Caspar Groot

• Professor (Associate) at Delft University of Technology

Historic Structures are commonly coated with mortar layers (plasters, renders, flooring) for protection and decoration. These well finished architectural stratigraphic surfaces often suffer from deterioration, such as lack of adhesion or detachment between support and mortar layers and even between mortar layers. Grouting and filling voids between...

For conservation interventions of historic masonry generally lime-based mortars such as pure air lime mortars, lime-pozzolan mortars, natural hydraulic lime mortars and ternary mortars (lime-pozzolan-cement) are used. The main reason is that their hygric and mechanical (strength and ductility) performance are easy to adapt to most existing historic...

The quality of repointing work in historic masonry is to an important degree determined by the composition of the repair mortar. Apart from this, good workmanship is a basic requirement for durable repointing. Over the past decades awareness has grown that the mortar composition of repointing should always be considered and applied taking into acco...

This book presents a state of the art in mortar characterisation, experimentation with and applications of new mortars for conservation and repair of historic buildings. This volume includes the following topics: characterisation of historic mortars (methods, interpretation, application of results), development of new materials for conservation (co...

Factors affecting the design of repair mortars for historic masonry are: the type of masonry, the condition of the masonry and the exposure conditions. Especially in case of low-strength masonry exposed to heavy rain and high salt contents the design of a repair mortar may be a challenge. The most important problem is obtaining adequate insight int...

This article gives a summary of functional and performance requirements for renders and plasters for historic masonry (design, execution and maintenance). Specific attention has been paid to degradation effects, such as caused by salt crystallization and freeze-thaw cycling. Traditional as well as designed prefab mortars are considered for repair i...

Deze rapportage ‘Uitvoeringswijzen inboetwerk – herstel transversaalscheuren - voegwerkherstel’ voor herstel van zwaar regenbelast massief metselwerk in kalkmortels is de laatste in het kader van het ‘Totaalonderzoek Vochtproblematiek Massief Metselwerk (monumenten)’. De onderzoekingen zijn in de volgende rapportages vastgelegd: • ‘Kwaliteitseisen...

In this paper a comparison is made between two views on solving rain penetration problems in solid historic fired clay brick masonry. The first one aims at protecting the masonry against rain penetration ("rain coat" concept). In the second approach the penetration of rain in the masonry is accepted and the measures taken are focused on improving t...

The effective design of a mortar for repairing masonry depends on a clear understanding of its function within masonry. The functions of mortar materials in masonry are classified as bedding, pointing, grout, render, plaster and mortars for surface repairs. The requirements that each type of mortar must meet in service depend on its environmental e...

The effective design of a mortar for repairing masonry depends on a clear understanding of its function within masonry. The functions of mortar materials in masonry are classified as bedding, pointing, grout, render, plaster and mortars for surface repairs. The requirements that each type of mortar must meet in service depend on its environmental e...

Moisture is a major source of damage in historic solid masonry. Therefore, control of moisture movement in masonry is instrumental to the durability of masonry buildings. From research and practical experience it is known that many factors may play a role regarding permeability problems in masonry. This paper is focused on materials aspects regardi...

The choice of a repair plaster or render by architects often appears to be the result of fortuitous circumstances, such as prior experience with a plaster or a recommendation by a producer. Seldom is the choice based on a sound assessment of the state of the building and the wall that is to be repaired. The service life of the repair plaster/render...

Moisture is a major source of damage in historic massive masonry. Therefore control of moisture movement in masonry is instrumental to the durability of masonry buildings. From research and practical experience it is known that a series of causes may play a role regarding permeability problems in masonry. This paper is focused on materials aspects...

In recent years several types of restoration plasters, especially developed for salt loaded substrates, have been introduced on the market. The behaviour of these plasters in the field is, however, not always satisfactory. The reasons for failures may be found both in the moisture and salt transport behaviour of the substrate/plaster combination an...

The mechanism of damage occurring in NaCl contaminated materials has not been clarified yet. Apart from crystallization pressure, other hypotheses have been proposed to explain the cause of decay. Irreversible dilation has been observed in a few cases but has never been studied in a more systematic way. The aim of the research is to contribute to t...

