This report presents the results of analyzing the critical void ratio concept on weakly cemented sand. The study consists of drained triaxial compression tests performed on artificially cemented sands created to simulate the natural behavior. In order to carry out this study, loose samples were prepared and subjected to different confining pressures such that failure at volumetric contraction could be obtained. The triaxial test results showed that the samples exhibited similar response to drained loading as compared to previous investigations on the static behavior of naturally and artificially cemented sands. Following the empirical method of determining the critical void ratio by plotting volumetric strain at failure against void ratio after consolidation, interpolation of the data points yielded critical void ratios of 0.735, 0.722, 0.703 and 0.668 for confining pressures of 60, 70, 80 and 95, respectively. A comparative analysis was made by plotting instantaneous void ratio during the loading against axial strain and this yielded values of 0.745, 0.735, 0.715 and 0.685 for confining pressures of 60, 70, 80 and 95 respectively. However, this method depends on the test accuracies at strain levels beyond 20% where the specimen becomes severely distorted, thus, making this method unreliable to use. Utilizing the result from volumetric strain-void ratio curves, the relationship between volumetric strain at failure and confining pressure was plotted and yielded critical confining pressures of 125, 94, 78, 67 and 60 psi for void ratios after consolidation of 0.66, 0.68, 0.70, 0.72 and 0.74, respectively. From the above results, the critical state line, which shows the variation of the critical void ratio, e_crit with the magnitude of the cr1 critical confining pressure, σ₃_crit, was defined for the artificially prepared samples with one percent cement. It would be interesting to compare this result with the critical state line of uncemented samples and of samples with higher amounts of cementation. The critical state concept is very important in evaluating the undrained strength of sands from drained tests data. The reader is referred to reference 7 since this is beyond the scope of this investigation. This concept is also an important study used in determining the liquefaction potential of sands. A paper by Castro [2] reported that liquefaction can only occur in sands that are looser than the critical state. The results of consolidated-undrained static tests will indicate whether the sand is looser or denser than the critical void ratio for the appropriate confining pressure, and thus whether the sand is susceptible to liquefaction. The reliability of the parameters obtained depends on a very limited number of data points. The author suggests that more tests on a wic!er range of relative density and confining pressure should be conducted to obtain more data points where a more accurate interpolation or extrapolation could be done. However, the results presented in this report are hoped to provide useful information for further studies to be made on the analysis of critical void ratio concept in cemented sands. / Master of Engineering

Ground improvement by deep mixing (DM) is a generic term used for a number of methods in which a binding agent, often lime and/or cement, is mechanically mixed with the soil to increase its engineering properties. The inherent variability with respect to the engineering properties of the improved soil is high due to the variations in geology and the complex mixing process. High variability introduces uncertainty in estimating improved soil properties and the performance of the structure. Current design methodology deals with soil properties deterministically and the uncertainties involved are incorporated in a single value represented by a total factor of safety (FS). The chosen FS is highly dependent on the engineer’s judgment and past experience, in which both of these factors vary between different geotechnical designers. Therefore, current design methodology used in practice for DM does not deal with uncertainties in a rational way. In order to design a geotechnical system with the desired level of confidence, the uncertainties involved must be integrated in the DM design. This can be achieved by using reliability-based design (RBD) methods. The research work in this thesis is presented as a collection of three papers. In the first paper, a comprehensive statistical analysis of cone penetration test (CPT) data is