Reinforced Concrete Procedures

Reinforced concrete is concrete with long bars inside to make it stronger. The reinforcing material has greater tensile strength than concrete has. Usually the bars are steel. Galvanizing saves the steel from rusting and corrosion. In rich countries, almost all concrete in buildings and roads is reinforced. Reinforced concrete is stronger than normal concrete.
Reinforced concrete (RC) (also called reinforced cement concrete or RCC) is a composite material in which concrete's relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars (rebar) and is usually embedded passively in the concrete before the concrete sets. 

Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with rebar or not. Reinforced concrete may also be permanently stressed (concrete in compression, reinforcement in tension), so as to improve the behaviour of the final structure under working loads. In the United States, the most common methods of doing this are known as pre-tensioning and post-tensioning.

For a strong, ductile and durable construction the reinforcement needs to have the following properties at least:
  1. High relative strength
  2. High toleration of tensile strain
  3. Good bond to the concrete, irrespective of pH, moisture, and similar factors
  4. Thermal compatibility, not causing unacceptable stresses (such as expansion or contraction) in response to changing temperatures.
  5. Durability in the concrete environment, irrespective of corrosion or sustained stress for example.
In getting a qualified concrete quality and economical, which can serve as guidelines in concrete quality control (quality control) on the implementation of a concrete construction in the field, to do a series of checks and tests / test lab on the materials (aggregate) which will be used to the manufacture of concrete.

Mix Design Procedure
1 Required material information -- sieve analyses of both fine and coarse aggregates, unit weight, specific gravities, and absorption capacities of aggregates.
2 Choice of slump -- Generally specified for a particular job. However, if not given, an appropriate value may be chosen from Table 1. As a general rule, the lowest slump that will permit adequate placement should be selected.
Table 1. Recommended Slumps for Various Types of Construction
3 Maximum aggregate size -- The largest maximum aggregate size that will conform to the following limitations:
  • Maximum size should not be larger than 1/5 the minimum dimension of structural members, 1/3 the thickness of a slab, or 3/4 the clearance between reinforcing rods and forms. These restrictions limit maximum aggregate size to 1.5 inches, except in mass applications.
  • Current thought suggests that a reduced maximum aggregate size for a given w/c ratio can achieve higher strengths. Also, in many areas, the largest available sizes are 3/4 in. to 1 in.
4 Estimation of mixing water and air content -- An estimation of the amount of water required for non-air-entrained and air-entrained concretes can be obtained from Table 2a and Table2b. Approximate mixing water (lb./yd.3) and air content for different slumps and nominal maximum sizes of aggregates 
Table 2a Non-Air-Entrained Concrete
Approximate mixing water (lb./yd.3) and air content for different slumps and nominal maximum sizes of aggregates
Table 2b Air-Entrained Concrete
5 Water/cement ratio - This component is governed by strength and durability requirements
(a) Strength -- Without strength vs. w/c ratio data for a certain material, a conservative estimate can be made for the accepted 28-day compressive strength from Table 3.
(b) Durability -- If there are severe exposure conditions, such as freezing and thawing, exposure to seawater, or sulfates, the w/c ratio requirements may have to be adjusted. 
Relationship between water/cement ratio and compressive strength of concrete
6 Calculation of cement content -- Once the water content and the w/c ratio is determined, the amount of cement per unit volume of the concrete is found by dividing the estimated water content by the w/c ratio.

weight of cement = weight of water
                                       w/c
However, a minimum cement content is required to ensure good finishability, workability, and strength.
7 Estimation of coarse aggregate content - The percent of coarse aggregate to concrete for a given maximum size and fineness modulus is given by Table 4.
The value from the table multiplied by the dry-rodded unit weight (the oven-dry (OD) weight of coarse aggregate required per cubic foot of concrete). To convert from OD to saturated surface dry (SSD) weights, multiply by [1 + absorption capacity (AC)].
Table 4 Volume of dry-rodded coarse aggregate per unit volume of concrete for different coarse aggregates and fineness moduli of fine aggregates

8 Estimation of fine aggregate content -- There are two standard methods to establish the fine aggregate content, the mass method and the volume method. We will use the "volume" method.
  • Volume Method -- This method is the preferred method, as it is a somewhat more exact procedure
  • The volume of fine aggregates is found by subtracting the volume of cement, water, air, and coarse aggregate from the total concrete volume.
9 Adjustment for moisture in the aggregate -- The water content of the concrete will be affected by the moisture content of the aggregate.

