Section 4184.  Reflectorizing Spheres for Traffic Paint

 

4184.01      DESCRIPTION.

 

A.    This specification covers two types of glass spheres or beads, dual coated and uncoated, for the production of reflectorized pavement markings.

·         Waterborne and VOC compliant solvent borne traffic paint: use dual coated beads (silicone and silane).

·         Epoxy pavement markings: use silicone only coated beads (no silane).

·         Refer to Table 4184.02-1 for gradations of waterborne and VOC compliant solvent borne traffic paint.

·         Refer to Table 4184.02-2 for gradations of multi-component liquid pavement markings.

 

B.   The glass beads shall not exhibit a characteristic of toxicity, relative to heavy metals. Glass beads shall not contain more than 200 ppm total of lead, antimony, or arsenic. Manufacturer shall provide a certificate of analysis stating total lead, antimony, and arsenic content for each batch of glass beads supplied. Use transparent, clear, colorless glass spheres that are:

·         Free from milkiness, dark particles, and excessive air inclusions.

·         Essentially clear from surface scarring or scratching.

·         Free of hard lumps and clusters

·         Readily dispensed under any conditions suitable for paint striping.

·         Virgin glass for 0.850 mm (20 Sieve) and larger glass spheres.

 

C.    Glass Beads shall meet AASHTO M247 requirements and the following specific requirements.

 

4184.02     SPECIFIC REQUIREMENTS.

 

A.    Gradation.

Meet the gradation requirements of Table 4184.02-1 or Table 4184.02-2 depending on marking type.

 

Table 4184.02-1: Gradation Requirements

(Standard Blend Glass Spheres/Beads)

Sieve Size

Percent Passing*

Percent Retained*

16

100

0

20

90-100 85-92

8-15

30

50-75 50-67

25-35

40

15-45 0-37

30-50

50

0-15

15-35

80

0-10

pan

0-2

*  Shall meet either Percent Passing or Percent Retained gradation but not required to meet both.

 

Table 4184.02-2 Gradation Requirements (Utah Blend Glass Spheres/Beads)

Sieve Size

Percent Passing

16

90-100

18

65-80

20

30

30-50

40

50

0-5

80

pan

 

 

B.    Roundness.

Minimum of 80% true spheres.

 

C.    Refractive Index.

Minimum refractive index of 1.50.

 

D.    Properties of Dual Coated Spheres.

 

1.     Coated with a dual coating that has both a moisture resistant silicone coating and an adhesion promoting silane coating.

 

2.     Passes the moisture resistance test and the adherence coating test.

 

E.    Properties of Silicone Coated Spheres.

 

1.     Coated only with a silicone coating (no silane).

 

2.     Passes the moisture resistance test and test negative for the adherence coating test.

 

4184.03      METHODS OF TEST.

Test the specific requirements according to Iowa DOT Materials Laboratory Test Method No. 814.