**1. Introduction**

Numerous scientific studies indicated superiority of the ancient concrete as being much more durable than their modern counterparts made with ordinary portland cement. It has been observed that calcium silicate hydrate formed as a result of the hydration of modern portland cement deteriorates, while the ancient cement remains intact under identical conditions. French scientist, Davidovits [1] proposed that the durability of ancient concrete was the result of the presence of alkaline aluminosilicates in the structure. Davidovits named this new class of cementitious material as geopolymers. This is a new generation material with diverse applications in the building industry. Geopolymers are produced from the alkali activation of an aluminosilicate source, for e.g. fly ash, metakaolin etc. These binders have similar chemical composition as the natural zeolitic materials but without the extensive crystalline zeolitic structure [1, 2]. It is formed by the polymerization of individual aluminate and silicate species, which are dissolved from their original sources at high pH in the presence of alkali sources and the products exhibit high mechanical strengths having the following general chemical formula.

$$\text{Mn} \left[ - \text{(Si - O}\_2\text{)z - Al - O} \right] \text{nwH}\_2\text{O} \tag{1}$$

where M is the alkaline element, which indicates the presence of a bond, z is 1, 2 or 3 and n is degree of polymerization. Theoretically, any alkali and alkali earth cation (Ca, Mg) can be used as a replacement of the alkaline element (M) in the reaction, However the majority of research has focused on the effect of sodium (Na+) and potassium (K+) ions [3], disregarding effect of alkaline earth cations (Ca, Mg). There have been many studies investigating the role of the Si/Al ratio, and how it relates to the mechanical properties of geopolymer. Theoretically, there should be a direct correlation with mechanical strength and silica content because increasing the amount of silica increases the amount of Si▬O▬Si bonds, which are stronger than Si▬O▬Al and Al▬O▬Al bonds [2]. However, it was found for metakaolin geopolymers with a Si/Al ratio lower than 1.40, the composites had a very porous matrix, which led to lower compressive strength. But when the Si/Al ratio was increased over 1.65 the composites showed an increase in strength. This increase was attributed to a homogenous microstructure in the geopolymer. Also in metakaolin based geopolymers it was found that the optimum strength was at an intermediate Si/Al ratio [4]. The reduction in strength for high Si/Al ratio mixes was the result of unreacted material, which was soft and acted as a defect in the binder phase [5].

Past research has also shown that the addition of calcium into metakaolin geopolymers has beneficial results for mechanical properties. But the role that calcium plays during the geopolymer reaction period has yet to be elucidated. It has been observed that both geopolymer gel and calcium silicate hydrate form during the reaction process [6, 7]. For metakaolin geopolymers, it appears that the alkali hydroxide concentration plays a vital role in determining if C▬S▬H forms in the geopolymer. At low alkali hydroxide concentration, the reaction product favors the formation of C▬S▬H, while at higher concentration (above 10 M) the reaction favors the formation of the geopolymer gel. This difference is due to the fact that the high hydroxyl concentration hinders the Ca2+ dissolution forcing the dissolved silicates and aluminum species to form geopolymer gel. On the other hand, when the OH<sup>−</sup> concentration is low, the amount of Ca2+ dissolving increases and causes more C▬S▬H to form. Addition of calcium has been observed to accelerate the hardening process and increase the strength for fly ash based geopolymers. It was also observed that addition of calcium increases strength for geopolymers cured at ambient conditions, while it reduces mechanical properties of geopolymer cured at elevated temperatures, because the presence of calcium hinders the development of the three-dimensional network structure in the geopolymer gel. However, other research indicates that the presence of both C▬S▬H and geopolymer gel in a geopolymer could have beneficial effects on strength because the C▬S▬H phase act like micro-aggregates for the geopolymer gel and

**57**

blocks in construction activity [14].

*Utilization of Iron Ore Mines Waste as Civil Construction Material through Geopolymer Reactions*

forms a denser and more uniform binder. More research needs to be conducted to understand the effects of composition and nanostructure on mechanical properties of both the geopolymer gel and the C▬S▬H phases in the geopolymer. There is a lack of documented research involving geopolymeric reaction mechanisms occurring in natural systems like ore minerals consisting of calcium and alkaline minerals and in such systems it is probable that both C▬S▬H gel and geopolymeric reactions could be forming simultaneously. As a result, an investigation into the role of calcium in dictating the chemical mechanism will provide answers to the fundamental question as to whether two separate phases will be formed, or a new

