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In post-tensioned systems, grouts act as a last line of defense to prevent the penetration of harmful compounds such as chlorides, moisture and other substances that cause corrosion in the prestressing steel. For this reason, improving grouts results in the enhancement of the overall durability of the structure. In this study, the physical properties of grouts with basalt microfiber additions in the amounts of 0.03, 0.07 and 0.10% with respect to the mix volume were evaluated. The fresh properties included flowability and unit mass. Specimens were fabricated to evaluate drying shrinkage, compressive strength, air permeability and rapid permeability to chloride ions. The incorporation of basalt microfibers showed a beneficial effect on the physical properties of the grout by increasing the drying shrinkage resistance and decreasing the permeability compared to the reference mix and two commercial dry prepackaged grouts. The optimal grout mix was the one with a percentage of basalt microfibers of 0.10%, which decreased drying shrinkage by 15.98% at 14 days compared to the reference mix, and permeability to chloride ions decreased by 10.82% compared to the control mix. [ABSTRACT FROM AUTHOR]

This study investigated the influence of fluorogypsum and KH 2 PO 4 on the mechanical properties and hydration mechanisms of aluminate cement based grouting materials. Physical properties including setting time, pH value and the compressive strength of aluminate cement based grouting materials with different mix design were investigated. The influencing factors and hydration mechanisms were quantified and discussed through XRD, TG, SEM and NMR. The water-cement ratio was fixed at 0.40, and the fluorogypsum content accounted for 10 wt% of the cement mass. With increasing KH 2 PO 4 content, the setting time initially decreased and then prolonged, while the compressive strength at 3d and 28d first increased and then decreased. Among these variations, a content of 0.2 wt% KH 2 PO 4 exhibited the optimal performance with initial and final setting times of 264 min and 308 min, respectively. The compressive strengths at 3 days and 28 days were recorded as 26.4 MPa and 60.5 MPa, respectively, exhibiting an increase of 76% and a remarkable enhancement of 228.80% compared to that of pure aluminate cement. The addition of fluorogypsum facilitated the formation of AFt, while KH 2 PO 4 regulated the slurry's pH, concurrently enhancing AFt production, and the morphology of AFt transformed from acicular to a more slender fiber shape, which exhibited improved interlacing and overlapped properties, thereby promoting strength development. The hydration process was analyzed in conjunction with low-field nuclear magnetic resonator analysis. The findings revealed that the samples containing 10 wt% fluorogypsum and 0.2 wt% KH 2 PO 4 in aluminate cement exhibited the highest levels of chemically bound water at both 3d and 28d, followed by samples with 10 wt% fluorogypsum in aluminate cement, while those composed solely of aluminate cement displayed the lowest content. The T 2 spectra data were also fitted to a function, revealing a positive correlation between pore evolution and the hydration rate of the samples. • Fluorogypsum and KH 2 PO 4 can shorten the setting time and increase the compressive strength of calcium aluminate cement. • Fluorogypsum contributed to AFt formation; KH 2 PO 4 further increased AFt and modified its morphology. • KH 2 PO 4 changed the morphology of AFt to elongated fibers and optimized the pore structure. • Hydration of aluminate cement can be significantly enhanced by combined addition of fluoropgypsum and KH 2 PO 4. • Fluoropgypsum alone could still cause a substantial promotion effect on the hydration rate of aluminate cement. [ABSTRACT FROM AUTHOR]

Geopolymers have gained much interest recently as a promising alternative to cementitious materials in some applications. However, research is still needed to use this technology for soil reinforcement grouts. The specifications of grouts mainly consist in rheological properties, strength and permeability. Grouting actually requires a low viscosity, and thus higher water content. The influence of relatively high water content on the other properties of the material, i.e. strength and microstructure, has been investigated. This effect highly depends on the concentration of the activator (sodium silicate solution) and the precursor (metakaolin, fly ash or blast furnace slag) associated with the activator. This paper deals with the main effects of high water content on the microstructure and mechanical properties of the materials, looking at physical and chemical aspects. Scanning electron microscopy and chemical phase analysis were used to highlight the nuances that are related to the precursors used, especially regarding the microstructure and kinetics of the geopolymerisation process. [ABSTRACT FROM AUTHOR]

