- May 27, 2020
Rubblization of Old Concrete Pavement
RUBBLIZATION OF OLD CONCERET PAVEMENT 23
Rubblizationof Old Concrete Pavement
Table of Contents
Rubblization of Old Concrete Pavement 5
Background to Concrete Pavement Rubblization Techniques 6
Theory Behind Rubblization 7
Procedure for Rubblization 8
Rubblizing Equipment 9
Multiple-Head Breaker (MHB) 9
Resonant Pavement Breaker (RPB) 10
Reflective Cracking 10
Performance and Cost of Rubblization 11
When to Rubblize Existing Concrete Pavement 13
Rubblization Project Evaluation 14
Evaluation of Existing Structures 15
Distress Survey 15
Existing Pavement Structure 15
Soil Condition 16
Project Evaluation Report 16
Construction Operation for Rubblization 16
Surface Preparation of the Existing Pavement 17
Location of Utilities and Underground Structures 17
Rubblization Recommendations 18
Figure (1), showing a guillotine machine 21
Figure (2), showing Multiple-Head Breaker (MHB) 21
Figure (3), showing Resonant Pavement Breaker (RPB) 22
Figure (4), showing reflective cracking 22
Table (1), Evaluation of existing structures 23
Themethod of old concrete pavement rubblization is gaining popularity inthe modern engineering constructions. The process helps to save timeand transportation cost through reducing concrete into rubble at thelocation where they are as opposed to transporting them to otherlocation. There are two application of Rubblization: decommissioningnuclear plants and developing a base for new roads. Rubblization ofpavement is a critical issue, and it demands the intervention of theengineers to make a judgment in the assessment process. The followingare some of the steps that must be followed during pavementrubblization: defining the exact problem, formulating potentialproblem solution and identification of the preferred option. Manyagencies are considering rubblization of concrete pavement as a majorissue within the field of engineering. Most of the pavements thathave been reconstructed have extensive layers of formerly linked andconstantly resistant concrete pavement that are almost approachingtheir durability end point. Earnestly, the first goal of rubblizationis to disintegrate the existing concrete pavements into smallerfragments that vary in sizes. The process of rubblization is enhancedthrough the use of two machines, with the first one identified as theResonant Pavement Breaker-RPB. The other device that compliments RPBis the Multiple-Head Breaker-MHB. Mostly, the call for rubblizationprevails when reflective cracks are witnessed on the current concretepavements. Notably, reflective cracks tend to appear on the surfaceof the pavements within the joints, especially where rigid pavementsresurfaced by the bituminous material. Of the all the common types ofdistress, reflective crack is the common one that appears on thecomposite pavements. Generally, when an existing concrete pavementshows some of the following material complications freeze-thaw,D-cracking, alkali-silica reactivity then rubblization is not anapplicable solution to that condition. In this paper, the concepts ofrubblization of old pavement to ensure that they regain theirprevious performance capabilities are covered.
Rubblizationof Old Concrete Pavement
Accordingto the concept of Rubblization within the construction andengineering, it is a method that helps to save time andtransportation cost through reducing concrete into rubble at thelocation where they are as opposed to transporting them to otherlocation. There are two application of Rubblization: decommissioningnuclear plants and developing a base for new roads(Rue & Schilling, 2001).For instance, in road construction, the Portland cement concrete thathas been worn-out can be subjected to Rubblization and again it canbe overlaid with a new surface. On the other hand, within the fieldof nuclear energy regulation, Rubblization is regarded as a techniquefor decommissioning a nuclear power plant (Rue& Schilling, 2001).
Additionally,existing pavement can be rubblized, but that remains to be a majorpavement priority that is experienced by state, local and federaltransportation agency. Utilization of Hot-mix Asphalt (HMA) providesan existing term and economical resolution as far as pavementrubblization is concerned (Rue& Schilling, 2001).HMA has numerous importance, for instance, it can increases themechanical capability of the existing pavement scheme and enhance thelong-term functional slab performance.Normally, designing of a newpavement system is much simple than the rehabilitation of a newpavement system since is associated with complexity. Therefore,rehabilitation is regarded as measures taken so that the service lifeof the pavement can be extended (Rue& Schilling, 2001).
