Fresh Grout Properties Research Articles

The Influence of Dry Hydrated Limes on the Fresh and Hardened Properties of Architectural Injection Grout.

Dry hydrated lime is an air binder often used in architectural injection grouts. This study compared the influences of three commercially available dry hydrated limes on the injection grouts’ workability and mechanical properties. The main differences between the limes were in their chemical and mineralogical composition and Blaine specific surface area. The grouts were composed of dry hydrated lime, finely ground limestone filler, water, and super plasticiser. Subsequent results obtained revealed that the Blaine specific surface area is not directly related to the fresh grout properties. Grain size distribution and shape of lime particles and their aggregates in the water suspension are key parameters influencing the following fresh grout properties: fluidity, injectability, the mixture’s stability, and water retention capacity. However, the lime injection grouts’ mechanical strengths were higher in relation to an increase in the content of portlandite and the Blaine specific surface area of the dry hydrate.

Using IBPs to improve the geotechnical properties of soil

The results of an experimental investigation involving the partial replacement of Portland cement with industrial by-products (IBPs) in grout suitable for suspension-type permeation grouting are described. Four suspension grouts were investigated in this study. Ordinary Portland cement and Portland cement with a 10% partial replacement by bentonite were used as controls. Two grouts containing IBPs were also tested with a 50% partial replacement by pulverised fuel ash (PFA) and ground granulated blastfurnace slag (GGBS). The results of this study clearly demonstrate that the use of IBPs, especially PFA, can enhance both fresh grout properties and the properties of permeated soil. Partial replacements with PFA reduced the apparent viscosity of the grout by an average of 13% compared with replacements with bentonite, while GGBS reduced the apparent viscosity of the grout on average by 25%. Partial replacement with PFA also yielded superior groutability results due to the combination of a lower apparent viscosity and a finer cement gradation compared with replacements with bentonite. Replacement of Portland cement with PFA also improved the grouted properties of the soil, with a decrease in the coefficient of permeability of 20% being obtained compared with replacements with bentonite.

Influence of superplasticizer, temperature, resting time and injection pressure on hydraulic lime grout injectability. Correlation analysis between fresh grout parameters and grout injectability

The grout injection technique is commonly used for the consolidation of old stone masonries. In particular, the multi-leaf masonries which generally exhibit low compactness in the inner core and very few links between the internal and external leaves. Grouts are concentrated suspensions that can be seen as mixtures of binder with water, and special admixtures. To ensure an adequate flow of the grout and a correct filling of the internal voids inside the masonry, it is essential to assure good fresh grout properties. Thus, the evaluation of the performance of the grout injectability is firstly started by checking the intrinsic properties of the grout (namely rheological parameters) and then by controlling the injectability, through injection tests in porous media that simulate old masonries.The main goal of this paper is to provide indications and valuable data about the combined effect of superplasticizer dosage, environmental temperature, resting times (i.e. the time after the grout mixing had ended) and injection pressure on grout injectability, aiming at a successful injection process. The lack of information about the influence of the referred parameters on the injectability of hydraulic lime grouts enhances the importance of a detailed research on the subject.

Evaluation of consolidation of different porous media with hydraulic lime grout injection

