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14 chapter two cURRENT PRAcTIcES FOR cOMPAcTION cONTROL OF UNBOUND MATERIALS INTRODUcTION This chapter presents the pursued approach, summary of the responses, and key findings of the survey conducted in this study to collect information from state DOTs and Canadian provincial transportation agencies on their practices related to compaction control of unbound materials and their experi- ences with different non-nuclear devices considered in this synthesis. SURVEY OVERVIEW A survey questionnaire was prepared and distributed to the materials/geotechnical engineers from all state DOTs and the Ontario Ministry of Transportation in Canada. The main objectives of this survey were to (1) identify the current prac- tices of various DOTs with respect to compaction control of unbound materials, and (2) learn about the DOTsâ experi- ences with different non-nuclear density, as well as stiffness- and strength-based compaction control methods and devices that they have evaluated, used, or implemented. The survey consisted of 33 close-ended, multiple choice-type questions, which were implemented using the TRB survey software for distribution as an online survey. A copy of the survey is provided in Appendix A. A unique link was then created and e-mailed on January 23, 2012, to materials/geotechnical engineers from 50 state DOTs and the Ontario Ministry of Transportation in Canada. The survey was kept open until March 4, 2013. Those who did not start the survey after three weeks were contacted by phone and asked to complete it. A weekly reminder e-mail was sent to participants who did not respond. A few respondents were subsequently contacted by phone to clarify any discrepancies found in their question- naire answers or to obtain additional information. SURVEY RESULTS The survey was sent to 50 state DOTs and the Ontario Ministry of Transportation in Canada, and a total of 41 responses (80.4%) were received. In the survey analysis presented in this chapter, the percentages were computed based on the 41 responses received. Salient survey findings are presented here; additional survey details can be found in Appendix C. Figures 1 through 3 present the number of respondents that dealt with different types of unbound materials in com- pacted subgrade soils, base course layers, and embankments, respectively. Respondents were allowed to choose more than one type of unbound materials. Therefore, the overall num- bers do not add up to the total number of respondents (i.e., 41). The majority of state DOTs have encountered low and high plasticity clay and silt, as well as sands, in their sub- grade soils and embankments. In addition, the majority of states have used gravel, limestone aggregate, and recycled hot-mix asphalt (HMA) and portland cement concrete (PCC) in their base course layers. Approximately 40% (17 of 41) of respondents have used recycled HMA and PCC in their embankments. Based on the results of the survey, Figure 4 presents a review of state DOT practices related to field compaction and construction quality control of unbound materials. More than 75% of responding state DOTs indicated that they require a minimum relative compaction higher than 90% in accepting compacted subgrade soils, unbound base course, and embank- ment layers. Most of these DOTs use AASHTO T99 and AASHTO T180 or a modified version of those standards to establish the target field density value. However, three state DOTs (Delaware, Ohio, and South Dakota) indicated that they use the one-point Proctor test based on the family of curves that they have developed to determine the target field density value. Although about half of respondents indicated that they specify moisture content limits in their compaction control acceptance criterion for base and subgrade soil, more than 65% include those limits for embankments. Most of those DOTs require that field moisture content be within ±2% of the optimum moisture content. The staff of two state DOTs (Minnesota and Indiana) mentioned that they use DCP and/or LWD in their compaction control specifica- tions for subgrade soils and base course layers, but only Indiana DOT uses DCP for compaction control of embankment lay- ers. Furthermore, three state DOTs (Rhode Island, Utah, and Wisconsin) indicated that they do not have formal acceptance criteria for compacted base course layers and embankments. Finally, although five respondents do not have any compac- tion control requirements for subgrade soils, some state DOTs, such as those of New Jersey and Oregon, use proof rolling to examine the quality of compacted subgrade soils. Figure 5 presents the results of survey questions related to the use of state DOTs for intelligent compaction in field projects. Although 24 states evaluated or demonstrated the