Many walls of ancient buildings are covered with plaster layers. Amongst the most recurrent causes of damage of plasters and substrates are moisture and salt decay processes. To combat these salt problems, special salt resistant plasters have been developed for application on salt loaded substrates. However, experience in the field has shown that f...

Laboratory weathering tests are important in the field of restoration as they provide a means of estimating, in a relatively short time, the longer-term performance of conservation materials when applied in practice. Accelerated tests to simulate the damage caused to porous materials by soluble salts such as sodium sulphate are well known and highl...

This paper reports preliminary test results and their analysis on moisture-salt transport in restoration plasters. Using various simple as well as advanced experimental techniques (pursuing a multidisciplinary interpretation on the test results) it was shown that differences in porosity significantly affect moisture-salt transport in plaster-substr...

Single wythe brick masonry in historic windmills in the Netherlands often shows serious water permeance problems. These cause damage to the brickwork (frost and salt damage) and the wood (rot) applied in the mills. Moreover, leakage has a detrimental effect on the living conditions in the mills. Investigations in 26 historic mills provided insight...

Sea salt damage to porous building materials is a well-known problem not only in regions located near the sea but also in continental areas. In walls, sea salts may stem from different sources: they may penetrate from the ground by rising damp, maybe carried by the wind in the form of salt spray, may be due to flooding, occasional or recurrent, or...

Groot, C.J.W.P. en Gunneweg, J.T.M. (2002), ‘Water permeance problems in masonry walls of wind mills’, in Santos, F.A. S., Carvalho Passos, M.C.R. and Moita, G.R. (eds), Proceedings of the VII International Seminar on Structural Masonry for Developing Countries, Belo Horizonte, Brazilie, University of Edinburgh, pp. 359-363.

With respect to the 18th century fortification Tenaille von Fersen , Suomenlinna , Finland (included in the UNESCO World Heritage list) the conditions of the building can be described as follows: the walls and vaults are water - logged and salt contaminated. The building was unused and unheated for a long period of time. Part of the building is now...

The purpose of this paper is to describe recent progress in research to simulate and recognise the brick deterioration as occurring in the Tenaille von Fersen building – Suomenlinna – Finland (within the European Union Raphael research program) by climatic cabinet tests. The test results show that the damage mechanisms as observed in the “test room...

There is considerable interest in the use of nondestructive (non-invasive) tests to investigate structures and determine the sub-surface arrangement of materials and their condition and whether any faults are present. This is particularly important for heritage masonry structures where large scale destructive tests, such as coring or dismantling wo...

Water loss from the fresh mortar is believed to be related to mortar-brick bond strength development in masonry. Recent research on mortar-brick bond has shown that, particularly, effects of water flow on the composition and the hydration conditions of the mortar-brick interface have to be taken into account to explain bond strength development. Ho...

Le cours a ete developpe pour l"Ecole Nationale d'Ingenieurs, a Bamako, Republique du Mali. Le cours vise a offrir a des ingenieurs de Constructions Civiles, la possibilite d'approfondir leurs connaissance en matiere de conception architecturale et de dessin du batiment. A travers un processus d'integration, les concepts du dessin et de l"architec...

The quality of bond in masonry is, to a large extent, a function of the (i) the hydration conditions and (ii) the mortar composition of the mortar-brick interface. For insight into the effects of these parameters on bond performance it is essential to dispose of quantitative information about water content changes and flow rates, occurring immediat...

Where the climate is favourable and skills are well developed, mud buildings can be made both durable and impressive, as in Djenné, in Mali, where traditional mud technology is modified by use of more durable materials at vulnerable points. Mr Groot worked in Mali for five years at the National Engineering College at Bamako and on World Bank projec...

A survey is given on the determination of some relevant mono-axial mechanical properties of glass-fibre reinforced polyester laminates. The considerable difference in mechanical properties of the components glass and polyester-resin leads to a dimensioning method based on a close relation between the amount of glass by weight in a laminate and any...