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Model for Vertical Hyperthermic Temperature Gradient Distribution in Concrete Box Girder in China
Issue:
Volume 8, Issue 3, May 2020
Pages:
48-56
Received:
1 May 2020
Accepted:
15 May 2020
Published:
18 May 2020
Abstract: The temperature field of concrete box girder under sunshine is an important factor to be considered in the design of bridge superstructure. Based on the meteorological parameters and the semi-empirical formula given by related bridge specifications, the vertical temperature gradient distribution model of prestressed concrete box girder was established using SPSS software. The amplitude of the temperature gradient model is calculated according to the theory of statistics. The index function model considering wind speed, solar radiation and temperature variation was obtained, and the method to determine the amplitude of vertical temperature gradient was summarized according to different building climate zones in China. The applicable conditions of the model are as follows: sunny and cloudless days with high radiation quantity should be selected; The selected months are generally from May to July, and June in extremely cold regions. It is verified that the calculated value fits well with the measured value by monitoring data of 3 real Bridges in different zones. The model of temperature gradient heating in warm areas was calculated. For the temperate climate regions without real bridge measured data, the recommended value of temperature gradient amplitude in this region is given after trial calculation. It explores the method of using only meteorological data without surveying and mapping, which can save a lot of manpower and material resources.
Abstract: The temperature field of concrete box girder under sunshine is an important factor to be considered in the design of bridge superstructure. Based on the meteorological parameters and the semi-empirical formula given by related bridge specifications, the vertical temperature gradient distribution model of prestressed concrete box girder was establis...
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Waste Rubber Tires: A Partial Replacement for Coarse Aggregate in Concrete Floor Tile Production
Gemeda Etefa,
Alemu Mosisa
Issue:
Volume 8, Issue 3, May 2020
Pages:
57-63
Received:
4 July 2019
Accepted:
7 August 2019
Published:
8 June 2020
Abstract: Concrete tile is one of the most used construction materials in the world. Cement and aggregate, which are the most important constituents used in concrete tile production, they are the vital materials needed for the construction industry. This led to a continuous and increasing demand of natural materials used for their production. Parallel to the need for the utilization of the natural resources emerges a growing concern for protecting the environment and a need to preserve natural resources (such as aggregate) by using alternative materials which are recycled or waste materials. In this research, a study was carried out on the use of used rubber tires as a partial replacement for coarse aggregates in concrete tile production using locally available waste tires. A review of relevant literatures was done to study previous works in the subject matter. The research was carried out by conducting tests on the raw materials to determine their properties and suitability for the experiment. Concrete mix designs are prepared using the DOE method and a total of 12 mixes were prepared consisting of two concrete grades (C25 and C30). The specimens were produced with percentage replacements of the coarse aggregate by 10, 20, 30, 40 and 50% of rubber aggregate with and without supper plasticizer (admixture). Moreover, a control mix with no replacement of the coarse aggregate was produced to make a comparative analysis. The prepared samples consist of concrete cubes, cylinders and beams. Laboratory tests were carried out on the prepared concrete samples. The lists of tests conducted are; material property, slump, unit weight, compressive strength, splitting tensile strength and flexural strength tests. The data collection was mainly based on the tests conducted on the prepared specimens in the laboratory. The test results were compared with the respective conventional concrete properties and show that there is a reduction in compressive strength of the concrete due to the inclusion of rubber aggregates. This is improved by using admixture to some extent, but lower density and enhanced ductility are the same, and there was a slight increase in flexural strength without admixture. The overall results show that it is possible to use recycled rubber tires in concrete tile production as a partial replacement for coarse aggregates. Nevertheless, the percentage of replacement should be limited to 10%.
Abstract: Concrete tile is one of the most used construction materials in the world. Cement and aggregate, which are the most important constituents used in concrete tile production, they are the vital materials needed for the construction industry. This led to a continuous and increasing demand of natural materials used for their production. Parallel to the...
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Study of Characteristics of Bricks Produced in Kathmandu, Nepal
Issue:
Volume 8, Issue 3, May 2020
Pages:
64-76
Received:
14 June 2020
Accepted:
30 June 2020
Published:
6 July 2020
Abstract: The quality of brick is determined by its physical, mechanical and microstructure characteristics. The main objective of this study was to assess the characteristics of different types of bricks produced under various clay composition, different types of kiln used, and various firing temperature, and cooling process, which are considered as the major factors affecting the brick quality. A mixed-method approach was used to carry out this study. Both primary and secondary data were collected form field observations, discussions, lab experiments, and literature review. Literature review was done to identify the relationship between affecting factors and brick characteristics. The status of bricks produced was assessed through lab tests. The results from both methods were compared and discussed thoroughly. The purposive sampling method was adopted to collect brick samples from six different brick factories situated in Kathmandu and lab tests were carried out in the Engineering Material Lab at Institute of Engineering (IOE) Pulchowk Campus, Lalitpur, Nepal. Deformation, bulk density, water absorption capacity, and compressive strengths of sampled bricks were observed and then compared with standard code values as well as with previous findings. The study showed that none of the brick samples was found within the standard benchmarks, and the bulk density was low, however, the water absorption capacity and compressive strength values of all the sampled bricks were found to be within the allowable limit, even though they were close to the lower bound. The study also discussed technical, social and environment policy related issues that are important for producing and making the best use of quality bricks. The study results may be applied to other places where similar situation exists.
Abstract: The quality of brick is determined by its physical, mechanical and microstructure characteristics. The main objective of this study was to assess the characteristics of different types of bricks produced under various clay composition, different types of kiln used, and various firing temperature, and cooling process, which are considered as the maj...
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