COMPRESSIVE STRENGTH OF CONCRETE MASONRY UNIT MADE BY PARTIAL REPLACEMENT OF FINE SAND WITH LOCAL SAND

Use of construction masonry unit has got wide acceptance in construction industry to deal with the numerous issues associated with burnt clay bricks. Normally cement, fine sand and crush are used as the ingredients of CMU. However unavailability of fine sand in the locality makes the resulting product expensive. To this end use of alternative material in place of fine sand remained active area of research since long. This research work studies the partial replacement of fine sand with local sand. 0% - 70% (with 10% increment) replacement of fine sand with local sand is used. Local sand is washed in purpose made tank with # 200 sieve at outlet. Eight batches of concrete masonry units are prepared. Each batch contains 6 specimen. The size of all specimen is 4" x 8" x 12". 1:4:8 concrete mix with water cement ratio of 0.45 is used in preparation of the CMU. Local sand is obtained from the vicinity of Nawabshah region. Specimen are prepared in concrete masonry unit making machine. Curing of the specimen is done for 7 and 28 days. Finally compressive strength of all specimen is evaluated using universal load testing machine both in horizontal and vertical position. Based on the results it is observed that compressive strength of concrete masonry unit cured for 7 days and tested in horizontal position is recorded as 720 psi (minimum) for 70% replacement and 1385 psi (maximum) for 40% replacement. Minimum and maximum compressive strength results recorded for vertical position are 500 psi for 70% and 1206 psi for 40% respectively. On the other hand 28 day cured CMU tested in horizontal position gave 747 psi for 70% and 1511 psi for 40% as minimum and maximum compressive strength values. The same for vertical position are recorded as 554 psi for 70% and 1315 psi for 70% respectively. Based on the results it is concluded that utilization of local sand as replacement of fine sand has positive effect on compressive strength and is found that 40% replacement of the fine sand with local sand gives better results.