Abstract The grout injection is a technique widely used for structural consolidation of the multi-leafs stone masonry, which often present low compactness and weak links between the internal and external leaves. Grouts can be seen as mixtures of binder with water, with or without special additives. To ensure an adequate flow of the grout and a correct filling of the internal voids inside the masonry, it is essential to assure good fresh grout properties, such as stability, water retention and a rheological behaviour. The grout specification involves the knowledge of the flow capacity within the masonry inner core and physic-chemical compatibility with the original materials present in the historic materials. Thereby, the scope of this paper is to evaluate the injection performance of hydraulic lime based grouts as a function of the porous media to be injected. For this purpose, simplified models were created to allow injectability tests in controlled conditions. To enable the simulation of different permeabilities and internal structures of masonries, the models were created by filling plexiglass cylinders with different grain size distributions of limestone sands and crushed bricks. Since, these materials exhibit different water absorption coefficients, it also was possible to study the influence of water loss from grout to porous media in grout injectability. Another variable studied with influence on grout injectability was the water content of porous media. As it is not expected that masonries are always dried, the pre-wetting of some cylinders by simple injection of water is of extreme relevance to compare the results of grout injectability in the two opposite situations. The grout injection performance was analysed both in the fresh and hardened states. The injectability of the grout as well as its link to the materials within the inner core of old masonries was assessed by tomography and mechanical tests. The mechanical results showed good correlation with injectability and high dependence with the position of the specimen analysed on the cylinder injected, creating tensile strength gradients along the height of the cylinder. Regarding the tomography, the tomographs demonstrate the compactness of the porous media after grout injection. In fact, according to the results obtained, it can be stated that the tomography allows the evaluation of the grout injection capacity to improve the physical and mechanical properties of the inner core of old masonries.

Injection capacity of hydraulic lime grouts in different porous media

Grout injection is a widely used technique for consolidation of multi-leaves masonries, aimed at increasing the compactness and to create links between the internal and external leaves that will improve shear, flexural and compressive resistances. Grouts can be seen as mixtures of binder with water, admixtures and/or additives, which should present low viscosity and high penetrability. The definition of a grout composition should involve the knowledge of the injection capacity within a specific type of masonry and good physical and chemical compatibility with the original materials present in the historic structures. The flow of the grout through the masonry depends on the fresh grout properties, such as stability, water retention and rheological behaviour. Thus, the evaluation of the performance of the grout as function of a porous medium is firstly started by checking the intrinsic properties of the grout (namely rheological and stability) and then by controlling the injectability of masonry by injection tests on cylinders. Since it is difficult to reproduce a real masonry and to visualize what is happening inside the porous medium being injected, masonry samples were created by filling plexiglass cylinders with a fraction of limestone sands and crushed brick. These materials are sieved to obtain different grain size distributions to enable the simulation of different permeabilities and internal structures for the masonry. The lack of information about the performance of hydraulic lime based grouts as a function of the properties of the porous medium to be injected enhances the need of a detailed research on the subject.

The use of rheology in the study of the composition effects on the fresh behaviour of hydraulic lime grouts for injection of masonry walls

The injection of grouts inside multi-leaf stone masonries is a technique widely used for structural consolidation. To ensure an adequate flow of the grout inside the masonry, it is crucial to assure good fresh grout properties, such as good rheological behaviour. The scope of this paper is to provide preliminary indications and valuable data about the effects of specific hydraulic lime grout composition on their rheological behaviour with the purpose of a successful injection process. Through the use of rotational rheometer together with the Taguchi method, it was possible to study the influence of water/binder ratio, the type and dosage of superplasticizer and the partial replacement of hydraulic lime by silica fume, upon the grout rheological properties. The study leads to the conclusion that polycarboxylate-based superplasticizers present better performance from a rheological point of view than the naphthalene-based superplasticizer and that the water/binder ratio and superplasticizer dosage are the most determinant factors in the fresh grout rheological behaviour. On the other hand, silica fume dosage turned out to be the factor with the least contribution to improve the grout rheological behaviour compared to the other two factors reported in this study. The results summarised in this paper are part of a larger study and precede the analysis of the performance of those grouts when injected into different porous media that simulate old masonries.

