| Popis: |
The use of hand-quarried weathered quartzitic aggregates as the coarse component of concrete was investigated. Samples of hand-quarried quartzite aggregates exhibiting different degrees of weathering were evaluated in quality and their suitability as coarse component of concrete. The 7, 14, 28 and 56 day compressive strengths were obtained from 100mm concrete cube samples prepared with the weathered aggregates in 1:1:2, 1:1.5:3, 1:2:4 and 1:3:6 concrete mixes and different water: cement ratios 0.45, 0.5 and 0.6. Modulus of rupture beams were tested aged 28-days. Control samples were also tested for compressive and tensile strengths using sound granite aggregates obtained from a commercial quarry. The quality tests showed very little difference between the un-weathered quartzite aggregates and the sound granite aggregates. The weathered quartzite aggregates except the highly weathered grade were found to have properties that met specification requirements for concrete. However, the partially weathered aggregates were marginal in quality and had high water absorption values. The 28-day compressive strength of the partially weathered quartzite concrete averaged 86% of the granite. It is concluded that except when the degree of weathering is very high, the partially weathered quartzite stone could be used as coarse aggregates in concrete that would be subjected to low stresses. |