described. The objective was to make a contribution to empirical knowledge by evaluating the strength variability of lime-cement columns within the group of tested columns. In the second paper, the effect of the spatial variability and statistical uncertainty with regard to the embankment’s reliability was investigated within the framework of RBD. The study in the third paper investigated the strength variability in lime-cement columns based on two test methods, namely CPT and column penetration test (KPS). In this study, the effect of different test methods on the evaluation of the design value was addressed. The main conclusions from this study can be summarized as follows. First, the probability distribution function (PDF) for the undrained shear strength of lime-cement columns can be modeled in RBD as normal or log-normal distributions. However, the use of log-normal distribution is recommended for RBD analyses. Second, the evaluated scales of fluctuation indicate ranges of 2 to 4 m and 0.2 to 0.8 m in the horizontal and the vertical directions respectively. This means that in order to fulfill the requirements of independent/uncorrelated samples for assessment of the design value, the spacing between samples must exceed the horizontal scale of fluctuation. It is therefore proposed that the spacing between individual samples should be at least 4 meters. Third, the design values evaluated using CPT and KPS were approximately the same. However, the inherent variability evaluated differs due to the larger volume tested with the KPS probe than with the CPT probe. However, this difference was not significant between the two tests. Fourthly, due to the limitation in the deterministic design in terms of dealing with uncertainties, it is recommended that RBD design should be used in parallel with the deterministic design of lime-cement column. / <p>QC 20120110</p>

In this dissertation the effects of different types of Pulverized Fuel Ash (PF A)-types on the workability of cementitious pastes containing relative large amounts of PF A were investigated. The different types of PF A were produced at the same source thus they were chemically similar but differed in terms of average particle size and size distribution (grading). By using a two-point measurement technique based on flow through a J-shaped tube it was possible to detect relative small differences in workability between pastes. It was found and concluded that the different types of PFA had a significant effect on the workability of pastes containing cement and PFA as well as PF A alone. The physical differences between the PF A-types were quantified and their effects on workability investigated. It was concluded that PF A with a broader particle size distribution range produced pastes with higher workability at constant water content. It was found that compressive strength as measured after 28 days were solely a function of the water/cementitious ratio for the curing regime employed. It was concluded that for curing conditions used the type of PF A used could have a significant effect on compressive strength when constant workability is required. / Dissertation (MSc (Transportation))--University of Pretoria, 2006. / Civil Engineering / unrestricted

In underground construction grouting is performed to seal tunnels and caverns against excessive water inflow or to reduce the lowering of the ground water table. The rheological properties, such as viscosity and yield stress, of the used grouts play a fundamental role in grouting. No method has been developed yet to measure these properties in-line in the field during grouting. Methods used today are rather primitive and not robust enough for field use and they are mainly performed in order to verify and fulfil stipulated quality criteria. Modern grouting rigs are today equipped with continuous measurement of flow and pressure but instruments for continuous monitoring of rheological properties and their changes with time in the field are still lacking. A relatively new method, known as ‘UVP-PD’, for continuous in-line measurements of the rheological properties of cement grouts, was tested in this work. Standard grouting equipment (UNIGROUT) and flow meter (LOGAC) was used to ensure field conditions. The objective of this work was to determine the feasibility of the ‘UVP-PD’ method for cement based grouts. After performing full scale experimental works, this method was found feasible for measuring the rheological properties of cement based grouts directly in-line.

