Rev. 8-20-96

MICROSILICA CONCRETE BRIDGE DECK OVERLAY

733-B-104

The Standard Specifications are revised as follows:

SECTION 733, BEGIN LINE 1, INSERT AS FOLLOWS:

SECTION 733 -- MICROSILICA CONCRETE BRIDGE DECK OVERLAY

733.01 Description.of the construction of a microsilica concrete overlay as shown on the plans This work shall consist on an existing deck or new concrete This work shall be in accordance with the requirements described herein and deck. the applicable requirements of 722.

MATERIALS

733.02 Materials. Materials shall be in accordance with the following:

Microsilica Admixtures 912.03(c)

Microsilica Concrete 912.05

The air-entraining, type A, and type D admixtures shall be certified in accordance with 913.03(c). The high range water reducing admixtures shall be certified prior to use.

The certification shall state the chloride content, whether or not chloride is added as an ingredient of manufacture, and that the admixture is in accordance with ASTM C 494, Type F.

The high range water reducing admixture certification shall be furnished to the Materials and Tests Division.

CONSTRUCTION REQUIREMENTS

733.03 Shipping and Storage. Shipping and storage shall be in accordance with 702.04.

733.04 Proportioning. Proportioning shall be in accordance with 702.05, except that high range water reducers shall be used in place of or in addition to water reducing admixtures.

The product manufacturers of the microsilica admixture and of the high range water reducing admixture system shall have a representative at the project site during the initial project site placement of the microsilica concrete bridge deck overlay.

733.05 Batching. The aggregate and cement shall be added first. The mix water shall then be added at a continuous, uniform rate. The air-entraining admixture shall be simultaneously added with the first portion of the mix water. The type A or type D chemical admixture shall be added simultaneously with the remainder of the mix water. The high range water reducing admixture shall then be added. The concrete shall then be mixed until a uniform consistency is achieved. The microsilica shall be added as recommended by the supplier. Batching shall otherwise be in accordance with 702.06.

733.06 Mixing. Mixing shall be in accordance with 702.07, except that concrete shall be ready-mixed. Additional water may not be added at the project site or in transit to increase slump. If additional slump is required at the project site, a high water range reducer shall be added as required to increase the slump.

733.07 Ready-Mixed Concrete. Ready-mixed concrete shall be in accordance with 702.09.

733.08 Construction Joints. Construction joints will not be permitted in the overlay unless otherwise directed.

733.09 Preparation of Bridge Floor. Preparation shall be in accordance with 722.05.

733.10 Patching of Bridge Floor. The bridge floor shall be patched as described below.

(a) Full Depth Patching. The material used for full depth patching shall be either bridge deck patching concrete or microsilica concrete. The surfaces of the prepared cavities shall be thoroughly soaked for a minimum of 12 h. The cavities shall then be filled with the microsilica concrete to the level of the adjacent deck surface. No bond coat will be required.

(b) Partial Depth Patching. The material used for partial depth patching shall be microsilica concrete. The patching material shall be consolidated by means of internal vibration at time of placement. The prepared cavity surfaces shall be thoroughly soaked for a minimum of 12 h. The cavities shall then be filled with microsilica concrete at the time that the overlay is placed.

733.11 Placing. After the surface has been cleaned and immediately before placing the overlay material, the surface shall be thoroughly soaked for a minimum of 12 h. The surface shall not be permitted to dry before placing the overlay material. There shall be no standing water at the time of placement. No bond coat will be required before placing the overlay material. The microsilica concrete overlay shall be placed to an elevation

approximately 13 mm (1/2 in.) above final grade.

733.12 Finishing. Evaporation retardant shall be applied in accordance with the manufacturer's recommendations immediately after screeding. Such retardant shall be reapplied when the surface is disturbed, such as during tining, prior to final cure.

The evaporation retardant shall be one of the products shown in the LIst of Approved or Prequalified Materials. Certification shall be in accordance with 912.03(d)2.

733.13 Texturing. Texturing shall be in accordance with 722.09.

733.14 Curing. The minimum curing time shall be 7 calendar days. After texturing, the plastic film which forms on the surface of the overlay shall be protected from shrinkage cracking with a single layer of well-drained wet burlap. This layer of wet burlap shall be placed as soon as the overlay surface will support it without deformation, but within 30 minutes after screeding. Approximately 1 h after placing the first layer of wet burlap, a second layer shall be placed. The entire covering shall be maintained in a wet condition for a minimum of 7 calendar days. Polyethylene film may be used in lieu of the second layer of wet burlap. If the polyethylene film is used for the second covering, then the burlap already in place shall be wetted just before placing the polyethylene film. The burlap shall be maintained in a wet condition. After the 7 calendar days have elapsed, all layers of covering material shall be removed.

