Physical-chemical characteristics of an eco-friendly binder using ternary mixture of industrial wastes

Ta-Peng Chang,Chun-Tao Chen,Tien-Dung Nguyen,Tzong-Ruey Yang,Hoang-Anh Nguyen

doi:10.3989/mc.2015.07414

Abstract

This study explores the physical-chemical characteristics of paste and mortar with an eco-friendly binder named as SFC cement, produced by a ternary mixture of industrial waste materials of ground granulated blast furnace slag (S), Class F fly ash (FFA), and circulating fluidized bed combustion fly ash (CFA). To trigger the hydration, the CFA, which acted as an alkaline-sulfate activator, was added to the blended mixture of slag and FFA. The water to binder ratio (W/B), curing regime, and FFA addition significantly affected the engineering performances and shrinkage/expansion of the SFC pastes and mortars. The SFC mortars had higher workability than that of ordinary Portland cement (OPC). With similar workability, the SFC mortars had compressive strengths and expansions comparable to OPC mortars. The main hydration products of the hardened SFC cement were ettringite (AFt) and C-S-H/C-A-S-H. The transformation of the AFt to the monosulfates was observed as the hydration time increased.

Highlights

RESUMEN: Características fisicoquímicas de un ligante eco-amigable usando una mezcla ternaria de residuos industriales
An eco-friendly binder named as SFC cement, produced by a ternary waste mixture of industrial waste materials of ground granulated blast furnace slag, Class F fly ash (FFA) from coal-fired power plant and circulating fluidized bed combustion fly ash (CFA), was used to produce high performance pastes and mortars with high workability, high engineering properties, and satisfactory shrinkage/ expansion
The spherical FFA particles as additive in the SFC cement could significantly reduce the friction between the particles and lead to the higher flowability

Summary

Materials and mix proportions

The Type I ordinary Portland cement (OPC) in accordance with ASTM C150 [29] was used as the control reference. Note: All the SFC and OPC mortar specimens were cast based on the weight ratio of sand to OPC or ternary blended mixture of slag, FFA, and CFA of 2.5. In contrast to FFA and CFA, the slag c omprises mostly amorphous CaO, SiO2, Al2O3, and MgO (Table 1 and Figure 1). The water absorption of sand was 0.8 wt.% In this investigation, the CFA with 15 wt.% of blended mixture of FFA and slag was used to trigger the hydration. The ratio of sand to OPC or ternary blended mixture of slag, FFA, and CFA was fixed at 2.5 by weight in all mortar mixes. The amount of SP was expressed by the percentage of the weight of total solid powder

Casting of specimens and test methods

Workability

Compressive strength

Microstructural analyses

CONCLUSIONS