To: Patrick L McDaniel/SC/MODOT@MODOT


From: Denis Glascock/SC@MoDOT

Subject: Perf Spec 625

I am not certain where we came up with the 15,000 rpm. That is REALLY fast. Are you certain we really mean this? It is magnitudes faster than what the ASTM spec calls for.

625.3.2 Preparation of grout shall be performed in accordance with ASTM C 938 with the following exceptions:

(a) Mixing shall be performed with a commercial type blender operating at approximately 15,000 revolutions per minute (rpm).

If 625.3.2 means "Preparation of grout for testing...... " it should say that. The way I read it I was thinking I have to mix my production that way.

In 625.4.3 ...... shall be notified.Water used...... needs a space between notifed. and Water.

The Last sentence is difficult to read. Also, how do you show it not detrimental?

625.4.3 Grout Mixer. The grout plant shall produce a homogeneous mixture. Mixed material shall not be held for more than the period designated in the contractor's mix design submittal. Grout may be re-tempered with water. Prior to re-temporing the grout, the engineer shall be notified.Water used to wash the drum of the mixer may be used as mixing water if it is shown not to be detrimental to the mix..

In 625.4.4.2 Why did we used to require 4 gauges? One on each side of the joint and each edge of the slab? Are we no longer requiring this?

625.4.4.2 The contractor shall furnish and maintain gauges with mounts, capable of detecting vertical slab movement of 0.001 inch (0.025 mm), simultaneously on each side of the joint or crack. The contractor shall also furnish and maintain a vehicle having a dual-tire single axle with an 18,000 pound (8 Mg) single axle load. The contractor shall furnish a truck operator and necessary personnel to conduct the deflection testing.