Engineerssuggested that routine maintenance measures that are employed topreserve an existing pavement so that it can have the capacity toaccommodate current traffic loadings. Rubblization of pavement is acritical issue, and it demands the intervention of the engineers tomake a judgment in the assessment process (Rue& Schilling, 2001).The following are some of the steps that must be followed duringpavement rubblization: defining the exact problem, formulatingpotential problem solution and identification of the preferredoption. Similarly, rubblization of Portland cement concrete can beachieved through the following measures: resurfacing, reconstructionand concrete pavement restoration (Rue& Schilling, 2001).
Duringconcrete pavement restoration (CPR) there are numerous challengesthat are encountered such as time, expenses, traffic delay andreconstruction. As a result, many agencies resort to rematerializingof PCC with HMA overlay because it is the only appealing option (Rue& Schilling, 2001).Alternatively, agencies are faced with problems while trying torubblize existing PCC pavements since there is a possibility ofreflection cracking that can occur when an HMA overlay is placed.Vertical and horizontal movements are the primer causes of reflectioncracking, and such movements usually take place within the underlyingPCC. Additionally, within the PCC cracks or the joints, those arethe potential positions for reflection cracking (Rue& Schilling, 2001).
Whenthe engineers want to achieve a long-term performance of the overlay,all the problems that are associated with reflection cracking must beaddressed immediately. That is because the primary objective ofrubblization is to eradicate reflection cracking that might occurwithin the HMA overlay. To successfully achieve that process the slabis rubblized into fragments. Any other factors such as temperatureand reinforcement steel are debonded from the concrete when they arepresent in the PCC through that process (Rue& Schilling, 2001).
Backgroundto Concrete Pavement Rubblization Techniques
Manyagencies are considering rubblization of concrete pavement as a majorissue within the field of engineering. Most of the pavements thathave been reconstructed have extensive layers of formerly linked andconstantly resistant concrete pavement that are almost approachingtheir durability end point. Similarly, additional life can beachieved through the black topping and white topping, but they aremajorly impacted by reflection cracking (Rue& Schilling, 2001).For that reason, the existing PCC is deteriorated structurally, andany simple overlay cannot provide adequate performance. Suchchallenges that are faced within the pavement have made fracturingtechnique to be more acceptable within the past two-decadegeneration. The initial fracturing to be utilized were crack andseat, or break and seat, and these were employed for plain jointpavements or reinforcement (Rue& Schilling, 2001).Specifically, the past techniques made use of the then populardevices namely the spring hammers and the guillotine, and figure (1)is an illustration of the guillotine type.
Mostly,the term “crack and seat” is always used within the context ofunreinforced concrete pavement, and the primary goal is to createproximately packed and tight cracks that can allow the conveyance ofloads through the aggregate knit with insignificant loss ofstructural value. Therefore, their main goal is to have a crackthrough entire layer. On the other hand, the term “break and seat”refers to the fracturing of the distributed steel, or an absolutedebond of the steel from the adjoining concrete, which in turn posesconsiderable impairment to the effectiveness of the slab length, thusthe recommendation for reinforced slab(Boyer& Buncher 2001).
Alternatively,rubblization is an entirely new technique whereby special equipmentare used to reduce the concrete into fragments, but they maintaintheir gradation and textural characteristics as a large aggregateflexible base (Fang,Luo & Zhu, 2016).Rubblization can be employed in structural design where it reducesPCC pavements’ stiffness, transforming it to a rather flexiblebase, and that calls for the need to reintroduce a thicker overlay. Of all the three slabs fracturing technique, rubblization is the mostexpensive, and that points to the reason why it is becoming liked inthe departments of transportation-DPOTs. That is because rubblizationis considered to be the most successful with respect to the creationof uniform pavement supports, and also aids in the lowering of thereflection cracking (Boyer & Buncher 2001).
Thefirst goal of rubblization is to disintegrate the existing concretepavements into smaller fragments that vary in sizes. For example,there are those fragments that are of the size of sand and those thatare approximately 100mm to 200mm in width. The concept was inventedas a result of controlling reflective cracking that took place inasphalt overly of concrete. As mentioned earlier, reflective crackingdefines the fracturing that takes place on top of the linkages ofconcrete pavements. The main reason why the crack occurs is that ofthe weak nature of asphalt that cannot withstand seasonal temperaturemovements of the underlying concrete (Boyer & Buncher 2001).
