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90-2.03 CONSTRUCTION

Maintain a concrete temperature of at least 40 degrees F for 72 hours after placing.

90-2.04 PAYMENT

Not Used

90-3 RAPID STRENGTH CONCRETE

90-3.01 GENERAL

90-3.01A Summary

Section 90-3 includes specifications for furnishing and curing RSC.

Section 90-3 applies only where the specifications allow the use of RSC.

90-3.01B Definitions

Reserved

90-3.01C Submittals

90-3.01C(1) General

Reserved

90-3.01C(2) Volumetric Proportioning

For volumetric-proportioned RSC, submit:

1. Aggregate moisture test results

2. Log of production data

3. Test samples of freshly mixed concrete for uniformity testing

Sampling facilities must be safe, accessible, and clean, and must produce a test sample that is representative of production. The sampling devices and methods must comply with California Test 125.

90-3.01C(3) Certificate of Compliance

Submit a certificate of compliance with each delivery of aggregate, cementitious material, and admixtures used for calibration tests. Include certified copies of the weight of each delivery.

The certificate of compliance must state that the source of the materials used for the calibration tests is the same source as to be used for the planned work. The certificate must be signed by your assigned representative.

90-3.01C(4) Weighmaster Certificate

Submit weighmaster certificates for RSC. Regardless of the proportioning method used, the certificates must include all the information necessary to trace the manufacturer and manufacturer's lot number for the cement used.

The weighmaster certificate for the cement must include:

1. Date of proportioning

2. Location of proportioning

3. Actual net draft cement weight, if proportioned into fabric containers

4. Net draft cement weight used in the load, if proportioned at the pour site from a storage silo

90-3.01C(5) Production Data

For volumetric-proportioned RSC, submit the daily production data in electronic or printed media at the end of each production shift. Report the data, including data titles, in the following order:

1. Weight of cement per revolution count

2. Weight of each aggregate size per revolution count

3. Gate openings for each aggregate size

4. Weight of water added to the concrete per revolution count

5. Moisture content of each aggregate size

6. Individual volume of admixtures per revolution count

7. Time of day

8. Day of week

9. Production start and stop times

10. Volumetric mixer identification

11. Name of supplier

12. Specific type of concrete being produced

13. Source of the individual aggregate sizes

14. Source, brand, and type of cement

15. Source, brand, and type of individual admixtures

16. Name and signature of the operator
The device controlling the proportioning of cement, aggregate, and water must produce production data that is captured at 15-minute intervals throughout daily production. Each capture of production data must represent the production activity at that time and must not be a summation of data. The quantity of material represented by each production capture is the quantity produced in the period from 7.5 minutes before to 7.5 minutes after the capture time.

Production data must be input by hand into a pre-printed form or captured and printed by the proportioning device. Present electronic media containing recorded production data in a tab-delimited format on a CD or DVD. Each capture of production data must be followed by a line feed carriage return with sufficient fields for the specified data.

90-3.01D Quality Assurance

90-3.01D(1) General

Reserved

90-3.01D(2) Penetration

The specifications for penetration in section 90-1.02G(6) do not apply to RSC.

90-3.01D(3) Aggregate Moisture

For volumetric-proportioned RSC, determine the aggregate moisture under California Test 223 at least every 2 hours during proportioning and mixing. Record the aggregate moisture determinations and submit them at the end of each production shift.

90-3.01D(4) Concrete Uniformity

For volumetric-proportioned RSC, the Engineer determines the uniformity of concrete mixtures based on differences in penetration measurements when tested under California Test 533. Differences in penetration are determined by comparing the penetration tests on 2 test samples of mixed concrete from the same batch or volumetric mixer load.

90-3.02 MATERIALS

90-3.02A General

RSC must be one of the following:

1. Concrete complying with section 90-1. You may use Type III portland cement.

2. Concrete complying with section 90-1, except:

2.1. You may use any cement that complies with the definition of hydraulic cement or blended hydraulic cement in ASTM C219 and must have the requirements for the quality characteristics shown in the following table:

Quality characteristic	Test method	Requirement^b
Contraction in air (%, max)	California Test 527, W/C ratio = 0.390 ± 0.010	0.053
Mortar expansion in water (%, max)	ASTM C1038	0.04
Soluble chloride^a (%, max)	California Test 422	0.05
Soluble sulfate^a (%, max)	California Test 417	0.30
Thermal stability (%, min)	California Test 553	90
Compressive strength at 3 days (psi, min)	ASTM C109	2,500
^aPerform the test on a cube specimen fabricated in compliance with ASTM C109, cured for at least 14 days, and then pulverized such that 100 percent passes the no. 50 sieve. ^bIf you use chemical admixtures, include them when testing.

2.2. You may use citric acid or borax if you submit a written request from the cement manufacturer and a test sample.
The requirement for air entrainment of concrete in freeze-thaw areas applies only when portland cement is used.

SCM is not required in RSC.

When tested for uniformity under section 90-3.01D(4), the difference in penetration between the 2 concrete test samples must not exceed 5/8 inch.

