Using Non Shrink Precision Grout for Precast Concrete

[Falck]

I am going to use Quickcrete's Cement based Non Shrink Precision Grout for a Pre-Cast Communications Vault and Lid I am making. The vault is 4x6x4. 3" thick Side Walls. I am adding 25#'s of 3/8" Pea Rock to each 60#pound bag of Grout per the instructions to keep its High Strength Properties. The reason I want to use this is because 9500#PSI 65.5 MPa 3 day Strength and its flow-ability. I will be adding 1/2 fiberglass rebar to the precast for strength as well. I talked to Quickcrete and they said it could be done. Let me know your thoughts.

 

[BridgeSmith]

Have you considered using a steel or pressure-treated wood frame with concrete board panels?

Rod Smith, P.E., The artist formerly known as HotRod10

 

[SwinnyGG]

I would prefer to use Pre-made mix for quality control reasons.

You are going to get WAY better quality control if you buy concrete from a concrete plant than you are if you try to mix it yourself. I can basically guarantee you you aren't going to get the result you want here. You're talking about mixing somewhere between a 1 and 1 1/2 full yards of concrete. Have you ever mixed concrete by hand? This is a LOT of concrete.

 

[ATSE]

Using non-shrink ground as a replacement for concrete is rarely a good idea. Grout requires confinement, and most grout manufs do not recommend placement that results in large open, unconfined surface areas. Do not confuse grout with concrete or mortar. Nonshrink grout (ASTM C1107) includes admixtures that cause a slight amount of expansion to offset the shrinkage. There are bagged pre-mixed concrete available that are high strength - that's what I recommend.

 

[bugbus]

I worked on a project that required two large precast elements to be prestressed together within a very short time window (rail project with short track possession). The stitch pour between the two elements was 200 mm (8") wide, and about 2 m x 2 m (6' x 6') in area.

Originally, this was proposed to be a conventional concrete stitch pour, but in the end, the contractor wanted to cast the stitch pour and apply the prestress in ~4 hours. Minimum strength at stressing was required to be 25 MPa (3600 psi). No readily supplied concrete mix was able to do this, so in the end the option was to go with a fast-setting grout with coarse aggregates (up to 10 mm / 3/8") added to it (25 MPa (3600 psi) strength in 4 hours, about 100 MPa (14,500 psi) at 28 days). An awful lot of planning and testing was put into the mix design to satisfy everyone that the strength would be achieved, and that there would be no issues with flash setting, shrinkage, excessive heat of hydration, etc. etc. The grout-aggregate mix was delivered from the supplier's batch plant in a concrete mixer.

So, I believe it can be done, but the grout-aggregate mix shouldn't be substituted for concrete without a lot of consideration.