9.0 Conclusions
The physical and mechanical properties of sandstone (sampled from Niche
of Sakyamuni Entering Nirvana) as a function of dry-wet cycle,
freeze-thaw cycle and acid rain cycle were weakened using a series of
tests on a macro-scale. The mineral, chemical compositions and
microstructure deteriorated on a micro-scale. The conclusions are:
(1) The main deterioration is granular disintegration under different
weathering conditions. The sandstone weathering is more significant on
sandstone with bedding development, and the weathering rate escalates
with various numbers of cycles.
(2) The variation in mass is attenuated by an exponential function,
while the variations in surface hardness and P-wave velocity are
attenuated by a power function. Besides, the approximate value of
weathering rate is derived from the variation in surface hardness and
P-wave velocity.
(3) The deterioration degrees affecting the sandstone weathering follow
this order: acid rain cycle, freeze-thaw cycle, dry-wet cycle. Notably,
higher H+, concentrations would enhance the sandstone
weathering. To control the harm of acid rain, antiseptic materials
should be applied on the statue surface.
(4) The deterioration of sandstone by water occurs from the surface to
the inner structure. The surface structure of sandstone is the most
susceptible to weathering effect. The dissolution of calcareous cement,
alteration of feldspar, and water swelling and drying shrinkage of
smectite on account of moisture change make the sandstone surface loose,
and the grains are taken away by water, leading to the granular
disintegration. SEM demonstrates that granular disintegration is
primarily driven by the widening inter-granular micro-cracks.
(5) In this paper, the weathering effects of sandstone of Niche of
Sakyamuni Entering Nirvana were studied experimentally. However,
laboratory experiments were limited by time period, and the sandstone
weathering effects of studied statues is longer and more intense. The
research is thus intended to experiment for a long time.