Esta investigación comprende la caracterización del suelo que conforma la subrasante de la Av. Padre Salas, Villa Rica, Pasco, el potencial de resistencia y la expansión que presenta el suelo en el sector indicado, la evaluación es realizada mediante ensayos CBR. Se utiliza la técnica de suelo cemento para mejorar las características físicas y mecánicas, este proceso consiste en mezclar al material con cemento Portland Tipo I formando suelo cemento 10%, 15% y 20%, los cuales presentan un incremento del CBR (máximo: 138.7% y mínimo: 91.9%) logrando un tipo de subrasante extraordinaria para resistir la estructura del pavimento y una reducción de 7.18% en la expansión de las muestras. / This study includes found the properties of the soil, which forms Av. Padre Salas, Villa Rica, Pasco subgrade, strength potential and expansion that soil presents at the indicated sector, the evaluation is executed through CBR tests. Soil cement technique is use in order to improve the physical and mechanical characteristics; this process is to combine the material with Ordinary Portland cement making soil cement 10%. 15% y 20%, which have a CBR increase (max: 138.7% and min: 91.9%) achieving an extraordinary subgrade type so as to bear up the pavement structure and an expansion reduction of 7.18% in specimens. / Tesis

Tunneldrivning är tidskrävande med varierande komplexitet från projekt till projekt, där en betydande del av sprängcykeln innefattar att låta injektering härda. Detta är tid där tunneldrivandet står stilla. Ifall denna tid skulle kunna reduceras skulle entreprenörer kunna spara in resurser genom att kunna spränga tidigare. Huvudsyftet med det här examensarbetet är att bidra med förståelse för hur utomstående krafter påverkar injektering. Detta för att man på ett korrekt sätt ska kunna dimensionera och reducera injekteringens härdningstid vid en tunneldrivning. Innan examensarbetets start hade tre olika kravställningar för cementbaserad injektering tagits fram. En del av examensarbetet inkluderade att formulera injekteringsrecept uppfyllande dessa krav, genom att få ökad förståelse för cementbruks reologi.  Genomförandet av arbetet delades upp i tre studier, där cementbruks reologi studerades på olika sätt. Arbetet började med att se hur viskositet och flytgräns ändrades med vattencementtal (VCT) med hjälp av en rheometer (roterande tester). Dessa undersökningar utgjorde studie 1. De vattencementtal som testades var 0,6; 0,8; 1,0 och 1,2. Från denna studie blev värdena höga och ansågs orimliga. Då cement är ett av de reologiskt mest komplicerade materialen rör det sig över stora delar av det viskoelastiska spektret. Det kunde konstateras att vidare studier bör utföras för att öka förståelsen för dels rheometern som mätredskap, dels cementets reologi. I studie 2 mättes samma parametrar som i den första studien, samt inträngningsförmåga, separation och densitet. Dessa tester genomfördes med hjälp av redskapen PenetraCone, Mud Balance, Marshkon, fallkon, muggprover och Yield Stick i laboratoriemiljö. Testerna genomfördes med samma vattencementtal som tidigare, men med två olika sorters cement: Injektering-30 och UltraFine 20. Från dessa tester kunde det konstateras att två av tre krav inte gick att uppfylla med UltraFine 20. Injektering-30 uppfyllde två av kraven med ett vattencementtal på 0,8 och det tredje kravet med ett vattencementtal på 0,6. Dessa resultat försöktes sedan återupprepas i ett fälttest vid Haga station (Västlänken) med blandning i en injekteringsrigg. Två blandningar som skilde sig lite från varandra gjordes under fältstudien. Den ena blandningen gav liknande värden som laboratorietesterna med en något högre flytgräns. Den andra blandningen var något mer lågviskös. Skillnaden mellan dessa två resultat misstänktes bero på skillnaden i tid de fick vara i injekteringsriggen. Det var från början planerat att utföra en ytterligare fältstudie, där Injektering-30 skulle injekteras med vattencementtalet 0,8 i två bergsskärmar. En sprängning skulle därefter ske efter tre timmar, men på grund av förseningar i produktionen har denna fältstudie skjutits upp till våren 2022. Studie 3 bestod av ytterligare rheometer-undersökningar, där oscillerande tester utfördes under en längre tid. Dessa tester gjordes för att se hur cementbrukets viskösa och elastiska skjuvmodul ändrar sig över tid. Genom att göra muggprov parallellt gick det att observera att när cementbruket övergick från att vara dominerat visköst till att vara dominerande elastiskt så ändrades brottsmekanismen i bruket. Cementbruket gick från att flyta fritt till att det uppstod ett cirkulärt skjuvbrott (okulärt observerat). Med resultatet från de oscillerande testerna delades cementets härdningsprocess in i fyra olika steg. Det första steget är när cementpartiklarna flyter vid ett muggprov (egentyngden är större än materialets flytgräns). Det andra steget är när bruket övergår från dominerande visköst till dominerande elastiskt och brottet som nu uppstår är ett cirkulärt skjuvbrott. Det tredje steget är när cementet härdat tillräckligt så att cirkulära skjuvbrott inte uppstår i ett muggprov. I detta stadie går det att peta ett hål i cementet utan att det läker sig själv. Det fjärde och sista steget är när cementen härdat så pass mycket att materialet börjat bete sig mycket sprödare och är som starkast.  För att kunna sätta en preliminär plan för dimensionering av härdningstid på cementbruket, så beräknades kraften som cementbruket upplever som en funktion av töjningarna i berget vid detonation. Detta gjordes med hjälp av Hookes lag och de oscillerande testerna som utfördes under längre tid för att mäta skjuvmodulen. Med detta så togs följande preliminära plan fram, för beräkning av härdningstiden på cementbaserad injektering:  Mät maximala deformationen i berget Mät den komplexa skjuvmodulen på bruket över tid   Ta reda på förväntad maximal sprickvidd Beräkna skjuvtöjning   Beräkna last     Gör fallkontest för att ta reda på hållfastheten i bruket Jämför teoretisk last och hållfasthet för bruket och se när hållfastheten blir större än teoretisk last Spräng efter den beräknade tiden. Planen har inte testats i praktiken och vidare studier behöver utföras. Sammanfattningsvis lägger examensarbetet grunden för vidare studier inom detta ämne. Indikationer från arbetet visar att härdningstiden teoretiskt bör gå att förkorta. Det spekuleras ifall det skulle gå att förkorta härdningstiden ytterligare ifall något sorts mikrofibrer eller likande används som armering i cementen, för att motverka det cirkulära skjuvbrottet som verkar uppstå. Det är självklart av yttersta vikt att denna armering inte påverkar inträngningsförmågan i någon större utsträckning / Tunnel excavation is time demanding with varying complexity. A significant part of the tunnel excavation cycle consists of letting grout harden. This is time where the excavation basically is put on hold. If this part of the excavation cycle could be reduced, the contractor would be able to save resources by conducting blasting earlier. The main purpose with this master thesis is to contribute with knowledge regarding how external forces affects grout. This is of significance to be able to design and to reduce the grout’s hardening time correctly. Before this master’s thesis began three different requirements for cement grout had been developed. One part of this master’s thesis included formulating grout recipes to fulfill these requirements, by gaining further knowledge regarding cement grout rheology. The execution of this work was divided into three part-studies where cement rheology was studied in different ways. The work started by investigating the water cement ratios influence on cements viscosity and yield point by performing rotating tests with a rheometer. This investigation was a part of study 1. The water cement ratios which were studied was 0.6, 0.8, 1.0 and 1.2. It was concluded that the results were way to high and was deemed unreasonable. Cement is rheologically one of the most complex materials, because it spans over great parts of the viscoelastic spectrum. It was concluded that further studies should be performed to further understand both how the rheometer works and cements rheology.  In study 2, the same parameters were measured as in the previous study with the addition of penetrability, separation, and density. These tests were performed with PenetraCone, Mud Balance, Marsh funnel, fall cone, mug tests and Yield Stick tests in a laboratory environment. The tests were conducted with the same water cement ratios as in study 1, but with two different brands of cement: Injektering-30 and UltraFine 20. From these tests the conclusion was that it was not possibly to fulfill two out of the three requirements with UltraFine20 whereas Injektering could fulfill all three requirements. Two out of the three requirements were fulfilled with a water cement ratio of 0.8. These results were then further investigated in a field environment at station Haga in Gothenburg. Two batches were produced, where one of the batches became slightly less viscous than the other and the lab results. It is believed that this was because the less viscous batch spent a longer amount of time in the mixer.  