THE QUALITY AND COST COMPARISON OF BORROW PIT SAND WITH RIVER SAND: THE CASE IN ADOLA TOWN

Abstract

This research aimed to investigate sand quality's effect on the compressive strength of concrete and to cost comparison of two sand sources. Initially, questionnaires and interviews were made with stakeholders and suppliers regarding the quality of sand as a construction input commodity. After that, borrow pit sand and river sand samples were collected from Adola town (Rone kebele) and Geneale river (Werabele river) locations. All sand samples were tested, which included: sieve analysis, fineness modules, silt & clay content, Organic impurities range, specific gravity, and water absorption capacity by ASTM, and concrete cubes were cast with a mix ratio of 1:2:3 and tested for compressive strength at the age of 7 and 28 days. The survey results found that about 61.9% of the stakeholders use borrowed pit sand as a significant sand source. On the other hand, 71.43% of the respondents replied that they only use PSEL natural sand for concrete production. Moreover, the result has shown that only 5.56% of the stakeholders use more than one source. Regarding quality satisfaction with the supply of sand, about 66.67% of the respondents have no joy with the quality of sand they purchase. Even though stakeholders give little attention to sand quality tests, relatively, gradation, silt, and clay content tests are given better attention. The test result shows that PSUW failed to meet most of the quality requirements. It is concluded that pit sand found in Adola Town and its surrounding contain silt and clay content and poor gradation that exceed the allowable limits. It results in result a significant reduction in concrete strength. It is recommended that the concrete mix design in the city should always consider the strength reduction due to the presence of these impurities and gradation to ensure that the target strength of the resultant concrete is achieved. Based on the research outcome, this can be improved by washing and blending to acquire the required proportion. Accordingly, with compressive strength of 25.95MPa, concrete was produced using a 50% proportion of both RVS and PSUW, with the best-producing cost that deviated 0.38% from the least PSW. This indicates that the proper balance of RVS and PSUW would improve compressive strength and be the best alternative source.