Early-Age Stiffness and Strength of Concrete Comprising Natural Pozzolans Available in Utah

Renewed interest in the use of natural pozzolans in concrete in Utah has led to new research, in which the properties and performance of locally available natural pozzolans are being evaluated in selected concrete mixtures. The objective of this laboratory research was to determine the 7-day stiffness, in terms of modulus of elasticity, and compressive strength of concrete mixtures comprising natural pozzolan for comparison with a baseline concrete mixture without natural pozzolan. For all three natural pozzolans evaluated in this research, both slump and air content requirements were met at the maximum water-cementitious materials ratio of 0.44 permitted by the Utah Department of Transportation. The results indicate average modulus of elasticity values ranging from 11,278 MPa (1,635,744 psi) to 11,665 MPa (1,691,867 psi) for mixtures comprising natural pozzolan compared to a modulus of elasticity value of 12,346 MPa (1,790,667 psi) for the baseline mixture. The results also indicate average compressive strength values ranging from 24.1 MPa (3498 psi) to 28.8 MPa (4183 psi) for mixtures comprising natural pozzolan compared to a compressive strength value of 33.1 MPa (4795 psi) for the baseline mixture. This research is expected to enhance understanding of natural pozzolan use in concrete mixtures in Utah projects.