Effect of cement additive on physical and mechanical properties of high calcium fly ash geopolymer mortars

Abstract

Geopolymer mortars were produced by replacement of high calcium fly ash with cement at the percentages of 5%, 10%, 15%, 20%, 25%, and 100%. Sodium hydroxide was used as the activator and sodium/binder ratios, by weight, were 10%, 12%, 14%, 16%, 18%, and 20% in mortar mixtures. Some physical properties such as unit weight, water absorption, apparent porosity and ultrasound pulse velocity tests were performed on specimens kept in ambient temperature. Flexural and compressive strength tests were made on specimens kept in ambient temperature, and exposed to temperatures of 200°C, 400°C, 600°C, and 800°C for residual performances of mortars. After exposing of specimens to high temperatures, ultrasound pulse velocity and loss in weights were also determined for deterioration levels. An experimental design is also achieved to find optimum solutions for Na/binder and cement/fly ash ratios by using D‐optimal design method after establishing response surface models for compressive and flexural tensile strengths. The highest compressive strength of 35.65 MPa was obtained in mortar specimens containing 14% sodium at 20% cement replacement with fly ash. Similarly, residual strengths were observed higher than those of other mortar specimens at the same sodium and cement replacement ratios.

The effect of micro-SiO2 and micro-Al2O3 additive on the strength properties of ceramic powder-based geopolymer pastes

“…It is known that the addition of A in geopolymer production reduces the unit weight [54]. It is similar to the literature that the unit weight increases with the increase in the activator ratio and the increase in the S/A ratio and amount [11,32,57,58,66,67].…”

“…Similarly, the unit weights increased with the increase in S/Al ratio in the mixture. In some studies, it was stated that the unit weight of the samples increased with the increase in the Na ratio and the increase in the S amount [11,52,58]. Compared to the control samples, it was observed that the unit weights of the samples increased with the increase in the S/A ratio.…”

“…Binder density has an effect on unit weight [67]. It is known that workability decreases porosity and increases unit weight [11,57,58]. Mahmoodi et al [32] stated that the workability increased with the increase of S/A and Na 2 O/SiO 2 ratios in geopolymers produced using the same liquid/solid ratio in all mixtures.…”

“…This relationship can be seen when considering the impact UPV and compressive strength of the geopolymer. Low strength geopolymer offers low UPV [57][58][59].…”

Kalsiyum Alüminat Çimentosunun Farklı Kür Koşullarında Atık Cam Tozu Esaslı Geopolimer Harçların Fiziksel ve Mekanik Özelliklerine Etkisi

“…Bu sebep ile farklı kür koşulları uygulanarak atık cam tozu tabanlı geopolimer harçlara kalsiyum alüminat çimentosu ikamesinin etkisi ortaya konmak için işlenebilirlik, su emme ve boşluk oranı, eğilme dayanımı ve basınç dayanımı deney yöntemleri uygulanmıştır. [20,21,22,23]. KAÇ kullanılarak ortama CaO ilave edilerek N-A-S-H jeli dışında C-A-S-H jeli de oluşumu sağlanmış böylece dayanımda bir miktar iyileştirme yapmıştır [11,22].…”