Cement-treated materials have been used successfully in road pavements since the thirties. In the past the research developments were mainly directed towards, and the emphasis during design was mainly placed on material properties, with very little attention being paid to thickness design. High-speed electronic computers and the appropriate programs became available during the sixties, and since then more effort has been devoted to the requirements for a successful structural layout and the behaviour of a pavement structure. This thesis, which is complementary to these studies, discusses the structural design of pavements having cementtreated layers. Some of the design requirements have been known for some time, three more have been added and finally a design procedure is proposed and verified. Chapter 1 portrays the development of structural pavement design theory. It indicates how design procedures gradually became more extensive but also more complex. A pavement design procedure which is based on layered elastic theory fits into this development pattern and it has the potential to comply with future requirements of structural design procedures. The requirements for a structurally well-designed cement-treated layer are summarized in Chapter 2. Some of these were obtained from a literature survey and they include the requirements that a cement-treated layer must be thick; it must be built on a proper foundation while bearing in mind the principles of a balanced design; and it must be designed to withstand the heavy vehicles expected to travel on it. In the thesis attention is paid to some of the other requirements, for example non-trafficassociated and traffic-associated cracking, fatigue behaviour, thermal stresses and the variability in the properties of field- and laboratoryprepared materials. Some other requirements which are mentioned but which will need further investigation, are the material characterization, design criteria and the general variability of construction materials. Cracking in cement-treated materials is discussed in a somewhat original approach in Chapter 3 and it is pointed out that a clear distinction is necessary between initial, that 1s non-traffic-associated, and traffic-associated cracking. The occurrence of initial cracking must be accepted as a fact and very little can be done to avoid it or prevent it from occurring! Traffic-associated cracking in cement-treated layers can be prevented by an appropriate structural analysis and design. This involves doing the analysis for an uncracked pavement and thereafter making some increase in the maximum stress to accommodate the stress increase caused by the initial, non-traffic-associated, crack. Prismatic solid finite elements are used to calculate the extent of the increase in the tensile stress next to the initial crack (Chapter 4). The various ways of modelling the pavement, and the accuracy of each of these methods, are discussed and the use of the L-model is suggested and justified. The vertical surface deflection and the increase in horizontal tensile and vertical compressive stresses next to the crack in eight different typical structural layouts are calculated and the percentages are reported. The percentage increase in tensile stress seems to be dependent on the width of the crack and the thickness of the cement-treated material, but it does not appear to exceed 40 per cent. It is therefore suggested that the stress calculated in an uncracked pavement should be increased accordingly and this increased value should be used as the design tensile stress. Thermal stresses in cement-treated layers have always been believed to be very important. A finite difference computer program is used to prove this for uncracked cement-treated layers in Chapter 5. It is also shown that once the layer has cracked, and all properly constructed cement-treated layers do crack, movement can take place at the crack which will prevent the development of excessive thermal stresses. The use of a thermal insulating layer is very beneficial and it seems that the thickness of the layer affects the insulating ability much more than the type of material used. It is therefore recommended that for major roads a 150 mm crusherrun layer should be used as a thermal insulator on top of the cement-treated layer. Chapter 6 discusses the difference in properties of materials prepared in the field and in the laboratory. It is important that the same quality of material should be prepared in both cases or alternatively, that the designer should know the extent of this difference to enable him to take account of it. Samples recovered from