Recommend modifying the…

Recommend modifying the draft specification to allow the use of cement-treated concrete sand bedding material in place of fine aggregate bedding material when precast concrete slabs are placed on open-graded aggregate base, cement treated base, or asphalt-treated base. The CTBM cement-treated bedding material will hydrate into a solid bedding layer and not allow migration of bedding material into open-graded aggregate drainage layer below.
We submitted proposed revisions to OPSS 363:

363.05.08 Fine Aggregate for Base Preparation – Fort Miller Super-Slab® Method
Add:
363.05.08 a Cement-treated Concrete Sand for Base Preparation - Fort Miller Super-Slab® Method
Cement-treated Concrete Sand bedding material consisting of one part Portland cement and six parts of concrete sand meeting the requirements of OPSS 1002 Aggregates-Concrete (add correct reference). Mix the cement and sand dry. Do not add water to the mixing process.
363.07.01.01 Fort Miller Super-Slab® Method
Add: or cement-treated concrete sand

…placing and grading fine aggregate or cement-treated concrete sand base material,…

363.07.05.01 General
Modify:
Leveling and bedding material shall be a flowable fill for the Michigan Method. For the Fort Miller Super-Slab® Method use fine aggregate or cement-treated concrete bedding material. All leveling and bedding material shall meet the requirement of this specification.

Add 306.07.05.03a – Cement-treated Concrete Sand - Fort Miller Super-Slab® Method

Cement-treated concrete sand shall be compacted then fine graded using a screeding device capable of grading the fully compacted bedding material to the required tolerance.

306.07.07.02 Precast Concrete Slab Installation
Add after the first sentence:
Dampen or wet the bedding material immediately before slab placement as follows:
For Fine Aggregate Bedding Material, Dampen the bedding material with water, if needed, so that the bedding material remains moist after slab placement.

For Cement-treated Concrete Sand Bedding Material, fully wet (do not saturate or puddle) the bedding material layer with water to ensure ultimate hydration of the cement.