Essay: Functional properties and the economic viability of milled Asphalt Pavements in road construction

When incorporated RAP is greater than 20%, suggested testing both the RAP and virgin binder (bitumen) using a blending chart. At a higher percentage the change in RAP mixture characteristics becomes evident; the effect of RAP in mix designs varies with the quantity of RAP in the mix. This combination must meet gradation specifications and Superpave consensus properties. Puttaguanta and others, (1996), found no significant difference when 25-50% of RAP is incorporated into the mixes. In summary, observations from literatures reviewed showed that low percentages (5-20%) RAP can be incorporated in superpave mix designs. Flow charts to design of RAP mixes are shown in Figure 2.2
(a) Step 1
(b) Step 2
(c) Step 3
Figure 2.2 RAP mix design procedure
2.3. Aggregate Tests
The specific aggregate tests are discussed in the subsequent section.
2.3.1 Gradation of RAP Aggregate
The gradation investigation is used to determine aggregate particle size distribution. The aggregate gradation is one of the most important properties related with the control of HMA mixes (Pavement Interactive, 2011). The rutting feature of pavements is controlled by aggregate gradation. The standard gradation and sieve analysis can be conducted according to AASHTO T27 and ASTM C136 “Sieve Analysis of Fine and Coarse Aggregate”. Millings are material fashioned by the milling method, removed from the existing pavement. Milling and crushing leads to RAP degradation, Milled RAP is finer than crushed RAP. RAP aggregate normally meets the ASTM specifications based on ASTM D692. The particle size distribution of a milled pavement varies depending on aggregate and equipment type. A representative of RAP size distribution is shown Table 2.2.
Table 2.2 Characteristic range of particle size distribution for reclaimed RAP
(http://www.tfhrc.gov/hnr20/recycle/waste/rap131.htm)
Sieve Size Percent Finer after Processing or Milling
37.5 mm (1.5 in) 100
25 mm (1.0 in) 95 – 100
19 mm (3/4 in)
84 – 100
12.5 mm (1/2 in) 70 – 100
9.5 mm (3/8 in) 58 – 95
7.5 mm (No. 4) 38 – 75
2.36 mm (No. 8) 25 – 60
1.18 mm (No. 16) 17 – 40
0.60 mm (No. 30) 10 – 35
0.30 mm (No. 50) 5 – 25
0.15 mm (No. 100) 3 – 20
0.075 mm (No. 200) 2 – 15
2.3.2 Specific Gravity
HMA volumetric examination is achieved through specific gravity test. Results of the test performed by William (2007), suggested that the traditional saturated surface dry method display the least extent of variation. The model for determining specific gravity of coarse and fine aggregates is described in ASTM C127 and ASTM C128, correspondingly. Specific gravity of RAP aggregates are determined by:
Technique 1: Specific gravity tests are carried out on sieved fractions according to ASTM C127 and ASTM C128 after obtaining aggregates either by solvent or ignition oven extraction process. The extraction method could modify the aggregate specific gravity. Mallick and others (1998) demonstrate the differences that exist in the specific gravity of virgin and aggregates obtained from ignition extraction method.
Technique 2, calculation based on the theoretical specific gravity
Gse = 100 – Pb
100 – Pb
Gmm Gb
Where:
Gse = aggregate effective specific gravity
Gmm= theoretical maximum specific gravity (AASHTO T209)
Pb = bitumen content (percent by total mass of mixture); and Gb= specific gravity of bitumen.
Gsb = Gse
Pba . Gse
100 . Gb + 1
Where: (El Sayed, 2012)
Pba= absorbed bitumen (percent by weight Gsb of aggregate); Gse= aggregate effective specific gravity; Gsb= aggregate bulk specific gravity; and Gb = RAP binder specific gravity.
The absorbed binder content in the aggregate is only assumed as the accurate binder content is difficult to determine (El Sayed, 2012).
2.3.3 Los Angeles Abrasion Test
RAP must be hard enough to withstand breakdown when subjected to traffic tonnes. Aggregates lacking enough hardness may result in construction failure (Hameed, 2009). About 94 percent of the states in the U.S prefer the Los Angeles abrasion test (Pavement Interactive, 2011). Ahmad and others (2004) performed research on degradation and abrasion of RAP aggregate in Malaysia. They focused on aggregates extracted from RAP from both full-depth recovery and milling. They concluded that the aggregate clearly degraded by further refinement of aggregate size, retaining considerable strength to defy wear and abrasion. This study also showed that millings are finer and denser than virgin aggregate.