From the start, another field study planned to be conducted where Injektering-30 would be used as grout with a water cement ratio of 0.8. A blast would then be detonated after three hours. Due to delays in the excavation of Haga Station this study was postponed to spring 2022. Study 3 consisted of further rheometer-investigations where oscillating tests were performed during a longer period of time, to see how the shear modulus changed over time. These tests measured the viscous and elastic shear modulus of the cement. By doing parallel mug tests it was observed that when the cement went from dominant viscous to dominant elastic the failure mechanism of the cement changed. The cement went from flowing freely to what looks like a circular shear failure (ocularly observed). With the results from the oscillating test, the cement’s hardening process was divided into four different stages. In the first stage, the particles flow freely (weight of particles are greater than the materials yield point). In the second stage the cement will be more elastic than viscous, and a circular shear failure occurs. In the third stage, the grout has hardened enough so a circular shear failure won’t occur in a mug test. It is now possible to point a hole in the cement without it flowing, and it will heal itself. In the fourth and final stage the cement has hardened enough that the cement has a high strength and behaves brittle.  To estimate a preliminary plan to design the hardening time on cement the forces on the grout has been calculated as a function of the deformations in the surrounding rock. This was done using Hookes law and the oscillating tests which was performed during a longer period of time to measure the shear modulus. With this logic the following plan was introduced, to design the grouts hardening time: Measure deformations in the rock Measure the complex shear modulus of the grout over time  Find the maximum joint width  Calculate shear strain Calculate load Do fall cone tests to determine the strength of the grout Compare theoretical load with strength of the grout and see when the strength becomes greater than the load  Perform blasting after calculated time.  This plan has not yet been tested and need further studies to determine its validity.  In conclusion this master’s thesis is the groundwork to further studies regarding this subject. Indications from this work shows that the hardening time could theoreticality be reduced. One could speculate if it would be possible to shorten the hardening time even further by introducing some kind of reinforcement to the grout, which would prevent the observed circular shear failure. It is obviously important that the reinforcement does not interfere with the penetrability of the grout.

OBJECTIVES: To evaluate various cements in vitro for adhesion to zirconia, light curing vs. self-curing, the effect of particle abrasion (APA) on the zirconia intaglio for maximizing retention, the effect of thermocycling, and the effect of cement space. METHODS: The tested cements included: Ceramir C&B (Doxa) Panavia F2.0 (Kuraray); Multilink Automix (Ivoclar); Theracem (Bisco); Duolink (Bisco); Bifix (Shofu); CemEZ (Zest Dental). For testing cements retention, custom made zirconia rings 12.5 mm outer diameter, 5.5 mm height and 6.147 mm inner diameter were used to emulate crowns. Round steel rods (McMaster) were manufactured to fit into the zirconia rings allowing a cement space of 50 Microns or 100 Microns. A cementing jig was used to keep the rods at the center of the zirconia rings. Cements were tested using light curing and self-curing (n=10 per each test). Groups of zirconia rings were air braded with 100 Microns aluminum oxide particles for 10 Sec. Half the specimens were stored in water for 24 hours at 37o C in dark environment or thermocycled for 5000 cycles. A ‘push-out’ test using an Instron universal machine at a crosshead speed of 0.5mm/min. Loads to failure were recorded to calculate cements retention. RESULTS: Statistical analysis was performed using JMP Pro 13 software. Data were analyzed using one way ANOVA, multiple t-test, and Tukey-Kramer HSD. For self curing method without APA, retention strength ranking for tested cements were: Ceramir C&B ≥ Theracem > Panavia F2.0 ≥ Duolink ≥ Multilink Automix ≥ Bifix. For light curing method without APA, retention strength ranking for tested cements were: CemEZ ≥ Theracem ≥ Multilink Automix ≥ Duolink ≥ Bifix ≥ Panavia F2.0. There was a significant influence in retention strength for light cured cements compared to self-curing method except for Theracem and Panavia F2.0. For the self-curing method