15 (17) (36) (28) (37) (24) (40) (33) (14) (14) (14) (11) 41% 88% 68% 90% 59% 98% 80% 34% 34% 34% 27% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Organic soil (OL and OH) Low plasticity clay (CL) High plasticity clay (CH) Low plasticity silt (ML) High plasticity silt (MH) Sands Gravel Limestone Sandstone Recycled HMA Recycled PCC Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 1 Survey results for types of unbound materials used in compacted subgrade soils. (1) (4) (3) (2) 0 (17) (33) (29) (13) (25) (29) 2% 10% 7% 5% 0% 41% 80% 71% 32% 61% 71% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Organic soil (OL and OH) Low plasticity clay (CL) High plasticity clay (CH) Low plasticity silt (ML) High plasticity silt (MH) Sands Gravel LimestoneSandstone Recycled HMA Recycled PCC Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 2 Survey results for types of unbound materials used in base course layers. (15) (32) (26) (33) (23) (36) (29) (16) (16) (16) (17) 37% 78% 63% 80% 56% 88% 71% 39% 39% 39% 41% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Organic soil (OL and OH) Low plasticity clay (CL) High plasticity clay (CH) Low plasticity silt (ML) High plasticity silt (MH) Sands Gravel Limestone Sandstone Recycled HMA Recycled PCC Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur ve y R es po nd en ts FIGURE 3 Survey results for types of unbound materials used in embankments.
16 use of intelligent compaction, only two state DOTs (Indiana and Minnesota) have actually implemented its use in field projects. Furthermore, 13 states indicated that they plan to use it in the future. Figure 6 presents survey results regarding DOTsâ interest in using non-nuclear density devices. Only four DOTs indi- cated that they are not interested in using non-nuclear density devices. The rest indicated interest but also noted obsta- cles that could stop or impede the implementation of such devices. According to Figure 7, slightly more than 50% of respondents (21 of 41) indicated a need for new non-nuclear density devices. However, 12 DOTs cited lack of confidence in the performance and reliability of currently available devices as a prime reason impeding their implementation. In addition, 20 DOTs found it problematic that contractors tended to be unfamiliar with available non-nuclear density device technology. Figure 8 presents the number of DOTs that have evaluated or used each of the available non-nuclear density devices. The majority of respondents (29 of 41) have not used or eval- uated any such device. The electrical density gauge (EDG) was the most evaluated device among respondents. This evaluation was mainly done through in-house research stud- ies. Figure 8 also shows that less than 15% of respondents evaluated the moisture density indicator (MDI) and soil den- sity gauge (SDG). (8) (34) (20) (10)(9) (31) (21) (11) (9) (34) (27) (7)19.5% 82.9% 48.8% 24.4%22.0% 75.6% 51.2% 26.8% 22.0% 82.9% 65.9% 17.1% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 Minimum average relative compaction values Individual relative compaction values Moisture content within limits Other Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts Base Compacted Subgrade Embankment FIGURE 4 Survey results for type of compaction control method. (2) (10) (11) (13) (17) 5% 24% 27% 32% 42% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Implemented in field projects Evaluated in research studies only Demonstrated its usage Plan to use in the future Not used nor evaluated Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 5 Survey results regarding intelligent compaction.
17 (3) (2) (18) (4) (14) 7% 5% 44% 10% 34% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Interested and have already implemented it Interested and will implement it Interested but have not implemented it Not Interested Other Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur ve y R es po nd en ts FIGURE 6 Respondentsâ interest in using non-nuclear density devices. (21) (11) (15) (20) (23) 51% 27% 37% 49% 56% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Need for new testing equipment Lack of funds Lack of trained personnel Familiarity of contractors with such devices Other Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 7 Main obstacles impeding implementation of non-nuclear density devices. (6) (12) (5) (29) (2) 15% 29% 12% 71% 5% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 MDI EDG SDG None Other Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 8 Number of respondents that used or evaluated non-nuclear density devices.
