Tímarit Verkfræðingafélags Íslands


Tímarit Verkfræðingafélags Íslands - 01.10.1959, Blaðsíða 23

Tímarit Verkfræðingafélags Íslands - 01.10.1959, Blaðsíða 23
TtMARIT VFl 1959 73 Table m No. Andreasen Surface Area cm2/g Blalne Surface Area cmVg Density Undissolved in 6% HCl, % Absorj 7 days >tion of Dime g 90 days CaO/lOOg poz 180 days zolan 360 days I 4200 4820 2.75 64.5 5.0 10.0 12.3 14.3 II 7000 7420 2.36 95.7 0.6 1.7 3.7 7.0 III 3580 4250 2.64 60.0 7.5 13.0 15.8 18.1 IV 4320 4420 2.65 93.0 0.6 1.6 . 3.0 5.0 V 2660 1830 2.82 34.6 0.6 1.7 3.0 5.4 VI 3000 3980 2.82 71.5 1.8 6.4 7.0 8.6 VII 3580 3030 2.49 61.0 6.9 10.4 10.4 18.8 VIII 6000 7390 2.42 54.0 7.7 12.0 16.0 20.7 IX 4140 2460 2.35 55.0 7.5 12.1 15.8 19.7 X 8500 9000 2.25 34.0 9.5 13.6 17.0 20.1 XI 2810 3630 2.54 27.5 7.7 11.8 14.2 16.7 XH 2040 1630 2.58 23.0 5.2 7.2 10.2 11.9 XIII 2130 1600 2.61 23.0 7.5 9.0 11.4 13.7 XIV 4030 4000 2.55 36.5 5.2 9.2 11.6 15.1 XV 4030 1990 3.31 38.5 1.2 3.2 4.5 7.8 XVI 99.5 0.1 2.0 2.8 4.9 XVII 99.6 0.3 1.2 2.0 3.9 Sement 3340 2. Surface area determinations are glven in table III. It is felt that surface area greatly influences the pozzo- lanic activity. 3. Reduction in alkalinity and silica dissolved is given in gi-aph I. On this graph the limiting line Rj + % Sj = 630 is drawn; where Rj = reduction in alka- linity in mM/1, and Sj = silica dissolved in mM/1. Most of the pozzolans undir investigation fall above the limiting line. The moberg samples reveal only slight dissolution of silica, but on the other hand a very great reduciton in alkalinity. In the well known graph of Mielenz and others (7), most of the móberg samples fall in the upper left hand corner where they seem to have a region of their own. Reduction in alkalinity exceeding 550 mM/1 is rare (7), but in the case of most of the moberg samples it is considerably higher. 4. The amount of lime absorbed or neutralized is shown in table III. The removal of lime is relatively low but is yet of the same magintude as for some pozzolans given by Savage (8). Graph II and III give the relations of lime depletion to compressive strenght. These graphs indicate that some relation may exist between compressive strenght and depletion of lime. Graphs IV shows the relation between neutralization of lime and reductions in alkalinity. 5. Solubility in boiling 5% HCl is given in table III. This test does not show any apparent relations to others test methods. 6. Compressive and flexural strenght of the pozzolans as pr. cent of 28 day strenghts of straight mortals is shown in graph VII—X. Strength graphs indicate strong pozzolanic activity for most of the materials and in parti- cular for the pumice sample. The v/c ratio of the straight portland cement mortar was 0.6, for 15% replacement 0,7, and for 30% replacement 0.85, except in the case of pumice were the v/c ratio was slightly higher. This increase in v/c ratio should lead to ca. 20% and 40% reduction in strenght respectively, if nothing else was taken into account. A number of samples show the recognized retrogress- ion in strenght (17, 18) at later ages when specimens are stored in. water. It is apparent, when comparing strength results for different pozzolans to the reference samples, that both flexural and compressive strengths are higher than should be expected, if no pozzolanic actions were taking place, particularly for 30% replacement. 7. Free lime determination is given in graph V. This graph shows a definite removal of lime by the pozzolan replacements. A correlation between strenght and free lime is visible from graph VI. 8. The lime-mortar test for pozzolans revealed a positive result only for sample No. 2. This seems to be a contradiction to the majority of the other tests. It should be borne in mind that this test is carried out at 55 °C whereas the rest of the strenght test were carried out at room temperature. A pozzolan may have both physical and chemical

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