the field indicate little variation in quality during a day's work and the section may be accepted as homogeneous with regard to the evaluated properties. The differences between work performed on different days are extremely significant, even if the sections were constructed with the same materials, by the same construction team and according to the same specifications. Thus sections constructed on different days may not be regarded as being of the same quality and as having the same properties. The variation in properties within a layer is significant and the upper half of the layer seems to have higher values than the lower half. The difference between field- and laboratory-prepared samples is significant, and the field samples generally tend to have lower values than the laboratory-prepared samples; not enough information is available to really indicate how much lower, but 30 per cent is recommended The Heavy Vehicle Simulator (HVS) was used to correlate the predicted and actual behaviour of pavements with cement-treated layers, and ten HVS tests were performed (Chapter 7). The excellent correlations between the predicted and actual elastic moduli and predicted and actual amount of traffic-associated cracking are described for seven of these tests. The chapter also shows the progress that was made over 5 years in interpreting the results from these tests. A pavement design procedure which is based on layered elastic theory, and the design requirements developed in this thesis, are outlined in Chapter 8. The definition of failure which is adopted and the design flow diagram with all its subdivisions, are explained. The design procedure incorporates the full spectrum of traffic wheel loading, fundamental material properties and failure criteria. Layered elastic theory is applied to calculate the stresses and strains at the various critical positions and these are compared with allowable values. Some variations in the outline, for example making allowance for mixed traffic and the use of standard designs, are discussed and explained. Finally the proposed procedure is verified by a description of the excellent agreement between the predicted and actual response and behaviour of several pavements. Five worked examples are also included. The thesis also contains four appendices. The first of these describes a theoretical study of pumping in pavements using the prismatic solids finite element computer program. The second outlines the use of the prismatic solids finite element computer program. In the remaining two the thermal properties required in Chapter 5 are calculated. AFRIKAANS : Sementgestabiliseerde materiale word reeds sedert die dertigerjare met sukses in paaie gebruik. In die verlede het die klem tydens navorsing, ontwikkeling en ontwerp op materiaaleienskappe geval en baie min aandag is gegee aan die ontwikkeling van 'n metode om die verciste dikte van die lae te bepaal. Sedert die hoëspoed- elektroniese rekenaars en die nodige rekenaarprogranune in die sestigerjare beskikbaar geword het, is meer aandag aan die vereistes van 'n geslaagde strukturele uitleg en die gedrag van die plaveisel gegee. Hierdie proefskrif, wat aanvullend is tot die vorige studies, bespreek die strukturele ontwerp van plaveisels met sementgestabiliseerde lae. Enkele van die ontwerpvereistes is reeds 'n geruime tyd bekend, drie word bygevoeg en bespreek en ten slotte word 'n ontwerpmetode voorgestel en geverifieer. Die ontwikkeling van plaveiselontwerpteorie word in Hoofstuk 1 bespreek. Daar word aangetoon hoe die ontwerpmetodes geleidelik meer omvattend geword het -maar ook steeds moeiliker om te gebruik. 'n Ontwerpteorie wat gebaseer is op die teorie van gelaagde elastiese sisterne en baie goed in die ontwikkelingspatroon inpas, het die potensiaal om te voldoen aan die toekomstige vereistes van strukturele ontwerpmetodes vir plaveisels. Die vereistes van 'n struktureel goedontwerpte sementgestabiliseerde laag word in Hoofstuk 2 bespreek. Sekere van hierdie vereistes is met behulp van 'n literatuurstudie bekom en sluit in dat 'n sementgestabiliseerde laag dik moet wees en 'n stewige fondament moet he. Die beginsels van 'n gebalanseerde ontwerp moet in gedagte gehou word en die laag rnoet so ontwerp word dat dit die swaar voertuie wat op die pad verwag word, kan dra. In die proefskrif word enkele ander vereistes bespreek naamlik die moontlike voorkoming van aanvanklike barste, ook bekend as krimpingsbarste, en barste wat deur verkeerspannings veroorsaak word, die vermoeidheidslewe, die hantering van termiese spannings en die verskil tussen die eienskappe van materiale wat in die veld en