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AC2.11 Sealers and Clear Surface Coatings

If sealers or clear surface coatings are specified for architectural surfaces, testing shall be performed on reasonable size samples of varying age. The performance shall be monitored over a suitable period of time and under representative exposure conditions. Prior experience that demonstrated acceptable performance under similar exposure conditions may substitute for testing. Clear sealers shall be guaranteed by the supplier or applicator not to stain, soil, darken, or discolor the finish. The clear sealer should not cause joint sealants to stain the panel surface or affect the bond of the joint sealant. The manufacturers of both the joint sealant and the sealer shall be consulted regarding compatibility prior to application, or the material shall be pretested.

Sealers or clear surface coatings may be considered for the possible improvement of weathering characteristics.

The quality of concrete normally specified for Category BA or CA products, even with minimum practical thickness, does not require sealers for waterproofing in most applications.

3.1 Concrete Materials 3.1 Concrete Materials

3.1.1 General

Frequent inspections shall be performed to check and evaluate test results and the finished product to identify changes that may adversely affect the properties of the concrete mix.

C3.1.1 General

3.1.2 Cement

The type and kind of cement shall be selected to provide predictable strength and durability. Cement shall conform to ASTM C150. Concrete mixes using cement conforming to ASTM C595, C845 or C1157 shall be tested and evaluated for the intended applications.

Each shipment of cement shall be referenced to a certified mill test report that indicates compliance with the specified type of cement and ASTM C150. The producer shall maintain the test reports on file.

C3.1.2 Cement

Unless specified, the producer should have the choice of the type and kind of cement to use for achieving the specified physical properties.

3.1.3 Fine Aggregate

Fine aggregate for concrete mixes, other than lightweight aggregate, shall consist of high quality natural sand or sand manufactured from coarse aggregate. The fine aggregate shall comply with ASTM C33 or applicable specified requirements.

Variations in fineness modulus of fine aggregate shall not exceed ±0.20 from the value used for the mix design. Additionally, the amount retained on any two consecutive sieves shall not change by more than 10% by weight of the total fine aggregate sample.

Fine aggregate shall be obtained from sources in which representative samples have been tested in accordance with the governing specifications.

Acceptable concrete-making properties of the aggregate shall have been demonstrated by trial mixes.

C3.1.3 Fine Aggregate

For the fine aggregate, the material passing the No. 100 (150 µm) sieve should not exceed 5%. In addition, the maximum variation of the material passing the No. 100 (150 µm) sieve, as established in the initial mix design, should not exceed 1% to ensure uniformity of the concrete mix.

3.1.4 Coarse Aggregate

Coarse aggregate for concrete mixes, other than lightweight mixes, shall conform to the requirements of ASTM C33.

The maximum size of coarse aggregate shall not exceed:

1. One-third of the minimum section thickness.

C3.1.4 Coarse Aggregate

Coarse aggregate may be selected on the basis of the desired material properties, cost, or availability provided the required level of strength, durability, finishability, and workability of the mix are met.

DIVISION 3 RAW MATERIALS AND ACCESSORIES

Standard Commentary

Page 3.2 MNL-116 4th Edition

2. Three-fourths of the minimum clear depth of cover.

3. Two-thirds of the spacing between individual reinforcing bars, bundles of bars, pretensioning tendons, or post-tensioning ducts.

Coarse aggregate shall be obtained from sources in which representative samples have been tested in accordance with the governing specifications.

Acceptable concrete-making properties shall have been demonstrated by trial mixes.

3.1.5 Aggregates for Lightweight Concrete Lightweight aggregate shall conform to the requirements of ASTM C330. Provisions for testing shall be as stipulated in Articles 6.2.2 and 6.2.3 of this manual except for testing of gradation, unit weight, and impurities. These tests shall be performed in accordance with the requirements of ASTM C330.

C3.1.5 Aggregates for Lightweight Concrete

Producers using lightweight aggregate should be experienced in mixing and placing lightweight concrete.

The effects of the aggregate weight and shrinkage characteristics often require special attention to ensure a reasonably uniform exposed aggregate finish is obtained.

Lightweight aggregate generally has a high absorption rate. If the aggregate is not saturated, it will absorb water from the mix, potentially causing a rapid slump loss. The ACI Committee 213 report titled, “Guide for Structural Lightweight Aggregate Concrete,” provides a thorough discussion of lightweight aggregate properties, including proportioning and mixing practices.

3.1.6 Mixing Water

Water, either potable or non-potable, shall be free from injurious amounts of substances that may be deleterious to the performance or quality of the concrete and steel.

Water from a source other than a municipal water supply shall be tested on an annual basis as required in Article 6.2.2. The water shall not exceed the maximum concentration limits given in Table 3.1.6.

C3.1.6 Mixing Water

Excessive impurities may cause efflorescence, staining, increased volume change, and reduce durability.

Accordingly, limits should be set on deleterious substances contained in the mix water. Some impurities have little effect on strength and setting time; however, can adversely affect durability and other properties. In particular, the chloride ion content should be limited to a level well below the recommended maximum, when practical. Chloride ions contained in the aggregate and in admixtures should be considered in evaluating the acceptability of the total chloride ion content of mix water.

Table C3.1.6 identifies some of the more common substances and concentration limits that are known to be deleterious to concrete. Also provided in Table C3.1.6 are associated ASTM test methods for identifying and quantifying such substances. Other recognized methods such as the Environmental Protection Agency (EPA) test methods may be used when applicable.