18 are the most evaluated and used devices among respondents. These evaluations were done through research conducted in house, as well as by universities and consultants. In addi- tion, whereas only one DOT evaluated the BCD and PSPA, six DOTs evaluated the Clegg hammer. Finally, 15 of the 41 DOTs did not evaluate any of the listed devices. A few DOTs indicated that they have developed or currently are develop- ing specifications for the DCP (5) and LWD (3). However, only two state DOTs (Indiana and Minnesota) have imple- mented the use of the DCP and the LWD in field projects. Figures 11 through 13 present survey results regarding DOTsâ experiences with different in situ stiffness devices. In terms of ease of use, the majority of respondents who evalu- ated the Clegg hammer (5 of 6), GeoGauge (12 of 18), DCP (16 of 19), and LWD (7 of 12) indicated that those devices were easy or moderately easy to use. In addition, while at least 50% of respondents who evaluated the Clegg ham- mer and DCP indicated that little experience was needed to operate those devices, the majority found that intermediate- level experience was needed to perform LWD tests. There was no consensus on the level of experience needed for the GeoGauge. The majority of DOTs (12 of 20) found the calibration of the DCP to be simple and quick, but there was no consensus about the LWD, GeoGauge, or Clegg hammer. According to Figure 11, most of the respondents who evaluated the DCP, LWD, GeoGauge, and Clegg hammer found the testing time Figure 9 presents survey results on the experience of respondents with non-nuclear density devices. More than half of the respondents who evaluated the EDG, MDI, and SDG devices indicated that those devices are slightly com- plex or complex compared with the NDG. In general, state DOTs that evaluated the MDI, EDG, and SDG devices found their calibration procedure to be time consuming. In addition, whereas the majority of them (4 of 5) found the testing time of the SDG to be moderately short, there was no consensus about the testing time of the MDI and EDG. It is clear that most respondents who evaluated the EDG (9 of 12), MDI (4 of 6), and SDG (5 of 6) devices thought that intermediate or high-level expertise was required to operate those devices. Although most state DOTs did not have information about the cost, durability, and GPS compatibility of the MDI, EDG, and SDG, all of them agreed that those devices required fewer safety precautions than did the nuclear density device. Most DOTs that evaluated the MDI, EDG, and SDG devices found the accuracy and repeatability of those devices to be fair or poor, suggesting a lack of confidence in their reliability. This may explain the consensus among respondents of not recom- mending the use of any of the available non-nuclear density devices. Figure 10 presents the DOTsâ responses with respect to devices that measure strength- or stiffness-related proper- ties and have been used or evaluated for compaction control of unbound materials. Among the currently available in situ test devices, the DCP (20), GeoGauge (19), and LWD (13) 0 1 2 3 4 EDG MDI SDG N u m be r o f R es po n se s Easy Moderately easy Slightly complex Complex 0 1 2 3 4 5 EDG MDI SDG N um be r o f R es po ns es Short Moderately Short Slightly long Long 0 1 2 3 4 5 EDG MDI SDG N um be r o f R es po ns es Good (a) (b) (d)(c) Fair Poor 0 1 2 3 4 5 EDG MDI SDG N um be r o f R es po ns es Good Fair Poor FIGURE 9 Experience of DOTs with the non-nuclear density devices: (a) ease of use, (b) calibration, (c) accuracy, and (d) repeatability.