10 Trial batch 
  • Using the proportions developed in the preceding steps, mix a trial batch of concrete using only as much water as is needed to reach the desired slump (but not exceeding the permissible w/c ratio).
  • The fresh concrete should be tested for slump, unit weight, yield, air content, and its tendencies to segregate, bleed, and finishing characteristics. Also, hardened samples should be tested for compressive and flexural strength.
Procedure For Mixing Concrete
1. Weigh out the designed proportions for a 1.6 cubic foot batch of concrete. Divide the water into two buckets, one with about 3/4 of the water. If using air entraining, put the air entraining agent in the 3/4 water bucket.
2 Put about half the coarse aggregate, half the fine aggregate and the 3/4 bucket of water with air entraining in the mixer. 
3 Start the mixer and mix until the aggregate is thoroughly wet
4 Carefully add all the cement with the mixer running. Try not to make a lot of dust! Add a little more water and mix until all the cement is blended in.
5 Incrementally add the rest of the coarse and fine aggregate – mix until blended in
6 In very small increments, add enough water from the final quarter of the water to produce a workable mix. A little water goes a long way!!
7 Mix for three minutes, followed by a three minute rest, followed by a two minute final mixing. Cover the mixer opening with a damp towel while resting.
8 Dump some mix out of the mixer into a pan. Perform a slump test. If results are satisfactory, skip to the next step, otherwise:
  • If the slump is less than required, return the concrete to the mixer, add any remaining water, and mix for one minute. 
  • Perform a second slump test. If results are satisfactory, move on.
  • If the slump is still less than required, return the concrete to the mixer, add additional water, as well as additional portland cement to maintain the desired water/cement ratio (Wt. of PC added = Wt. of water added/WC ratio), and mix for one minute. 
  • Continue taking slump tests and adding water and cement until the desired slump is obtained. 
9 Record the final slump and the actual weight of water and cement used.
10 If using superplasticizer, add it to the mixer and mix for one minute. Perform another slump test and record the value.

Procedure For Slump Test 
1 Dampen the slump test mold and place it on a flat, moist, nonabsorbent, rigid surface, like a steel plate. 
2 Fill the mold to 1/3 full by volume (about 2 1/2 inches), and rod the bottom layer with 25 evenly spaced strokes. 
3 Fill the mold to 2/3 full (about 6 inches), and rod the second layer with 25 strokes penetrating the top of the bottom layer. 
4 Heap the concrete on top of the mold, and rod the top layer with 25 strokes penetrating the top of the second layer. 
5 Strike off the top surface of the concrete even to the top of the mold. 
6 Remove the mold carefully in the vertical direction (take about five seconds). 
7 Immediately invert an place the mold beside the slumped concrete and place the rod horizontally across the mold, and measure the slump, in inches, to the nearest 1/4 inch. The slump test should take approximately 2 1/2 minutes. 

Procedure For Casting Cylinders Or Cubes
1 Place the casting molds on the concrete floor. 
2 Fill the mold to 1/3 full by volume (4 inch depth) and rod the bottom layer with 25 strokes evenly spaced. 
3 Fill the mold to 2/3 full (8 inch depth) and rod the second layer with 25 strokes penetrating the top of the second layer. 
4 Heap the concrete on the top of the mold and rod the top layer with 25 strokes penetrating the top of the second layer. 
5 Tap the sides of the mold lightly to close the voids left by the rod. 
6 Strike off the top surface of the concrete using a sawing action with the rod. Take special care to smooth the surface. Be sure to mark the cylinders with your group number, cylinder/cube number, batch number, and date. 
7 Carefully move the cylinders/cubes to temporary storage. 
8 Cover the cylinders/cubes with a cap or plastic bag. 
9 After 20 to 48 hours two people must return to the lab to remove the molds and place them in the wet room. 
10 Transfer your identifying marks from the molds to the top of the cylinders. 