Additionally,during construction, when asphalt overlay is introduced on a concretethat is not rubblized, then the pavement system is made up ofconcrete as the main structural component. Moreover, the function ofthe asphalt is to act as a riding surface. When there aretemperatures fluctuations, the concrete is subjected to expansion andcontraction, and that causes the joints to open and close.Nevertheless, it has been established that asphalt is too week toaccommodate these sudden movements. As a result, a shear stress isgenerated in the asphalt-riding layer resulting in cracking (Boyer &Buncher 2001).
Therefore,there was a need to stop reflective cracking and that resulted in twofractural procedures, which are already identified as the crack andseat, and the break and seat. These techniques were brought forth sothat they can decrease the slab length (Boyer & Buncher 2001).The main reason of reducing the slab length is because it is believedthat when the slab is shorter, the movements at the cracks and thejoints are significantly reduced, and that implies that there will beno reflective cracking. Coincidentally, these two techniques thatwere proposed were not successful in limiting reflective fracturing.That is because even when the movements of smaller slabs werereduced, the cracks were observed bin the asphalt layer (Boyer &Buncher 2001).
Therefore,a better method was formulated that helped to reduce the slab lengthto the extreme and it is known as the rubblization. It entirelyimpairs the slab action of the concrete through disintegrating itinto smaller size pieces. Nonetheless, the main objective to beachieved through that action is to redesign the present pavement toform part of the base course. Alternatively, that concept was facedwith some challenges such as lack of gradation or density controlwithin the rubblized pavements (Boyer & Buncher 2001). Accordingto the standards and specifications, it is recommended that basecourses must have both gradation and density control. The threetechniques that have been proposed, namely rubblization, crack andseat, as well as the break and seat, do not explicitly addressasphalt overlay cracks. Nonetheless, the concrete is destroyed sothat the asphalt does not crack. As a result, such procedure leads tothe destruction of the pavement system’s structural constituent,thereby limiting its capabilities of accommodating more loads (Boyer& Buncher 2001).
Theprocess of rubblization is enhanced through the use of two machines,with the first one identified as the Resonant Pavement Breaker-RPB.The other device that compliments RPB is the Multiple-HeadBreaker-MHB. The aforementioned machines are involved in the breakingof slab into smaller pieces, but none of them shatter the concreteinto the desired standardized base course of high quality.Alternatively, rubblization generates concrete that varies fromparticles with sizes reminiscent of sand, to some debris that measureroughly 150-200 mm in width. But the major limitation of thesemachines is that they are not associated with gradation and densitycontrol. The RPB has ahead that is about 150-mm wide that vibrates athigh frequency and low amplitude that because of shattering of theslab (Boyer& Jones, 2004).Meanwhile since the size of the head is small it can only breaksmall, longitudinal stripe every time. Therefore, the machinerequires approximately 50 passes to entirely disintegrate a pavementof an estimated width of 7.3 m. On the other hand, MHB machine canpulverize the whole lane in a single pass. The machine utilizes anamplitude hammer that impacts the slab and shatters it in flexure. In that case, the concrete is not rubblized, but it has beenpulverized(Boyer & Jones, 2004).
Boththe machine does not provide a uniform base, and that can introduceeffects to the subgrade and make it vulnerable. For instance, whenthe resonant breaker is used for rubblization, the damages are causedsince the two wheels are heavy and they spin on the concrete which isdismantled, and that can force the disjointed sections into theunderneath subbase or subgrade (Boyer& Jones, 2004).On the other hand, MHB causes destructions to the subgrade due to itsforceful crushing procedure that can push the slab into the subgradeor subbase. If the subgrade and subbase have been destroyed, itcannot sustain a uniform support. Therefore, during the designingprocedure, that must be thoroughly stressed, and the options ofrepairing or eliminating it is practically accepted (Boyer& Jones, 2004).
Thereare two types of commonly used equipment for rubblization process:MHB and RPB. Ideally, the procedure of rubblization has far reachingadvantages in the long-run functioning of pavements.
MHB,shown in figure 2, is equipment that is used for rubblization and itis a machine that is self-contained and self-propelled. The machinehas the ability of rubblizing any pavement over any width not lessthan thirteen feet for every single pass. The hammers that areutilized by the baker are strategically positioned (Mahdi& Wu, 2014).The spacing is sufficient enough that can permit breaking of theconcrete from side to side. Adjustment can make on the lift height ofthe hammers independently. Similarly, MHB can cause damages to thesubgrade during the instances in which its forceful crushing actionsaffect the concrete and compel the latter to drift to the subbase orsubgrade. Notably, MHB machine is very significant since it reducesmultiple passes and subgrade stability limitations. Moreover, thisproduced has been established to have an effect on the subgradestrength properties since it cannot provide a uniform base due to thedestruction caused on the subgrade(Mahdi & Wu, 2014).