19 (6) (19) (20) (13) (1) (0) (1) (6) (15) 15% 46% 49% 32% 2% 0% 2% 15% 37% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Clegg Hammer GeoGauge DCP LWD PSPA SCS BCD Other None Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 10 In situ devices used or evaluated for compaction control of unbound materials. of those devices to be short or moderately short. In terms of cost, at least 60% (12 of 20) of DOTs that evaluated the DCP found that it was inexpensive. Furthermore, the majority of the DOTs that used the LWD found it was expensive or mod- erately expensive. Finally, about 30% of DOTs reported that the GeoGauge (7 of 19) and Clegg hammer were moderately expensive. In terms of durability, at least half of respondents that eval- uated the DCP (14 of 20), LWD (7 of 13), and Clegg hammer (3 of 6) indicated that the durability of those devices was good or very good. Roughly one-third (6 of 19) indicated that the GeoGauge had good durability. The majority of state DOTs considered the DCP (15 of 20), GeoGauge (12 of 19), LWD (8 of 13), and Clegg hammer (3 of 6) to be safe or moderately safe devices. With regard to GPS compatibility, whereas none of the state DOTs indicated that the GeoGauge and Clegg hammer were GPS compatible, a limited number had GPS-compatible DCP (1 of 20) and LWD (4 of 13) devices. As for repeatability and accuracy, around 50% of respon- dents who evaluated the DCP (12 of 20) and the LWD (6 of 13) indicated that those devices were very good or good. By contrast, about half of the DOTs that evaluated or used the GeoGauge found it to have poor to fair accuracy and repeat- ability. Finally, there was no agreement among state DOTs about the repeatability and accuracy of the Clegg hammer. According to Figure 13, more than 50% of respondents who evaluated the DCP (11 of 20) and LWD (9 of 13) rec- ommended using them for compaction control of unbound materials. Two respondents (Colorado and Florida) recom- mended the Clegg hammer; however, no one recommended using the GeoGauge. As shown in Figure 14, survey results indicate that more than 50% of the state DOTs that evaluated or used the DCP and LWD found them to be compatible with various types of unbound materials. However, a lower percentage indicated that the DCP is compatible with unbound base materials as com- pared with sand and fine-grained materials. In addition, fewer DOTs found the LWD to be compatible with fine-grained soils as compared with the other listed types of unbound materials. According to Figure 14, higher percentages of DOTs that evaluated the GeoGauge indicated that it is compatible with fine-grained soil (37%) and sands (42%) as compared with unbound base materials (21%). Figure 15 presents the results of the survey question on the level of interest for implementing stiffness- and strength- based compaction control specifications. The majority of respondents (27 of 41) are interested in implementing stiffness- and strength-based specifications for compaction control of unbound materials. However, only two state DOTs (Indiana and Minnesota) have implemented such specifications. As for the reason that may stop or impede implementa- tion, 18 DOTs indicated that such reasons include the need for new testing equipment, lack of trained personnel, and familiarity of contractors with such devices. In addition, 10 DOTs indicated lack of funds as a reason that might stop the implementation of stiffness devices. Some DOTs also indicated that the effect of moisture on in situ stiffness/ strength measurements must be addressed to implement a stiffness-based specification. Currently, four state DOTs (Missouri, Indiana, Illinois, and Minnesota) have stiffness- and strength-based production specifications for compaction control. Four additional states have developmental or exper- imental specifications. The staff of the Indiana and Illinois
20 Device Ease of use Calibration Testing time Clegg Hammer DCP GeoGauge LWD (4) 67% (1) 16% (1) 17% Easy Moderately easy I don't know : 67%(4) : 16%(1) : 17%(1) (1) 17% (1) 17% (2) 33% (2) 33% Difficult Time-consuming Simple&quick I don't know : 17%(1) : 17%(1) : 33%(2) : 33%(2) (3) 50% (2) 33% (1) 17% Short Moderately Short I don't know : 50%(3) : 33%(2) : 17%(1) (7) 35% (9) 45% (1) 5% (3) 15% Easy Moderately easy Slightly complex I don't know : 35%(7) : 45%(9) : 5%(1) : 15%(3) (1) 5% (2) 10% (12) 60% (5) 25% Difficult Time-consuming Simple&quick I don't know : 5%(1) : 10%(2) : 60%(12) : 25%(5) (5) 25% (8) 40% (4) 20% (3) 15% Short Moderately Short Slightly long I don't know : 25%(5) : 40%(8) : 20%(4) : 15%(3) (6) 31% (6) 32%(1)5% (6) 32% Easy Moderately easy Complex I don't know : 31%(6) : 32%(6) : 5%(1) : 32%(6) (3) 16% (1) 5% (6) 32% (9) 47% Difficult Time-consuming Simple&quick I don't know : 16%(3) : 5%(1) : 32%(6) : 47%(9) (8) 42% (4) 21% (7) 37% Short Moderately Short I don't know : 42%(8) : 21%(4) : 37%(7) (2) 17% (5) 42% (4) 33% (1) 8% Easy Moderately easy Slightly complex I don't know : 17%(2) : 42%(5) : 33%(4) : 8%(1) (1) 8% (3) 23% (3) 23% (6) 46% Difficult Time-consuming Simple&quick I don't know : 8%(1) : 23%(3) : 23%(3) : 46%(6) (3) 23% (7) 54% (1) 8% (2) 15% Short Moderately Short Slightly long I don't know : 54%(7) : 23%(3) : 8%(1) : 15%(2) FIGURE 11 Experience of DOTs with in situ devices related to use, calibration, and testing.
