2. Suliman AYEADH Al-Otaibi 424101812

1. Howaidi Mutlaq Al-Shaibani 424104337

Challenges of the Kingdom:

• Pumping Concrete in high-rise structures.

• Producing concrete in volumes.

• Hot weather conditions.

Pumping Concrete in High Rise Structures

Al-Zoebi Towers Al-Khobar

Al-Zoebi Towers in Khobar,

136 meters high, 32 story office tower,

is the tallest building in Eastern Province.

What is Ready Mixed Concrete:

It is the concrete which is prepared in a computerized

concrete batching plant.

Advantages of Ready Mixed Concrete:

1. Better quality concrete is produced.

2. Selected materials can be used in the production of RMC

and stored properly in the batching plant.

3. Ingredient materials for concrete production are weighed

and mixed by automated devices.

4. Elimination of storage space for basic materials at site.

5. Wastage of basic materials is avoided.

6. Labour associated with production of concrete is

eliminated.

7. Time required is greatly reduced.

8. Noise and dust pollution at site is reduced.

Quality Control of RMCQuality Control of RMC

It is defined as:It is defined as:

““Producing, improving, planning and servicing Producing, improving, planning and servicing with the most economical and practical with the most economical and practical way”way”Classification of Quality Control of RMC:Classification of Quality Control of RMC:

(a)(a) Forward ControlForward Control

(b)(b) Immediate ControlImmediate Control

(c)(c) Retrospective ControlRetrospective Control

Forward Control:Forward Control:

• Material storageMaterial storage

• Monitoring of qualities of materialsMonitoring of qualities of materials

• Modification of concrete mix designModification of concrete mix design

• Batching plant maintenanceBatching plant maintenance

• Transfer and weighing equipmentTransfer and weighing equipment

• Plant mixers and truck mixers Plant mixers and truck mixers

It covers the following:It covers the following:

Immediate Control:Immediate Control:

• WeighingWeighing

• Observation of concrete during production,Observation of concrete during production,

• Workability of the fresh concreteWorkability of the fresh concrete

• Making adjustments at the plant automatically Making adjustments at the plant automatically or manually to batched quantitiesor manually to batched quantities

• Inspection at delivery by driver and customer Inspection at delivery by driver and customer for uniformity and adjustments to workability for uniformity and adjustments to workability within company policy.within company policy.

It covers the following:It covers the following:

Retrospective Control:Retrospective Control:

• Sampling of concreteSampling of concrete

• Testing and monitoring of test resultsTesting and monitoring of test results

• Stock control of materialsStock control of materials

• Diagnosis and correction of faults identified Diagnosis and correction of faults identified from complaintsfrom complaints

It covers the following:It covers the following:

Concrete Construction PracticesConcrete Construction Practices• Batching and mixingBatching and mixing

In ready mixed concrete, the material quantities (cement, In ready mixed concrete, the material quantities (cement, coarse aggregate, fine aggregate, water and admixtures) coarse aggregate, fine aggregate, water and admixtures) are measured with a high degree of accuracy using the are measured with a high degree of accuracy using the computer.computer.

Fig-1

• Handling of Aggregates:Handling of Aggregates:

The aggregates are stocked in piles under the sheds to The aggregates are stocked in piles under the sheds to

protect them from weather and adequate drainage is protect them from weather and adequate drainage is

provided to eliminate gross variations in aggregate provided to eliminate gross variations in aggregate

moisture contents.moisture contents.

[[Fig-4]]

[[Fig-2]]

To maintain concrete temperature in the specified To maintain concrete temperature in the specified

range, ice or the chilled water should be used.range, ice or the chilled water should be used.

• Use of Ice or Chilled Water:Use of Ice or Chilled Water:

[Fig-3][Fig-3]

• Batching Equipment:Batching Equipment:- ManualManual

- Semi AutomaticSemi Automatic

- AutomaticAutomatic

[Fig-5][Fig-5]

Through mixing is essential for the complete blending Through mixing is essential for the complete blending

of the materials that are required for the production of of the materials that are required for the production of

homogeneous, uniform concrete. Long mixing times do homogeneous, uniform concrete. Long mixing times do

not improve the quality of concrete and may cause some not improve the quality of concrete and may cause some

breakdown of the aggregate and decreases the air content.breakdown of the aggregate and decreases the air content.

• Mixing of concrete ingredients:Mixing of concrete ingredients:

• Mixing Times:Mixing Times:

The optimum mixing time depends on:The optimum mixing time depends on:

[Fig-5][Fig-5]

(a)(a) Type of mixerType of mixer

(b)(b) Condition of mixerCondition of mixer

(c)(c) Speed of rotationSpeed of rotation

(d)(d) Size of chargeSize of charge

(e)(e) Nature of constituent materialsNature of constituent materials

A good thumb rule for minimum mixing time is 1 min A good thumb rule for minimum mixing time is 1 min of mixing time for 1 m of mixing time for 1 m3 3 of concrete plus ¼ min for of concrete plus ¼ min for

each each additional 1 m3 additional 1 m3

• Types of Mixers:Types of Mixers:(a)(a) Drum mixersDrum mixers

(b)(b) Pan mixersPan mixers

(c)(c) Continuous mixersContinuous mixers

• Mixing of Concrete:Mixing of Concrete:

(a)(a) Transit Mixed (or "truck-mixed") Concrete:Transit Mixed (or "truck-mixed") Concrete:In this method, all the raw ingredients are charged directly in the truck In this method, all the raw ingredients are charged directly in the truck mixer. Most or all water is usually batched at the plant. The mixer drum mixer. Most or all water is usually batched at the plant. The mixer drum is turned at charging (fast) speed during the loading of the materials. is turned at charging (fast) speed during the loading of the materials. There are three options for truck mixed concrete: There are three options for truck mixed concrete: • Concrete mixed at the job site.• Concrete mixed in the yard.• Concrete mixed in transit.