Table C3.1.6 Chemical Limits for Non-Potable Silt or suspended particles p H a Other methods such as EPA or those used by water

testing companies are generally acceptable b No ASTM method available.

3.1.7 Admixtures

If a satisfactory history of admixture performance with specific concrete materials is not available, a trial mixture program with the concrete materials, particularly the cement, shall be conducted. The trial mixture program shall demonstrate satisfactory performance of the admixture relative to slump, workability, air content, finishability, and strength.

Variations in temperature and humidity that may affect the admixture performance shall be addressed in the trial mixture program. Admixtures shall be carefully checked for compatibility with the cement or other admixtures. Effects of variations in the dosage rate and the sequence of charging the admixtures into the mixer shall be determined from the recommendations of the admixture supplier or by trial mixes.

C3.1.7 Admixtures

Admixtures should be materials of standard manufacturing that have established records of tests to confirm acceptable properties and performance.

Expected performance of a given brand, class, or type of admixture may be obtained from one or more of the following sources:

1. Results from jobs, which have used the admixture under good technical control, and preferably using the same materials, under similar service conditions.

2. Technical literature and information from the manufacturer of the admixture.

3. Laboratory tests made to evaluate the admixture.

Trial mixtures can be made at midrange slump and air contents expected or specified for the project. The cement content or water-cementitious material ratio (w/cm) should be that required for the specified design strength and durability requirements of the job. Trial mixtures also can be made with a range of cement contents, w/cm, slumps, or other properties to bracket the project requirements. In this manner, the optimum mixture proportions can be selected for achieving the required results.

Admixture performance will vary due to differences in dosage rates; cement composition and fineness; cement content; aggregate size and gradation; interaction with other admixtures; sequencing; changes in w/cm; and variations in weather conditions.

DIVISION 3 RAW MATERIALS AND ACCESSORIES

Standard Commentary

Page 3.4 MNL-116 4th Edition

Air entraining admixtures shall conform to the requirements of ASTM C260. Water reducing, retarding, or accelerating admixtures shall conform to the requirements of ASTM C494. High-range water-reducing admixtures (HRWR), also referred to as superplasticizers, shall conform to the requirements of ASTM C494, Type F or G, or ASTM C1017, Type 1 or 2, for flowing concrete. Calcium chloride or admixtures containing chloride ions (Cl^-), other than impurities from the admixture ingredients, shall not be used in prestressed concrete. This is to ensure against the development of deleterious concentrations of chloride ions in the mixing water that may cause corrosion.

Mineral admixtures or pozzolans meeting ASTM C618 or C1240 may be added for additional workability, increased strength, reduced permeability, and reduced efflorescence. If an HRWR is used with silica fume, the admixture shall be compatible with any admixture that may be contained in the silica fume. The amount of silica fume or metakaolin used in concrete shall not

The use of air entrainment is recommended to enhance durability when concrete will be subjected to freezing and thawing in wet conditions.

Water reducing admixtures can be used in a variety of ways to potentially enhance the characteristics and performance of concrete. The following are several such examples:

1. A reduction in the water content while maintaining the same level of consistency.

2. Increasing the workability without increasing the water content.

3. Increasing or maintaining strength while maintaining or lowering the cementitious material content, respectively.

The reduction in w/cm achieved by reducing the mix water may produce a greater strength improvement than a similar reduction in the w/cm obtained by adding cement.

There are a variety of water-reducing admixtures classified by the amount of potential water reduction that the admixture can facilitate at a given dosage rate. The general effect of any type of water-reducing admixture on hardened concrete is increased compressive strength and a reduction in permeability. The degree to which this is achieved is primarily dependent on the amount of water reduction facilitated by the admixture.

Retarding admixtures are used primarily to offset the accelerating effect of high temperature on the set characteristics of the concrete. This is frequently used to help maintain concrete plasticity between succeeding lifts to avoid the development of cold joints or discontinuities in the unit.

High-range water-reducing admixtures can be used to increase slump without adding more water, or reduce water content without a corresponding loss in slump.

Concrete mixes containing these admixtures, particularly those with initial slumps less than 3 to 4 in. (75 to 100 mm) and low w/cm, tend to lose slump and stiffen rapidly. Some high-range water-reducers combined with a retarder maintain slump for an extended period.

When a particularly smooth surface is desired, the addition of fine minerals or pozzolans conforming to ASTM C618 may be desirable. These materials also may be added to improve workability, durability, or to reduce the possibility of efflorescence. The use of fly ash or silica fume (microsilica) in a concrete mixture will darken the concrete color. The color of silica fume

exceed 10% by weight of the portland cement unless it is demonstrated that the concrete will satisfy strength, durability, and volume stability requirements.

depends on carbon content and several other variables.

Silica fume from one source may be nearly white in color, while from another, may be black. Metakaolin is a white, dry powder and does not darken white or gray concrete.

3.2 Reinforcement and Hardware

3.2.1 Reinforcing Steel

Steel reinforcing bars shall be deformed bars of the designated type, size, and grade. The bars shall conform to the following applicable specifications as shown on the production drawings:

Billet-Steel Deformed Bars ASTM A615/A615M Low Alloy Steel Deformed Bars ASTM A706/A706M Rail-Steel Deformed Bars ASTM A616/A616M Axle-Steel Deformed Bars ASTM A617/A617M