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1 COMPARISON OF ISI AND ACI METHODS FOR ABSOLUTE VOLUME CONCRETE MIX DESIGN Amarjit Singh, University of Hawaii at Manoa, USA Kamal Gautam , University of Hawaii at Manoa, USA Abstract: The concrete mix design methods used in India and USA are built on the same basic principles and empirical relations, developed after substantial experiments of locally available materials. However, some minor differences exist between them. This research paper evaluates the major differences found between the American Concrete Institute (ACI) and Indian Standards Institution (ISI) concrete design methods. Step by step, this paper compares the calculation processes between the ACI and ISI methods for absolute volume method. The scope of this comparison is limited to absolute volume method, which is widely used for designing concrete mixes of 28 days compressive strength of less than 6000 psi (~ 40 MPa). This paper evaluates the similarities and differences between the ACI and ISI concrete mix designs and compares the experimental results. It is seen that design calculations of aggregates content, cement content, and water cement (w/c) ratio are the major difference. In the ACI method, sand is calculated after coarse aggregate is calculated, while in the ISI method the process is reversed. The results show that ISI uses higher cement content than ACI, perhaps due to the rural conditions and relatively low quality of cement in India. As a result, the w/c ratio is higher in the ACI mix than ISI mix. Although, sand content decreases as the strength requirement increases in both cases, it is lower in the ISI mix than the ACI mix; this probably accounts for the less dense and lower strength results in the ISI method at higher strength requirements. It appears that the ISI technique performs better for lower strengths than for higher strengths. The correlation and deviation analysis between designed and actual strengths indicates that the ACI method is more reliable and more likely to meet 30 and 40 MPa strength requirements than the ISI method. Key words: Aggregates, cement, sand, air entrainment, workability, NMSA, w/c ratio
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2 1. Introduction Mix design is a process of specifying the mixture of ingredients required to meet anticipated properties of fresh and hardened concrete. Concrete mix design is a well established practice around the world. All developed countries, as well as many developing countries, have standardized their concrete mix design methods. These methods are mostly based on empirical relations, charts, graphs, and tables developed as outcomes of extensive experiments and investigations of locally available materials. All of those standards and methods follow the same basic trial and error principles. Some of the prevalent concrete mix design methods are: a) ACI Mix Design Method, b) USBR Mix
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This note was uploaded on 11/30/2010 for the course CIIVIL WNG 33155 taught by Professor Y.bahie during the Spring '10 term at The British University in Egypt.

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