Concrete that is partially mixed in a plant mixer and then discharged into Concrete that is partially mixed in a plant mixer and then discharged into the drum of the truck mixer for completion of the mixing is called shrink the drum of the truck mixer for completion of the mixing is called shrink mixed concrete. mixed concrete.

(b) S(b) Shrink Mixed Concrete:hrink Mixed Concrete:

(c) (c) Central Mixed Concrete: Central Mixed Concrete:

Central mixing concrete batch plants include a stationary, plant-mounted Central mixing concrete batch plants include a stationary, plant-mounted mixer that mixes the concrete before it is discharged into a truck mixer. mixer that mixes the concrete before it is discharged into a truck mixer. Central-mix plants are sometimes referred to as wet batch or pre-mix Central-mix plants are sometimes referred to as wet batch or pre-mix plants. The truck mixer is used primarily as an agitating haul unit at a plants. The truck mixer is used primarily as an agitating haul unit at a central mix operation. Dump trucks or other non-agitating units are central mix operation. Dump trucks or other non-agitating units are sometimes be used for low slump and mass concrete pours supplied by sometimes be used for low slump and mass concrete pours supplied by central mix plants. Principal advantages include: central mix plants. Principal advantages include:

• Faster production capability than a transit-mix plantFaster production capability than a transit-mix plant• Improved concrete quality control and consistency and Improved concrete quality control and consistency and

reduced wear on the truck mixer drums.reduced wear on the truck mixer drums.• There are several types of plant mixers, including: There are several types of plant mixers, including:

- Tilt drum mixer- Tilt drum mixer- Horizontal shaft paddle mixer - Horizontal shaft paddle mixer - Dual shaft paddle mixer - Dual shaft paddle mixer - Pan mixer - Pan mixer - Slurry mixer- Slurry mixer

[FIG-6][FIG-6]

Transportation of Ready Mixed Concrete:Transportation of Ready Mixed Concrete:

• Freshly mixed concrete may be transported in a open dump truck Freshly mixed concrete may be transported in a open dump truck if the jobsite is near the plant. if the jobsite is near the plant.

• It is remixed once it arrives at the jobsite to ensure that the proper It is remixed once it arrives at the jobsite to ensure that the proper slump is obtained.slump is obtained.

• The concrete that is remixed at jobsite tends to set more rapidly The concrete that is remixed at jobsite tends to set more rapidly than concrete mixed only once. than concrete mixed only once.

• Materials, such as water and some varieties of admixtures, are Materials, such as water and some varieties of admixtures, are often often added to the concrete at the jobsite after it has been batched to added to the concrete at the jobsite after it has been batched to ensure that the specified properties are attained before placement.ensure that the specified properties are attained before placement.

• Slight agitation of the concrete during transit prevents segregation Slight agitation of the concrete during transit prevents segregation of the materials and reduces the amount of slump loss. of the materials and reduces the amount of slump loss.

SAMPLING OF CONCRETESAMPLING OF CONCRETE

Sampling is done by:Sampling is done by:

• The Company - To maintain the required standard, the company performs cube and cylinder tests and the test results are analyzed.

• The Municipality - The mobile teams of Riyadh Municipality takes random samples of mixed concrete and test the physical properties of concrete and prepare report for the renewal of the licensee for the next year.

Sampling concrete from a ready mixed concrete truck:Sampling concrete from a ready mixed concrete truck:  

Molding and Curing Concrete CylindersMolding and Curing Concrete Cylinders

A representative sample of concrete is obtained from the truck A representative sample of concrete is obtained from the truck mixer. mixer.

Concrete should be sampled from the middle of the load.Concrete should be sampled from the middle of the load.

Ice Plants, Aggregate washing plants to ensure high quality of Ice Plants, Aggregate washing plants to ensure high quality of concreteconcrete

Almost any natural water that is drinkable and has no pronounced taste or odor may be used as mixing

water for concrete. However, some waters that are not fit for drinking may be suitable for concrete .

Excessive impurities in mixing water not only may affect time and concrete strength, but also may cause

efflorescence, staining, corrosion of reinforcement, volume instability and reduced durability .

Specifications usually set limits on chlorides, sulfates, alkalis, and solids in mixing water unless

tests indicate that the water will not negatively impact concrete properties .

Well equipped Quality Control lab in accordance with BS and ASTM.

The aggregates should be clean and free from any matter The aggregates should be clean and free from any matter that might affect the quality of the concrete. that might affect the quality of the concrete.