ResonantPavement Breaker (RPB)
RPB,see figure (3), is a machine for rubblization and vibrating hammersare attached to it that assists in demolishing existing pavements.This machine has a system of breaking the slab, and the connectionsthat persist between the concrete and the steel is also destroyed(Qiu,Ling & Wang, 2013). The principle that guides the machine’s operation posits that thevibrating force frequency remains adjustable up to the point at whichthe body’s resonant frequency can be ascertained. The machinecomprises of a hammer that is positioned at the pedestal’sterminus, and it is engraved to the shaft and a counterweight locatedat the beam surface. The machine can produce low amplitude thatalternates from 32mm to 38mm blows with a force of about 2000 Ibs.Additionally, the blows are extracted from present PCC pavement at aprevalence of at least 44 cycles for every second. The following aresome factors that impact the rubblization process: loading pressure,operating frequency, beam width, and shoe size(Qiuet al., 2013).
Presently,the Resonant Pavement Breaker (RPB) is not being often used.Additionally, it is suggested that several passes are required tocomplete the pavement’s full-lane width. Conversely, if the spacingis wide, some of the unbroken strips of the concrete are likely toremain (Qiuet al., 2013).Moreover, if there is a second pass over in the entirely rubblizedregion, that is likely to generate more damages to the pavement.Often, such challenges as shoving, distortion, or punching have beenreported. Those problems come to life when the rubblized PCCpavement, subgrade, and subbase’s unit thicknesses, as at themoment of structuring, are not enough to accommodate repeated passesmade by the RPB (Qiuet al., 2013).
First,reflective cracks (figure 4) tend to appear on the surface of thepavements within the joints, especially where rigid pavementsresurfaced by the bituminous material. Of the all the common types ofdistress, reflective crack is the common one that appears on thecomposite pavements. The cracks move throughout the HMA overlaysurface that as a result of the movement that is found within thecracks that generate tensile stress. The following are some of thefactors that can cause the stress: longitudinal cracks in the oldersurface, varying temperature conditions, and discontinuities in theunderlying layer(Lee etal.,2007).
Similarly,continuous traffic loading are very dangerous since they can generatedifferential vertical movement within the joints and crack that areon the slab. Such stresses are generated when the strain due totension is exerted underneath the HMA layer(Harrell, Gillen & Yaede, 2016).The HMA layer is a zone that positions atop the joints and the cracksthat are found in the PCC slab. On the other hand, the HMA layer issomehow weak, and it cannot accommodate the localized strains thatare induced in it and that leads to reflective cracks on the concrete(Leeetal.,2007).Reflective cracks do not pose more dangers to the performance of thepavement but are permits water to infiltrate, and that can causedamages to the underlying layers. Therefore, the best direction totake is to seal the cracks to avoid spreading to other places. Crackscan vary in sizes, for instance some are wider measuring to 6 mm,and they are sealed with asphalt-emulsion slurry and fine sand (Leeetal.,2007).
Additionally,during the repair, one can decide to place an open-graded frictioncourse-OGFC amid HMA and concrete pavement layers. That technique isvery significant since its action is buffer-like, which helps toreduce the incidences of reflection cracking. Moreover, OGFCcomprises of a big proportion of single-sized rough aggregate, whichfacilitates effective drainage (Leeetal.,2007).Conversely, stripping condition can take place directly beneath theOGFC, and that can cause some problems. Therefore, before theconstruction of the pavement, it is critical to cover all the cracks,and the technique is imperative before the pavement loses itsskid-resistance which comes about because of aggregate flushing.Therefore, of all the techniques available to control the reflectivecracks, rubblization can be applied to achieve that objective (Leeetal.,2007).
