Colloidal nano-particles of lime for stone and plaster consolidation

CaLoSiL® contains nano-particles of lime hydrate [Ca(OH)2] suspended in different
alcohols. Typical concentrations are between 5 and 50 g/L. The average particle size
is 150 nm. The extremely fine size of the synthetic nano-lime results from its preparation,
which is based on chemical synthesis. Ethanol, iso-propanol or n-propanol serves
as solvents. Due to the low particle size stable sols are formed that means the solids
do not sediment for a long time.
CaLoSiL® is a ready-to-use stone and plasters consolidate. Treatment of stone, mortar
or plaster with CaLoSiL® results in the formation of solid calcium hydroxide after
evaporation of the alcohol. That converts into calcium carbonate in a way similar to
traditional lime mortars by reaction with atmospheric carbon dioxide. All alcohols
evaporate without any residues. Chemicals or residues deteriorating stone or mortar
are not formed.
CaLoSiL® can be applied using either a flow coating procedure, by dipping, spraying
or injection. It is important that the complete weathered zone of the stone down to
the sound is treated.

Available types of CaLoSiL® / Packaging
CaLoSiL® is available in concentrations between 5 and 50 g/L. The letters behind the
name “CaLoSiL®” indicate the used solvent, the numbers give the total calcium hydroxide
concentration in g/L. E –stands for ethanol, IP for iso-propanol and NP for npropanol.
For example, E-25 means, 25 g/L calcium hydroxide dispersed in ethanol.
Standard products are:
CaLoSiL® E-5, E-25 and E-50
CaLoSiL® IP-5, IP-15 and IP-25
CaLoSiL® NP-5, NP15 and NP-50
All CaLoSiL® types are available in 500 mL, 1 Litre, 2.5 Litre, 5 Litre and 10 Litre containers.

Properties of formed calcium hydroxide / calcium carbonate
The calcium hydroxide particles formed after evaporation of the alcohol cover the
surface of treated cracks, pores or joints. Dense films of calcium hydroxide films are
formed, depending on the number of treatment cycles and the concentration of the
used sols. Typical particles sizes are in the range of few hundred nano-metres. Their
detection by means of standard optical microscopy may be difficult, the use of SEM
is recommended.
Calcium carbonate formation by reaction with atmospheric carbon dioxide requires
the presence of humidity. Depending on the conditions and the amount of calcium
hydroxide brought into stone, mortar or plaster carbonations takes place within few
days and weeks. In some cases, after treatment by spraying of water aerosols on the
treated materials may be used to accelerate the carbonation process.

Penetration behaviour
The penetration into mortar, stone or plaster depends on many factors, of special
importance are:
– Characteristics of the CaLoSiL® type applied
– Structure and surface characteristics of the materials to be treated,
– Porosity and capillary rise,
– Moisture content of the material
– Air temperature and air humidity during the application
When dense materials are treated with highly concentrated CaLoSiL® products
(CaLoSiL® E-50, CaLoSiL®-paste like etc.) the penetration behaviour may be only low.
Especially the presences of dense surface layers (for examples gypsum crusts on mortars,
plasters) prevent a penetration of CaLoSiL® into deeper zones.
The penetration into materials with high moisture contents is generally more difficult
than into dry substances. When necessary, pre-wetting with ethanol may help to reduce
the moisture content of the material. After evaporation of the ethanol, it should
be possible to apply all CaLoSiL® products without any problems.

White haze formation
The formation of a white haze on the surface of the treated material depends not
only on the penetration behaviour of CaLoSiL® but also on the evaporation conditions
of the alcohol. Fast evaporation is connected in the most cases with a retransport
of the nano-particles to the surface. There was not enough time for the fixation
of the calcium hydroxide particles within the treated materials. General rules to
prevent / reduce the formation of white haze are:
– Start the treatment with low concentrated products, increase the calcium hydroxide
concentration step by step
– Avoid the treatment of wet materials, reduce the moisture content pretreatment
with ethanol or ethanol-water mixtures (1:1).
– In the case of sensitive surfaces try to use CaLoSiL®-grey, which has a special
consistency allowing deep penetration without white haze formation
– Avoid an “oversaturation” of the treated stone, plaster or mortar. Remove all
CaLoSiL® which could not penetrate into the treated material for example,
with a sponge.
– Test the addition of small amounts of acetone or heptanes.

The alcohols evaporate within few hours. The carbonation process itself requires between
few days and weeks, depending on the amount of calcium hydroxide formed
and the environmental conditions (humidity, possibility of carbon dioxide migration).

CaLoSiL® and silicic acid esters
The combination of CaLoSiL® with silicic acid esters allows the successful consolidation
and strengthening of materials at which pure silicic acid esters do not work satisfactorily.
It is recommended to treat the materials in question in a first step by
CaLoSiL® (for example E-25 or IP-25) and apply silicic acid esters after the evaporation
of the alcohol. The calcium hydroxide formed from CaLoSiL® acts as an adhesion
promoter as well as catalyst accelerating the hydrolysis of the silicic acid ester. The
final strength is in many cases much higher than can be achieved by single treatment
with silicic acid esters. All commercially available silicic acid esters can be
used. Detailed information are summarised in a special technical leaflet.

Mixability with other materials
All CaLoSiL®-products can be intermixed. Blending with ethanol, n- or iso-propanol is
also possible without any difficulties. In contrast to that, the addition of water results,
when amounts greater than 10 wt.-% are added, in the formation of solutions characterised
by a gel like consistency. Higher water amounts will flocculate the calcium
hydroxide precipitates.

All materials have to be stored between + 5 °C and +30 °C. When CaLoSiL® remains
in unopened, original containers, storage for at least three months is possible. After
that time, agglomeration and connected with that, sedimentation may occur. The
settled particles, however, can be re-dispersed by shaking the closed bottle or by
ultrasonic treatment. The properties of the nano-sols remain unaffected.

CaLoSiL® is flammable/combustible. Keep away from oxidizers, heat, sparks and
flames. Avoid spilling, skin and eye contact. Ventilate well, avoid breathing vapours.
CaLoSiL® reacts strongly alkaline. Do not breathe vapour or mist. Do not smoke. Keep
container closed. Use with adequate ventilation. Wash thoroughly after handling.
Keep away from sources of ignition. Please store in a cool, dry place and in a tightly closed container.

Further information
Concerning safety during transport, storage and handling as well as for disposal and
ecology can be found in our latest Material Safety Data Sheet.
Before using in large scale we recommend to treat a small test field with CaLoSiL® in
order to find out the most favourable application method and the required volumes
of CaLoSiL®.