A large testing program was devised to determine the compressive strength of masonry grouts made with various combinations of class F fly ash and ground granulated blast furnace slag to replace high amounts of Portland cement. In a first phase, mixes were proportioned by volume and batched with 0, 20, 30, 40, 50, and 60 percent Portland cement replacement; specimens were cured in a dry and wet environment. The objective of the first phase was to determine the viability of and the methodology for the overall project. In the second phase, mixes were proportioned by weight, the more common practice in the United States, and batched with 0, 20, 30, 40, 45, 50, 55, 60 and 65 percent Portland cement replacement. Specimens in the second phase were cured in a wet environment only. In the first and second phases, Portland cement was replaced only by fly ash. In the third phase, mixes were proportioned also by weight and batched with 0, 50, 60, 65, 70, 75, 80, and 85 percent Portland cement replacement. In the third phase, Portland cement was replaced by combinations of fly ash and ground granulated blast furnace slag; however, the fly ash content was maintained constant at 25 percent. Specimens in the third phase were also cured in a wet environment only. Specimens were typically tested at 14, 28, 42, 56, and 90 days; in Phase I specimens were also tested at 7 days but not at 90 days. Three specimens were tested for each replacement rate, age, and curing conditions. Several mixes developed satisfactory strength, i.e., the mixes achieved the ASTM specified minimum compressive strength of 13.8 MPa at 28 days. The results show that mixes with up to 55 percent fly ash and 85 percent fly ash-ground granulated blast furnace slag substitutions reached the minimum compressive strength required at 28 days. Mixes with up to 60 and 65 percent fly ash achieved the minimum compressive strength of 13.8 MPa in 44 and 54 days, respectively. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation on the effect of the replacement rate and fineness of natural zeolite on the rheological properties of cement-based grouts. For this purpose, natural zeolites with two different finenesses were used to partially replace Portland cement at 20%, 30%, and 40% by weight. While preparing the grout mixtures, a constant water to cementitious material ratio (w/CM) of 0.60 was used together with a superplasticizer (SP). Setting times and compressive strength of grouts were also determined as part of the experimental study. Test results indicated that the rheological properties of cement-based grouts were significantly affected by the replacement rate and the fineness of natural zeolite. The replacement rate of cement by natural zeolite for a constant SP content significantly increased the yield stress and apparent and plastic viscosities, and reduced the fluidity and deformability of the cement-based grouts. Moreover, incorporation of a fine natural zeolite resulted in a further decrease in the rheological and workability properties of grouts. With an increase in the dosage of SP, both yield stress and plastic viscosity decreased significantly. Grouts made with natural zeolite also showed pseudoplastic behavior, and shear thinning increased with the increase of zeolite amount and fineness. Test results also indicated that the natural zeolite with different fineness had a marked effect on the setting time and compressive strength of grout mixtures. Therefore, the use of natural zeolite confirms that grouts with satisfactory rheological and mechanical properties can be successfully obtained. Cet article présente une étude expérimentale sur l’effet de zéolithes naturelles, du taux de remplacement et de leur granulométrie sur les propriétés rhéologiques des coulis à base de ciment. Des zéolithes naturelles de deux granulométries différentes ont été utilisées pour remplacer 20 %, 30 % et 40 % en poids du ciment Portland. Lors de la préparation des mélanges de coulis, un rapport constant eau sur matériel cimentaire de 0,60 a été utilisé en plus d’un superplastifiant (SP). Les temps de prise et les résistances à la compression des coulis ont aussi été déterminés dans le cadre de cette étude. Les résultats des essais indiquent que les propriétés rhéologiques des coulis à base de ciment ont été sensiblement affectées par le taux de remplacement et la granulométrie des zéolithes naturelles. Un taux de remplacement plus élevé de ciment par des zéolithes naturelles pour un contenu constant en superplastifiant a augmenté de manière significative la limite d’élasticité, les viscosités apparentes et plastiques, et a réduit la fluidité et la déformabilité des coulis à base de ciment. De plus, l’incorporation de zéolithes naturelles fines a diminué encore plus les propriétés rhéologiques et la maniabilité des coulis. En augmentant la concentration en superplastifiant, la limite d’élasticité et la viscosité plastique ont toutes deux grandement diminué. Les coulis fabriqués à partir de zéolithes naturelles ont montré un comportement pseudo plastique et la fluidification s’est accrue avec l’augmentation de la quantité de zéolithes et des particules fines. Les résultats des essais ont également indiqué que les zéolithes naturelles de granulométries différentes avaient un effet marqué sur le temps de prise et la résistance en compression des mélanges de coulis. L’utilisation de zéolithes naturelles confirme donc qu’il est possible d’obtenir des coulis possédant des propriétés rhéologiques et mécaniques satisfaisantes. [ABSTRACT FROM AUTHOR]

• Expandable foam grout (EFG) is a material to repair underground cavities. • EFG specimens with five admixture-cement ratios (AD/Cs) are used for strength test. • Strength and stiffness of the specimens are evaluated at each curing time. • Regression models for EFG properties are established from curing time and AD/C. Underground cavities induced by damaged slurry walls or soil erosion in urban areas require suitable repair materials and methods. The objective of this study is to evaluate the strength and stiffness of expandable foam grout (EFG) as a repair material. EFG consists of water, ordinary Portland cement, and admixtures. EFG was prepared at a fixed water-cement ratio of 100% and different admixturecement ratios (AD/Cs), ranging from 0 to 8%. The unit weights of EFGs with different AD/Cs at the slurry and expanded states are measured, and the air contents for both states and the theoretical expansion ratio (ER) are subsequently estimated. Stressstrain curves are obtained using unconfined compressive strength tests to evaluate the unconfined compressive strength and modulus of elasticity. The experimental results show that the air content in the slurry state gradually increases with the AD/C, while the air content in the expanded state and the ER rapidly increased and then converges. The strength and modulus of elasticity increased with curing time, whereas they decreased with increasing AD/C. Based on logarithmic and exponential regression models, the relationships between the strength/modulus, curing time, and AD/C are established with high values of the coefficients of determination. Thus, the relationships proposed in this study can be effectively used to predict the strength and modulus of EFG with respect to curing time and AD/C. [ABSTRACT FROM AUTHOR]