Performanceand Cost of Rubblization
Rubblizationaction has been evaluated over a period, and they have varied fromgood to extremely poor. To measure the performance of rubblization,it is important to evaluate the condition under the concrete slabs.Additionally, more investigation involves assessing the uniformity ofthe rubblized layer. Furthermore, conducting such assessment seems tobe challenging and difficult(Gucunski etal.,2009).Nonetheless, some of the materials used for rubblization such asasphalt overlays are in most situations under designed. For instance,a practical example of this interstate (1-85) is evidenced aroundSouth Carolina’s Greenville, and the establishment of the overlaywas accomplished in the year 1998. Similarly, it was structured as200 mm asphalt overlay placed on a rubblized concrete pavement. Inthe event of construction, there are severe problems that are causedby traffic, and they are induced up to the asphalt overlay. Aftersome period, an assessment was conducted, and it was established thatthe soils that occurred beneath progressively became weaker than theywere prior to rubblization. That pointed to the fact that prior torubblization, the concrete bridged over the weak soil to give it itsinitial strength (Gucunskietal.,2009).
Therefore,for the state to enhance the strength of the pavement, they wererequired to put in 100-mm of asphalt to potentiate the alreadydesigned 200-mm. The additional asphalt is very costly, and it isapproximate $2.5 million to as high as $15 million project. Besides,the state of Michigan reported poor performance regarding rubblizedand asphalt pavements (Gucunskietal.,2009).The damage that been severe and available sources show that they hada 5-year distress index (DI) for about 65.8 km pavement of rubblizedand asphalt overlay. It is imperative to know that when the distressindex (DI) is higher that translate to poor performance (Gucunskietal.,2009).
Thefollowing are some of the recommendation approved by the state ofMichigan concerning their pavements: when the asphalt pavements haveDI greater than eight then rehabilitation must be conducted. Thefollowing were the criteria of rehabilitation: range between 47-64%that comprises asphalt overlays of five years old on the concretepavements that are rubblized, and that requires rehabilitation(Gucunskietal.,2009).
Additionally,for those pavements that are concrete, the state resolved that theyshould be unsparingly reinstated when the DI stands above four.Therefore, within the state of Michigan when that regulation wasimplemented it means that about 67-87% of all the projects that arerubblized needed to be rehabilitated. Additionally, the state isexperiencing a substantial distress, since about 28% of rubblizedoverlay projects marked as five-year-old have a DI above 15.Similarly, the state of Michigan suggested that there is poorperformance and the cost of rubblization and asphalt is much higheras compared to concrete overlays. A good example is a set of proposedrehabilitation project that is to be constructed on 1-96 (Gucunskietal.,2009).
Thereare certain projects that have been done, and their constructioncosts have been compared, and there is a big disparity. For instance,in Clinton County, there is a concrete overlay project that was donein 1991 and it was 190 mm, and another project in the county foIngham, which is a 152 mm consisting of an overlay of asphalt andconcrete which is rubblized, and it was done in the year 1992 (Wu& Xiao, 2016).The concrete overlay expense was about $1,034,437 for every milecovered, while the expenditure for rubblization and asphalt overlaystotaled $1,437,500 for every single mile of construction. Thevariation noted from the two projects is about 395 of the initialproject (Gucunskietal.,2009).The controlled experiments that have been conducted on rubblized andconcrete overlays reveal that they have poor performance. One of theprojects that were used as a control experiment was the strategichighway research program-SHRP, and it was developed in the year 1992.Its primary objective was to control reflective cracking, but thatseems to fail with time. The construction was assessed, and thefindings showed that there are a considerable amount of fatigue andlongitudinal carjacking that has been developed within the wheelpaths. The pavements have been showing quantifiable incidences ofdistress, although it has been operational for only six years(Gucunskietal.,2009).
Researchwas conducted on the performance and cost of the asphalt overlay anda rubblized and the findings show that those techniques are forshort-term solutions that can last for about 8-12 years (Gucunskietal.,2009).Additionally, due to their short life span, the rubblized concretepavements and asphalt overlay are always under constant repair.Similarly, when their costs are compared to other methods of concretepavement rehabilitation, it is evident that they are more expensive.As a result, other techniques are much more viable, sustainable andappropriate solutions (Gucunskietal.,2009).
Whento Rubblize Existing Concrete Pavement
Accordingto the researches that have been conducted, it shows that pavementsthat are still structurally sound should not be subjected torubblization. Additionally, they indicated that damaging a pavementthat is structurally sound to reduce reflective cracking is notethical since it waste resources (Gucunskietal.,2009).As a result, it can be important to save and use the existingpavement in their conditions. Moreover, pavements that have beenrubblized have no any other rehabilitation option in the current andfuture. For instance, once a structurally sound pavement has beenrubblized, the only thing that the agencies can perform is to overlaythe pavement. Alternatively, there are certain problems that comewith such options since they create elevated crowns and raised gradesfor any rehabilitation in the future. When the pavements are keptintact, that implies that any rehabilitation option is applicable inthe future (Gucunskietal.,2009).