21 Device Level of Expertise Cost Durability Clegg Hammer DCP GeoGauge LWD (2) 22% (3) 33% (4) 45% Intermediate Low I don't know : 22%(2) : 33%(3) : 45%(4) (3) 33% (2) 22% (4) 45% Moderately Expensive Not Expensive I don't know : 33%(3) : 22%(2) : 45%(4) (3) 33% (1) 11% (5) 56% Good Fair I don't know : 56%(5) : 33%(3) : 11%(1) (7) 39% (10) 56% (1) 5% Intermediate Low I don't know : 5%(1) : 39%(7) : 56%(10) (4) 22% (12) 67% (2) 11% Moderately Expensive Not Expensive I don't know : 22%(4) : 67%(12) : 11%(2) (6) 33% (8) 44% (3) 17% (1) 6% Very Good Good Fair I don't know : 33%(6) : 44%(8) : 17%(3) : 6%(1) (7) 39% (10) 56% (1) 5% Intermediate Low I don't know : 39%(7) : 56%(10) : 5%(1) (6) 31% (6) 32% (1) 5% (6) 32% Expensive Moderately Expensive Not Expensive I don't know : 32%(6)) : 31%(6) : 5%(1) : 32%(6) (1) 6% (5) 31% (3) 19% (7) 44% Very Good Good Fair I don't know : 6%(1) : 31%(5) : 19%(3) : 44%(7) (8) 67%(1)8% (3) 25% Intermediate Low I don't know : 8%(1) : 67%(8) : 25%(3) (5) 39% (5) 38% (3) 23% Expensive Moderately Expensive I don't know : 39%(5) : 38%(5) : 8%(1) (2) 15% (5) 39%(2)15%(1)8% (3) 23% Very Good Good Fair Poor I don't know : 15%(2) : 39%(5) : 15%(2) : 8%(1) : 23%(3) FIGURE 12 Experience of DOTs with in situ devices related to level of expertise, cost, and durability.
22 Device Accuracy Repeatability Recommendation Clegg Hammer DCP GeoGauge LWD (2) 25% (1) 12%(5) 63% Good Poor I don't know : 25%(2) : 12%(1) : 63%(5) (2) 29% (1) 14% (4) 57% Good Fair I don't know : 14%(1) : 29%(2) : 57%(4) (2) 33% (1) 17% (3) 50% Yes No I don't know : 17%(1) : 33%(2) : 50%(3) (4) 23% (8) 47% (3) 18% (1) 6% (1)6% Very Good Good Fair Poor I don't know : 23%(4) : 47%(8) : 18%(3) : 6%(1) : 6%(1) (1) 6% (9) 53% (5) 29% (1) 6% (1)6% Very Good Good Fair Poor I don't know : 6%(1) : 53%(9) : 29%(5) : 6%(1) : 6%(1) (11) 65% (2) 12% (4) 23% Yes No I don't know : 23%(4) : 65%(11) : 12%(2) (2) 12% (3) 19% (7) 44% (4) 25% Good Fair Poor I don't know : 12%(2) : 19%(3) : 44%(7) : 25%(4) (1) 7% (2) 13% (2) 13% (7) 47% (3) 20% Very Good Good Fair Poor I don't know : 13%(2) : 7%(1) : 13%(2) : 47%(7) : 20%(3) (8) 42% (11) 58% Yes No I don't know : 0%(0) : 42%(8) : 58%(11) (2) 17% (4) 33% (6) 50% Very Good Good I don't know : 17%(2) : 33%(4) : 50%(6) (1) 8% (6) 50% (1) 8% (4) 34% Very Good Good Fair I don't know : 50%(6) : 8%(1) : 8%(1) : 34%(4) (9) 69% (4) 31% Yes No I don't know : 0%(0) : 69%(9) : 31%(4) FIGURE 13 Experience of DOTs with in situ devices related to accuracy, repeatability, and recommendation.