2.3.4 Aggregate Crushing Value Test
Aggregates should have an acceptable resistance to crushing and enough strength under loads (Han and others, 2011). Low aggregate crushing value is preferable
ACV = B x 100
A
Where, B = Weight of the fraction passing 2.36mm sieve
A = Total weight of dry sample
The mean of the two tests equals the aggregate crushing value (Al kourd and Hammad, 2009). The standard specification is < 30%
2.3.5 Aggregate impact value Test
Aggregate impact value is a measure of the toughness of the material. The aggregates should therefore have enough toughness to defy disintegration.
Weight of dry sample (W1 gm)
Weight of fraction passing 2.36 mm sieve (W2 gm)
Aggregate impact Value (percent) = W2 / W1 X 100 (Transportation Engineering Lab Manual, 2013; The constructor, 2015).
Aggregate Impact Value Toughness properties
<20% Extraordinarily tough
10 – 20% Very tough
20-30% Satisfactory for surface pavement
>30% Weak for surface pavement
2.3.6 Flakiness and Elongation Index (Shape Test)
Proportion of flaky and elongated particle in a mixture determine aggregate shapes and arrangements, flaky and elongated aggregates are damaging as they may cause intrinsic flaw under heavy tonnes. An excessive amount of these materials in the HMA mix may lead to construction failures.
Aggregates are classified flaky if: Width > 2.0
Thickness
Aggregate are classified elongated if: Width > 2.5
Thickness
2.4 RAP Variability
One of the main worry of incorporating a large percentage of RAP in HMA mixes is variability. Opus of RAP from diverse sources varies. The exact make-up of milled RAP depends on age, type, properties of bitumen, configuration and performance of the milling process. The consistency of aggregate is determined by evaluating gradation, specific gravity, coarse aggregate angularity, and fine aggregate angularity (Pavement Interactive, 2011). The following, affects the consistency of binder: fatigue factor (G*sin (δ)), complex modulus (G*), and phase angle (δ°). Lee and others (1983) in an effort to quantify the plant mixing efficiency of asphalt mixtures with incorporation of RAP observed that the performance of the recycled mix depends on interaction between the virgin aggregate and asphalt binder, which indicates the need for consistency of samples. Mixing efficiency is usually measured by bituminous mixtures appearance in respect to distribution and coating. Lee and others (1983) resolved the difficulty associated with rejuvenating agents by a “Dye Print Technique”. A variability study on RAP stockpile (Figure 2.3), different test results, such as gradation of aggregate, asphalt content, air void, penetration and viscosity, and stability, are shown in (Solaimanian and Tahmoressi, 1996). Figure 2.4 shows the variations in gradation obtained in their research. Incorporating higher percentage of RAP shows a higher variation in gradation as observed in Figure 2.5. Changes in the viscosity of the binder from the RAP and plant mix are shown in Figure 2.6.
Figure 2.3 RAP Stockpile
http://ntl.bts.gov/lib/42000/42800/42817/KUO92-final.pdf
Figure 2.4 Daily gradations from extraction
Figure 2.5 Mean deviations from Job Mix Formula (JMF) for Sieve #10
Figure 2.6 Sample daily viscosities
Table 2.3 shows that RAP obtained from road cores were highly variable and the aggregate gradation became finer after milling and processing (Han and others, 2011).
Table 2.3 RAP compositions of cores and stockpiles
Location of roads % passing
2.36 mm % passing 0.075
mm Asphalt Cement
Content
n ave. σn-1 ave. σn-1 ave. σn-1
California Road Cores 12 54 8.30 9.9 2.01 5.4 0.71
California Stockpiled after
Milling 5 69 6.50 11.8 0.34 5.2 0.04
North Carolina Road Cores 12 69 3.20 6.1 0.66 5.7 0.11
North Carolina Stockpiled
after Milling 5 72 0.90 8.0 0.11 5.7 0.11
Utah Road Cores 12 52 3.80 8.7 2.60 6.5 0.28
Utah Stockpiled after Milling 10 58 2.80 9.9 1.15 6.2 0.44
Virgina Road Cores 12 41 2.10 9.7 0.79 5.3 0.20
Virginia Stockpiled after
Milling 6 52 1.10 13.0 0.30 5.2 0.12
Average σ of HMA Surface
Course 2.81 0.94 0.28
A laboratory test was carryout by Huang and others (2004) using four category of mixtures consisting of various kind of bitumen (PG 64-22, PG 70-22, and PG 76-22) each made-up of varying RAP percentages (Han and others, 2011). 0% RAP mixture serves as the control mixes. Various characterization tests were carryout. The result shows the effect of variability of RAP on virgin mixtures. Figure 2.7 exemplify no major dissimilarity in the aggregate gradation from the worksite stockpiles, different worksites shows a little variation. Changes was recorded FAA and specific gravity of RAP from diverse worksites are shown in Figure 2.8 however, samples obtained from altering locations show no significant difference (Han and others, 2011). Figure 2.13 shows the differences in phase angle of the binder from the worksite CNC 302 and other worksite while Figure 2.9 shows the values of binder from worksite CNC 302.
