Concrete is one of the most usable and durable cement-based materials in the construction field with different applications [
1,
2,
3,
4,
5,
6,
7]. It has several advantages over other construction materials such as high strength, fire resistance, and high durability which extends the service life of structures. Numerous researchers have recently focused on concrete durability and factors affecting it, and on finding different methods to improve durability-related characteristics. Concrete durability can be evaluated by its performance under severe weather conditions, abrasion, chemical and physical attacks, and other deterioration processes [
8,
9]. Improving the durability of concrete increases its serviceability and keeps its original characteristics even under severe environmental attacks. According to ACI 201-2R-2008 [
9], concrete is mostly exposed to both physical and chemical sulfate attacks that accelerate the deteriorating process in weak concrete. Amongst the most essential matters concerning the durability of concrete structures are their resistances to sulfate exposure. The cement matrix suffers from deterioration due to spalling, softening, and expansion in the sulfate environment [
10,
11,
12]. There are four main factors that affect concrete resistance to sulfate attack; (1) Cement type; (2) Sulfate type and concentration; (3) Quality of concrete; (4) Exposure conditions [
12]. This attack occurs when concrete is exposed to a sulfate source through rainwater, soil, or groundwater. The attack of sulfate is typically manifested through cracking of concrete and spalling, followed by expansions and strength reduction. Several factors, including water to cement (w/c) ratio, transportation characteristics, mix components, and cement fineness and composition govern the performance of concrete when exposed to aggressive sulfate attack [
12]. Some types of soil with concentrations of sulfate might be categorized as moderate or severe conforms to ACI 201-2R-2008 [
9], as shown in
Table 1, which can have adverse effects on concrete service life. Camacho and Afif [
13] indicated sulfate proportions in soils as 0.11% to 0.70% and in groundwater and wastewaters as 288 to 10,000 parts per million [
14]. Calcium, potassium, sodium, and magnesium ions were observed in association with the other ions that originated in seawater, soil, and groundwater [
15]. Hazardous ions such as sulfate ions enter concrete and form ettringite having a higher volume than the initial components in the reaction, which began due to the reaction with calcium hydroxide (Ca(OH)
2) and tri-calcium aluminate hydrate (C
3AH
6) [
15]. The ettringite and gypsum generated due to a sulfate attack have much more volume (1.2–2.2 times) than the original chemical reactions. This can cause cracking and softening in concrete structures and ultimately decrease their durability [
15]. All of the above responses are followed by a significant decrease in the strength of concrete.
Calcium hydroxide (Ca(OH)
2) reacts with sulfate ions (SO4
2−) in the pore solution, producing gypsum in the case of sodium sulfate (Na
2SO
4) attack, leading to strength deterioration of concrete. As a result of this reaction, ettringite is created as a secondary product that increases volume, resulting in expansion and cracking owing to the reaction with tricalcium aluminate (C
3A), monosulfate (C
4A¯SH
12), and calcium aluminate hydrate (C
4AH
13) [
16]. However, Ca(OH)
2 reacts with magnesium sulfate in case of magnesium sulfate (MgSO
4) attack to create brucite (Mg(OH)
2) and gypsum. Calcium silicate hydrate (C-S-H) and ettringite are thus destabilized at low pH levels of brucite. Therefore, the reaction of C-S-H with MgSO
4 is accelerated to produce MgSO
4 and acts rapidly with C-S-H to silica gel (S
2H) and gypsum. Additional amounts of free lime have existed in the system, which can respond to react with MgSO
4 to produce more brucite; consequently, a higher content of brucite and gypsum is created in the microstructure of the concrete matrix. With such a high increase in brucite concentration, it reacts with S
2H. As a result, C-S-H gradually decomposes, forfeits its lime, and transforms to another phase, non-cementitious M-S-H (magnesium silicate hydrate) [
17]. To deal with sulfate attacks in many countries, blast furnace cement (BFC) improves sulfate and chloride resistance due to its stable characteristics under such severe conditions. Frearson [
18] reported that ordinary Portland cement (OPC) suffers tremendous damage due to an aggressive attack of sulfate. He studied the effect of using different water to binder (w/b) ratios and different contents of granulated-blast furnace slag (GGBFS) as substitutes of OPC on concrete resistance to the attack of sulfate. The result of the content of slag was concluded to be greater than the effect of the w/b ratio on improving resistance to sulfate [
19]. In other research work, the high content of slag in concrete has been reported to increase resistance to sulfates by reducing the permeability and densifying the microstructure, and refining the pores, which reduce the penetration of water and severe ions into concrete. Improved concrete resistance to sulfate and chloride attacks associated with the addition of optimum slag content is primarily owing to the decrease in tricalcium aluminate and rising in concentration of slag in cement-concrete. Furthermore, incorporation of particles of slag in the cement-based material system reduced the content of calcium hydroxide and increased the concentration of C-S-H phases, which improves concrete mechanical characteristics and reduces its reaction rate between sulfate ions and calcium hydroxide [
19]. Blended types of cement composed of OPC mixed with various mineral additives such as slag, fly ash, or natural pozzolana showed good resistance to severe sulfate attack due to pozzolanic reaction, densifying the matrix, reducing C
3A content, and minimizing CH content in the system [
20,
21]. Although both fly ash and blast furnace slag achieved an enhancement in concrete sulfate resistance, the contribution varied with the initial moist curing time [
22]. In addition, the incorporation of silica fume (SF) to concrete enhances the durability aspects of concrete through refining the pore system [
22], decreasing the permeation, minimizing harmful substances diffusion, and consuming calcium hydroxide leading to better resistance to severe sulfate exposure. These parameters help protect the reinforcement embedded in concrete from severe corrosion [
23]. It is also reported that the addition of 5–10% of SF to replace cement by mass can help significantly to improve resistance to the attack of sodium sulfates without any indication to concrete spalling even after 365 days in solution with 5% concentration of sodium sulfate [
24,
25]. Replacing cement with fly ash causes concrete mass loss that is owing to the less formation of the components like Ca (OH)
2 during the process of deterioration [
25].
Recently, several studies have been carried out to reduce the harmful impact of sulfate attack on concrete using supplementary cementitious materials as well as nanomaterials [
26,
27,
28,
29,
30,
31]. Most of the researchers focused on three ways to reduce concrete deterioration under sulfate attack. The first one was by minimizing the portlandite content in the pore solution. The second way was by decreasing C
3A content, and the third one was by reducing the permeability of concrete to prevent the sulfate solution from penetrating the concrete [
26]. Incorporation of fly ash, metakaolin, silica fume, and slag can mitigate sulfate attack significantly depending on the replacement level and sulfate attack degree [
26,
27,
28]. However, there are contrary effects on concrete durability such as reducing alkalinity of the pore solution. On the other hand, it was reported that incorporation of nanosilica and nano metakaolin reduces the strength loss and improves the resistance of concrete to sulfate attack [
29,
30]. Baldeman et al. [
31] studied the influence of limestone on sulfate resistance and concluded that the performance of concrete can be improved when the replacement level is lower than 50%. The performance of cement-based materials under sulfate attack is dependent mainly on the mix composition as well as the exposing degree and period.