Whenan existing concrete pavements shows some of the following materialcomplications freeze-thaw, D-cracking, alkali-silica reactivity thenrubblization is not an applicable solution to that condition. That isbecause material problems lead to deterioration and loss ofstructural integrity of concrete pavement. On the other hand, ASR isnot effective since it lowers concrete pavements long-lastingcapacity by developing water absorptive gel, which expands and crackthe concrete after gaining significant amount of water (Gucunskietal.,2009).Immediately the pavement has developed a crack it loses its strengthand that leads to deterioration. Conversely, the following are someof the situations that can cause D-cracking when there are certainmixtures that are saturated, freeze and expansion. The expansioncauses the stress on the concrete pavement, and that causes thenearby concrete to crack (Gucunskietal.,2009).
Pavementconcrete that consists of a poor entrained-air system is prone tofreeze and thawing and that cause damages on the slab. Hence,air-entraining is a system that consists of tiny bubbles of airwithin the slab, meant to safeguard it while it faces freeze-thawactions. Additionally, the volume and the spacing must be adequate toprevent further cracking when there is when freezing is taking place.It takes an extended period for these material problems to crop up,and the magnitude of weakening bases on the extent of feeblecompounds present in the concrete (Gucunskietal.,2009).
Duringrehabilitation of concrete slab, not every pavement that is rough orworn-out qualifies for rubblization with an HMA overlay. Therefore,the following evaluation must be conducted on the existing pavement:traffic, environmental condition, and subgrade. Additionally, theoutlined steps are significant to confirm that a particular pavementqualifies for rubblization. On the other hand, there is what is knownas the condition survey of the existing slab that helps in theunderstanding of the foundation material for the overlay. Moreover,having an informed knowledge of the soil and moisture content issignificant before making a decision on the type of rehabilitation touse. Nevertheless, some PCC pavements can be rehabilitated throughrubblization overlaid with HMA (Gucunskietal.,2009).
Evaluationof Existing Structures
Evaluationof condition of concrete pavement is very imperative as that can formthe basis of formulating the method to employ for rehabilitation. Forinstance, the damage can be prone, and that implies that thesetechniques that involve removal and replacement cannot be appropriate(Mun& Kim, 2009).Therefore, the table below provides ways through which a designerengineer can utilize to evaluate the project effectively, seetable (1).
Distresssurvey can be completed by using “Distress Identification Manualfor the Long-Term Pavement Performance Project (2).” That manual isimperative since it helps to assess the situation of the currentconcrete pavement. According to the regulation of evaluatingdistress, one must be in a position to recognize the type of distressand estimate the magnitude of distress on the concrete. The long-termperformance of a concrete pavement system can only be establishedwhen the pre-construction conditions are known (Mun& Kim, 2009).
Thereare various processes that can be utilized to evaluate an existingpavement structure including trenching, coring or combination ofboth. The following elements must be determined during evaluationnature and type of material, the thickness of existing layer andconditions. Those factors are very imperative to the engineers whenthey intend to construct new pavement system (Mun& Kim, 2009).Secondly, the engineers are required to develop a sampling plan thatprovides a draft of the pavement portion that should bereconstructed. As a requirement, two samples need to beindiscriminatingly selected for every mile of a lane. Additionally,the inclusion of critical areas in the representative cut and filllocations is a must. Similarly, regions that show structural distressthat is obvious must be assessed and it is better to remove andreplace them (Mun& Kim, 2009).The status of the concrete pavement shoulder must be investigated andwhen rubblization has kicked off, all the traffics are diverted toallow rehabilitation to take place. The importance of the shoulder isthat during the process of building, they can support the trafficloading, hence their inclusion is essential.
Afterthe evaluation techniques have been conducted, that is succeeded bysoil testing that assists to establish the structural adequacy of thefoundation material. Hence, two tests are performed as they aredecisive in the determination of material characteristics, and thefirst one is the dynamic cone penetrometer-DCP. Another test thatreinforces the first one is the field California Bearing Ratio-CBR.Soil materials that are in-situ are always determined concerningmoisture content. Therefore, the data derived from the field arevalues that can be used to develop the project (Mun& Kim, 2009).Additionally, according to the Department of Transport (IDOT)suggested that within the top twelve inches should be split into twoequal parts. That will give an opportunity to evaluate the DCP forevery layer, and the mean value of the two layers assist in knowingthe kind rubblization method to be employed. Moreover, soil data arevery imperative as they can help the engineer to formulate decisionrelating to the rehabilitation process. If the constructor identifiessoft subgrades, the extent of rubblization must be limited, or otherrehabilitation strategies can be implemented, which may comprise ofthe crack and seat or break and seat (Mun& Kim, 2009).