Figure 2.7 RAP Gradation for worksite a
Figure 2.8 RAP Gradation for worksite b
Figure 2.9 RAP Gradation for worksite c
Figure 2.10 RAP Gradation for worksite d
Figure 2.11 RAP FAA and SG from altered worksites
Figure 2.12 G*sin (delta) for altered worksites
Figure 2.13 RAP Phase angles at altered worksites
The abstract from this study show:
• Similar results between IDT tests and Semi-circular bending results.
• Incorporation of RAP reduces aggregate toughness and increases strength.
• No observed differences at 0 to 10% RAP.
• Strength increases at 20 and 30% RAP.
2.5 Effect of Ignition Testing on Aggregate Properties
RAP where extracted through the ignition method. Mallick and others (1998) in their study showed that aggregate properties were considerably affected. Table 2.4 indicates the effect of ignition. Hall and Williams (1999) did not find any disparity in RAP gradation as evident in Table 2.5. However, disparity was evident in specific gravity of coarse aggregate as shown in Table 2.4 (Hans and others, 2011).
Table 2.4: Bulk specific gravity, absorption, and percent passing through 4.75 mm and 0.075mm of granite aggregate before and after ignition
Description Virgin
average Burnt
aggregate
average Burnt mix
average
Bulk specific gravity of coarse aggregate 2.688 2.680 2.653
Absorption of coarse aggregate,% 0.583 0.673 1.277
Bulk specific gravity of fine aggregate 2.659 2.687 2.640
Absorption of fine aggregate,% 0.627 0.467 1.020
Percent passing 4.75 mm sieve 56.0 56.6 56.7
Percent passing .075 mm sieve 4.0 4.1 5.8
NAA uncompacted void of fine aggregate 49.5 46.4 49.5
Table 2.5 Gradations of selected blends
In Figures 2.14 and 2.15 the disparity in specific gravity tests of ignition and virgin aggregates was observed.
Figure 2.14: Bulk specific gravity of virgin and burnt fine aggregates
Figure 2.15: Bulk specific gravity of virgin and burnt coarse aggregates
2.6 RAP Millings Behaviour
The Washington State Department of Transportation (1986) evaluating 16 completed hot mix recycled projects behaviour observed that they were comparable with conventional at that particular time (Hans and others, 2011). Early data from projects constructed after that time also show promising results. RAP percentages used in these projects ranges from 9% to 80%. High percentage of RAP exhibited a little more distress, but at 15% RAP provides acceptable pavement behaviour. The work of Kandhal and others (1995) in Georgia serves as a testimony to the behaviour of these secondary materials as RAP percentages ranging from 15-70% were incorporated in road construction and rehabilitation.
2.7 Economic Considerations
Appraisal of recycled aggregates for construction application is not complete unless the economics of recycling is considered. Sustainable application of recycled aggregates can only be appreciated if it is a viable alternative to virgin aggregate. For decades, roads have played effective and preferred role for transportation and movement of goods and persons, buttressing the UN report that, road transportation explains the 80% of passengers and merchandise movement in Africa (Oke, 2007). Julius Berger and RCC used polymer bitumen on Lagos-Ibadan-Expressway.
