Fernando M.A. Henriques

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.

Contribution to the design of hydraulic lime-based grouts for masonry consolidation

AbstractGrout is a concentrated suspension that can be employed for the homogenisation and consolidation of systems presenting pores, voids and cracks, such as inner core of old stone masonries. A grout should be well conceived, taking into account the optimisation of its performance; this means that simple binder and water formulations prove to be inadequate. Hence, the effect of different admixtures and pozzolans, which are traditionally used in concrete, on the fresh and hardened properties of hydraulic lime grouts, were investigated. Hydraulic lime binder plays a role of great importance in the rehabilitation of historic structures, due to its compatibility with pre-existing materials, like mortars. However, hardly any information is presently known regarding the effect of these materials on the behaviour of hydraulic lime grouts. The improvement of their properties through the use of these products is still an open field. Hence, and as a first step, the prediction of grout properties in a laboratory ...

Hygrothermal analysis of historic buildings

Purpose – The purpose of this paper is to verify the applicability and efficiency of two statistical methods to obtain sustainable targets of temperature and relative humidity in historic buildings located in temperate climates. Design/methodology/approach – The data recorded along one year in a non-heated historic building in Lisbon (Portugal) was analysed with the two methodologies, EN 15757 and FCT-UNL. To evaluate their adequacy it was calculated the performance index for each target and it was verified the mechanical and biological degradation risks. Findings – While the use of the two approaches is suitable for temperate climates, there is a higher efficiency of the FCT-UNL methodology, allowing a better response for the three parameters in evaluation. Research limitations/implications – Despite the better results obtained, the FCT-UNL methodology was only tested for one city; therefore the application to other situations may be required to obtain more robust conclusions. Practical implications – Th...

Experimental Study and Modeling of Rheological and Mechanical Properties of NHL Grouts

AbstractThis paper aims to model the effect of grout composition on properties of two natural hydraulic lime (NHL) grouts based on the correlation between grout rheometer results and simple flow tests. First, the effects of water:binder ratio and superplasticizer dosage on its rheological properties and flowability were analyzed. Dosage of superplasticizer and water:binder ratio were varied from 0.6 to 1.2% (by mass of binder) and 0.45–0.55, respectively. A good correlation between classical flow tests and the rheological properties was obtained. Then, statistical models were formulated in order to estimating the grout parameters, such as plastic viscosity and yield stress just by performing simple flow tests. The models coefficients were calculated using multiple regression analysis. The statistical modeling results indicated that the properties of the grouts studied are linearly related to water:binder ratio, superplasticizer dosage, and specific surface area of natural hydraulic limes. Finally, the acc...

Performance improvement of hydraulic lime based grouts for masonry consolidation: an experimental study

Grouting is currently a repair technique for consolidating and strengthening old masonry structures. Grouts can be seen as mixtures of binder with water, admixtures and/or additives, which should present low viscosity and high penetrability. 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 structures. Nevertheless, the grout properties are affected by a large number of parameters, including binder type and composition, mixing procedure, admixture type and dosage, environmental conditions, like temperature that may lead to different grout injection capacities, as reported by other studies. This paper deals with the effect of environmental temperature over superplasticised hydraulic lime-based grouts with partial replacement of lime by silica fume. Grout performance was analysed in fresh and hardened state by testing its rheological and mechanical behaviour, as well as its hydration reactions kinetics. In spite of the considerable amount of information that exists for cement based mixtures with superplasticisers, there is little information about the effects of superplasticisers when used in natural hydraulic lime mixtures proportioned with silica fume. This study aims to contribute to better understand the behaviour that superplasticised hydraulic lime grouts present under different temperatures. The results showed that hydraulic lime grouts performance could be improved, regarding rheological parameters and strength capacity if they are properly design and a suitable processing temperature were ensured.

