual elastic modulus of concrete. The concrete’s density was found to be a major factor in the resulting E of concrete as the statistics had shown that the correlation was highly significant (P = 2.39 x 10-7 %). Concrete strength on the other hand, a factor that most models use as a primary basis for their estimations, was not as influential as assumed. In fact, the statistical results showed the correlation to have a level of significance of 11.1 %. It was therefore highly recommended that E estimation models should, at least, include the density of concrete as a common parameter more than the inclusion of concrete strength. Separate to the topic of concrete E, this research also assessed the average strength relationship between concrete cylinders and concrete cubes. The average cylinder-cube strength relationship slightly increases with the increase in curing age indicated by a correlation coefficient of 0.998. The strength of the cylinders were found to be, on average, approximately 85 % of the cube strengths. , M.Tech. (Civil Engineering)
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Validation of post-installed anchors tested to European technical approval guideline 001 in South African concrete using portable test equipment
- Authors: Sillman, C.R.
- Date: 2012-06-04
- Subjects: Ready-mixed concrete - Specifications - South Africa , Concrete construction , Concrete - Testing , Concrete - Quality control
- Type: Thesis
- Identifier: uj:2345 , http://hdl.handle.net/10210/4801
- Description: M. Phil. , The purpose of this research is to see if on-site portable pull-out tests in South Africa on post-installed chemical and mechanical fixings can produce similar results to internationally laboratory tested fixings. The method used in the field study was to use typical South African 25 MPa, 75 mm slump ready mix concrete as supplied by a reputable supplier and to test several types of fixings in common situations, some covered in the European Technical Approval Guidelines (ETAG) and some not. The results were analyzed against published international values and theoretical calculations for the fixings. The findings showed that the results produced using the portable equipment can show values similar to the published and theoretical values. It was also shown that this methodology can be used as a diagnostic tool to reveal installation errors. The pull-out test operator needs to be skilled to ensure a satisfactory outcome of the tests. The implications of the findings have direct bearing on: The on-site pullout testing of post installed anchors in South Africa; The diagnosing of bad anchor installation. And secondarily bearing on: The education of post-installed fixing installers and designers; The lack of standards for post-installed anchors in South Africa; The transportability of data from international research to South African conditions.
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