Internal curing of high performance concrete using cenospheres

Abstract

This study explores a novel internal curing agent, perforated cenospheres. Cenospheres are hollow fly ash particles produced from coal burning power plants. The shell of the cenospheres is inherently porous that is sealed by a thin layer of glass-crystalline film. By removing this film through chemical etching, the pores on the shell can be exposed, perforating the cenospheres and providing paths for water propagating into the internal volume of cenospheres. The perforated cenosphere were found to have water absorption as high as 180 wt.%. The loaded water can be readily released from the cenospheres under high relative humidity (95%). When incorporating saturated cenospheres into cement mortar for internal curing, the autogenous shrinkage of the mortar was almost eliminated. The internal curing also improved the compressive strength of the cement mortar. All these results suggest that perforated cenospheres can be used as an efficient internal curing agent for HPC.

An overview on the effect of internal curing on shrinkage of high performance cement-based materials

“…General requirements for internal curing materials of cement-based materials include: 1) thermodynamic availability requires the water to have an activity close to one, in other words an equilibrium RH close to 100%; and 2)kinetic availability refers to the transport of water from the reservoir to all parts of the self-desiccating cementitious material [19]. Several materials can be used for internal curing of cement-based materials, including LECA (lightweight expanded clay) [11,[20][21][22][23], Pumice [24,25], expanded shale [7], zeolite [21], perlite [26], cenospheres [15], SAP [27], recycled aggregate [28], wood-derived powders and fibers [29], rice husk ash (RHA) [30], coal bottom ash [31], bio-LWA [32], and bentonite clay [33]. Among these materials, SAP and LWA are the most commonly used because they are inexpensive due to abundant supplies, and other materials, such as RHA, coal bottom ash and bentonite clay, were found with the function of internal curing recently.…”

“…Rice husk ash (RHA) has been used as an internal curing material for UHPC in recently years [13]. In addition, people have also found several other internal curing materials, such as bottom ash [14] and cenospheres [15]. Internal curing was firstly defined in ACI 308-2001 [16].…”

The Effect of Fly Ash Microspheres on the Pore Structure of Concrete

“…In addition, they have been studied for the production of ceramic composite foams with different properties. The fly ash microspheres are currently used as lightweight filler, which improves the thermal insulation properties of mortars and concretes based on mineral binders [10,11,16,17].…”

Pozzolanic Reactivity and the Influence of Rice Husk Ash on Early-Age Autogenous Shrinkage of Concrete

“…However, the economic factor due to the general un-availability of LWA, and the negative impacts of SAP on pore structure adversely affects other properties of HPCs (Dudziak and Mechtcherine, 2008;Möser et al, 2010). Therefore, some other studies urge using porous supper fine powders such as rice husk ash, cenospheres, boron mud, and bottom ash as they can significantly contribute in reducing autogenous shrinkage of HPCs (Tuan et al, 2010;Wyrzykowski et al, 2016;Liu et al, 2017). These powder materials were found very effective in controlling autogenous shrinkage of HPCs due to their relatively smaller particle size, high specific surface area (SSA), mesoporous structure, and strong water absorbing ability (Huang and Zhang, 2015).…”