mini review A Review on Nano-Silica Based Concrete
Bashar
S Mohammed*, Veerendrakumar C Khed,
Muhd Fadhil Nuruddin
Citation: Mohammed BS, Khed VC, Nuruddin MF (2017) A Review on Nano-Silica Based Concrete. J Nanomed Nanosci: JNAN-128. DOI: 10.29011/JNAN-128. 100028
1. Abstract
Nanomaterials are being used in concrete technology to enhance the performance and sustainability of the construction materials. In most of the previous studies, nano-silica was used as an additive for the cementitious material. It was depicted that nano-silica improves the mechanical and durability properties due to its physico-chemical reactive characteristics. Contrarily the addition of nano-silica reduces the workability of concrete and that can be diminished through adjusting the superplasticizer by maintaining the optimum quantity of water.
2.
Keywords: Calcium-Silicate-Hydrate(C-S-H) gel; Physico Chemical Effect; Nano Silica;
Nanotechnology
1. Introduction
Concrete is one of the essential construction material due to its significant features such as the ability to mold for any shapes, low cost and high strength, most of the ingredients are naturally available despite its concern with the environment. In the world, around 8% of carbon dioxide emitted due to the production of cement [1] which can be used to produce 20 billion metric ton of concrete approximately [2]. This huge percentage of carbon dioxide emission has become an issue of environmental concern. Day to day new ideas are being established in the construction industry in order to maintain the environmental sustainability [3]. Concrete is a composite material which comprises of the materials in a range of micrometer to the millimeter. Generally, concrete is considered to be a single unit for its fresh and hardened engineering properties, then again at micro and Nano level, it has complex characteristics along with different compositions. There has been a correlation between the strength properties and microstructure of concrete, which created the interest for the researchers in establishing the relationship. Contemporarily the construction sector is functioning on the development of the new and advanced cementitious material. Proper utilization of the materials in the cementitious system helps in enhancing the strength, durability, sustainability and also cost-effective in terms of maintenance.
On the
other side, in science and technology, nanotechnology has been developing to be
an advanced science for the future. Nano-engineered materials proven to be
better performance than their higher sized materials [4].
According to Drexler et al. [5] nanotechnology
can be defined as “In a matter, control of the structure based on the molecule
products and its by-products”. Some of
the researchers defined the nanotechnology that “The understanding, manufacturing, and control of the matter into
the nanometers in creating the materials for the modern properties and
functions” [6]. In concrete science the term
nanotechnology may be defined as the bulk properties of the concrete can be
altered by controlling the material properties at the nanometer scale. The
importance of nano-silica in concrete
technology has been graphically elaborated in (Figure 1).
By
using the ultrafine substances like nano-silica
as an additive in the cement based products improves the properties of hardened
concrete. Both physical and chemical effects due to the addition of nano-silica play role in producing the high-performance concrete [9]. Physically nanoparticles
have the ability to fill the voids
between the cement particles. Best composition of materials can produce high
packing density resulting in low water demand leading towards the enhancement
of strength due to its reduced porosity. Chemically
nano-silica addition increases the
pozzolanic reactivity when compared with the silica fume. Besides this, the hydration of cement can be speeded by
the addition of nano-silica. The nano-silica in the cementitious matrix create
additional C-S-H gel by the formation of
reaction between H2SiO2-4
and Ca2+,
thus the C-S-H gel spread between the cement particle
leading towards better compaction of cement particles. This additional
C-S-H gel accelerates the hydration of cement [9].
In this work, the previous researches on fresh and mechanical properties of Nano-silica, which was added in percentage of cementitious material on various types of concrete have been reviewed and the conclusion remarks were drawn.
2. Fresh Properties
Nano silica in concrete absorbs some part of mixing water because of its high reactivity and the high specific area which induces the reduction in workability. To increase the workability superplasticizer was added [10]. The addition of nano-silica in concrete reduces the bleeding and segregation and helps in increasing the cohesiveness of concrete. Nano silica addition requires more water to maintain its workability [11]. The addition of nano-silica in Engineered Cementitious Composite (ECC) demanded a higher percentage of superplasticiser to retain the optimum amount of water for the required workability [12]. One of the study says that nano-silica effect on the cement paste induces an instantaneous reaction between the liquid segment of cementitious and the nano-silica to form the gel with a high retention of water capacity [13]. In a self-compacting mortar, increased quantity of Nano-silica reduced the slump value [14]. In most of the studies confirm that the mineral particles having high surface area prone to the low workability that led to the higher quantity of water and admixture requirement.
