PARTIAL REPLACEMENT OF SAND WITH GRAVEL IN SANDCRETE BLOCK PRODUCTION

In the investigation described in this paper gravel has been used to partially replace sand in sandcrete block manufacture. The percentage of gravel by volume of sand was varied in steps of 5 percent to a maximum of 30 percent. The test results showed that the replacement of sand with gravel content in the cement-sand matrix increased the density of the blocks and also has a very significant effect on the compressive strength of the sandcrete blocks. The compressive strength of the blocks increased as the percentage gravel content in the mix increased. The optimum compressive strength of 8.11 N/mm 2 was obtained at age 28 days and at 25 percentage gravel content. This value represents an over 160 percent increase over the control value. The 28-day compressive strength obtained is appreciably higher than the 3.45 N/mm 2 minimum compressive strength requirement specified for machine-vibrated load- bearing sandcrete blocks in the Nigerian Industrial Standard document for sandcrete blocks. These blocks are thus strong enough to be used for loadbearing purposes in building construction.