Preparation For Foundation Work
1. Installation bowplank and made center line and elevation that will guide the implementation of the basic foundation work.
2. Installation of auxiliary markers made at least 3 M 'from the foundation walls.
3. BM making at least 1 point.

Construction For Foundation Work
1 Excavation of land in accordance with the design drawings elevation will be covering, with existing Soil and sand gravel.
2 When backfill is solid, it can proceed with lean concrete work / work floor with a minimum thickness of 5 cm, the quality of concrete Fc-175.
3 Fabrication of form work / formwork foundation.
4 Reinforced fabrication in accordance with bending which has been approved by the user.
5 Pile cutting (cutting pile) are above the lean concrete and iron was not cut, which will be used as steak / anchor.
6 Marking the position of pile cup and pedestal will be installed form work / foundation formwork so that the position can e changed ( Fix ) .
7 When marking is complete , then proceed with the installation of form work on the outside of the foundation ( installed around the foundation ) until it becomes a circle .
8 After installation of the foundation form work outside completed , then proceed with the reinforced installation pile cap and pedestal . Reinforced installation work can be done on the day and night .
9 Once the form work and reinforced installation work 100 % foundation completed , the inspection may be requested from the user to the foundry and made plans to be at the inspection list .
10 For casting concrete foundation , using ready mix concrete ( if any ) with the quality of concrete Fc-300 . But if there is no concrete ready mix , it can be done with the site mix .
11 When the job is finished joint inspection and approved by the supervisor / user , it can be done the first stage of the concrete slab casting , foundry execution is done in the daytime using ready mix concrete mix or site , and at the time of casting the field , made an prepared Concrete gutters cord Vibrator minimal 2 units . To Concrete vibrator is for leveling and compacting concrete in order not porous . Each casting 50 cubic yard sample taken 1 pieces cube / cylinder.

Preparation For Floor And Roof Concrete Work
1 . Stop Rubber / Rubber Water Stop installed together with the installation floor deck 
2 . To add strength to the connection piece floor deck, must be carried out with pliers clamping jaws .
3 . After the entire field floor deck installed , followed with the installation of shear connector at a meeting floor deck by Steel IWF ( The Valley of the line shear connector installed ) .
4 . Wire Mesh that serves as the foundation reinforcement and shrinkage reinforcement can installed after the installation of shear connector, The addition of welding / welding can be done if the shear connector necessary .
5 . Installation edge form of work done around the floor (Dimension Edge Form made in accordance with the planned slab thickness ) .
6 . Along the Edge Form is required fastener to keep spills castings /concrete when casting takes place .
7 . After six stages above work is done , the casting for the floor areas can be carried out before the job is done , the floor cleaned before work.

Inspection And Testing At Laboratory
Inspection and testing at the Laboratory include:
1. Examination / analysis fine and coarse aggregate gradation: ASTM C-35, SK SNI M-08-9989-F.
2. Fineness modulus of fine aggregate: ASTM C-33, SK SNI M-08-1989-F.
3. Examination of specific gravity of fine aggregate and coarse; ASTM C-12, SK SNI M-09-1989-F and SK SNI M-10-1989-F
4. Examination of the contents of heavy fine and coarse aggregates.
5. Examination of fine and coarse aggregate infiltration; Sk-SNI M-09-1989 and SK SNI M-10-1989-F.
6. Levels examination Lumpur fine and coarse aggregates.
7. Wear testing of coarse aggregate with Los Angeles Abrasion, SNI 03 M-04-1991.
8. Unit weight of concrete inspection; SK SNI M-13-1990-F
9. Slump examination; SK SNI M-12-1989-F
10. Manufacture and testing of concrete test samples; SK SNI M-14-1989-F

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