Development and Testing of Geopolymer Mortar
3.2 Experimental Investigation
3.2.2 Mix proportions
Mix proportion of the UGGBS based GPM was prepared based on provisions mentioned in IS 1727 1967 [81] and is presented in Table 3.1. The total binding agent mentioned here is defined as the total amount of UGGBS and FA in the mix. Na2SiO3 and/or NaOH solution was used as the alkali activator.
Chapter 3 Development and Testing of Geopolymer Mortar
Table 3.1: Mix proportion for GPM (kg).
Mix UGGBS FA a/b Na2SiO3
NaOH (Molarity)
SP dosage
(%) SP Type SP addition type
GM1 100 - 0.50 25 25 (10 M) - - -
GM2 100 - 0.50 - 50 (10 M) - - -
GM3 100 - 0.55 27.5 27.5 (10 M) - - -
GM4 100 - 0.55 - 55 (10 M) - - -
GM5 100 - 0.60 30 30 (10 M) - - -
GM6 100 - 0.60 - 60 (10 M) - - -
GM7 100 - 0.65 32.5 32.5 (10M) - - -
GM8 100 - 0.65 - 65 (10 M) - - -
GM9 80 20 0.60 - 60 (10 M) - - -
GM10 70 30 - 60 (10 M) - - -
GM11 60 40 - 60 (10 M) - - -
GM12 50 50 - 60 (10 M) - - -
GM13 80 20 0.65 - 65 (10 M) - - -
GM14 70 30 - 65 (10 M) - - -
GM15 60 40 - 65 (10 M) - - -
GM16 50 50 - 65 (10 M) - - -
GM17 70 30 0.60 - 60 (10 M) 0.5 SN Type I
GM18 70 30 - 60 (10 M) 0.5 PE Type I
GM19 70 30 - 60 (10 M) 1.5 SN Type I
GM20 7 0 30 - 60 (10 M) 1.5 PE Type I
GM21 70 30 - 60 (10 M) 3.0 SN Type I
GM22 70 30 - 60 (10 M) 3.0 PE Type I
GM23 70 30 0.60 - 60 (8 M) 1.5 SN Type I
GM24 70 30 - 60 (8 M) 1.5 PE Type I
GM25 70 30 - 60 (12 M) 1.5 SN Type I
GM26 70 30 - 60 (12 M) 1.5 PE Type I
GM27 70 30 - 60 (14M) 1.5 SN Type I
GM28 70 30 - 60 (14 M) 1.5 PE Type I
GM29 70 30 0.60 - 60 (10 M) 1.5 PE Type II
GM30 70 30 - 60 (10 M) 1.5 SN Type II
GM31 70 30 - 60 (10 M) 1.5 PE Type III
GM32 70 30 - 60 (10 M) 1.5 SN Type III
Note: Total binder: fine aggregate = 1:3, a/b = alkali/total binder.
The mortar mixes presented in Table 3.1 were prepared and tested to study the effect of following on setting time, workability and strength gain of GPM :-
i. Use of Na2SiO3 and NaOH; and only NaOH as alkali activator.
ii. Variation in the amount of alkali activator in the mortar.
iii. Addition of FA of varying amounts of 20, 30, 40 and 50 % by weight of total binding agent in the mortar.
iv. Addition of SP of varying amounts of 0.5, 1.5 and 3 % by weight of total binding agent in the mortar.
v. Variations of NaOH concentrations of 8, 10, 12 and 14 molar (M) in the mortar.
vi. Variation in the time of addition of SP.
Total 32 numbers of GPM mixes were prepared for conducting the laboratory tests.
Mixes GM1 to GM8 consisted of only UGGBS and no FA and were prepared using varying amount of alkali activator. The mixes either consisted of both Na2SiO3 and NaOH or only NaOH as alkali activator. Mixes GM9 to GM12 and GM13 to GM16 having alkali/total binder (a/b) ratio of 0.6 and 0.65 respectively consisted FA of varying amounts along with UGGBS and were activated by NaOH only. Mixes GM17 to GM22 were modifications of GM10 where, two different types of SP of varying amounts were added. In mixes GM23 to GM28, consisting of UGGBS, FA and SP, the concentration of alkali activator (NaOH) was varied.
GM29 and GM30; and GM31 and GM32 were similar to GM19 and GM20 respectively having difference in method of SP addition only.
The ratio of total binding agent to fine aggregate was 1:3 [81] . The ratio of Na2SiO3
to NaOH solution was kept constant at 1 when both Na2SiO3 and NaOH were used as alkali activator. Na2SiO3 and/or NaOH were used as alkali activator based on the works and recommendations of the researchers dedicated in the field of geopolymeric systems. The a/b ratios were selected within the range of 0.50 - 0.65 because a/b ratio less than 0.50 causes the mix to be quite dry which leads to trouble of handling (workability). Upper limit was set as 0.65 so as to avoid the occurrence of bleeding and segregation in the mixes. Maximum content of FA was kept at 50 % since studies showed that amount higher than this causes significant reduction of early and later compressive strength of geopolymer cured at ambient temperature [106 - 109]. Moreover, addition of FA of amount lower than 20 % cannot produce significant change in the properties of UGGBS based geopolymer. Lower limit of SP content was selected 0.5 % because amount lower than that have minimal effect in altering the properties of fresh geopolymer mortar and concrete, especially in case of PE based SP [110]. Meanwhile,
Chapter 3 Development and Testing of Geopolymer Mortar
upper limit was set as 3 % to observe the effect of high dosage of SP on geopolymeric systems.
SP of both SN and PE types were added to the GPM in either of the following three types:-
i. Type I: SP added after the addition of NaOH solution to the mix.
ii. Type II: SP was mixed with NaOH solution and then added to the mix.
iii. Type III: SP added before the addition of NaOH solution to the mix.
The difference in all the three types depends upon the time of SP addition. In Type I, the SP was added to the wet mix which consisted of UGGBS, FA, fine aggregates and NaOH solution. After the addition of SP to the wet mix, it was blended thoroughly so that the SP got homogenously distributed. In Type II, SP was added to the NaOH solution and stirred properly. Later, the SP contained NaOH solution was added to the dry mix. In Type III, SP was added to the dry mix prior to the addition of NaOH solution. On addition of the SP, it was thoroughly mixed for homogenous distribution. NaOH solution was added to the mix at the end of this step of SP addition.
Table 3.2 presents the mix proportion of PCM. The mix proportion was prepared as per the recommendations in IS 1727 1967 [81] for testing of cementitious mortar. Controlled mix, CM1 was prepared using PCM. The water/cement (w/c) ratio of PCM was equal to the water/solid (w/s) ratios of the GPM mixes, excluding some mixes. Water/solid (w/s) ratios of GPM is the ratio between water and total solids in the GPM mix excluding fine aggregates.
Table 3.2: Mix proportion for PCM (kg).
Mix Cement Fine Aggregate Water/cement (w/c)
CM1 100 300 0.40