512PREPARATION FOR CONCRETE REPAIRS

New Hampshire Department of Transportation Standard Specifications – 2016 Description

1.1This work shall consist of inspecting and preparing existing deteriorated concrete surfaces for rep airs at the locations shown

on the plans and as directed by the Engineer. Since a significant portion of the work may involve discovering and repairing hidden deteriorated concrete, the Contractor should carefully inspect the work area before bidding. Construction Requirements

3.1Scaffolds shall be furnished and erected at those locations where necessary to perform inspection, preparation and repair

work.

3.2Cleaning the concrete in preparation for the repairs shall include the following work as required and directed:

3.2.1 Visually examining and testing the concrete surface by sounding with a hammer to detect hidden deterioration which is indicated by a hollow sound when struck. While work is in progress, the Contractor and Engineer shall jointly inspect and sound the concrete areas to be repaired to determine the limits of the work. 3.2.2 Removing deteriorated concrete to a sound concrete surface free of laitance, dirt, or other foreign material shall be done by power brushing, the use of jackhammers where their use is allowed, sawing, sandblasting, water blasting, mechanical abrading, hosing with water, air -blast cleaning, or other approved methods. If reinforcing steel is exposed when removing concrete to a sound surface, or if exposure of the reinfor cing steel in prepared areas is required by the plans, the minimum depth of removal shall be 1-1/2” behind the main reinforcing steel. If reinforcing steel is not exposed when removing concrete to a sound surface, and if exposure of the reinforcing steel in prepared areas is not required by the plans, the minimum depth of removal shall be 1/2” plus the maximum coarse aggregate size of the patching material. 3.2.3 The edges of all prepared areas shall be saw cut to a minimum depth of 1/2 ” plus the maximum coarse aggregate size of the patching material. On vertical surfaces, if forms are to be used, the shape of the areas to be patched shall be such that the entire area to be patched is easily accessible, as determined by the Engineer. Although an occasional distribution or tie reinforcing bar may be cut, main reinforcing steel shall not be saw cut except as shown on the plans. 3.2.4 Reinforcing steel or other steel to be in contact with the new concrete shall be cleaned of all grease, dirt, concrete mortar and injurious rust. Injurious rust shall be interpreted to mean rust which is not firmly bonded to the steel. Rust which is difficult to remove by vigorous scrubbing with a wire brush shall be considered firmly bonded to the steel. Method of Measurement

4.1Preparation for concrete repairs will be measured by the square yard to the nearest 0.1 of a square yard as determined by

actual surface measurements of the lengths and widths of all the surfaces prepared.

4.2Areas prepared to a sound surface without exposing reinforcing steel will be measured as Class I preparation areas. Areas

prepared to a sound surface a minimum of 1-1/2” behind the reinforcing steel will be measured as Class II preparation areas. Basis of Payment

5.1The accepted quantity of preparation for concrete repairs will be paid for at the Contract unit price per square yard complete.

Pay items and units:

512.01Preparation for Concrete Repairs, Class I Square Yard

512.02Preparation for Concrete Repairs, Class II Square Yard

New Hampshire Department of Transportation Standard Specifications – 2016

Description

General. This work shall consist of furnishing and placing Portland cement concrete of the classes specified including fly -

ash, silica fume, or ground granulated blast furnace slag as shown on the plans or as ordered. 1.1.1 The work also consists of furnishing, placing, and curing structural Portland cement concrete as shown on the plans or as ordered, to be accepted under Quality Assurance (QA) provisions.

1.2Classes of concrete. The following classes of concrete are included in these specifications Table 520 -1A - Method and

Table 520-1B - Performance (QC/QA).

Table 520-1A - Classes of Concrete

Concrete Class Minimum Expected 28 Day Compressive Strength1

Maximum Water/Cement Ratio2

Entrained Air Percent

Permeability Target Value6

PSI kΩ-cm AAA3 AAA 5,000 5,000 0.400 0.444 5 to 9 5 to 9 AA3 4,000 0.400 5 to 9 20 AA 4,000 0.444 5 to 9 20 A 3,000 0.464 4 to 7 10 B 3,000 0.488 3 to 6 T 3,000 0.559 ---- F 304 3.0 to 4.05 15 to 255

Table 420-1B - Class of Concrete – Performance Requirements (QC/QA) Concrete Class Minimum Expected 28 Day Compressive Strength Permeability Air Content Water/Cement Ratio Concrete Cover PSI kΩ Percent Percent Inch Minimum LSL USL LSL USL TV ± T AA 4.000 5 5.0 9.0 Mean - 0.030 Mean + 0.030 1/2 (T = ± 12) A 3,000 5 4.0 ---- ---- ---- ---- B 3,000 ----- 3.0 ---- ---- ---- ---- LSL - lower specification limit USL - upper specification limit Mean - calculated mean of all test results for a lot. TV - Target Value1 T - Tolerance 1 Target value is defined as the typical clearance as shown on the plans or as ordered by the Engineer, for each location to be evaluated. 1.2.1 Unless otherwise shown on the plans, the specified class of concrete shall be used in the following applicati ons. 1.2.1.1 Method Requirements.