An Elucidative Review of the Nanomaterial Effect on the Durability and Calcium-Silicate-Hydrate (C-S-H) Gel Development of Concrete

Abstract

Concrete as a building material is susceptible to degradation by environmental threats such as thermal diffusion, acid and sulphate infiltration, and chloride penetration. Hence, the inclusion of nanomaterials in concrete has a positive effect in terms of promoting its mechanical strength and durability performance, as well as resulting in energy savings due to reduced cement consumption in concrete production. This review article discussed the novel advances in research regarding C-S-H gel promotion and concrete durability improvement using nanomaterials. Basically, this review deals with topics relevant to the influence of nanomaterials on concrete's resistance to heat, acid, sulphate, chlorides, and wear deterioration, as well as the impact on concrete microstructure and chemical bonding. The significance of this review is a critical discussion on the cementation mechanism of nanoparticles in enhancing durability properties owing to their nanofiller effect, pozzolanic reactivity, and nucleation effect. The utilization of nanoparticles enhanced the hydrolysis of cement, leading to a rise in the production of C-S-H gel. Consequently, this improvement in concrete microstructure led to a reduction in the number of capillary pores and pore connectivity, thereby improving the concrete's water resistance. Microstructural and chemical evidence obtained using SEM and XRD indicated that nanomaterials facilitated the formation of cement gel either by reacting pozzolanically with portlandite to generate more C-S-H gel or by functioning as nucleation sites. Due to an increased rate of C-S-H gel formation, concrete enhanced with nanoparticles exhibited greater durability against heat damage, external attack by acids and sulphates, chloride diffusion, and surface abrasion. The durability improvement following nanomaterial incorporation into concrete can be summarised as enhanced residual mechanical strength, reduced concrete mass loss, reduced diffusion coefficients for thermal and chloride, improved performance against sulphates and acid attack, and increased surface resistance to abrasion.

Keywords: C-S-H gel; concrete; durability; energy savings; nanomaterial.

Figure 1

The action by which nanoparticles enhance the durability of concrete.

Figure 2

SEM images showing concrete with nanoparticles. Reproduced with permission from [51] (Journal of Building Engineering); published by (Elsevier), (2021). (Note: milled nanometakaolin (NMK), nanowaste glass (NWG), nano rice husk ash (NRHA), nanosilica (NS), control concrete (C0)).

Figure 3

XRD patterns for 28-day self-compacted concrete under (a) normal curing (NC) and (b) self-curing (SC). Q = unhydrated SiO₂, E = ettringite, CSH = calcium silicate hydrate, and CH = calcium hydroxide. Reproduced with permission from [53] (Journal of Building Engineering); published by (Elsevier), (2022).

Figure 4

Compressive strength of concrete under different temperatures [71,73,74,75,76,77,80,81,82].

Figure 5

Compressive strength of control concrete, 5% nanosilica concrete, and 5% nanoclay concrete at 22, 200, 400, and 600 °C [80].

Figure 6

Tensile strength of concrete under different temperatures [71,74,77].

Figure 7

Compressive and tensile strength loss of concrete at 600 °C [71,73,74,75,76,77].

Figure 8

Schematic illustration showing the damage zones caused by an acid attack between plain concrete and nanomodified concrete.

Figure 9

The reduction in concrete compressive strength loss (%) due to a sulphate attack after the addition of nanomaterials (a) The effect of different contents of nanometakaolin on reducing compressive strength loss of concrete subjected to 360 days of magnesium sulphate [89]. (b) The effect of different contents of nanosilica on reducing compressive strength loss of concrete subjected to 360 days of magnesium sulphate [89]. (c) The effect of different contents of multi-walled carbon nanotubes (MWCNTs) on reducing compressive strength loss of concrete subjected to 90 days of sodium sulphate [98]. (d) The effect of different contents of ZnO + TiO₂ on reducing compressive strength loss of concrete subjected to 28 days of a sulphate solution [99].

Figure 10

Residual compressive strength of air-cured, nanomodified concrete subjected to a sulphate solution [51].

Figure 11

Correlation between the reduction in compressive strength loss and reduction in weight loss for concrete with nanomaterials [89,98,99,100,101].

Figure 12

The chloride ion resistance of graphene oxide-modified, steel fibre-reinforced concrete. Reproduced with permission from [109], (Cement and Concrete Composites); published by (Elsevier), (2022) (Note: SFRC: 0% graphene oxide, GOSFR-1: 0.01%wt. graphene oxide, GOSFRC-3: 0.03 wt.%, GOSFRC-5: 0.05 wt.%, GOSFRC: 0.07% graphene oxide).

Figure 13

Free Cl⁻ concentration in nanoconcrete at different nanomaterial dosages (0–5 mm). Reproduced with permission from [110], (Case Studies in Construction Materials); published by (Elsevier), (2023) (Note: NS: NanoSiO₂, NZ: Nano-ZnO, N = number of cycles).

Figure 14

The relationship between electrical resistivity and durability parameters of nanoconcrete. Reproduced with permission from [111], (Construction and Building Materials); published by (Elsevier), (2020).

Figure 15

Percentage of porosity for carbon nanofiber concrete (CNFC) in different dosages (0.1–0.5%). Reproduced with permission from [112], (Construction and Building Materials); published by (Elsevier), (2020).

Figure 16

The relationship between the index of abrasion resistance and compressive strength for all mixtures of concrete. Reproduced with permission from [117], (Wear); published by (Elsevier), (2006) (Note: PC: control concrete, PPC: polypropylene fibre concrete, NSC: nanosilica concrete, NTC: nano-TiO₂ concrete).

Figure 17

The results of wear resistance for nano-double-doped concrete. Reproduced with permission from [52], (Construction and Building Materials); published by (Elsevier), (2017) (Note: H1: 1% nanoSiO₂ + 3% nanoSIC, H2: 3% nanosilica + 1% nanoSIC, H3: 2% nanoSiO₂ + 2% nanoSIC, H4: 2% nanoSiO₂ + 1% nanoSIC).

Figure 18

The abrasion loss of reactive powder concrete containing nanomaterials. Reproduced with permission from [118], (Construction and Building Materials); published by (Elsevier), (2018). (Notes: R: cured at room temperature, H: heat curing, NS: nano-SiO₂, NT: nano-TiO₂, NZ: nano-ZrO₂).

Figure 19

The loss of concrete volume per surface area after 16 periods of wearing. Ref: control concrete, SF: silica fume concrete, HNT: nano-halloysite MMT: montmorillonite, NS: nanosilica. Reproduced with permission from [119], (Construction and Building Materials); published by (Elsevier), (2020).

Figure 20

The pore volume of nanoconcrete. REF: control concrete, SF: silica fume concrete, HNT: nano-halloysite MMT: montmorillonite, NS: nanosilica. Reproduced with permission from [119], (Construction and Building Materials); published by (Elsevier), (2020).