Development of biocolonization resistant mortars: preliminary results

The negative impact of biocolonization on buildings, particularly rendered ones, prompted the evaluation of a hydraulic mortar formulation to which copper metal, either as a powder or as fibres, was added as a means to control this problem. The study used in situ exposure in a location prone to biocolonization for over nine years. The results have proved that over this time period, no biocolonization occurred on samples containing 0.35 % by weight of copper powder with regards to the dry mortar mix. The mortar proved to acquire a slightly bluer-green hue which diminished after the nine year outdoor exposure. The mortars formulated with copper have a lower porosity as well as a lower capillary water absorption coefficient a definite advantage for their eventual life span. On the other hand, the mechanical resistance is slightly decreased but not significantly so. Further studies are envisioned to assess the performance with other types of binder, such as aerial lime.

Rheology of Grouts for Masonry Injection

Grout injection technique applied in a multiple leaf masonry walls aims at increasing the compactness of the masonry and, therefore, improving their monolithic behaviour by bonding the separated segments together without compromising the architectural value of the masonry building. The success of the injection grouts depends mainly on their rheological properties. This means that the flow properties of fresh grouts are as important as their properties in the hardened state, since they govern the ability of the grout to flow and fill the voids within masonry. In practice, the variability of voids within masonry requires ability to fine tune the rheological properties of the grout, in order to optimal fill all voids with grout. So, models were developed with the main purpose of predict and control the rheological properties of grouts just performing simple flow tests traditionally used in the field. It is well known that flow tests commonly performed (such as Marsh cone and slump test), which try to describe the workability of cementitious materials, only give a qualitative result that can not be expressed in physical rheological units. However, the proposed models allow calculating a physical parameter (e.g. viscosity) instead of an empirical one (e.g. fluidity). This research shows the effect of grout design variables on the properties of natural hydraulic lime grouts based on the correlation between rheometry measurements and simple flow tests. Furthermore, the proposed models can be very useful to smooth the grout design methodology, since these models enable the prediction of rheological properties of the grout without the need for expensive and complex equipment, such as rheometers or viscometers.

Study of hydraulic lime grout injections in different porous media: an experimental study

Grout injection is a widely used technique for masonry consolidation of multileaves masonries, aimed at increasing the compactness and to create links between the internal and external leaves that will improve shear, flexural and compressive resistances. The lack of information about the performance of hydraulic lime based grouts as a function of the porous media to be injected enhances the importance of a detailed research on the subject. Since it is hard to reproduce real masonry and because it is difficult to visualize what is happening inside the porous media being injected by grout, masonry samples were created by filling plexiglass cylinders with a fraction of limestone sands and crushed bricks. These materials are sieved to obtain different grain size distributions to enable the simulation of different permeabilities and internal structures for the masonry. The flow of the grout through the masonry depends on the fresh grout properties, such as stability, water retention and a rheological behaviour. Thus, the evaluation of the performance of the grout as function of porous media is firstly started by checking the intrinsic rheological properties of grout and then by controlling the injectability of masonry by injection tests on cylinders.

Pozzolanic Components in Lime Mortars: Correlating Behaviour, Composition and Microstructure / Puzzolanische Bestandteile in Kalkmörteln: Zusammenhang zwischen den Eigenschaften, der Zusammensetzung und dem Mikrogefüge

Thermal analysis and scanning electron microscopy were used to evaluate the composition and microstructure of lime mortars containing pozzolanic materials, such as natural pozzolan, fired clays and fly-ash. A correlation between the microstructure and the mechanical performance of these mortars could be drawn. The most uniform growth of calcium silicate hydrates (CSH) was obtained by the addition of metakaolin, in this study obtained by firing natural kaolin to 800 °C for 3.5 hours.

Selection of Consolidants for Use on the Tower of Belem / Auswahl eines Steinfestigers für den Turm von Belem

Abstract During the exterior conservation project of the Tower of Belem, Lisbon, it was noticed that although most of the Lioz limestone used in its construction was in good condition, some specific areas presented severe powdering and flaking deterioration patterns. These are mainly due to the effect of natural weathering, including anthropogenic air-pollution, on poorer quality Lioz limestone. Since the deterioration affects mainly the immediate surface and subsurface of the stone blocks, the application of stone consolidants was considered as the most appropriate solution for this problem. This paper describes the difficulties encountered in the evaluation of the tested consolidants-an ethyl silicate ester, an acrylic resin and an epoxy resin-applied in situ. The laboratory and on-site testing used in the final selection are described as well as the actual approach to consolidating the different areas that required this treatment.