If the ambient temperature falls below 10EC (50EF) during either the wet or dry curing periods, the time that the temperature is below 10EC (50EF) shall not be considered as part of the total 7 calendar days curing period.

Immediately after the end of the wet cure period, the surface shall be checked for cracks.

If cracks are found to be greater than 0.5 mm (0.02 in.) in width, the cracks shall be sealed by means of gravity feeding such cracks with an approved low viscosity epoxy sealant. The sealant shall be ponded over the crack by the use of dams or routing of the crack surface.

If it is determined by sounding or coring that adequate bonding between the class C concrete with microsilica and the bridge deck has not been attained, the deficient areas shall be removed and replaced as directed.

733.15 Method of Measurement. This work will be measured in accordance with 722.13.

733.16 Basis of Payment. This work will be paid for in accordance with 722.14.

SECTION 912, AFTER LINE 58, DELETE AND INSERT AS FOLLOWS:

(c) Microsilica Admixtures for Concrete. The microsilica admixture shall be one of the products shown in the List of Approved or Prequalified Materials.

(c) (d) Certification. Prior to furnishing admixtures, each manufacturer shall

SECTION 912, AFTER LINE 160, INSERT AS FOLLOWS:

912.05 Microsilica Concrete. The material shall be class C concrete in accordance with 702 and the requirements as follows:

(a) A minimum of 390 kg (658 lb) of cement shall be used per cubic meter (cubic yard) of concrete.

(b) A minimum of 30 kg (50 lb) of microsilica shall be used per cubic meter (cubic yard) of concrete.

(c) The maximum water-cement ratio shall be 0.400.

(d) The coarse aggregate shall be size No. 11.

(e) Entrained air, by volume, shall be 6.5 " 1.5 percent at the time of placement. The admixture shall be a tall oil or a vinsol resin based air entraining agent.

(f) Sufficient high range water reducing admixture shall be used to transform a 25 to 50 mm (1 to 2 in.) slump mix to a 125 to 200 mm (5 to 8 in.) slump mix.

The Contractor shall submit the mix design for approval. The Contractor shall obtain a written statement from the manufacturer of the microsilica admixture indicating satisfaction with the compatibility of all admixtures used.

All concrete for the key at the end of the bridge slab, and all partial depth patches shall be the same material as the bridge deck overlay material. Such concrete shall be poured monolithically with the overlay.


APPROVED MICROSILICA ADMIXTURES FOR CONCRETE

1. SIKA CORPORATION. The microsilica admixture shall be Sikacrete 950 as manufactured by Sika Corporation, 2930 Switzer Road, Columbus, OH 43219.

2. W.R. GRACE AND COMPANY. The microsilica admixture shall be Force 10000 as manufactured by W.R. Grace and Company, 6051 West 65th Street, Chicago, IL 60638.

3. ELCHEM MATERIALS, INC. The microsilica admixture shall EMSAC F-100 or EMSAC F-100T as manufactured by Elchem Materials, Inc., 10 Parkway View Drive, Pittsburgh, PA 15205.

4. MASTER BUILDERS TECHNOLOGIES. The microsilica admixture shall be MBSF as manufactured by Master Builders Technologies, 3715 Bargetown Road, Room 124, Louisville, KY 40218.

 

APPROVED MICROSILICA EVAPORATION RETARDANTS

1. MASTER BUILDERS TECHNOLOGIES. The evaporation retardant shall be Confilm as manufactured by Master Builders Technologies, 3715 Bargetown Road, Room 214, Louisville, KY 40218.

2. SIKA CORPORATION. The evaporation retardant shall be Sika-Film as manufactured by Sika Corporation, 2930 Switzer Road, Columbus, OH 43219.

3. EUCLID CHEMICAL COMPANY. The evaporation retardant shall be Eucobar as manufactured by Euclid Chemical Company, 19218 Redwood Road, Cleveland, OH 44110.

4. VEXCON CHEMICALS. The evaporation retardant shall be Certi-Vex Envioassist as manufactured by Vexcon Chemicals, 7240 State Road, Philadelphia, PA 19135.