materiale wat in die laboratorium voorberei is. Enkele van die ander vereistes wat genoern word, maar waarvoor verdere studie nog nodig is, is die karakterisering van die materiaal, die ontwerpkriterium en die algemene veranderlikheid van konstruksiemateriale. Barste in sementgestabiliseerde materiale word op 'n ietwat oorspronklike manier in Hoofstuk 3 bespreek en daar word aangedui dat die verskil tussen aanvanklike barste en barste wat deur verkeerspannings veroorsaak word, baie goed verstaan moet word. Die verskyning van aanvanklike barste moet aanvaar word as 'n feit en baie min kan gedoen word om te voorkom dat die barste op die oppervlak van die pad verskyn! Barste wat deur verkeerspannings veroorsaak word kan vermy word deur 'n toepaslike analise en ontwerp te doen. Dit behels die ontleding van 'n ongebarste plaveisel en die verhoging van die berekende maksimum spanning waardeur dan voorsiening gemaak word vir die toename in spanning wat veroorsaak word deur die aanvanklike bars. 'n Eindige elemente-analise is gebruik om die toename in trekspanning langs die aanvanklike bars te bereken (Hoofstuk 4). Die verskillende maniere waarop die plaveisel gemodelleer kan word met eindige elemente en die akkuraatheid van elkeen van die metodes word bespreek. Daarna word die gebruik van die L-model aanbeveel. Die oppervlakdefleksie en die toename in horisontale trekspanning en vertikale drukspanning langs die bars in agt verskillende maar tipiese strukturele uitlegte word bereken en die persentasietoename in die maksimum horisontale trekspanning vir elke geval word gegee. Die persentasietoename in trekspanning is waarskynlik afhanklik van die wydte van die bars en die dikte van die sementgestabiliseerde lae maar skynbaar oorskry dit nie 40-persent nie. Daarom word daar voorgestel dat die berekende spanning in 'n ongebarste plaveisel dienooreenkomstig vergroot moet word en dat hierdie verhoogde waarde dan gebruik moet word as ontwerptrekspanning. Daar is nog altyd geglo dat termiese spannings in sementgestabiliseerde lae baie belangrik is. In Hoofstuk 5 word 'n eindige verskille-rekenaarprogram gebruik om dit te bevestig ten opsigte van ongebarste sementgestabiliseerde lae. Daar word ook aangetoon dat sodra die laag gebars het, en alle goedgeboude sementgestabiliseerde lae bars, word die opbou van oormatige hoë termiese spannings voorkom, want daar kan beweging by die bars plaasvind. Dit is baie voordelig om 'n termiese isoleerlaag bo-op 'n sementgestabiliseerde laag te plaas en dit blyk dat die dikte van die laag die isoleervermoë meer beinvloed as die tipe materiaal wat in die laag gebruik word. Daarom word aanbeveel dat 'n klipslaglaag van 150 mm bo-op die sementgestabiliseerde laag van 'n hoofpad gebruik moet word. In Hoofstuk 6 word die verskil tussen die eienskappe van materiale wat in die veld voorberei is en materiale wat in die laboratorium voorberei is, bespreek. Dit is belangrik dat die kwaliteit van die materiaal in albei gevalle dieselfde moet wees of andersins moet die ontwerper bewus wees van die grootte van die verskil sodat hy daarvoor voorsiening kan maak in die ontwerpstadium. Toetse het aangetoon dat die gedeelte van 'n laag wat op een dag gebou is, as homogeen ten opsigte van die gemete eienskappe aanvaar mag word. Die verskille in sementgestabiliseerde gedeeltes wat op verskillende dae gebou word, is uiters betekenisvol - selfs al word dieselfde materiale, dieselfde konstruksiespan en dieselfde spesifikasie in elke geval gebruik. Daarom mag daar nie aanvaar word dat gedeeltes wat op verskillende dae gebou is dieselfde kwaliteit en eienskappe sal hê nie. Selfs die variasie in eienskappe binne-in die laag is betekenisvol en dit blyk dat die boonste gedeelte van 'n laag hoër waardes het as die onderste gedeelte. Die verskil tussen veld- en laboratoriumvoorbereide monsters is betekenisvol en oor die algemeen neig die veldmonsters om laer waardes te hê as die laboratoriumvoorbereide monsters. Daar is nie duidelikheid oor hoeveel laer nie, maar 30-persent word tans aanbeveel. Die swaarvoertuignabootser (SVN) is gebruik om die verwagte en werklike gedrag van plaveisels met sementgestabiliseerde lae te korreleer en hiervoor is tien SVN-toetse uitgevoer (Hoofstuk 7). Die uitstekende ooreenstemming, in terme van elastisiteitsmoduli en hoeveelheid verkeersbarste, word vir sewe van die toetse beskryf. Die hoofstuk toon ook die vordering aan wat gedurende die afgelope vyf jaar gemaak is met die interpretasie van die toetsresultate. 