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40 33.63 28.30 60 53.19 47.85 45.04
Compressive strength at 28 days 30 25.04 19.85 14.37 10.37 Compressive strength at 28 days 40 38.81 29.19 19.85
35
50

25
20
30
15
20
10

0 5 10
M30 M30-PA20 M30-PA40 M30-PA60 M30-PA80 M30-PA100 0 M50 M50-PA20M50-PA40M50-PA60M50-PA80M50-PA100
Specimen Specimen
(a) Different M30 concrete mix compressive strength at 28 days (b) Different M50 concrete mix compressive strength at 28 day
Figure 3: Compressive strength test eesults

drop, with 20 % pumice substituted. The M30-PA40 mix strength results in a more significant loss of strength. Though the strength
further decreased to 25.04 MPa with 40 % replacement, a 25.5 % remained comparatively greater, the decline was not as great
decrease. The M30-PA60 mix strength decreased by 40.9 % as at higher levels (above 60 %). Therefore, it was determined
to 19.85 MPa with 60 % pumice. The compressive strengths of that a 40 % pumice substitution was ideal for M30 concrete in
the M30-PA80 and M30-PA100 mixes decreased to 14.37 MPa applications requiring considerable strength and workable for
and 10.37 MPa, respectively, upon 80 and 100 % replacement, M50 concrete in situations requiring somewhat less strength
representing decreases of 57.3 and 69.2 %. Likewise, the initial but still significant strength. Considering these results, the 40 %
compressive strength of the M50 mix was 53.19 MPa. The M50- pumice replacement level was chosen for additional testing to
PA20 mix strength decreased by 10.0 % to 47.85 MPa when 20 % assess the modulus of rupture tests on prism specimens and the
pumice was substituted. The M50-PA40 mix strength dropped split tensile strength tests on cylinder specimens.
to 45.04 MPa with 40 % replacement, a 15.3 % decline. The 5.3 Split tensile strength
M50-PA60 mix strength further decreased to 38.81 MPa with
60 % pumice, a 27.0 % drop. The compressive strengths of the On control concrete and concrete with the optimal dose of
M50-PA80 and M50-PA100 mixes dropped to 29.19 MPa and pumice aggregate, a split tensile strength test was carried out as
19.85 MPa with 80 % and 100 % replacement, respectively, shown in Figure 4(a). The test findings showed that replacing the
indicating decreases of 45.1 and 62.7 %. The 20 % replacement coarse aggregate with pumice caused a decrease in the tensile
level seems to be the dose for both M30 and M50 concrete, strength of the M30 and M50 concrete mixes. The split tensile
where the strength drop was still within allowable bounds. When strength of the M30 concrete was first determined to be 3.54
compared to 20 % replacement, the 40 % replacement level MPa. But when pumice was used in place of 40 % of the coarse
Split tensile strength
4.50
4.00 3.54 3.82
Split tensile strength (MPa) 3.00 1.42 1.84
3.50

2.50
2.00
1.50
1.00
0.50
0.00
M30 M30-PA40 M50 M50-PA40
Specimen
(a) Split tensile strength on M30 concrete mix cylindrical specimen (b) Different M30 and M50 concrete mix split tensile strength at 28 days
Figure 4: Split Tensile strength test

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