23 (3) (7) (13) (7) (4) (8) (13) (10) (2) (4) (10) (9) 50% 37% 65% 54% 67% 42% 65% 77% 33% 21% 50% 69% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 2 4 6 8 10 12 14 16 18 20 Clegg Hammer GeoGauge DCP LWD Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur ve y R es po nd en ts Fine grained Soil Sand Unbound base material FIGURE 14 Compatibility of in situ devices with different types of unbound materials. (2) (6) (19) (9) (5) 5% 15% 46% 22% 12% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 0 5 10 15 20 25 30 35 40 45 Interested and have already implemented it Interested and will implement it Interested but have not implemented it Not Interested Other (please specify) Pe rc en ta ge o f S ur ve y R es po nd en ts N um be r o f S ur v ey R es po nd en ts FIGURE 15 Interest in stiffness- and strength-based compaction control specifications. DOTs indicated that they frequently use those specifications. Indiana DOT staff reported that stiffness- and strength-based specifications are used in projects with more than 15 million cubic yards of fill, which represents more than 80% of con- struction projects in Indiana. At least three states have devel- oped DCP and LWD target values for compaction control of various unbound materials. With regard to survey results on the use of non-nuclear devices for in situ moisture content measurement, the respon- dents were most familiar with the speedy moisture tester (22) and the field microwave (14) among all other in situ devices. In addition, most respondents have not evaluated or used the other devices to measure moisture content of unbound materials. Figure 16 presents survey results related to the experience of state DOTs with in situ moisture content mea- surement. As shown in Figure 16, at least 13 states found the speedy moisture tester and field microwave to have good or very good repeatability and accuracy. Most respondents indicated that the speedy moisture tester and field microwave are easy or moderately easy to use. According to Figure 17, 13 states have recommended using those devices for mea- surement of in situ moisture content of unbound materials. However, at least four states did not recommend them.
24 Device Accuracy Repeatability Ease of use Speedy Moisture Tester Field Microwave (3) 11% (10) 36% (5) 18% (2) 7% (8) 28% Very Good Good Fair Poor I don't know (3) 11% (10) 36% (5) 18% (2) 7% (8) 28% Very Good Good Fair Poor I don't know (7) 27% (9) 35% (4) 15% (2) 8% (4) 15% Easy Moderately easy Slightly complex Complex I don't know (2) 9% (13) 54% (1) 4% (1) 4% (7) 29% Very Good Good Fair Poor I don't know (2) 9% (13) 54% (1) 4% (1) 4% (7) 29% Very Good Good Fair Poor I don't know (6) 26% (9) 39% (1) 4% (7) 31% Easy Moderately easy Slightly complex I don't know FIGURE 16 Experience of DOTs with in situ devices for moisture content measurement. FIGURE 17 Recommendation of DOTs for using in situ devices for moisture content measurement. Speedy Field Microwave (13) 50% (9) 35% (4) 15% Yes No I don't know (13) 57%(4) 17% (6) 26% Yes No I don't know
