CMAT

Item 900-

Structural Concrete -  THIS ITEM SHALL CONSIST OF FURNISHING, PLACING AND FINISHING CONCRETE IN BUILDINGS AND RELATED STRUCTURES, FLOOD CONTROL AND DRAINAGE, PORTS, AND WATERS STRUCTURES IN ACCORDANCE WITH THIS SPECIFICATION AND CONFORMING TO THE LINES, GRADES, AND DIMENSION SHOWN ON THE PLANS

 

FIVE CLASSES OF CONCRETE- CLASS A, CLASS B, CLASS C, CLASS P, CLASS SEAL

 

1. Class A- All superstructures and substructures which includes the important ones such as slabs, columns, girders, beams, arch ribs, etc.

2.  Class B- Pier shafts, Pipe beddings, slab on fill, gravity walls (unreinforced or with only a small amount of reinforcement), and other miscellaneous concrete structures

3. Class c- Thin Reinforced sections, railings, precast r.c. piles amd cribbing, and for filler in steen grib floors

4. Class P- prestressed concrete structures and members

5. Class seal- cocnerete deposited in water

 

 

 

Important notes:

900.2.2 - Concrete aggregates

Concrete aggregates- shall conform to astm c33m, standard specification for concrete aggregates

Lightweight concrete aggregates- shall conform to astm c330m

 

 

THE AGGREGATE SHALL BE OR NOT LARGER THAN 1/5 OF THE NARROWEST DIMENSIONS BETWEEN SIDES OF FORMS OF THE MEMBER FOR WHICH THE CONCRETE IS TO BE USED NOR LARGER THAN 3/4 OF THE MINIMUM CLEAR SPACING BETWEEN INDIVIDUAL REINFORCING BARS OR BUNDLES OF BARS OR PRE-TENSIONING STRANDS.

 

 

900.2.2.1 - Fine aggregates

Fine aggregates- should consist of natural or crushed sand, stone screenings, and other inert materials with similar characteristics

 

The fine aggregate- may be used if the relative strength in its 7th and 28th day is not less than 95%

 

900.2.2 - Coarse Aggregates

 

Coarse aggregates- shall consist of crushed stone, gravel, blast furnace slag, or other inert materials of the same characteristics

 

IF THE SLAG IS USED, ITS DENSITY SHALL NOT BE LESS THAN 1,120 KG/M³.

 

 

 

Note: THE MEASURED CEMENT CONTENT SHALL BE WITHIN PLUS (+) OR MINUS (-) 2 MASS PERCENT OF THE DESIGN CEMENT CONTENT.

 

 

900.2.3 WATER

WATER USED IN MIXING- CURING OR OTHER DESIGNATED APPLICATION SHALL BE REASONABLY CLEAN AND FREE OF OIL, SALT, ACID, ALKALI, GRASS OR OTHER SUBSTANCES INJURIOUS TO THE FINISHED PRODUCT

 

WATER WHICH IS DRINKABLE MAY BE USED WITHOUT TEST.

 

 

For water: TIME OF SETTING DEVIATION FROM CONTROL, H:MIN A = FROM 1:00 EARLIER TO 1:30 LATER

 

 

 

900.2.4- Metal Reinforcements

 

REINFORCING STEEL BARS- SHALL CONFORM TO THE REQUIREMENTS OF SUBSECTION 902.2, MATERIAL REQUIREMENTS OF ITEM 902, REINFORCING STEEL

 

 

 

900.2.5 ADMIXTURES

 

AIR-ENTRAINING ADMIXTURES- IF USED, SHALL CONFORM TO ASTM C260M, STANDARD SPECIFICATION FOR AIR ENTRAINING ADMIXTURES FOR CONCRETE.

 

AIR-ENTRAINING ADMIXTURE- SHALL CONFORM TO THE REQUIREMENTS OF AASHTO M 154, STANDARD METHOD OF TEST FOR TIME OF SETTING OF HYDRAULIC CEMENT PASTE BY GILLMORE NEEDLES.

 

CHEMICAL ADMIXTURES,- IF USED, SHALL CONFORM TO THE REQUIREMENTS OF ASTM C494M, STANDARD SPECIFICATION FOR CHEMICAL ADMIXTURES FOR CONCRETE OR AASHTO M 194, STANDARD SPECIFICATION FOR CHEMICAL ADMIXTURES FOR CONCRETE.

 

FLY ASH, IF SPECIFIED OR PERMITTED AS A MINERAL ADMIXTURE AND NOT EXCEEDING 20 PARTIAL REPLACEMENT OF PORTLAND CEMENT IN CONCRETE MIX SHALL CONFORM TO THE REQUIREMENTS OF ASTMC618, STANDARD SPECIFICATION FOR COAL FLY ASH AND BA OR CALCINED NATURAL POZZOLAN FOR USE IN CONCRETE.

AS WORK PROGRESSES, AT LEAST ONE (1) SAMPLE CONSISTING OF THREE (3) CONCRETE CYLINDER TEST SPECIMENS, 150 MM X 300 MM, SHALL BE TAKEN FROM EACH 75 M³ OF EACH CLASS OF CONCRETE OR FRACTION THEREOF PLACED EACH DAY.