3. Mechanical Properties
Mohammed
et al studied the compression strength of
rubberized concrete by varying the nano-silica
addition up to 5% and it was observed that compressive strength increased
gradually due to the physico-chemical
effect of nano-silica which filled the micropores of the rubberized concrete as shown in (Figure
2 (a)) [4]. In a combination with fly ash, the addition of nano-silica helps in increasing the early
strength of concrete as shown in (Figure 2(b)) [10,15,16]. The C-S-H gel formation due to the
pozzolanic reaction was quicker and faster when the addition of nano-silica in
the cement paste, this led to the improvement in the compressive strength and
flexural strength [9, 17,18]. The Nano-silica addition increased the bending
strength, tensile strength, abrasion strength [19].
Nanosilica in fiber-phenolic composite,
the bending strength increased by 13% up to
the addition of 3% of nano-silica and
decreased for 5% addition of Nano silica [20].
Addition of nano-silica improves the Interfacial
Transition Zone (ITZ) property which further helps in improvement of
compression strength, flexural strength,
and modulus of elasticity [21]. In rubberized
roller compacted concrete, the loss of strength due to crumb rubber was
mitigated by the addition of Nano-silica [22].
In sawdust-crete, sawdust particles were
pre-coated by Nano-silica, which improved the compression strength by reducing
the MIP (mercury intrusion porosimetry) and ITZ [23]{Mohammed, 2016
#138}. Sodium silicate
demand was reduced due to the addition of nanosilica
[24]. The addition of Nano-silica up to 4% had resulted in an increase in the compression strength of ECC
gradually and beyond 4% it was decreased [25]. Up to
15 MPa strength of solid bricks can be produced by utilizing Nano-silica in rubberized concrete [26].
4. Durability Properties
The durability in terms of sulphuric acid attack was investigated and compared with micro and nano-silica, it was found that the effect of inclusion of 7% of micro silica was equivalent 2% of Nano silica [27]. In sugarcane bagasse, ash mortar with nano-silica improved durability performance in terms of chloride ingress, better electrical resistivity, improved pore structure [28]. Nano silica played a better role in the reduction of water absorption and chloride penetration [29]. The addition of Nano-silica reduced the thermal conductivity and sorptivity [30]. The extension of cracks was prevented when exposed to the elevated temperature due to the inclusion of nano-silica [31]. Nano-silica enhanced the corrosion resistance due to its binding nature with Ca(OH)2 in Portland cement [32]. A significant reduction in plastic shrinkage was observed for the Nano-silica based cement mortar [33].
5. Conclusion and Remarks
Using nanomaterial such as nano-silica in concrete improves the hardened properties, durability characteristics and contrarily reduces the workability which can be adjusted by adding the superplasticizer. Thus, by using nanotechnology in the construction industry can produce high-performance concrete for the future engineering structures. Hence the nanotechnology proved to be an advanced technology in the concrete domain.
6. Future scope
Maximum
researchers worked on nano-silica have
been limited to the fresh and mechanical properties of conventional concrete.
More research needs to work on other
types of concrete such as geopolymer, ECC, rubbercrete.
Furthermore, research to be carried out on dynamic and durability properties of
Nano-silica modified concrete. In addition to Nano-silica, nanotechnology can
be extended for various other nano-materials.
Figure 1: Importance of Nano
silica in concrete technology [7,8].
Figure 2(a): Effect of compression
strength of nano-silica in combination with crumb rubber concrete [4].
Figure 2(b): Effect of
compression strength of nano-silica in self-compacting mortar.
Figure 2: Effect of nano-silica on compression strength of
rubberized concrete.
5.
Drexler KE,
Peterson C, Pergamit G (1991) Unbounding the future," William Morrow, New
York, p. 294, 1991.
8.
Adamu M, Mohammed
BS, Shafiq N (2016) Nano silica modified roller compacted rubbercretean
overview. in Engineering Challenges for Sustainable Future: Proceedings of the
3rd International Conference on Civil, Offshore and Environmental Engineering
(ICCOEE 2016, Malaysia, 15-17 August 2016 pg no: 483.
23.
Mohammed BS, Nuruddin
M, Ishak N (2016) Hardened properties of sawdust-crete containing pre-coated
sawdust with nano-silica. in Advances in Civil, Architectural, Structural and
Constructional Engineering: Proceedings of the International Conference on
Civil, Architectural, Structural and Constructional Engineering, Dong-A
University, Busan, South Korea, August 21-23, 2015 pg no: 3.
26.
Mahamood N,
Mohammed B, Shafiq N, Eisa S (2016) Development of Nano silica modified solid
rubbercrete bricks. in Engineering Challenges for Sustainable Future:
Proceedings of the 3rd International Conference on Civil, Offshore and
Environmental Engineering (ICCOEE 2016, Malaysia, 15-17 Aug 2016 pg no: 443