90-3.02B Volumetric Proportioning

90-3.02B(1) General

RSC may be proportioned and placed using a volumetric mixer.

90-3.02B(2) Proportioning

Volumetric mixers must proportion cement, water, aggregate, and additives by volume.

Proportion aggregate using a belt feeder that is operated with an adjustable cutoff gate delineated to the nearest quarter increment. The gate opening height must be readily determinable.

Proportion cement by any method that complies with the accuracy tolerance specifications in section 90-1.02F(3).

Proportion water with a meter.

Proportion liquid admixtures under section 90-1.02F(4)(b), except proportion liquid admixtures with a meter.

90-3.02B(3) Mixer Requirements

Mix volumetric-proportioned RSC in a mechanically operated mixer. You may use an auger-type mixer. Operate the mixer uniformly at the mixing speed recommended by the manufacturer. Do not use a mixer that has an accumulation of hard concrete or mortar.

Volumetric mixers must comply with the following:

1. Aggregate feeders must connect directly to the drive on the cement vane feeder.

2. Cement feed rate must be tied directly to the feed rate for the aggregate and other ingredients. The ratio of cement to aggregate must be changed only by changing the gate opening for the aggregate feed.

3. Drive shaft of the aggregate feeder must have a revolution counter reading to the nearest full or partial revolution of the aggregate delivery belt.
Do not use equipment with components made of aluminum or magnesium alloys that could have contact with plastic concrete during mixing or transporting of the RSC.

Cover the rotating and reciprocating equipment on volumetric mixers with metal guards.

The identifying numbers of volumetric mixers must be at least 3 inches in height and must be located on the front and rear of the vehicle.

Each mixer must have metal plates that state the designed usage, the manufacturer's guaranteed mixed concrete volumetric capacity, and the rotation speed.

Locate cement storage immediately before the cement feeder. Equip the system with a device that automatically shuts down power to the cement feeder and aggregate belt feeder if the cement storage level is less than 20 percent of the total volume.

Equip each aggregate bin with a device that automatically shuts down the power to the cement feeder and the aggregate belt feeder if the aggregate discharge rate is less than 95 percent of the scheduled discharge rate.

The proportioning device indicators must be in working order before starting proportioning or mixing and must be visible when standing near the volumetric mixer.

90-3.02B(4) Mixer Calibration

Calibrate the cutoff gate for each volumetric mixer used and for each aggregate source. Calibrate each volumetric mixer at 3 different aggregate gate settings that correspond to production needs. Perform at least 2 calibration runs for each aggregate gate.

Individual aggregate delivery rate check-runs must not vary by more than 1.0 percent from the mathematical average of all runs for the same gate and aggregate type. Each test run must be at least 1,000 lb.

Individual cement delivery rate check-runs must not vary by more than 1.0 percent from the mathematical average of 3 runs of at least 1,000 lb each.

When the water meter operates from 50 to 100 percent of production capacity, the indicated weight of water delivered must not differ from the actual weight delivered by more than 1.5 percent for each of 2 runs of 300 gal for pavement or 75 gal for structures.

Calibrate the water meter under California Test 109. The water meter must be equipped with a resettable totalizer and must display the operating rate.

Conduct the calibration tests for aggregate, cement, and water proportioning devices using a platform scale located at the calibration site. Platform scales for weighing test-run calibration material must have a maximum capacity of 2.75 tons with maximum graduations of 1 lb. Error test the platform scale within 8 hours of calibrating the volumetric mixer proportioning devices. Perform error testing with test weights under California Test 109. Furnish a witness scale that is within 2 graduations of the test weight load. The witness scale must be available for use at the production site throughout the production period. Equipment needed for the calibration of proportioning systems must remain available at the production site throughout the production period.

The volumetric mixer must be equipped such that accuracy checks can be made. After production starts, recalibrate the proportioning devices at least every 30 days for pavement or 90 days for structures or when you change the source or type of any ingredient.

Each time 55 tons of cement passes through the volumetric mixer, perform a 2-run spot calibration of only the cement proportioning system. If the spot calibration shows that the cement proportioning system does not comply with the specifications, complete a full calibration of the cement proportioning system before you resume production.

90-3.02B(5) Mixing Concrete

At the time of batching volumetric-proportioned RSC:

1. Aggregates must be dried and drained to a stable moisture content. Do not proportion aggregates with visible separation of water from the aggregate.

2. Free moisture content of the fine aggregate must not exceed 8 percent of its saturated surface-dry weight.
If the proportioning plant has separate supplies of the same size group of aggregate with different moisture content, specific gravity, or surface characteristics affecting workability, exhaust one supply before using another supply.

Do not use ice to cool volumetric-proportioned RSC directly. If ice is used to cool the water used in the mix, it must be melted before entering the mixer.

Proportion and charge the cement into the volumetric mixer such that there is no variance of the required quantity due to conditions such as wind or accumulation on equipment.

Do not mix more material in the volumetric mixer than will allow complete mixing. Reduce the volume of material in the mixer if complete mixing is not achieved. Continue mixing until a homogeneous mixture is produced at discharge. Do not add water to the RSC after discharge.

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