with APA, retention strength ranking for tested cements were: Theracem > Duolink ≥ Panavia F2.0 ≥ Multilink Automix ≥ Bifix > Ceramir C&B. For the light curing method with APA, retention strength ranking for tested cements were: Theracem ≥ Multilink Automix ≥ CemEZ ≥ Duolink ≥ Panavia F.0 ≥ Bifix. A significant increase in retention strength with APA compared to self-curing method with APA. There was no significant effect of thermocycling treatment on retention strength of the cements tested. There was no significant effect of different cement spaces on retention strength except for Ceramir C&B without APA and Multilink Automix with and without APA (P < 0.0001). CONCLUSIONS: 1- There was a significant difference in retention strength to zirconia among tested cements in self and light curing methods. 2- Light curing resin cements influenced retention strength to zirconia for the tested cements. 3- APA influenced the retention strength to zirconia for tested cements except for Ceramir C&B. 4- Increasing the cement space from 50μm to 100μm had no significant difference in retention strength to zirconia except for Ceramir C&B without APA and Multilink Automix with and without APA. 5- Thermocycling had no significant effect of on retention strength to zirconia for the tested cements. / 2020-07-30T00:00:00Z

Soil-Cement is not a new material; its low cost but high quality make it well-known and the use of this material for highway, dam, and airfield purposes increases every year. The origin of the idea of mixing soil and cement to priduce a structural material has not been definitely established; informal records show that mixing soil and cement was tried in Iowa, Ohio, Texas and probably in other places by 1920 (1). Since the first controllled soil-cement construction was carried out near Johnsonville, South Carolina in 1935 (2), soil-cement has been considered a valuable engineering material. It is now an accepted practice to denote the result of adding cement to soil as a soil-cement mixture (3), or in other words, soil-cement is the stabilization of soil with portland cement, and water. As the cement hydrates, the mixtrue becomes a hard, durable paving material (4).

Ce travail de thèse rentre dans le cadre de la problématique générale, en plein développement actuellement, concernant l’exploitation des nanotechnologies pour le développement d’écomatériaux, dont les propriétés sont significativement améliorées et élargies. A cause de leur surface spécifique particulièrement élevée, l’ajout d’une infime quantité (de l’ordre du % par rapport au ciment) de particules nanométriques à une formulation d’un matériau cimentaire peut entrainer des modifications significatives des propriétés du produit. Ces modifications peuvent intervenir à tout niveau de maturation du matériau en impactant les propriétés correspondantes : état frais (rhéologie), jeune âge (cinétique de prise, retrait, fissuration) et état durci (propriétés mécaniques, thermiques et durabilité).Le principal travail de cette thèse a consisté à étudier l’impact de nano particules isotropes (nano silice) et anisotropes (nano argile) sur la rhéologie des matériaux cimentaires à l’aide d’un nouveau protocole : la rhéologie oscillatoire aux grandes amplitudes. De plus, l’impact de celle-ci sur le processus d’hydratation des matériaux contenant de hauts dosages en laitier de haut fourneaux a aussi été étudié. / This PhD gets in the larger topic of the use of nano-technology to develop eco-friendly materials whose properties are improved. Due to their very high specific surface, a very low quantity (only a few percent) of nano particles into a cement-based material can induce significant changes of materials properties. These changes can take place at every ages of materials such as fresh state (rheology), young age (kinetic of hydration, shrinkage) or long term (mechanical, thermal properties and durability). During this PhD, different types of nano particles are considered: isotropic (nano silica) or anisotropic (nano clay). The main objective is to consider the impact of nano particles on rheological properties considering a new rheological protocol: large amplitude oscillation shear (LAOS). Besides, interaction between nano particles and hydration products in the case of cement based material containing high dosage of slag is also considered. This study will help to understand how nano particles change material properties at fresh state and young age. Indeed, it is at these ages that materials properties are lower when cement is replaced by other material.

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