Sumiyanto, Sumiyanto (2023) STUDI LABORATORIUM PERBAIKAN KEKUATAN CLAY SHALE TERDEGRADASI DENGAN METODE INJEKSI SEMEN DAN GEOPOLYMER. Doctoral thesis, UNDIP.

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Abstract

Clay shale is a sedimentary rock with low durability. In open conditions, clay shale will
be exposed to changes in the dry-wet cycle weather. This condition causes the clay shale
to undergo a weathering process which causes degradation in the future. Stabilization by
the mixing method will be difficult, this is related to the presence of the existing structure
and weathering of the clay shale which is quite deep. Injection grouting is a proposed
method for repairing degraded clay shales. Laboratory research was conducted to study
the effectiveness of the injection grouting method on clay shale, with the grouting
materials used were cement paste and fly ash-based geopolymer. Observation of the
success of this injection method was carried out based on the grouting column formed
and the strength of the unconfined compression test results. The results showed that the
geopolymer was more suitable for injection into clay shale. Cement paste injection was
not successful in forming the grouting column and the strength was not significantly
increased. Meanwhile, geopolymer injection succeeded in forming a grouted column and
its strength increased significantly. The formation of this grouting column proves that the
geopolymer has succeeded in spreading in the pores of the clay shale and forming bonds
between fragments. The presence of geopolymers in the grouting column was confirmed
by microstructural observations using SEM. The result of the geopolymer injection
research shows that porosity, moisture content, fly ash activator ratio, pressure and
injection duration are variables that affect the volume of geopolymer injection. This
injection volume is correlated with the size of the grouting column formed. The strength
of clay shale injected with geopolymer is influenced by the initial conditions of the clay
shale, the size of the grouting column, and the fly ash activator ratio. Based on the strength
of clay shale at densities of 0.85 and 0.95 MDD which has been injected with geopolymer,
the optimum fly ash activator ratio is in the range of 1.
Keywords: clay shale, stabilization, injection, cement, geopolymer.

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