Mechanical Properties and Chemical Resistance of Auger Grout

The major constituent in the augered cast-in-place (ACIP) pile is the grout, and hence, understanding the grout behavior is essential. A laboratory study was undertaken to evaluate the working and mechanical properties and chemical resistance of grout mixtures of which one batch was collected from a field project. Grout behaviors of interest were fluidity, setting time, mechanical properties, and chemical resistance. Chemical resistance of the grout mixes was studied by immersing the specimens in sulfuric acid (pH = 4), hydrochloric acid (pH = 4), sodium sulfate (0.5%), and sodium chloride (0.5%) solutions for a period of two years. Use of additional fluidifier and flyash in the grout and their effects on the flow properties and compressive strength on the grout was quantified and compared to the field samples. Variation of compressive strength, modulus and pulse velocity with curing time for the field samples has been quantified. Grout cube strength was higher than the cylinder strength. The ratio of cylinder strength to cube strength varied from 0.89 to 0.93 with an average of 0.91. Increasing the flyash content 25 to 35% did not affect the fluidity or compressive strength of the standard grout. During the two years of immersion test on grouts weight change and the amount of calcium leached from the specimens has been quantified. The weight changed observed varied from -3 to +3% and the maximum calcium leached was 0.5%. Of the solutions studied, 0.5% sodium sulfate solution has the greatest damage on the grout. The data suggests that ACIP piles maybe more susceptible to sulfate attack than concrete piles.