In past, industrial wastes have been utilized in manufacturing of bricks. For instance, manufacturing of bricks using waste foundry sand at industrial scale has shown promising results [8]. Similarly, IOT can be a very favorable material for manufacturing of bricks at industrial scale. The suitability of IOT as a partial replacement of sand in mortar for masonry was studied. It was found that up to 20% IOT can be replaced for sand with desired compressive strength [9]. Masonry units made of IOT in compressed earth block as a replacement for natural sand at 25, 50 and 100% rates were evaluated [10]. Optimum mix proportion of soil, sand and cement was utilized for manufacturing of stabilized mud blocks. It was found that the water absorption increased with the increase in IOT content, but was within permissible limits. It is also reported that when 7% of cement is used, the wet compressive strength is 7 MPa. The experimental results showed that the significant amount of sand can be replaced by IOT without compromising the strength parameters [10]. Lamani S R et al. [11] investigated the utility of iron ore waste (IOW) in preparing non-fired bricks by using cement and fly ash. Bricks were prepared with different proportions of cement, fly ash, and IOW. The manufactured bricks were cured for 7, 14, 21, and 28d. Compressive strength and water absorption of bricks were evaluated. The results of the study reveals that mixture with 70% IOW, 15% cement and 15% fly ash shows the minimum required compressive strength and water absorption properties of bricks for a minimum curing period of 7d. The potential of IOT in sandcrete block was evaluated [12]. Maximum IOT used was 30%, which was replaced for sand in the production of sandcrete blocks. Accordingly the study reported increase in compressive strength with increased IOT replacements from 0 to 30%, and curing period from 7 to 28d. In another study the sustainability of IOT as a replacement to fine aggregate in mortar for masonry work was studied. It was found that the strength attained was approximately 37 MPa for the optimum combination of IOT and river sand. In selfcompacting concrete the replacement of fine aggregate with IOT up to 40% and red mud by cement up to 4% was evaluated [13]. Accordingly the maximum compressive strength was achieved for 30% IOT mixtures [13]. Nagaraj and Shreyasvi [14], made an explorative study to prepare compressed stabilized earth blocks utilizing various proportions of mine spoil waste (MSW), quarry dust as aggregates, cement, and lime as stabilizers. In their study the researchers used 30–50% waste along with cement and lime. Cement varied in proportions of 6 and 8% with 2% lime. Blocks of 230 × 110 × 75 mm were prepared using Mardini press. The wet compressive strength and water absorption was evaluated for various curing periods of 7, 15, 30, 60 and 1800d. They concluded that wet compressive strength, water absorption and flexure strength of the blocks are meeting the requirements of Indian standards; accordingly they suggested that these blocks can be effectively used as eco-friendly

In the present work, research is conducted with the addition of GGBS and lime (commercial grade) in IOT system with fixed amount of sodium silicate.

*DOI: http://dx.doi.org/10.5772/intechopen.81709*

material will be produced.

#### *Utilization of Iron Ore Mines Waste as Civil Construction Material through Geopolymer Reactions DOI: http://dx.doi.org/10.5772/intechopen.81709*

forms a denser and more uniform binder. More research needs to be conducted to understand the effects of composition and nanostructure on mechanical properties of both the geopolymer gel and the C▬S▬H phases in the geopolymer. There is a lack of documented research involving geopolymeric reaction mechanisms occurring in natural systems like ore minerals consisting of calcium and alkaline minerals and in such systems it is probable that both C▬S▬H gel and geopolymeric reactions could be forming simultaneously. As a result, an investigation into the role of calcium in dictating the chemical mechanism will provide answers to the fundamental question as to whether two separate phases will be formed, or a new material will be produced.

In past, industrial wastes have been utilized in manufacturing of bricks. For instance, manufacturing of bricks using waste foundry sand at industrial scale has shown promising results [8]. Similarly, IOT can be a very favorable material for manufacturing of bricks at industrial scale. The suitability of IOT as a partial replacement of sand in mortar for masonry was studied. It was found that up to 20% IOT can be replaced for sand with desired compressive strength [9]. Masonry units made of IOT in compressed earth block as a replacement for natural sand at 25, 50 and 100% rates were evaluated [10]. Optimum mix proportion of soil, sand and cement was utilized for manufacturing of stabilized mud blocks. It was found that the water absorption increased with the increase in IOT content, but was within permissible limits. It is also reported that when 7% of cement is used, the wet compressive strength is 7 MPa. The experimental results showed that the significant amount of sand can be replaced by IOT without compromising the strength parameters [10]. Lamani S R et al. [11] investigated the utility of iron ore waste (IOW) in preparing non-fired bricks by using cement and fly ash. Bricks were prepared with different proportions of cement, fly ash, and IOW. The manufactured bricks were cured for 7, 14, 21, and 28d. Compressive strength and water absorption of bricks were evaluated. The results of the study reveals that mixture with 70% IOW, 15% cement and 15% fly ash shows the minimum required compressive strength and water absorption properties of bricks for a minimum curing period of 7d. The potential of IOT in sandcrete block was evaluated [12]. Maximum IOT used was 30%, which was replaced for sand in the production of sandcrete blocks. Accordingly the study reported increase in compressive strength with increased IOT replacements from 0 to 30%, and curing period from 7 to 28d. In another study the sustainability of IOT as a replacement to fine aggregate in mortar for masonry work was studied. It was found that the strength attained was approximately 37 MPa for the optimum combination of IOT and river sand. In selfcompacting concrete the replacement of fine aggregate with IOT up to 40% and red mud by cement up to 4% was evaluated [13]. Accordingly the maximum compressive strength was achieved for 30% IOT mixtures [13]. Nagaraj and Shreyasvi [14], made an explorative study to prepare compressed stabilized earth blocks utilizing various proportions of mine spoil waste (MSW), quarry dust as aggregates, cement, and lime as stabilizers. In their study the researchers used 30–50% waste along with cement and lime. Cement varied in proportions of 6 and 8% with 2% lime. Blocks of 230 × 110 × 75 mm were prepared using Mardini press. The wet compressive strength and water absorption was evaluated for various curing periods of 7, 15, 30, 60 and 1800d. They concluded that wet compressive strength, water absorption and flexure strength of the blocks are meeting the requirements of Indian standards; accordingly they suggested that these blocks can be effectively used as eco-friendly blocks in construction activity [14].