'n Plaveiselontwerpmetode wat gebaseer is op die teorie van gelaagde elastiese sisteme en die ontwerpvereistes wat in die proefskrif ontwikkel is, word in Hoofstuk 8 beskryf. Die aanvaarde definisie van swigting en die vloeidiagram vir die antwerp asook al sy onderafdelings, word verduidelik. Die ontwerpmetode sluit die hele spektrum van wielbelastings, fundamentele materiaaleienskappe en swigtingskriteria in. Die teorie van gelaagde elastiese sisteme word gebruik om die spanning en vervormings op die verskillende kritiese posisies te bereken en daarna word hierdie waardes met die toelaatbare waardes vergelyk. Enkele variasies van die voorgestelde metode, soos byvoorbeeld om voorsiening te maak vir gemengde verkeer en die gebruik van standaardontwerpe, word bespreek en verduidelik. Ten slotte word die voorgestelde metode geverifieer met 'n beskrywing van die uitstekende ooreenstemming tussen die voorspelde en die werklike gedrag van etlike plaveisels. Vyf uitgewerkte voorbeelde word ook ingesluit. Die proefskrif bevat 4 aanhangsels. Die eerste een beskryf 'n teoretiese studie van pompaksie in plaveisels en hiervoor is 'n spesiale eindige elemente-rekenaarprogram gebruik. Die tweede aanhangsel beskryf die gebruik van die eindige elemente-rekenaarprogram wat in Hoofstuk 4 en aanhangsel A gebruik is. In die oorblywende twee aanhangsels word die termiese eienskappe bereken waarna in Hoofstuk 5 verwys word. / Thesis (DSc)--University of Pretoria, 1978. / Civil Engineering / unrestricted

A laboratory testing program was conducted on cement-treated soil mixtures fabricated to represent materials produced by the wet method of deep mixing. The testing program focused on investigating the influences that variations in laboratory testing conditions and in the mix design have on measured property values. A base soil was fabricated from commercially available soil components to produce a very soft lean clay that is relatively easy to mix and can be replicated for future research. The mix designs included a range of water-to-cement ratios of the slurries and a range of cement factors to produce a range of mixture consistencies and a range of unconfined compressive strengths after curing. Unconfined compressive strength (UCS) tests and unconsolidated-undrained (UU) triaxial compression tests were conducted. Secant modulus of elasticity were determined from bottom platen displacements, deformations between bottom platen and cross bar, and from LVDT's placed directly on the cement-treated soil specimens. Five end-face treatment methods were used for the specimens: sawing-and-hand-trimming, machine grinding, sulfur capping, neoprene pads, and gypsum capping. Key findings of this research include the following: (1) The end-face treatment method does not have a significant effect on the unconfined compressive strength and secant modulus; (2) a relationship of UCS with curing time, total-water-to-cement ratio, and dry density of the mixture; (3) the secant modulus determined by bottom platen displacements is significantly affected by slack and deformations in the load frame; (4) the secant modulus determined by local strain measurements was about 630 time the UCS; (5) typical values of Poisson's ratio range from about 0.05 to 0.25 for stress levels equal to half the UCS and about 0.15 to 0.35 at the UCS; (6) Confinement increased the strength at high strains from less than 20% the UCS to about 60% the UCS. In addition to testing the cured mixtures, the consistency of the mixtures were measured right after mixing using a laboratory miniature vane. A combination of the UCS relationship along with the mixture consistency may provide useful information for deep mixing contractors. / MS / Deep mixing is a ground improvement technique that mixes cement with in-situ soil to improve the quality of the soil for supporting embankments, buildings, and other facilities. Deep mixing is also used for earth retention and to form subsurface seepage barriers. When the cement is added in dry powder form, the process is called the dry method of deep mixing, and when the cement is added in the form of cement-water slurry, the process is called the wet method of deep mixing. When using the wet method, both the water-to-cement ratio of the slurry and the amount of slurry added to the soil have important effects on the strength of the cured mixture. Laboratory mixtures are often tested in advance of field mixing to estimate the proportions of cement, water, and soil necessary to produce the desired outcomes. The laboratory test conditions influence the test results, and a wide variety of test conditions are used in practice. This research investigated different testing conditions and different mix designs to demonstrate their impacts on laboratory test results.