This is an outcome of a joint laboratory experiment carried out at Germany. A little bit of recycling has been done in the Northern part of the country; this was only used to patch roads (Eyo, 2004). PW Nigeria Limited also carried out maintenance on the runway at Murtala Mohammed International Airport Lagos, by milling the asphalt wearing course, pulverized it and laid it as the road base asphalt was then used as an overlay (PW Nigeria Ltd, 2007). Laboratory study was also carried out using reclaimed asphalt pavement aggregates from distressed sections of Ikwerre Road, Port Harcourt. The results revealed an average asphalt recovery from of 5.1% with penetration value of 21. This rather high asphalt content indicates large wastage of bitumen by discarding the pavement. Cost comparison also shows that there would have been a loss of N3, 222.00 per tonne of asphalt if the material was discarded. With the current scarcity of funds in Nigeria, there is need to seek alternative methods of pavement maintenance and rehabilitation that would require optimal use of aggregates and bitumen. Although there is no evidence in literature about the details of the performances of pavements produced from these few recycling practices which really, are not on a large scale, they are pointers to the fact that pavement recycling is possible in Nigeria once the proper pavement material characterization and mix design has been done.
The Leadership Newspaper of 26 September, 2007 reported that the Federal Government is concluding plans to introduce the recycling of asphalt for the strengthening of road pavements in Nigeria. The economic growth of Nigeria is highly dependent on its road network; hence the need to proffer solution to the problem cannot be overemphasized. It has been estimated that billions of naira is needed for road construction and rehabilitation. Adopting the pavement recycling option will save tax payers money, since from experience, pavement recycling will cost about 50% of the cost of conventional rehabilitation method and considering that more economical methods of pavement recycling are emerging daily.
2.7.1 The UK Experience: in-situ deep recycling in Perth and Kinross was a huge success in the UK. The strategic link, from the west central belt of Scotland over the Kincardine Bridge to the industrial areas of Fife, was completed in five-week instead of the 14 weeks for conventional reconstruction. The recycling option took away 35% of the time, 65% of the cost and 22% of the conventional method’s requirement resulting in reduced road maintenance budget.
2.7.2 The Tilbury Dock Experience: The project comprised the repair of an existing paving surfaced with hot rolled asphalt using recycled material. Independent cube testing confirmed the suitability of the material in terms of compressive strength. The execution of the contract was carried as predicted, despite periods of stormy weather in six working days, representing a time saving of 40% and cost savings of 7-10% as compared to conventional method
2.7.3 The America Experience: Since 1969, in Kansa, more than 1.9million2 of roads have been recycled. In Arizona, a net saving of $4.02 per ton of asphalt has been accomplished in a recycling project. Probably far more than any state, Wisconsin has made a serious commitment to recycling old pavements. In 1980 alone, it worked on over 30 pavement recycling jobs (McCarthy, 1985). By switching to pavement recycling; Texas was able to rehabilitate its pavements thus yielding a cost saving over conventional method of 50%. California has in recent time been involved in pavement recycling as commitment to sustainable development. These are just few of the several scenarios of success recorded in pavement recycling in the US. Economic evaluation is important in recommending an alternative aggregate recycling option. It is time Nigeria takes on this excellent opportunity.
2.8 Production and Sales Cost Projections
Production cost and sales projection is a forecast establish on earlier production cost and sales behaviour. Forecasting looks into the future. An enterprise that recognizes yesterday stays aware of the now and accurately sees into its tomorrow (opportunity). Analyzing production cost and conducting a sales forecast will provide the recycling venture with an evaluation of past and current sales and production levels. Engineering economic analysis focuses on the future consequences of current decisions. Because these consequences are in the future, usually they are unknown, thus, must be estimated. The outcome is only as good as the quality of the numbers used to reach the decision, it is therefore very vital to make careful estimates. In general, the analysis portion of the feasibility study involves calculating the profitability of the proposed investment. Profitability of an operation can be projected using the estimated prices and production cost. It is critical in determining the proposed aggregate recycling plant true economic viability. Operating cost is calculated by cost of goods sold minus operating expenses. Operating expenses consist of administrative and office expenses (rent, salaries and staff insurance) and selling and distribution expenses like advertisement and salaries. The developing interest in pavement recycling has been worldwide, with many countries now becoming increasingly involved in various forms of pavement recycling; some of them are presented in the following sections (Oke, 2007).
