UVU Civil Engineering Capstone Project

Comparing the Effects of Different Pozzolans on Slump and 28-day Compressive Strengths of Concrete Cylinders

Prepared By: Madison Clyde

Mentors:
Khaled Shaaban, Ph.D., P.E., PTOE, Associate Professor, Civil Engineering, UVU
Amanda Bordelon, Ph.D., P.E., Associate Professor, Civil Engineering, UVU

SLC Airport Garage

The old parking garage at the Salt Lake City airport was built in 1989 with silica fume concrete. The parking garage was sampled and cored before it was demolished in October of 2020. Its original mix design contained 7.4% silica fume and 15% class F fly ash replacement of cement. The design was changed on-site to meet the project’s concrete specs. The project’s batch tickets were destroyed in a fire. Recalled from memory, the structure was built with a 9% micro silica slurry and had a 28-day strength of 15,000 psi. This project’s purposes are 1) to replicate the mix design of the parking garage with 9% silica fume, and 2) to compare it with several, local pozzolans. This study also explores the option of using silica fume to reduce cracking in Utah bridge decks. Silica fume is expensive, has low workability, but increases concrete’s hardened properties. The other pozzolans selected were pumice, waste glass powder, and two kinds of class F fly ash. Each pozzolan replaced 15% by weight of cement. One trial included the original mix design containing 7.4% silica fume and 15% fly ash. This trial achieved a slump of ¼ in. and an average 28-day compressive strength of 8,455 psi. The pumice trial achieved a slump of ¾ in. and a strength of 6,877 psi. The glass powder achieved a slump of 8.5 in. and a strength of 7,069 psi. The fly ash from Delta, Utah achieved a slump of 8.5 in. and a strength of 6,615 psi. The fly ash from Prairie States achieved a slump of 8.5 in. and a strength of 8,036 psi. ASTM standards were followed when mixing and testing the trials. Except the trials containing silica fume. They were mixed according to the instructions published by the Silica Fume Association. The study concluded that silica fume concrete is very strong. It is recommended that silica fume concrete be tested in a few bridge decks in Utah. Especially in areas where a lot of freeze-thaw cycles and cracking occur. It costs more than other pozzolans but may make up for it in the increase in concrete’s service life.

Students' Presentation