Earnestly,the engineers must ensure that within their evaluation report theyprovide covers the conditions of the materials as at the time whensamples were obtained. Additionally, they should include thefollowing in their report: clearance for any contract’s overheaditems, the position of culverts and utilities present in thepavement, position of all buildings occuring 50 feet from where theconcrete pavement to be rubblized is, and the state of the drainagechannels beneath the pavement (Mun& Kim, 2009).
ConstructionOperation for Rubblization
Thissection is very important as it will attempt to provide a requiredguideline for the rubblization process.
SurfacePreparation of the Existing Pavement
Beforerubblization takes place, it is recommended that the HMA overlay thatis present must be eliminated. Similarly, when the surface is clean,that enhances the transition of rubblization energy within theunderlying concrete. There are some deviations that can result inform faulting and milling operation and thin layers are likely to bepresent, but that cannot interfere much with the rubblizationprocess. Material such as loose patching material, expansion, andjoint filters must be removed from the surface (Mun& Kim, 2009).Some agencies remove loose materials when the process of rubblizationgenerates the materials. The adequate course of action must be takento patches on the existing PCC surfaces, and full repair of theconcrete joint is not important before rubblization. Additionally,when the patches are PCC, then they can be rubblized together withthe entire pavement. Similarly, when the HMA are very small, and,they are also sound they can just maintain their position. Onlypatches that are large and unsound should be replaced withrubblization and material used for replacement can be HMA binder oraggregate. Finally, before rubblization, the relocation of load inthe working PCC pavement in proximity to the PCC must conform tofull-depth saw cut. This process is very since it helps to identifyrubblized area (Mun& Kim, 2009).
Beforethe rubblizing, the constructors must ensure that the underdrainssystems are fixed and functional. Similarly, there are regions thathave weak subgrade, or sometimes, water table that reaches near thesurface the drainage system in these regions must be functional topermit subgrade to be stable as possible. Drainage is very importantsince it help to get rid of the rainwater runoff from the rubblizedpavement section, subgrade, and the underneath layer during thebuilding process. When rubblization is taking place, it is advisableto monitor how water flows steadily in the drainage system (Mun& Kim, 2009).
Locationof Utilities and Underground Structures
Forthe utilities and underground elements, it is significant to identifytheir location before rubblization of the pavement begins. Criticalattention should be directed towards the covers that are hidden fromthe surface. Within the sensitive utilities, it is advisable that thebreaking energy must be reduced so that further damages can beavoided. When rubblization specifications are followed as requiredthat can assist the engineers to dispose off the pavement over andaround utilities, then refill the empty sections with aggregate (Mun& Kim, 2009).
Duringrubblization it is advisable that when the engineers can achievesmaller cracking spacing, then the scenarios of reflection crackingcan be curbed in the overlay of HMA. That is because when there issmaller crack spacing that is likely to reduce structural layercoefficient and that results in the greater thickness of the overlayneeded (Mun& Kim, 2009).Additionally, rubblization must start at the free end, or theconcrete pavement’s centerline. Standard rubblization requirementstates that concrete must be broken down into maximum particledimension that can permit the contractor to allow maximum particledimension. As a result, the specified particles dimensions are whatare anticipated when rubblizing over a batter subgrade. The natureof the sizes of the particles that can be realized is directlyassociated with the status of the subgrade, rubblization equipment,reinforcement type, seasonal vibration, and the slab thickness (Mun& Kim, 2009).
Basesthat are not firm should be reinforced so that they gain theirstability since that can permit the production of smaller particlesizes. All the judgment must be done within the engineering conceptswhen evaluating rubblization process, putting in mind thatrubblization objective is to generate structurally sound base thateliminates reflective cracking by eliminating existing slab jointsand distress. It is important to note that the intent ofrubblization is not to meet the gradation requirement (Gucunskietal.,2009).