2.9 Sensitivity Analysis
Since many data gathered in solving a problem represent projections of future consequences, there may be considerable uncertainty regarding the data’s accuracy. Since the desired result of the analysis is decision making, an appropriate question is, to what extent do variations in the data affect the decision (Uzochukwu and Others, 2014). Sensitivity analysis looks at variables affecting the outcome of a result. We stated specific assumptions concerning applicable revenue and cost to the economic analysis. It was assumed that a high degree of confidence could be placed in all estimated values. This is rather misleading in that there rarely is a scenario in which the best of estimates can be assumed to be certain. To better evaluate the effect of any particular estimate we compute the variation to a particular estimate that would necessary to change a particular decision. Sensitivity analysis is a study to see how economic decision will be altered if certain factors are varied.
CHAPTER THREE: MATERIALS AND METHODS
To investigate the properties of recycled asphalt pavement (RAP) in comparison with virgin aggregates (VA), a series of laboratory tests was carried out in conformity with relevant standards (SEE APPENDIX 1). A major part of this study involved an economic assessment of utilizing RAP in road construction in Nigeria. An outline of the objectives includes:
Segment I
Study the aggregate characteristics with respect to the literature review of recycled asphalt pavement, its effects on the behaviour of RAP and various economic considerations.
Segment II
In this phase, the procurement/sampling, mix design, laboratory testing and characterization were highlighted. Production capacity, cost, sales and energy projections and subsequent cash flow assumptions were developed for the economic assessment.
Segment III
Experimental work was executed; analysis of laboratory tests and results of economic assessment of viability of the business were reported. All results were completed in the form of tables and graphical representation for comparison of natural and recycled asphalt aggregates. Finally conclusions and recommendations were drawn.
3.1 Research Design
Varying percentages of RAP was incorporated into the mix design. RAP was introduced at levels of (20%, 30%, 40% and 50%) also a mix design of 100% RAP was evaluated. Control samples not containing RAP (100% Virgin) were also used throughout the testing.
3.2. Sampling and Laboratory Techniques
Random sampling from stockpiles, splitting, material preparations and testing are required to determine whether quality of materials are in reasonably close conformance with standards and specifications. All materials were prepared and tested according to the specific standards,
Extraction
Extraction of samples using extraction ignition machine to extract bitumen at a temperature of 90-1100c, (See appendix 3a) the ignition test (ASTM D6307, “Standard Test Method for Asphalt Content of Hot-Mix Asphalt by Ignition Method”)
Figure 3.1 Aggregate obtained after RAP burnt in the ignition furnace
3.2.1 Sieve Analysis or Aggregate Gradation
To determine particle size distribution of the coarse and fine aggregates, sieve analysis was conducted to obtain the gradation (SEE APPENDIX 2a) for details:
Figure 3.2 Riffling of Sample
Figure 3.3 Washing of Sample
Figure 3.4 Drying of Sample (using Gas Burner)
Figure 3.5 Sieve Analyses.
Figure 3.6 Aggregate fractions after sieve analysis
3.2.2 Specific Gravity and Water Absorption Test
The important steps of specific gravity, bulk specific gravity, absorption, apparent specific gravity and bulk specific gravity tests for the aggregates are illustrated in the Figures. 3.7, 3.8, 3.9 and 3.10 Three samples were tested for specific gravity of the coarse and fine aggregate (SEE APPENDIX 2b) for details.
Figure 3.7 Fine aggregate in an SSD condition
Figure 3.8 Slump test to determine the SSD condition of fine aggregate
Figure 3.9 Removal of the air bubbles from the pycnometer using vacuum
Figure 3.10 Pycnometer after removal of air bubbles
3.2.3 Determination of Los Angeles (L.A) Abrasion Value
Los Angeles test machine is used in the determination of the resistance to abrasion of aggregates (Transportation Engineering Lab Manual, 2013). (SEE APPEDIX 2c) for details: Figures 3.11 shows a representative of the L.A. abrasion test machine
Figure 3.11 L.A. Abrasion Machine
3.2.4 Determination of Aggregate Impact Value
Toughness is a property of an aggregate to withstand effect; it is determined by the effect value test (SEE APPENDIX 2d) for details (Transportation Engineering Lab Manual, 2013).
