۱- Introduction

۲- Experimental procedure

۳- Result and discussions

۴- Conclusions

References

Abstract

This study investigates the simultaneous effect of nano-silica and steel fiber on the fresh and hardened state performance of self-compacting geopolymer concretes (SCGC). For this purpose, self-compacting geopolymer concretes without and with nano-silica (0, 1% and 2%), and without and with steel fiber (0, 0.5% and 1%) were produced. Hooked-end steel fibers were used with a length of 30 mm and an aspect ratio of 40. Self-compacting geopolymer mixes were produced using 50% fly ash (FA) and 50% ground granulated blast furnace slag (GGBFS) with a constant alkaline activator to binder ratio of 0.5. For the alkaline activator, sodium silicate solution (Na2SiO3) and sodium hydroxide solution (NaOH) were utilized with a ratio (Na2SiO3/NaOH) of 2.5. Fresh state experiments were carried out via slump flow, L-Box, and V-funnel tests, while hardened state experiments were conducted using compressive strength, flexural strength, and bonding strength tests to estimate the effects of nano-silica and steel fiber together on the resulting performances of SCGC specimens. Test results were also evaluated statistically in order to clarify the contributions of the important parameters on the resulting performance. Moreover, correlations between the experimental data were studied to investigate the relationships between the fresh and hardened state performances. The results demonstrated that incorporation of nano-silica and steel fiber affected the fresh state properties adversely; however, a combined utilization of them improved bond strength and flexural performance of the SCGC specimens significantly. In addition, the effect of nano-silica was found to be dominant on fresh state properties and compressive strength, while the effect of steel fiber was found to be superior on flexural performance and bonding strength.

Introduction

Concrete is the most commonly used structural material due to the availability of raw materials and ease of shaping. However, significant amount of greenhouse gases (CO2, etc.) are released to the environment due to the combustion of fossil fuels and the decarbonization of limestone during the cement production process. In addition, after aluminum and steel material, ordinary Portland cement (OPC) can be considered as the most energy requiring material [1,2]. Therefore, the negative impacts of CO2 on the environment and the high amount of required energy are significant issues for both cement industry and future of mankind. New enviroment-friendly structural materials should be utilized instead of ordinary concrete to cope with environmental problems [3,4]. Recently, the geopolymer concrete has started to emerge as an environment-friendly concrete as an alternative to ordinary (OPC) concrete [5–۷]. Geopolymer concretes have received vast amount of attention due to the significant reduction in both the amount of CO2 release and necessity of natural resources. Unlike to OPC, the manufacture of the raw materials does not require a calcining process leading to reduction in the energy consumption. It is pointed out in literature that amount of CO2 release of the geopolymer concrete is 5–۶ times lower as compared to the OPC concrete [8,9]. Furthermore, the usage of geopolymer concrete not only decreases the CO2 emissions considerably, but also uses the byproduct wastes of the alumino-silicate composition to fabricate innovative construction materials [10,11].