Influence of aggregate soundness on mechanical properties and durability of concrete

Abstract

Regarding the issue of the soundness value excessive of artificial aggregates in long-distance water conveyance tunnel engineering, the influence of aggregates with different soundness values on the mechanical and durability performance of concrete was studied. Using raw rocks with different firmness, four grades of coarse and fine aggregates are prepared. Among them, Grade I is fine aggregate ≤ 8%+coarse aggregate 9%~11%, Grade II is fine aggregate 8%~10%+coarse aggregate 14%~16%, Grade III is fine aggregate 10%~15%+coarse aggregate 19%~21%, and Grade IV is fine aggregate>15%+coarse aggregate>25%. The result show that as the strength level of aggregates decreases, the compressive strength, axial tensile strength, and ultimate tensile value of concrete show an overall downward trend. The frost resistance, and impermeability of concrete also show a gradually decreasing trend. The diffusion coefficients of chloride ions in the second, third, and fourth stages are 1.3×10^-12 m²/s, 2.8×10^-12 m²/s, and 2.5×10^-12 m²/s higher than those in the first stage, respectively. The concrete prepared with Class I to IV aggregates can achieve a sulfate resistance level of KS120, but the strength level of aggregates has no significant impact on the sulfate resistance performance of concrete. The result provide technical reserves and references for solving similar problems with other aggregate sources in water conservancy and hydropower projects, laying a technical foundation for expanding the selection range of aggregate sources and promoting relevant regulations to better adapt to actual engineering needs.

Keywords

aggregate / soundness value / lining concrete / mechanical properties / durability