Additionally,it is recommended that a working platform must be provided byrubblized layer mainly for stable foundations and paving operationsfor the pavement overlay. In the vent that there are certain isolatedregions of weakness within the subgrade, measures must be taken toensure that they are repaired. In such event, one of the strategiesthat can be implemented is choosing an alternative rubblizationprocess. Similarly, that can help to identify rubblization processthat generates less energy in the subgrade, and that is appropriateand necessary (Gucunskietal.,2009).
Moreover,within the compacted rubblized, there should be no any trafficallowed since unseating risks are likely to be generated on theparticles of rubblized pavement. Within the intersections, it isadvisable that there needs to be limited restrictions regarding crosstraffic and the weight of designing traffic pavements need to beadjusted on the rubblized surface, for instance, in the regions wherethere is weak subgrade (Gucunskietal.,2009).
Rubblizationprocess is not affected much by moderate rainfall, but the entireprocess must stop when the rains are intense, and they areaccompanied by lightning. Drainage system must be enhanced, and thatcan be approved when the edge drains are operating properly. Pavingoperations can resume immediately when the rains have stopped andrubblization must be conducted over moisture of subgrade and cautionmust be taken to ensure that subgrade is not exposed to excessivemoisture (Gucunskietal.,2009).
Agenciesare working hard to make sure that they resort to cheap techniques torehabilitate PCC pavements, but it is evident that rubblizationpresents a successful tool for consideration by the pavementconstruction professionals. The engineers can work on the pavement toreconstruct a currently impaired PCC into a permanently functionalHMA pavement, causing minimal distractions to the traveling public.Even though there is certain disparity relating to the cost andperformance of rubblized pavement, there are efforts to keep the costat a minimum as possible. Therefore, the process is not under study,and concrete pavement rubblization with the overlay of HMA provides asufficient performance of the concrete.
Boyer,R., & Jones, W. (2004). STATE-OF-THE-PRACTICE: RUBBLIZATION OFHEAVY LOAD CONCRETE AIRFIELD PAVEMENTS. IN: AIRFIELD PAVEMENTS.CHALLENGES AND NEW TECHNOLOGIES. In AirfieldPavements. Challenges and New Technologies.
Fang,H., Luo, H., & Zhu, H. (2016). The feasibility of continuousconstruction of the base and asphalt layers of asphalt pavement tosolve the problem of reflective cracks. Constructionand Building Materials,119(56),80-88
Gucunski,N., Sauber, R., Maher, A., & Rascoe, C. (2009). Modulus ofrubblized portland cement concrete from surface wave testing.TransportationResearch Record: Journal of the Transportation Research Board,(2104), 34-41.
Harrell,M. J., Gillen, S. L., & Yaede, J. (2016). Validation of StagedConstruction Pavement Design with the Falling Weight Deflectometer.TransportationResearch Record: Journal of the Transportation Research Board,103(2591),19-22.
Lee,S. W., Bae, J. M., Han, S. H., & Stoffels, S. M. (2007).Evaluation of optimum rubblized depth to prevent reflection cracks.Journalof transportation engineering,133(6),355-361.
Mahdi,M., & Wu, Z. (2014, May). Potential Application of UsingMulti-Head Pavement Breaker for Concrete Pavement Rubblization overWeak Subgrade. In Geo-Shanghai2014.
Mun,S., & Kim, Y. R. (2009). Backcalculation of subgrade stiffnessunder rubblised PCC slabs using multilevel FWD loads. InternationalJournal of Pavement Engineering,10(1),9-18.
Pavements,C. A. (2001). Robert Boyer l, Ph. D., PE, F. ASCE and Mark Buncher 2,Ph. D., PE, M. ASCE.
Qiu,X., Ling, J., & Wang, F. (2013). Concrete pavement rehabilitationprocedure using resonant rubblization technology andmechanical–empirical based overlay design. CanadianJournal of Civil Engineering,41(1),32-39.
Rue,D., & Schilling, C. J. (2001). Concrete Pavement RubblizationUsed as a Base Course for Runway Reconstruction. In AdvancingAirfield Pavements(pp. 299-308). ASCE.
Figure(1), showing a guillotine machineFigure(2), showing Multiple-Head Breaker (MHB)Figure(3), showing Resonant Pavement Breaker (RPB)Figure(4), showing reflective cracking
Perform a distress survey of the existing pavement
Evaluate existing pavement structure
Determine soil condition
Table(1), Evaluation of existing structures