This research focused on designing a grout mixture using lightweight aggregate that achieves the minimum 28-day compressive strength required for normal-weight grout, 2000 psi. This research specifically studied the effects of aggregate proportion, slump, and aggregate soaking on the compressive strength of the mixture. The variable ranges investigated were 3-4.75 parts aggregate to cement volumetrically, 8-11 in. slump, and 0 and 2 cycles of soaking. The statistical model developed to analyze the significance of variable effects included a three-way interaction between the explanatory variables. All three explanatory variables had a statistically significant effect on the grout compressive strength, but the effect of soaking was minimal and decreased as aggregate proportion decreased. This research also showed that lightweight grout, when prepared using aggregate proportion and slumps within the ranges suggested in American Society for Testing and Materials C476, reaches the required minimum 28-day compressive strength with a factor of safety of at least 2.7.