The specific objectives of this research were to quantify the effects of certain environmental factors on the relative strength loss of soil-cement subjected to compaction delay and to develop a numerical tool that can be easily used by engineers and contractors for determining a maximum compaction delay time for a given project. These objectives were addressed through extensive laboratory work and statistical analyses. The laboratory work involved testing an aggregate base material and a subgrade soil, each treated with two levels of cement. Environmental factors included in the experimentation were wind speed, temperature, and relative humidity, and three levels of each were evaluated in combination with varying compaction delay times. The primary response variables in this research were relative compaction and relative strength. The findings indicate that relative strength is sensitive to variability among the selected independent variables within the ranges investigated in this research, while relative compaction is not. Inferring relative strength from relative compaction is therefore not a reliable approach on soil-cement projects. Consistent with theory, higher wind speed, higher air temperature, lower relative humidity, and higher compaction delay time generally result in lower relative strength. With the nomographs developed in this research, the maximum delay time permitted for compaction of either a base or subgrade material similar to those tested in this research can be determined. Knowing in advance how much time is available for working the soil-cement will help contractors schedule their activities more appropriately and ultimately produce higher quality roads. When acceptable compaction delays are not obtainable due to adverse environmental conditions, a contractor may consider using set retarder, mixing at water contents above OMC, or constructing at night as possible solutions for achieving target relative strength values.

The technical and economic feasibility of an inverted pavement has been proven abroad and in Brazil, but there are still doubts relating to the parameters that may affect the performance of this type of pavement, particularly in Brazil. There is a lack of studies that identify and characterize the variables that are directly related to the structural behaviour of the cement-treated layer and the contribution of each layer (thickness and elastic modulus) to inverted pavement performance as a whole. Furthermore, the main Brazilian specifications allow designers to make most decisions based on their experience, often generating doubts and uncertainties ranging from the design of the structure to the execution of quality control, directly reflecting on the pavement’s service life. Two test sections designed as inverted pavements, which were evaluated in Brazil, are assessed to identify and characterize the variables directly related to the structural behaviour of inverted pavements. In addition, a comparative analysis of the design, materials, construction, and quality control methods for Brazilian and South African inverted pavements is assessed. Both test sections were built based on the same design principles, but have been presented through different structural performances since their implementation in 2001. Each test section was monitored with deflection measurements between 2003 and 2016. In 2017, two inspection pits were opened in each test section. Samples were collected from all layers, and sent to the laboratory. Additionally, the tests carried out in the laboratory and in-situ in both sections during their construction in 2001, requested in the quality control, were also analysed in this study. The test results from the quality control and the test results obtained exclusively for this study (alongside the available literature) were compared and analysed against each other. Based on the analyses and discussions carried out throughout this research, it is possible to conclude that both the thickness and elastic modulus variables of the unbound base and the cement-treated layer played the most important roles in the behaviour of the inverted pavement, besides the support provided to the cement-treated layer by the underlying layer. Furthermore, the difference in the behaviour of both test sections can be linked to these three variables in addition to the constructive techniques adopted. No direct correlations were found for obtaining resilient modulus through CBR, and obtaining CBR values through DCP tests may vary according to the type of soil. The back-calculated modulus are good and reliable indicators of resistance, however, it is essential to apply adjustment factors. Furthermore, it was possible to identify a linear function with R² = 0.845, where ITS varies as a function of USC, according to the tests result carried out in 2001. However, unfortunately, no satisfactory correlations were found between UCS and ITS, UCS and ft, and ITS and ft from the results obtained in 2017. It is possible that these results are due to the specimens being damaged. / Dissertation (MSc (Transportation Engineering))--University of Pretoria, 2021. / Civil Engineering / MSc (Transportation Engineering) / Unrestricted

