PORTLAND CEMENT CONCRETE PRODUCTION SECTION 1022 662 a. Weigh individual aggregates to within ±1 percent of the target weight.
b.Weigh combined aggregates to within ±1 percent of the total target aggregate weight.
c.Measure water, by weight or volume, to within ± 1 percent of the required batch quantity of water.
d.Weigh cement to within +1 percent of the target batch weight.
e.Maintain the admixture dispenser accuracy to within ± 1 percent of target volume.
2.Provide a computer printed ticket for each batch issued by the plant to the truck driver. The ticket must contain:
a.The name and location of the plant.
b.The approved mix designation.
c.The size and proportions of the batch.
d.The type and dosage rate of admixtures used.
e.The batch time (determined by the time water is introduced to the mixture).
f.The gallons of water withheld from the mixture that meets the maximum allowable water/cement ratio for the approved mix design.
3.Weighing scales:
a.Scales for weighing material must have a rugged design constructed to support the hopper or belts with minimum adjustments and be consistent with the accuracy required.
b.Scales rated to 5,000 -pounds or less measure in graduations not greater than 5 -pounds.
c.Scales rated greater than 5,000 -pounds measure in graduations not greater than 0.1 percent of the maximum rated load.
d.Maintain scales within a maximum tolerance of 0.5 percent of the net load in the hopper.
e.Retain at least 1 set of the following calibration weights for verifying scale calibrations:
i.10 standard 50 -pound blocks, ii. 11 standard 20 -kg blocks, 1 standard 5 -kg block, and 2 standard 1 -kg blocks, iii. Construct the weights of high quality cast iron and finished in such a manner that foreign materials do not adhere to the surface. iv. The engineer may perform an inspection of these weights.
4.Trucks for batch mix plants:
f.Mix each batch at a rate of rotation specified by the manufacturer more than 70 but less than 100 revolutions.
g.Inspect mixer drums for wear. The Materials and Research Section will verify the condition annually.
h.Keep interior drum surfaces clean of accumulations of hardened concrete material.
i.Replace drum blades when wear exceeds 1 -inch of the original height. PORTLAND CEMENT CONCRETE PRODUCTION SECTION 1022 663 j. Do not exceed the manufacturer’s rating for the size of the batch that may be transported in these units when used as an agitator.
B.Central mix plants.
1.Central mix plants must have the capability of weighing and mixing all materials for PCC before placing batches into approved transport vehicles.
2.Weigh individual aggregates to within ±1 percent of the target weight.
3.Weigh combined aggregates to within ±1 percent of the total target aggregate weight.
4.Measure water, by weight or volume, to within ± 1 percent of the required quantity of water.
5.Weigh cement within +1 percent of the target batch weight.
6.Admixture dispensers must be accurate to ± 1 percent of target volume.
7.The minimum mixing time for batches of 10 cubic yards or less is 60 -seconds.
8.The engineer will determine the minimum mixing time for batches greater than 10 cubic yards.
9.Mixing time begins when all material, except for mix water, has been added to the mixing drum.
C.Volumetric truck mixers .
1.Volumetric truck mixers must be calibrated annually by the Materials and Research Section prior to use.
2.Equip each truck with a 1/4 cubic yard box constructed of suitable rigid materials for calibration purposes.
3.Provide approved trucks capable of mixing batched materials sufficiently to dispense a uniformly homogenous mix at the point of placement with no further mixing required.
4.Dispense cement at a constant volumetric weight equivalent during mixing operations. Calibrate aggregate bins at various gate openings to discharge the volumetric weight equivalent of aggregate required for the approved concrete mix.
5.Dispense water through a calibrated meter displaying the discharge rate into the mixing auger.
6.The following tolerances for proportioning the various ingredients are as follows:
a.Cement: -0 percent to +4 percent of target weight.
b.Fine aggregate: ±2 percent of target weight.
c.Coarse aggregate: ±2 percent of target weight.
d.Admixtures: ±3 percent of target weight or volume.
e.Water: ±3 percent of target weight or volume.
1022.13 Material Production Test Methods.
Mix properties will be verified by:
A.Mix consistency (slump): AASHTO T119
B.Temperature of fresh concrete: AASHTO T309
C.Air content: AASHTO T152 modified or AASHTO T196 PORTLAND CEMENT CONCRETE PRODUCTION SECTION 1022 664 D. Permeability: AASHTO T277 , cured in accordance with the Accelerated Moist Curing Method.
E.Making and curing concrete test specimens: AASHTO T23
F.Unit weight: AASHTO T121
G.Compressive strength of concrete: AASHTO T22
1022.14 Mix Temperature Limitations.
A.Measure all temperatures at the point of placement.
B.The maximum allowable temperature for Class D concrete for bridge decks is 85 degrees F.
C.The maximum allowable temperature for Rapid -set concrete is 95 -degrees F.
D.The maximum allowable temperature for all other classes of concrete is 90 degrees F.
E.The minimum allowable temperature for Rapid -set concrete is 70 -degrees F.
F.The minimum allowable temperature for all other classes of concrete is 50 degrees F.
G.Take appropriate actions in accordance with ACI 318 recommendations for hot weather concrete when batch temperatures at the mixing plant reach 6 degrees F below the maximum allowed for the class of concrete produced.
H.Take appropriate actions in accordance with ACI 306 recommendations for cold weather concrete when batch temperatures at the mixing plant reach 6 degrees F above the minimum allowable for the class of concrete produced.
1022.15 Delivery Time of Concrete Batches.
A.The maximum allowable elapsed time between the introduction of the mix water and the final placement of the concrete is 45 -minutes for non -agitating transport vehicles and 60 -minutes for agitating transport vehicles.
B.Delivery time restrictions may be extended with the use of approved water reducing/retarding admixtures, set retarding admixtures, and/or replacement of a portion of the Portland cement content with fly ash cement or GGBFDS cement.
C.The interval between successive loads cannot exceed the lesser of 20 -minutes, or if the surface of the previous load exhibits signs of setting and cannot be mobilized using mechanical concrete vibrators.
1022.16 Additional Self -Consolidating Concrete Requirements.
A.The Department will allow use of self -consolidating concrete on precast and prestress applications with approval of the engineer.
B.Self-consolidating concrete is to conform to all requirements within Section 1022 for the class of concrete specified in addition to the requirements listed in Table 1022. 16-1. Table 1022.16 -1 Self -Consolidating Concrete Requirements Property Test Method Requirement Slump flow ASTM C1611 20 to 30 but within +/ - 3 inches of target slump
Source: Delaware Standard Specifications for Road and Bridge Construction, 2025 Edition. Pages 672–674 of 779.