Investigations on Factors Related to Sustainable Development of Concrete Technology in Bangladesh – Part IV
In this Part, the following four thesis topics were investigated:
1. Quality of Various Cement Brands in Bangladesh – Part III
Amjad Hossain and Ashish Kumar Debnath
In this thesis, ten cement brands were collected from market and investigated for normal consistency, initial setting time, final setting time, bleeding, fineness, and compressive strength at 3, 7, 14, and 28 days. The results were incorporated with twenty cement brands investigated in the previous two thesis works. Most of the cement brands satisfy ASTM C150 strength requirement at 3 and 7 days but not at 28 days. Based on the results of thirty cement brands, strength versus time relationship of cement mortar is proposed. The cement brand with unspecified composition, low clinker content, high initial setting time, more bleeding, less fineness (#200 sieve) gives less compressive strength.
2. Recycling of Demolished Concrete as Coarse Aggregate – Part II
Md. Azharul Islam
Demolished concrete blocks from five different building sites were collected and crushed into coarse aggregate for possible recycling as coarse aggregate for new construction. First the properties of aggregate, such as absorption capacity, abrasion and specific gravity were investigated. Concrete cylinder specimens of height 300 mm and diameter 150 mm were made with W/C=0.45 and 0.55. The concrete cylinders were tested for compressive strength, tensile strength, and stress-strain curves at 7, 14, and 28 days. Young’s modulus of concrete was valuated from the stress-strain curves. All of these data were incorporated with the data of the previous thesis conducted on recycling of concrete. Based on the experimental data, it is understood that the demolished concrete can be recycled for required strength of concrete 2500 to 3500 psi. The properties of concrete made with recycled aggregate were very similar to the properties of concrete made with first class brick aggregate commonly used in Bangladesh.
3. Investigation on the Properties of Concrete Made with Different Aggregates
Md. Zahangir Alam
Compressive strength, Young’s modulus and stress-strain curves of concrete made with different aggregates, such as brick aggregate, picked brick aggregate, first class brick aggregate, second class brick aggregate, third class brick aggregate, stone aggregate, shingles and jhama brick aggregate were investigated. Water to cement ratios were 0.55, 0.45, and 0.4. Cement contents of concrete were 340 and 400 kg/m3. The test results of these cases were incorporated with the previously investigated cases, such as moisture variation of aggregate, dust in sand, etc. The test results associated with the aggregates were summarized in this thesis.
4. Mechanical Properties of Concrete Made with Different Aggregates
Mohammed Shamim Miah
Based on the stress-strain, compressive strength, and Young’s modulus data of concrete investigated in different thesis works, the relationships between stress and strain; compressive strength and time, Young’s modulus of concrete and compressive strength were proposed. The type of aggregates include picked brick aggregate, first class brick aggregate, stone aggregate, shingles, jhama brick aggregate, and recycled aggregate.