While cement treatment is a proven method for improving the strength and durability of soils and aggregates, cement hydration causes shrinkage strains in the cement-treated base (CTB) that can lead to reflection cracking in asphalt surfaces. Cracking may then cause increased pavement roughness and lead to poor ride quality. The overall purpose of this research was to utilize data collected through the Long-Term Pavement Performance (LTPP) program to investigate the use and classification of CTB layers and evaluate the relative impact of cement content on the development of roughness and cracking in asphalt concrete (AC) pavements constructed using CTB layers. The data included 52 LTPP test sites, which represented 13 different states and one Canadian province, with cement contents ranging from 3.0 to 9.5 percent by weight of dry aggregate. Statistical procedures were utilized to identify the factors that were most correlated to the observed pavement performance and to develop prediction equations that transportation agencies can use to estimate the amount of roughness for a given pavement at a given age and the amount of distress associated with a particular crack severity level for a given pavement. The data collected for this study suggest that wide ranges of cement contents are used to stabilize soils within individual American Association of State Highway and Transportation Officials soil classifications. The data also suggest that CTBs comprising flexible pavement structures are constructed mainly on rural facilities. A backward-selection model development technique was used to develop sets of prediction equations for roughness and cracking. Age, AC thickness, CTB thickness, and cement content were determined to be significant predictors of International Roughness Index, while age, air freezing index, AC thickness, CTB thickness, cement content, and traffic loads in thousands of equivalent single-axle loads were determined to be significant predictors of low-severity, medium-severity, and high-severity block, fatigue, longitudinal (wheel-path and non-wheel-path), and transverse cracking in AC pavements constructed using CTB layers. Investigation of the relationships between CTB modulus and the development of roughness and cracking is recommended for further study.

The primary purposes of this research were to identify construction factors most correlated to specific mechanical properties of cement-treated base (CTB) layers and to determine which construction factors exhibit comparatively high variability within individual construction sections of the two pavement reconstruction projects included in this study. In addition, differences between construction sections tested in this research were evaluated. The research focused on the construction of CTB layers in two pavement reconstruction projects in northern Utah, one along Interstate 84 (I-84) near Morgan and one along U.S. Highway 91 (US-91) near Richmond. The significant predictor variables associated with California bearing ratio (CBR), Clegg impact value (CIV), 7-day unconfined compressive strength (UCS), and 28-day UCS at the I-84 sites include reclaimed asphalt pavement (RAP) content; cement content; amounts of aggregate particles finer than the No. 8, No. 50, and No. 200 sieves; 7-day moisture content, and 28-day moisture content. The significant predictors of the same response variables on US-91 were in-situ moisture content, cement content, amount of aggregate particles finer than the No. 50 sieve, time between mixing and compaction in the field, dry density in the field, 7-day dry density, 7-day moisture content, 28-day dry density, and 28-day moisture content. The factors that were found to be the most variable on both I-84 and US-91 were CBR, cement content, time between mixing and compaction in the field, and time between mixing and compaction for each of the manually compacted specimens. On I-84, 16 of 27 factors were found to be significantly different between the sites, while 17 of 26 factors were found to be significantly different between the sites on US-91. The results of this research suggest that tighter specifications are warranted with respect to RAP content, cement content, and time between mixing and compaction. Concerning full depth recycling (FDR) projects, milling plans should be utilized to achieve improved uniformity in RAP content, and inspection protocols for encouraging improved control of cement content should be implemented during construction to ensure high-quality work. Compaction should be performed as soon as possible after mixing to minimize the adverse effects of cement hydration on the ability to achieve maximum dry density in the field.