• High-performance grout for the corrosion protection of post-tensioned (PT) tendons was developed. • Developed grout is made with two fly ashes to improve the packing density and fluidity. • Developed grout has excellent resistance against shrinkage and the formation of voids, bleedwater and softgrout. • A set of stringent performance specifications for PT grouts are developed. In order to provide corrosion protection of tendons in post-tensioned (PT) concrete systems, the congested interstitial spaces between the strands and duct are ideally to be filled with cementitious grouts. However, many currently used grouts do not have the desired fluidity and resistance to segregation – leading to formation of voids, frothy grout materials, and premature corrosion of strands. This paper presents a 3-phase study on the development of high-performance, pre-blended grouts. Several grouts were formulated with various proportions of ordinary portland cement (OPC), fly ash and chemical admixtures. The fluidity, bleed (i.e., standard, wick-induced, pressure-induced, and -inclined tube), softgrout, rheological, and shrinkage parameters of the formulated grouts were assessed; based on which a systematic selection of grouts was performed in three phases. Finally, a grout with 52 and 48% of OPC and fly ash, respectively (by volume) and optimal dosages of chemical admixtures was formulated and pre-blended in an industrial facility. This grout satisfies a set of performance specifications on fluidity, resistance against segregation (say, bleedwater and softgrout formations), and shrinkage. Therefore, the grout is capable of filling the ducts and providing long-term corrosion protection of PT strands. [ABSTRACT FROM AUTHOR]

• Properties of Ca(OH) 2 -GGBS and MgO-GGBS grouts were investigated. • Compared with MgO, Ca(OH) 2 was more effective on activating GGBS in short term. • Effect of activator/GGBS ratio on viscosity of grouts was limited when W/C ratio ≥ 1. • Bleeding and setting times of MgO-GGBS grouts were lower due to hydration of MgO. Hydrated lime (Ca(OH) 2)- and reactive magnesia (MgO)-activated ground granulated blast-furnace slag (GGBS) have shown advantages in geotechnical applications compared with Portland cement (PC). To apply these two novel binders in slurry form to field applications, the properties of their grouts need to be investigated, which is the objective of this study. The heat of hydration, bleeding, viscosity, and setting behavior of Ca(OH) 2 -GGBS and MgO-GGBS grouts were investigated and compared with PC and pure GGBS grouts in this study. All grouts indicated a decrease in bleeding and setting time, but an increase in viscosity with decreasing the water/cementitious material (W/C) ratio. Compared with the PC grout, the pure GGBS grout with the same W/C ratio demonstrated higher bleeding and setting time, and lower heat rate and viscosity. Bleeding and setting time decreased and peak heat rate and viscosity increased with an increase in the activator (Ca(OH) 2 or MgO)/GGBS ratio within GGBS-based grouts. The peak heat rate in Ca(OH) 2 -GGBS grouts was higher than that of pure GGBS or Ca(OH) 2 grout, indicating that Ca(OH) 2 was effective on activating hydration of GGBS. The peak heat rate in MgO-GGBS grouts was significantly lower than MgO grout and the heat rate was limited after 8 h. The bleeding and setting times of MgO-GGBS grouts were significantly lower than those of Ca(OH) 2 -GGBS grouts, which was primarily attributed to the hydration of MgO. [ABSTRACT FROM AUTHOR]

• The axial yield strain in all zeolite-cement grouted specimens is less than 1%. • The q (y) and c′y increase by increasing the Z in the grouted specimens up to 30%. • An increase of more than 30% in Z leads to a decrease in q (y) and c′y. • With increasing Z content, the φ′ y increases with a slight slope. Permeation grouting with cementitious materials is a widely used soil behavior improvement technique. Since the Portland cement production leads to environmental pollution and is also an energy-intensive process, replacing a part of the cement with cheaper and more environmentally friendly materials, such as zeolite, is very important. In the present study, a series of consolidated undrained triaxial tests were carried out on zeolite-cement grouted sand specimens to investigate the effect of cementation on the yield stress (q (y)) through shear loading. The results showed that the axial yield strain (ε (y)) in all zeolite-cement grouted sand specimens is less than 1%. Beyond the yield point (YP), a sudden increase in the strain occurs, and the stress–strain curve continues with a slight gradient. The effect of cementitious bonds is significant up to the YP and then gradually decreases. The effective stress path (ESP) of the grouted specimens rises approximately vertically up to the YP. Beyond the YP , the abrupt change of the curvature occurs and the ESP turns to the right. The q (y) and cohesion corresponding to the YP (c′y) increase by increasing the amount of cement replacement with zeolite (Z) in the grouted specimens up to 30%. An increase of more than 30% in Z leads to a decrease in q (y) and c′y. Therefore, the optimum Z to achieve the maximum q (y) and c′y is 30%. With increasing Z content, the effective internal friction angle corresponding to yield (φ′ y) always increases with a slight slope. [ABSTRACT FROM AUTHOR]