A review on strength development of high performance concrete
Introduction
HPC can be defined as a concrete in which utmost care has been taken in all necessary operations in order to give the concrete the most appropriate performance properties in the environment in which it is placed [1]. HPC usually refers to concrete with superior mechanical and durability properties [2], or a concrete with 28d compressive strength above 70 to 80 MPa, w/b ratio below 0.35 and durability factor above 80% and it should consist of good quality aggregates, high cement content (450-550kgm−3), high dosage of mineral admixtures and superplasticizer (5–15 lm−3) [3]. HPC is also defined as a concrete with high strength, high ductility and high durability [4]. Therefore, one of the most important mechanical properties of HPC is high strength. However, it is worth noting that high strength is a property of both high strength concrete (HSC) and HPC. HSC was mainly introduced to eliminate the problems of low strength in concrete, and it evolved gradually by producing concrete with higher and higher strengths [1]. However, it was later shown that HSC presented durability and workability issues, which led to production of HPC as a concrete that is not only characterized by high strength but also by high modulus of elasticity, high workability, high density, low permeability and high resistance to some forms of attack [1]. Hence, HPC possesses superior mechanical and durability properties as compared to HSC. Although high strength is a shared property for both HSC and HPC as shown above, it is important to note that the present work has mainly focused on the literature that is relevant to HPC rather than that of HSC. High strength is required for tall buildings [4], [5], [6], rigid pavement construction for exclusive bus lanes [7], and long span bridges [8], just to mention few.
To produce a concrete with high strength, a reduced w/b ratio is required, usually in the range of 0.22–0.35 [1]. The fact that a required low w/b ratio for HPC does not only lead to strength improvement but also affects other properties of the concrete paves the way towards a need to understand the microstructure and composition of HPC. In fact, studying concrete behaviour at microstructure scale is vital in a way that both its mechanical and durability properties are mainly influenced by reactions and transformations taking place at that scale. Referring to four major concrete pores described in [9], the compressive strength may be affected by pores with diameter larger than 10 μm [10]. One of the most important phenomena (taking place at the microstructure scale) is that a gel produced from the hydration of cement and chemical reaction of pozzolanic materials can satisfactorily contribute towards enhancing the early age strength of the concrete [11]. The main product of hydration of cement and water in normal strength concrete is the cementitious calcium silicate hydrate (C-S-H), which is an intrinsically porous amorphous gel [4]. The porosity in concrete is not only due to these produced gel pores, but also to capillary pores and voids. C-S-H acts as a low density phase, space filling, but strength limiting [4] due to its amorphous property. Among the above mentioned pores, reducing the capillary pores will help to increase the concrete strength but the final strength will still be lower than 50 MPa, hence this will become a limitation when higher strengths are required unless the gel pores are also reduced to provide a substantial porosity reduction in the concrete [10]. In this regard, transforming the amorphous C-S-H gel into crystalline C-S-H gel to reduce the gel pores [12] and filling up the empty space inside concrete through the use of a suitable admixture, lowering w/b ratio to improve the particle packing in the ITZ zone [4], and using good quality of aggregate and appropriate design and curing methods can probably reduce the porosity thereby resulting in an improved strength and other desired properties of HPC. Experimental study results have confirmed that total porosity can be used to predict the strength; thus the most commonly used relationships between compressive strength of cement-based materials and porosity have been established [10]. Currently there are many studies related to enhancement of the strength of HPC using various techniques including partial or fully replacement of ordinary Portland cement (OPC) by various mineral and chemical admixtures [13], [14], [15], use of different types of aggregates [16], [17] and fibers [18], [19], [20], [21], [22] and different curing methods [23], [24]. Some of the existing studies showed beneficial effects on strength enhancement of HPC while others showed adverse effects. This can be attributed to a number of factors. An interesting concern, for example, is that various types