The objective of this research was to measure and analyze the long-term modulus values of cement-treated base (CTB) layers constructed in Utah using microcracking. Because modulus values of pavement layers are among the most influential inputs affecting mechanistic-empirical pavement design, obtaining reasonable estimates of modulus values is critical. Testing was performed with a portable falling-weight deflectometer, also called a lightweight deflectometer, and modulus values were backcalculated with the computer program BAKFAA. Testing occurred at five asphalt pavement sites in northern Utah, where reconstruction with full-depth reclamation and cement stabilization, in the form of cement slurry, was performed approximately 2 to 14 years previously. Unconfined compressive strength (UCS) data collected for the CTB materials during earlier projects were compiled for all five sites. The correlation between backcalculated CTB modulus values, which ranged from 42 to 433 ksi, and 7-day UCS values, which ranged from 366 to 559 psi, was analyzed, and uniformity and sensitivity analyses were performed. Based on the results of this research, a new correlation is proposed for estimating the long-term modulus values of microcracked CTB layers constructed in a seasonally cold climate, such as northern Utah. For an average 7-day UCS of 450 psi, a CTB modulus value of 114 ksi would be estimated using this correlation, whereas a much higher modulus value of 630 ksi would be estimated from an existing correlation chart that was published in 1972 before microcracking was developed as a CTB construction practice. The results of the uniformity analyses indicate that statistically significant spatial variability in the CTB modulus values exists at each site. In comparison to a proposed maximum threshold coefficient of variation of 40 percent presented in the literature for aspects of CTB construction, the CTB modulus at all of the sites would be characterized as having low uniformity, with values ranging from 42.9 to 90.3 percent. The results of the sensitivity analyses indicate that backcalculated CTB modulus values are sensitive to typical deviations from design values that may occur in pavement layer thicknesses and suggest that CTB modulus estimation errors may range from -22,561 to 62,097 psi, or -3.73 to 10.81 percent, for pavements similar to those studied in this research when the actual asphalt and CTB layer thicknesses are different than the assumed values by up to 0.25 or 0.50 in., respectively.

No description available.

Full-depth reclamation (FDR) in conjunction with cement stabilization is an established practice for rehabilitating deteriorating asphalt roads. Conventionally, FDR uses dry cement powder applied with a pneumatic spreader, creating undesirable fugitive cement dust. The cement dust poses a nuisance and, when inhaled, a health threat. Consequently, FDR in conjunction with conventional cement stabilization cannot generally be used in urban areas. To solve the problem of fugitive cement dust, the use of cement slurry, prepared by combining cement powder and water, has been proposed to allow cement stabilization to be utilized in urban areas. However, using cement slurry introduces several factors not associated with using dry cement that may affect road base strength, dry density (DD), and moisture content (MC). The objectives of this research were to 1) identify construction-related factors that influence the strength of road base treated with cement slurry in conjunction with FDR and quantify the effects of these factors and 2) compare the strength of road base treated with cement slurry with that of road base treated with dry cement. To achieve the research objectives, road base taken from an FDR project was subjected to extensive full-factorial laboratory testing. The 7-day unconfined compressive strength (UCS), DD, and MC were measured as dependent variables, while independent variables included cement content; slurry water batching temperature; cement slurry aging temperature; cement slurry aging time; presence of a set-retarding, water-reducing admixture; and aggregate-slurry mixing time. This research suggests that, when road base is stabilized with cement slurry in conjunction with FDR, the slurry water batching temperature; haul time; environmental temperature; and presence of a set-retarding, water-reducing admixture will not significantly affect the strength of CTB, provided that those factors fall within the limits explored in this research and are applied to a road base with similar properties. Cement content and cement-aggregate mixing time are positively correlated with the strength of CTB regardless of cement form. Additionally, using cement slurry will result in slightly lower strength values than using dry cement.