Natural hydraulic lime based grouts – The selection of grout injection parameters for masonry consolidation

The goal of this research was to develop a methodology for grout composition optimization concerning specific applications. It could be developed for masonry consolidation or bonded prestressed tendon grout, pre-placed aggregate grout, among others. The grout development does not only depend on its intrinsic properties but also on the nature and features of the support. The purpose of a grout injection technique applied in a multiple leaf wall is to increase the compactness and create links between the internal and external leaves, which improve not only shear and flexural resistance but also the compressive strength. In practice, the variability of voids within masonries requires an ability to fine tune the rheological properties of the grout in order to optimally fill the voids. The methodology proposed here for testing grout injectability in a porous media like masonry is a logical tool to use in grout optimization. It shows that several grout parameters should be controlled for a successful injection. Concerning the support and its typology, the mortar between stones plays a fundamental role in the effectiveness of the intervention, due to its reduced porosity and composition. Besides that, earth and mortar, for example, can be present in the interior of masonry and make difficult, with their absorption, the injection. Thus, the water retention capacity of grout should be controlled to prevent that problem, as it was made in this work, using the optimized mixing procedure that takes into account that and other fresh grout properties. This study analyses some relevant grout properties such as yield stress, plastic viscosity, flowability and injectability for natural hydraulic lime based grouts in different porous media. The research shows that there are differences in the grout behaviour, especially in rheological properties, when different mixing procedures and/or grout composition (different water/binder or fly ash/binder ratios) are used and that fresh grout properties may be optimized for injection purpose.

Effect of calcium chloride and kaolinite on shear strength and shrinkage of cement grout

Grouting is injecting a liquid (cement and additives) into voids within a structure or soft soils for displacing the gases and liquids from within these. The varieties of additives for different grouting purposes are using with cement. Calcium chloride is known as accelerator in the grout, it causes to decrease the set time of grout and it has a minor effect on fresh grout properties. Kaolinite or some other fine mineral soils are used as filler in the grout to get cost-effective grout. In this study, the different effects of calcium chloride and kaolinite were investigated on shear strength of soil treated by cement grout, and shrinkage of the grout. Samples were prepared by mixing specific amounts of cement, water, and organic soil with different ratios of calcium chloride and kaolinite. Unconfined compressive strength (UCS) of the soil treated was evaluated after curing for 3 and 30 days and the linear shrinkage of each grout were measured after 30 days. The results indicated that, kaolinite has positive effect on shear strength of soil treated and shrinkage of the cement grout. By increasing kaolinite, the shear strength of samples increased and the shrinkage of grout decreased respectively. On the other hand, calcium chloride seemed to have different effects on the shear strength of samples and shrinkage of grout. It did no’t have tangible effect on shrinkage of the grout except in the grout with 1% calcium chloride. Key words: Grouting, kaolinite, calcium chloride, cementation, pozzolanic reactions.

Effect of environmental temperature and fly ash addition in hydraulic lime grout behaviour

The purpose of grout injection is to increase the compactness of the masonry and its injection optimization is a task of major importance for masonry consolidation. Fresh grout properties seem to be as important as the ones in the hardened state since grout consistency is an essential characteristic to allow the filling of voids. Since the grout rheological behaviour is associated with its fresh properties, they should be well understood and controlled so that the fluid may be pumped and flow correctly inside the porous media. This paper analyses some relevant rheological properties for natural hydraulic lime grouts, such as yield stress, plastic viscosity, consistency and power-law index. The study envisage to increase the understanding of the influence of environmental temperature and of the addition of fly ash in fresh grouts behaviour. An attempt was made to achieve an optimal grout composition by using the Taguchi method. The paper shows that fly ash is capable of substantially changing the grout rheological parameters, while the effect of temperature is negligible for the parameters tested.

The influence of the mixing procedures on the optimization of fresh grout properties

The purpose of a grout injection technique applied in a multiple leaf wall is to increase the compactness and create links between the internal and external leaves. The correct grout selection should take into account many characteristics, in particular injectability and stability. This paper analyses the variations of some fresh grout properties that may affect injectability and stability—water retention, rheological behaviour and bleeding. The study has sought to increase the understanding of the influence of the mixing procedure in grout behaviour and how it may improve some essential injection characteristics. For this purpose, a natural hydraulic lime grout has been considered. The paper shows that there are differences in the grout behaviour when different mixing procedures are used and that fresh grout properties may be optimized if a proper mixing procedure is chosen.