Page 67 - DILMUN 14

S٨ND
Lo2y ،sand : Ycllowish in colour, it is the only quarry sand available, Howevcr, it
sccms to bc too uniformly gradcd as wcll as too ricl in Sulphatc.

Wahed arine sand : It is too salty.

Doble washed rine sand ٠ Although the most cxpcnsive, it sccms to be thc
best choicc.

Whether to use the sand from archaeological cxcavations has often been
discussed in Bahrain and is still controversial. lndecd, it would be mostly suitable
for matching-colour purposes; yet it is scarccly sharp, highly salty and largely
composed of dusty, muddy material.

AGGREGAES
Aggregates (gravel) suitable for restoration vork do not seem to be available

from material suppliers. An effective solution, although time-consuming, can be
represented by the gravel sieved from the material excavated on site, provided it is
carefully washed to get rid of the salt and the dust.

MORAR EXPERIMENS FOR CONSERVAION WORK
A BAHRAIN FOR

o ifnd a good mortar is a veyr important task for the conservation and the
restoration of Bahrain fort, Many tests have, therefore, been made to determine a
suitable mi for working on the Portuguese structures. Portland Cement has been
totally avoided since it proved to be a particularly faulty material for historic
buildings in the aggressive environment of the island.

Based on mortar analysis, a gypsum / lime was chosen in the attempt to match,
chemically and physically, the original material; yet, the laboratory breakdown
allowed for wide spectrum of different mixes, so that the final section could only be
made through a set of practical tests. Lastly, to improve the curing of the lime
lacking any poolanic material PFA٣ have been added which also gave the right
colour. Eventually, the following mix has been selected :

2 Hydrated lime
1 Gypsum
2.5 Double washed marine sand
1 Washed gravel (sieved from excavated materials)
0.25 PFA

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