Figure 3.12: Aggregate impact test
3.2.5 Determination of Aggregate Crushing Value (ACV)
The strength under a progressively applied compressive force is known as the aggregate crushing value (Transportation Engineering Lab Manual, 2013). (SEE APPENDIX 2e) for details
Figure 3.13: Apparatus for the 10% fines test and aggregate crushing test (Millard, 1993)
3.2.6 Flakiness Index
When the least dimension is of a concern, flakiness index is evaluated (Transportation Engineering Lab Manual, 2013). (SEE APPENDIX 2f) for details
3.2.7 Elongation Index:
When the greatest dimension is of a concern, flakiness index is evaluated (Transportation Engineering Lab Manual, 2013). (SEE APPENDIX 2f) for details
Figure 3.14 Flat, elongated, flat and elongated particles
(http://pavementinteractive.org/index.php?title=Flat_and_Elongated_Particles
Figure 3.15: Flakiness Gauge
Figure 3.16: Elongation Gauge
Figure 3.17 Flakiness test and Elongation test
3.3 Effect of Haulage on Cost and Energy for Recycled Asphalt Pavement
Cost and energy for aggregates are influenced by variations in haulage distances. Different modes exist for the procurement of aggregate. The benefits of recycled asphalt pavement aggregate (RAP) in respect to cost and energy are outlined in this study. The question remains, to what extent has haulage distance effects aggregate cost and energy? A scenario was assumed using Ihube, Imo state, as the worksite and tested for altering haulage distances. Three different scenarios were examined. The first scenario considered was to mill the asphalt pavement using a milling machine and reuse RAP. The second scenario was to discard the reclaimed asphalt pavement at a nearby borough pit and then procure virgin aggregate from the nearest quarry. The third scenario was to haul the reclaimed asphalt to a recycling plant and then buy the processed product from the recycling plant. The amount of fresh aggregate procured was abridged by ten percent because characteristically RAP has a lower density than virgin aggregate. Cost calculation was made on the premise of local price quotations. The energy utilization of 82Kj/kg for crushing was assumed in reference to (BEES) Technical User Guide Manual. Energy necessary for the haulage of aggregates per 100km is 265.5kJ/kg (Bonilla and Salling, 2008). An estimated 8,250 tonnes of aggregate is required for the construction of 1km single lane road in the South-Eastern region of the country.
List of Assumptions
1. The investigation commenced after the asphalt pavement was processed.
2. The energy utilization for crushing is assumed equivalent in all three scenarios.
3. The energy utilization for Haulage is assumed equivalent in all three scenarios.
Limitations of the study
1. Milling/crushing, and incorporation of the recycled aggregate (RA) on the site requires longer periods than procuring quarried virgin aggregate. This feature was not captured.
2. Environmental factors were ignored.
This chapter comprises of four sections: (a) Gradation/Sieve Analysis of aggregates (b) characterization of RAP and Virgin aggregates (c) comparison between different proportions of RAP and their corresponding original mixes. (d) Effects of haulage distance on energy and cost.
Sieve analysis was performed on extracted RAP aggregates. Table 4.1, 4.2 and 4.3 shows the gradations curve of the RAP samples, the gradation of RAP coarse aggregates and the virgin coarse aggregate, which indicates that the gradation of the RAP coarse aggregates falls within the upper control points (fine region) and the virgin coarse aggregate falls within the lower control points (coarse region)
Tables 4.4 and 4.5 shows the test results of specific gravity and absorption of coarse and fine RAP respectively while Tables 4.6 and 4.7 shows the test results for virgin coarse and fine aggregates respectively. The test results demonstrate that the coarse and fine aggregates had similar bulk specific gravity but the coarse aggregate had higher absorption than the fine aggregate.
The L.A. abrasion value for RAP was 35.2% and that of virgin aggregate was 19.1%. This result implies that this RAP aggregate has lost its hardness. But at 80% virgin/20% RAP, the hardness result of 20.2% is within the specification.
The impact value test on two samples each was carried out. Tables 4.13, 4.14, 4.15, 4.16 and 4.17 presents the test data of aggregate impact value, it is shown that this value increase with the increase in RAP. At 20% RAP the aggregate impact value is within the specification.
The aggregate crushing value test on two samples each was carried out. Tables 4.18, 4.19, 4.20, 4.21 and 4.22 presents the test data of aggregate crushing value, it is shown that this value increase with the increase in RAP. At 20% RAP the aggregate crushing value is within the specified limit
The percentage of elongated virgin and RAP aggregate were determined as 17 and 18% respectively. This shows that the aggregate shapes are within the specified limit of 30%
The percentage of flat virgin and RAP aggregate were determined as 18 and 22 % respectively. This is within the specified limit of 35%
Subsequent conclusions were drawn from this research:
• Recycling reduces wastages, preserve natural resources, saves energy and cost while reducing environmental disturbances.
