This study investigated the durability of alkali-activated binders based on blends of fly ash (FA) and ground granulated blast furnace slag (GGBFS). Five fly ash-to-slag ratios of 100/0, 75/25, 50/50, 25/75, and 0/100 by mass were selected to produce alkali-activated fly ash/slag (AAFS) concrete. Sodium oxide (Na2O) concentrations of 6% and 8% of binder weight and activator modulus ratios (mass ratio of SiO2 to Na2O) of 0.8, 1.0, and 1.23 were used as alkaline activators. Test results show that the total charge passed of AAFS concrete is between 2500 and 4000 coulombs, higher than the comparable OPC concrete. However, AAFS concrete exposed to sulfate attack performed better than OPC concrete. Based on the results, 100% slag-based AAFS concrete with Na2O concentration of 8% and activator modulus ratio of 1.23 has the superior performances.

Facing the cement and concrete development process, reducing greenhouse gases and the consumption of natural resources has become an important issue. To reduce the cement content in concrete, the increased use of concrete combining large amounts of industrial by-products is expected. Ground granulated blast furnace slag (GGBFS) has been used as a supplementary cementitious material in ordinary Portland cement (OPC) concrete. In this study, GGBFS at different cement replacement ratios of 0%, 20%, 40%, and 60% by weight were used to produce concrete. Compressive strength test, water absorption, electrical resistivity, and rapid chloride penetration test (RCPT) were performed to investigate the effect of GGBFS on compressive strength and durability of concrete. Test results show that GGBFS concrete with 40% cement replacement (G40) has the highest compressive strength. The water absorption and chloride permeability reduced with the increasing cement replacement percentage by GGBFS. Meanwhile, the electrical resistivity increased with an increasing GGBFS replacement percentage. Based on the results, GGBFS concrete with 40% cement replacement seems to be the optimum replacement in this study.

Circulating fluidized bed combustion (CFBC) fly ash is a promising admixture for construction and building materials due to its pozzolanic activity and self-cementitious property. In this study, CFBC fly ash and coal-fired fly ash were used in Portland cement to investigate the pozzolanic and cementitious characteristics of CFBC fly ash and the properties of cement-based composites. Tests show that CFBC fly ash has the potential instead of cementing materials and as an alternative of pozzolan. In fresh specimens, the initial setting time of mortars increases with the increasing amount of cement replacement by CFBC fly ash and coal-fire fly ash. In harden specimens, adding CFBC fly ash to replace OPC reduces the compressive strength. Meanwhile, CFBC fly ash would results in a higher length change when adding over 30%. Based on the results, the amount of CFBC fly ash replacement cement was recommended to be limited below 20%.

This study presents an investigation into high-temperature resistance of alkali-activated slag concrete (AASC). Sodium oxide (Na2O) concentrations of 4%, 5% and 6% of slag weight and liquid sodium silicate (SiO2) with modulus ratio of 0.8 ( mass ratio of SiO2 to Na2O ) were used as activators to activate granulated blast furnace slag (GBFS). All cylindrical specimens with the same binder content and liquid/binder ratio of 0.5 were cast and cured in the air, under the saturated limewater and in a curing room at relative humidity of 80% RH and temperature of 60 °C, respectively. Test results demonstrate that the high-temperature resistance of AASC decreased with an increase of temperature. The compressive strength and high-temperature resistance of AASC improved with an increase dosage of Na2O and AASC cured at relative humidity of 80% RH and temperature of 60 °C has the superior performance, followed the AASC by air curing and saturated limewater curing. The higher compressive strength and superior high-temperature resistance have been obtained in AASC than comparable OPC.

This study presents an investigation into durability performance of concrete with various combinations of circulating fluidized bed combustion (CFBC) fly ash and coal-fired fly ash. All cylindrical specimens with the same binder content of 420 kg/m3 and water/binder ratio of 0.5 were cast and cured in the saturated limewater. Permeability test, sulfate attack resistance test, rapid chloride ion penetration test (RCPT) and carbonization test were performed. Test results demonstrate that the adding of CFBC fly ash and coal-fired fly ash would reduce the water permeability and chloride ions penetration, and increase the sulfate attack resistance, but an increase in carbonization depth. The carbonization depth increases with an increasing contents of CFBC fly ash and coal-fired fly ash. There exists a negative relationship between compressive strength and carbonization rate. Based on the test results, CFBC fly ash and coal-fired fly ash can be considered as cement replacement materials and employed in concrete.