Mechanical property and microstructure of alkali-activated Yellow River sediment-coal slime ash composites

Abstract

This work focuses on the production of a new composite material using Yellow River sediment and coal slime ash via alkali-activating method. XRD, FTIR and SEM/EDS were used to characterize the alkali-activated products and microstructure of the composite material. Compressive strength was tested to characterize the mechanical property of the composite material. It is found that the compressive strength of the Yellow River sediment-coal slime ash composites increases as the added Ca(OH)₂ content grows. The compressive strength increases fast in the early stage but slowly after 28 days. The strength of the composites can be significantly improved via the addition of small amount of NaOH and gypsum. The products (C-S-H, ettringite and CaCO₃), especially C-S-H, make much contribution to the enhancement of strength. The highest strength of the composites can reach 14.4 MPa after 90 days curing with 5% Ca(OH)₂, 0.2% NaOH and 7.5% gypsum. The improved properties of the composites show great potential of utilizing Yellow River sediment for inexpensive construction materials.

Keywords

Yellow River sediment / coal slime ash / alkali activation / compressive strength / microstructure

References

[1] Wu BS, Wang ZY, Li CZ. Yellow River Basin Management and Current Issues[J]. J. Geogr. Sci., 2004, 14(1): 29-37.

[2] Qian N, Wang KQ, Yan LD, et al. Effect of Coarse Sediment Source Region in the Middle Yellow River on Scour and Siltation in the Lower Yellow River[C]. First International Academic Conference Proceedings on River and Sediment, 1980 Beijing China: Waterpower Press.

[3] Yu L. The Huanghe (Yellow) River: a Review of Its Development, Characteristics, and Future Management Issues[J]. Cont. Shelf. Res., 2002, 22(3): 389-403.

[4] Wright L D, Jr W J W, Yang Z S, et al. Processes of Marine Dispersal and Deposition of Suspended Silts off the Modern Mouth of the Huanghe (Yellow River) [J]. Cont. Shelf. Res., 1990, 10(1): 1-40.

[5] Xu JH, Wu CJ, Lin LP, et al. Definition on Source Area of Centralized Coarse Sediment in Middle Yellow River[J]. J. Soil. Water Conserv., 2006, 20(1): 6-14.

[6] Kong LW. Alkali Excitation Gelled Material Research Status and Future Development [J]. Sichuan Cem., 2015, 11: 84.

[7] Rashad AM, Zeedan SR. The Effect of Activator Concentration on the Residual Strength of Alkali-activated Fly Ash Pastes Subjected to Thermal Load [J]. Constr. Build. Mater., 2011, 25(7): 3098-3107.

[8] Sofi M, Van Deventer JSJ, Mendis PA, et al. Engineering Properties of Inorganic Polymer Concretes (IPCs)[J]. Cem. Concr. Res., 2007, 37(2): 251-257.

[9] de Vargas AS, Dal Molin DCC, Vilela ACF, et al. The Effects of Na₂O/SiO₂ Molar Ratio, Curing Temperature and Age on Compressive Strength, Morphology and Microstructure of Alkali-activated Fly Ashbased Geopolymers[J]. Cem. Concr. Compos., 2011, 33(6): 653-660.

[10] Palomo A, Grutzeck MW, Blanco MT. Alkali-activated Fly Ash: a Cement for Future[J]. Cem. Concr. Res., 1999, 29(8): 1323-1329.

[11] Li CM, Zhang TT, Wang LJ. Effect of Dosage of Fly Ash and NaOH on the Properties of Alkali Activated Pisha Sandstone-based Mortar[J]. ACI Struc. Mater. J., 2016, 113(2): 173-183.

[12] Li CM, Zhang TT, Wang LJ. Mechanical Properties and Microstructure of Alkali Activated Pisha Sandstone Geopolymer Composites[J]. Constr. Build. Mater., 2014, 68(15): 233-239.

[13] Dong JL, Wang LJ, Zhang TT. Study on the Strength Development, Hydration Process and Carbonation Process of NaOH-activated Pisha Sandstone[J]. Constr. Build. Mater., 2014, 66(4): 154-162.

[14] Li CM, Zhang TT, Wang LJ. Pozzolanic Activity of Pisha Sandstone and Mechanical Properties of Alkali-activated Pisha Sandstone Materials[J]. J. Chin. Ceram. Soc., 2015, 43(8): 1090-1098.

[15] Li CM, Zhang TT, Wang LJ. Development of Building Material Utilizing a Low Pozzolanic Activity Mineral[J]. Constr. Build. Mater., 2016, 121: 300-309.

[16] Lian HZ, Zhang ZL, Wang YH. Rapid Evaluation on Activity of Pozzolanic Materials[J]. J. Build. Mater., 2001, 3: 299-304.

[17] Yang NR. The Physical and Chemical Basis of the Formation of Alkali Cementitious Materials (I)[J]. J. Chin. Ceram. Soc., 1996, 24(2): 209-215.

[18] Yang NR. The Physical and Chemical Basis of the Formation of Alkali Cementitious Materials (II)[J]. J. Chin. Ceram. Soc., 1996, 24(4): 459-465.

[19] Ke CJ. Activity Mechanism of Feldspar for Autoclaved Fly Ash Products[J]. J. Chin. Ceram. Soc., 2006, 34(8): 1011-1016.

[20] Zhang CS, Fang LM. Hardening Mechanisms of Alkali Activated Burned Gangue Cementitious Material[J]. Mater. Sci. Tech-lond., 2004, 12(6): 597-601.

[21] Haha M B, Saout G L. Influence of Activator Type on Hydration Kinetics, Hydrate Assemblage and Microstructural Development of Alkali-activated Blast-furnace Slags[J]. Cem. Concr. Res., 2011, 41(3): 301-310.

[22] Bakharev T. Durability of Geopolymer Materials in Sodium and Magnesium Sulfate Solutions[J]. Cem. Concr. Res., 2005, 35(6): 1233-1246.