• Decision to recycle should be based on cost effectiveness analysis.
• The gradation shows that the RAP are finer than the virgin aggregate as it occupies the upper limit (fine region) while the virgin occupies the lower limits which is the coarse region.
• The bulk specific gravity of the coarse and fine RAP aggregates are less than that of the original mixes, which indicates that the virgin aggregates, has higher density than RAP.
• The absorption of the coarse and fine RAP aggregates is higher than that of the original mixes, which makes them more ideal for concrete works.
• The effect values and the crushing values of 20% RAP and 80% virgin aggregates shows a comparable toughness and strength performance to the 100% virgin aggregate.
• The L.A. Abrasion values (hardness) of RAP aggregates shows high value at 30% to 50% which is out of specification. The percentages of flat and elongated RAP particles are within the specification.
• The first scenario is the preferred alternative in reference to cost effectiveness and energy efficiency.
• Based on the assumptions, adopting a 80/20 virgin/recycling option will be saving about N2,685,375 on aggregate procurement for a 1km road pavement construction in Nigeria.
• Cost and energy utilization is dependent on haulage distance. At a distance of 13km and 42km fresh aggregate seems a favourable
 Asphalt consists of aggregates and binder, the characteristics of the binder content should be investigated.
 Environmental effects affecting asphalt recycling should be studied.
 Local knowledge should be broaden by carrying out tests on samples obtained from different geopolitical zones in Nigeria to ensure a better understanding of RAP and enhance accurate generalization.
 Other extraction methods should be used to compare the results to that of the ignition method used in this study.
 Not more than 20 percent RAP should be utilized in the mix design.
This study confirms the results shown on the literature review chapter. But no recent work has addressed the issue of economic assessment in Nigeria. For this, the thesis, functional properties and economic assessment of recycled aggregate for road and pavement construction in Nigeria. The research findings show that RAP can be incorporated into the aggregate mix in Nigeria. At a proportion of 20 percent RAP we observe a comparative and cost effective performance to the conventional aggregate
ABSTRACT
This investigation seeks to appraise the functional properties and the economic viability of milled Asphalt Pavements in road construction in Nigeria. Samples were obtained from Setraco Nigeria Limited stockpiles along Umuahia-Enugu Expressway and Amasiri quarry. Ignition method was used for extraction, and aggregates tested for properties such as gradation, Los Angeles Abrasion Value, Aggregate Crushing Value (ACV), specific gravity, Water Absorption, Impact Value, Flakiness and Elongation. The modifications in the properties of RAP with virgin aggregates are discussed. The economic assessment looks at the different methods of aggregate acquisition. Cost effectiveness of recycled asphalt pavement aggregate (RAP) and virgin aggregate (VA) in terms of material cost and energy was conducted. Ihube, Imo State, was assumed the jobsite and effect of material cost and production energy for varying Haulage distances was tested. We discovered; 1}. 20% RAP performs as the conventional aggregate 2}. Incorporating milled asphaltic pavement into the design mix offers a better alternative in terms of energy and cost to the used of 100 percent virgin aggregates only 3}. Haulage distance has a direct relationship on energy and cost
APPENDIX 1: ASTM STANDARDS AND THEIR AASHTO DESIGNATIONS
(Standards May Not Be Identical)
British Standards
Sieve Test on Aggregates BS812:Part103.1:1985; Flakiness Index BS812: Section 105.1:1989
Elongation Index BS812: Section 105.2:1990; Aggregate Crushing Value (ACV) BS812: Part 110:1990
Aggregate Effect Value (AIV) BS812: Part 112:1990; Slump Test BS1881: Part 102:1983
APPENDIX 2a: Sieve Test
All methods used are according to (Transportation Engineering Lab Manual, 2013)
Equipment
• Sieves.
• A weigh balance of 0.5 g accuracy.
• Riffle boxes.
• A gas burner.
• Metal containers and trays.
• Lids and receivers.
• Scoop and sieve brushes.
Sample Preparation:
Appropriate sample size
1. 75µm test sieve, fitted with a guard sieve 1.18mm or 2.36mm on top.
2. Position the weighed desiccated sample (W1) in a container and put in sufficient water, incite the contents to separate fines and coarse aggregate.
3. Empty the suspension of fine solids on the secured 75µm sieve. Wash the coarse remains pending the clarity of the water.