Dentre a vasta gama de alternativas estruturais possíveis para a construção de pavimentos, os revestimentos com blocos pré-moldados de concreto têm sua aplicação consolidada em pavimentação de áreas portuárias. Além disso, em muitos países, este tipo de pavimento tem sido utilizado com sucesso em aplicações rodoviárias, aeroportuárias, em pátios industriais e em demais aplicações para tráfegos veiculares e de pedestres. No Brasil, no entanto, devido a insucessos em sua utilização, motivados, muitas vezes, pela inobservância de parâmetros técnicos relevantes a essa tecnologia, contribuíram para que este tipo de pavimento tenha sido subutilizado. Todavia, as recentes revisões nas normas nacionais que tratam deste tema, a criação de novas normatizações e a recente construção de importantes rodovias utilizando este tipo de revestimento, contribuem para o aperfeiçoamento de profissionais e a diminuição do prejulgamento desta tecnologia. Neste sentido, é de suma importância estudar o comportamento estrutural e funcional deste tipo de pavimento. De modo que, neste trabalho, foram estudadas quatro seções de dois trechos experimentais construídos entre julho e setembro de 2010. Foram realizadas avaliações destrutivas e não destrutivas para análise dos materiais, suas espessuras e confronto com os parâmetros construtivos oriundos do projeto e da literatura, bem como a verificação das condições para realização de retroanálise dos módulos de resiliência das camadas do pavimento. Os levantamentos deflectométricos apresentaram patamares muito elevados de deflexões reversíveis em todas as seções estudadas. Das aberturas de cavas e confronto com a estrutura de projeto, verificou-se incompatibilidades entre os materiais e espessuras das camadas do pavimento projetado x pavimento construído, destacando-se a condição verificada na camada de base por apresentar significativa desagregação do material, cujo projeto indicava utilização de concreto compactado com rolo (CCR), o que evidencia problemas no controle tecnológico dos materiais e falhas no gerenciamento da obra. Por meio das retroanálises foram verificadas diminuições significativas dos módulos de resiliência das camadas do pavimento, quando comparado com os parâmetros de projeto. Os índices de condições do pavimento (ICP) apontaram condições distintas nas seções avaliadas mesmo sujeitas ao mesmo tráfego de veículos. / Among the wide range of possible structural alternatives for the construction of pavements, interlocking concrete pavements are the orthodox solution for paving ports. Furthermore, in many countries, this type of pavement has been successfully used in highways, airport applications, in industrial areas and other applications for vehicular traffic and pedestrians. In Brazil, however, due to failures in its use, driven often by the lack of relevant technical parameters to this technology, contributed to the fact that this type of pavement has been misused. Although, recent reviews from the national standards that deal with this type of pavement, the creation of new standards and the recent construction of important highways using this type of structure, have contributed to the improvement of professionals and decreased the prejudice of this technology. In this sense, it is extremely important to study the structural and functional behavior of this type of pavement. Therefore, in this research it was studied two experimental sections built between July and September 2010 that carried out destructive and nondestructive evaluations for the analysis of materials, their thicknesses and constructive confrontation with the parameters derived from the project and the literature, as well verifying the conditions to accomplish the back calculation of the elastic modulus of the pavement layers. The displacement tests surveys demonstrated very high levels of reversible displacements in all studied sections. From the inspection pits openings and confrontation with the project structure, there is incompatibility between the materials and thicknesses of the layers of the designed pavement versus constructed pavement, the condition verified highlighting the base layer for introducing significant breakdown of the material, which design indicated use of roller-compacted concrete (RCC), which indicates problems in the quality control of materials and failures in the management. The back calculation showed that decreases were observed elastic modulus of the pavement layers when compared with the design parameters. Surveys concerning pavement condition index (PCI) showed different conditions for the evaluated sections even supporting the same traffic.