In the present work, research is conducted with the addition of GGBS and lime (commercial grade) in IOT system with fixed amount of sodium silicate.

*Geopolymers and Other Geosynthetics*

that the durability of ancient concrete was the result of the presence of alkaline aluminosilicates in the structure. Davidovits named this new class of cementitious material as geopolymers. This is a new generation material with diverse applications in the building industry. Geopolymers are produced from the alkali activation of an aluminosilicate source, for e.g. fly ash, metakaolin etc. These binders have similar chemical composition as the natural zeolitic materials but without the extensive crystalline zeolitic structure [1, 2]. It is formed by the polymerization of individual aluminate and silicate species, which are dissolved from their original sources at high pH in the presence of alkali sources and the products exhibit high mechanical

Mn[−(Si − O2)z − Al − O]n.wH2O (1)

where M is the alkaline element, which indicates the presence of a bond, z is 1, 2 or 3 and n is degree of polymerization. Theoretically, any alkali and alkali earth cation (Ca, Mg) can be used as a replacement of the alkaline element (M) in the reaction, However the majority of research has focused on the effect of sodium (Na+) and potassium (K+) ions [3], disregarding effect of alkaline earth cations (Ca, Mg). There have been many studies investigating the role of the Si/Al ratio, and how it relates to the mechanical properties of geopolymer. Theoretically, there should be a direct correlation with mechanical strength and silica content because increasing the amount of silica increases the amount of Si▬O▬Si bonds, which are stronger than Si▬O▬Al and Al▬O▬Al bonds [2]. However, it was found for metakaolin geopolymers with a Si/Al ratio lower than 1.40, the composites had a very porous matrix, which led to lower compressive strength. But when the Si/Al ratio was increased over 1.65 the composites showed an increase in strength. This increase was attributed to a homogenous microstructure in the geopolymer. Also in metakaolin based geopolymers it was found that the optimum strength was at an intermediate Si/Al ratio [4]. The reduction in strength for high Si/Al ratio mixes was the result of unreacted material, which was soft and acted as a defect in the

Past research has also shown that the addition of calcium into metakaolin geopolymers has beneficial results for mechanical properties. But the role that calcium plays during the geopolymer reaction period has yet to be elucidated. It has been observed that both geopolymer gel and calcium silicate hydrate form during the reaction process [6, 7]. For metakaolin geopolymers, it appears that the alkali hydroxide concentration plays a vital role in determining if C▬S▬H forms in the geopolymer. At low alkali hydroxide concentration, the reaction product favors the formation of C▬S▬H, while at higher concentration (above 10 M) the reaction favors the formation of the geopolymer gel. This difference is due to the fact that the high hydroxyl concentration hinders the Ca2+ dissolution forcing the dissolved silicates and aluminum species to form geopolymer gel. On the other hand, when the OH<sup>−</sup> concentration is low, the amount of Ca2+ dissolving increases and causes more C▬S▬H to form. Addition of calcium has been observed to accelerate the hardening process and increase the strength for fly ash based geopolymers. It was also observed that addition of calcium increases strength for geopolymers cured at ambient conditions, while it reduces mechanical properties of geopolymer cured at elevated temperatures, because the presence of calcium hinders the development of the three-dimensional network structure in the geopolymer gel. However, other research indicates that the presence of both C▬S▬H and geopolymer gel in a geopolymer could have beneficial effects on strength because the C▬S▬H phase act like micro-aggregates for the geopolymer gel and

strengths having the following general chemical formula.

**56**

binder phase [5].

It is envisaged, that this will lead to a number of reaction products and the type and number of these products will be dependent on the experimental conditions and, more importantly, depending on the form of calcium present. It is anticipated that likely products to be formed will be calcium silicate hydrate and aluminum silicate geopolymers. Also the isomorphs nature of iron in combination with aluminum will most probably produce alkali (Al + Fe) geopolymers. It will be interesting to find the application of this waste as regards to its mechanical strength as construction material through calculation of Si/Al, Si/(Al + Fe), Ca/Si ratios. As regards to industrial application the present research explores the possibility of utilizing IOT for the production of eco-friendly bricks. These bricks are produced in Mardini block making machine. The formed bricks are kept in room temperature for extended time periods after which different properties are determined.