4. Sieve wash remains. Decant surplus water through the 75µm sieve, and arid by heating in a gas burner. Cool, weigh and tag as W2
5. W1-W2 = Mass passing the 75µm sieve
6. Arrange the relevant sieves in increasing opening size, hand-shake for an acceptable time to fractionize the different size. Wobble until all aggregate passes.
7. Weigh retained aggregate on each sieve.
Calculation: (% passing this sieve) = (% passing previous sieve) – (% retained on this sieve)
APPENDIX 2b: Specific Gravity and Water Absorption
Equipment
• A gas burner
• A balance of 0.5g accuracy.
• A glass vessel.
• Dry soft absorbent
• Tray and airtight container
• 5mm sieve and clean water
Sample Preparation
Carefully wash sample on the 5mm sieve to remove finer constituent.
Procedure
1. Thrust the sample in the glass vessel containing water for 24hours. Tilt the vessel gently to eliminate enclosed air. Fill the vessel with water, ensure no entrapped air. Dry the vessel, weigh and document as (mass C).
2. Decant and refill with water, dry vessel and weigh it as (mass B).
3. Surface-dry aggregate with fabric
4. Air aggregates away from direct sunlight.
5. Gas dry aggregate, cool and weigh as (mass A).
Calculations
Bulk Specific Gravity (Dry Basis) A/ (B – C)
Bulk Specific Gravity (SSD Basic) B/ (B-C)
Apparent Specific Gravity A/ (A-C)
Absorption in Percentage (B – A)/A x100
Where
A = weight of gas dried sample in air (in g)
B = weight of saturated surface dry sample in air (in g)
C = weight of saturated surface dry sample in water (in g)
APPENDIX 2c: Los Angeles (L.A) Abrasion Value
Principle
Standard steel balls produce the abrasive action when swivel in a drum for exact amount of revolutions, the %wear due to rubbing with steel balls is hardness
Apparatus
• Los Angeles Machine
• Cast iron or still ball as abrasion charge
• 1.70mm IS sieve
• Weigh balance, gas burner and Tray
Procedure
Aggregate samples coarser than 1.70mm sieve size
1. Place the sample and the abrasive charge inside the machine
2. Rotate machine at 500 revolutions and 1000 revolutions for different ratings
3. Sieve through the 1.7mm IS sieve
4. Record the weight of aggregate passing through 1.7mm sieve
Results
Record the value in percentage
APPENDIX 2d: Aggregate Impact Value
Apparatus
1. Testing machine
2. A cylindrical steel cup
3. A metal hammer
4. A tamping rod, rounded at one end.
5. A weigh balance
Procedure
1. Gas dry and cool aggregates.
2. Sieve through 12.5mm and 10.0mm sieve. Passing through 12.5mm and retained on 10.0mm are the sample.
3. Fill to a depth of one-third depth of cylinder give 25gentle blows
4. Weigh the aggregates
5. Give 25gentle strokes with tamping rod to the aggregates in the firmly fix cup, freely allow the hammer to fall on the sample
6. Sieve crushed aggregate through 2.36mm sieve, weigh the fraction passing the sieve. Also weigh the fraction retained in the sieve.
7. Calculation = B X 100
A
APPENDIX 2e: Aggregate Crushing Value
Apparatus
1. A 15cm diameter open ended steel cylinder with plunger and base plate
2. A straight metal tamping rod
3. A weigh balance
4. A compression testing machine
Procedure
Dry and cool the aggregate.
1. Sieve through 12.5mm and 10.0mm sieve, aggregates passing through 12.5mm sieve and retained on 10.0mm sieve
2. Each third is subjected to 25strokes with the tamping rod.
3. Level aggregate and
4. Apply load at a uniform rate
5. Release load and sieve aggregate through 2.36mm sieve, weigh the fraction passing and record the result.
Aggregate Crushing Value = B/A X 100
APPENDIX 2f: Shape Test
A. Flakiness
Apparatus
1. A balance
2. Metal Gauge
3. Sieves
Procedure
1. Sieve samples
2. Gauge fractions for thickness and weigh the aggregate passing the gauge.
Flakiness index = 100*w/W
W = weight of passing
W = weight of passing + weight retaine
B. Elongation
Apparatus
Same as in flakiness + the gauge
Procedure
Same as step 1 to step 3 of the flakiness index
Step 4: weigh aggregate retained