of aggregates have been adopted in concrete production, but which ones can be appropriate for the strength (and other properties) required for HPC and which ones cannot? Similar concern arises for other materials such as fibers, SCMs and additives. It can be inferred that studies attempting to gather and compare information from different studies can help in knowing the appropriate materials. Besides, it is generally known that the replacement of OPC by SCM or by two or more SCMs can enhance the strength of HPC; however, another concern that arises in some cases is that the existing literature shows a dispersion of results on the optimal replacement for the same type of SCM, or on synergic effect from two or more SCMs, despite using same materials and design procedures. Additionally, some SCMs such as rice husk ash and calcined clay [13] and some additives are still new in the preparation of HPC and their performance is not yet well understood, hence need to be further studied. In fact, the aforementioned concerns show a need to review various studies and present comparative perspectives, hence be able to provide rational arguments on the current trends, and use the observed trends to help to predict what can be focused on in future researches. This can play a major role in providing a roadmap for researchers who are looking for advancing the state of the art. However, there is a few or no review papers attempting to address the aforementioned concerns in a way that is explained above. Consequently, the present paper accumulates the recent progress, presents comparative analysis wherever possible, and provides insights and suggestions for further research on the effect of the influential factors (SCMs, aggregates, fibers, curing methods, SAPs, EPAs, SRAs and w/b ratio) on the compressive, flexural and splitting tensile strengths of HPC.
Section snippets
Methods
In this review paper the adopted methodological framework for producing a comprehensive structured literature review is shown in Fig. 1. The framework comprises the following steps: (1) setting the main goal of the research; (2) defining a research question referring to the main goal; (3) identifying the variables that respond to the research question; (4) performing a structured literature search focusing on the identified variables; and (5) writing and producing a structured review paper.
Supplementary cementitious materials
A number of mineral admixtures including silica fume (SF), fly ash (FA), metakaolin (MK), ground granulated blast furnace slag (GGBFS), calcined clay (CC), limestone powder (LS) and rice husk ash (RHA) have been widely studied and their influence on the strength of HPC has been reported. A detailed description of each of these admixtures and their production process has been provided [25], and effects of these admixtures on strength of HPC are detailed in the following section.
Conclusion and future research needs
This paper accumulates and reviews the effects of supplementary cementitious materials, aggregate, fibers, curing methods, water-to-binder ratio, and expansion-promoting and shrinkage reducing additives on the strength development of high performance concrete. The following conclusions can be drawn:
The strength of HPC is significantly improved by addition of SCMs. Optimal replacement of OPC by MK, SF, RHA, AAM, CS-LS, NS have generally been reported to be 10%, 10–15%, 20%, 100%, 30%, 0.5–1.5%,
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
References (170)
- et al.
Strength, permeability and shrinkage cracking of silica fume and metakaolin concretes
Constr. Build. Mater.
(2012) - et al.
Use of high performance concrete on rigid pavement construction for exclusive bus lanes
Constr. Build. Mater.
(2010) - et al.
Application of Ultra-High Performance Concrete in bridge engineering
Constr. Build. Mater.
(2018) - et al.
Capillary tension theory for prediction of early autogenous shrinkage of self-consolidating concrete
Constr. Build. Mater.
(2014) - et al.
Investigations on the relationship between porosity, structure and strength of hydrated portland cement pastes. II. effect of pore structure and of degree of hydration
Cem. Concr. Res.
(1985) - et al.
A design consideration for durability of high-performance concrete
Cem. Concr. Compos.
(2001) - et al.
Low clinker high performance concretes and their potential in CFRP- prestressed structural elements
Cem. Concr. Compos.
(2019) - et al.
Influence of nano-SiO 2 on properties of fresh and hardened high performance concrete : A state-of-the-art review
Constr. Build. Mater.
(2017) Scaling resistance of high performance concretes containing a small portion of pre-wetted lightweight fine aggregate
Cem. Concr. Res.
(2005)- et al.
A review on the use of LWA as an internal curing agent of high performance cement-based materials
Constr. Build. Mater.
(2019)