Drying Shrinkage and Permeability of Geopolymer Lightweight Aggregate Concrete

*Ibtesam F. Nasser, Wasan I. Khalil and Waleed A. Abbas* 

#### **Abstract**

 Geopolymer lightweight aggregate concrete (GPLWAC) has many benefits. Many researches have been carried on solutions for the sources of construction materials by using geopolymer technology. This paper presents information on fly ash-based geopolymer concrete using artificial lightweight aggregates, and it describes the experimental investigation on drying shrinkage and permeability of GPALWAC with artificial lightweight coarse aggregate and natural fine aggregate (reference mix), as well as four GPALWAC mixes with different volumetric replacement to natural normal weight fine aggregate (sand) (25, 50, 75, and 100%) by artificial lightweight fine aggregate, and also two GPALWAC mixes reinforced with 0.25% and 0.5% steel fiber were investigated. The results show that the all heat-cured GPALWAC mixes undergo very low drying shrinkage. The drying shrinkage values for various types of GPALWAC are increased by the partial and total replacement of natural sand by increased artificial fine aggregate. On the contrary the partial and total replacements of natural sand by artificial fine aggregate show increase in water penetration.

**Keywords:** geopolymer concrete, artificial lightweight aggregate, drying shrinkage, permeability, geopolymer lightweight aggregate concrete (GPLWAC)

#### **1. Introduction**

 The environment matters pertaining to the process of ordinary Portland cement (OPC) are common. Carbon dioxide emitted through the manufacturing of OPC is 1 ton to each OPC ton being produced. The availability of fly ash as a by-product of burning coal worldwide creates a big problem; such amounts of fly ash needs to be utilized, as partial or total replacement for OPC. Fly ash in itself has no binding properties, within the presence of water, and in ambient temperature, fly ash reacts with the calcium hydroxide during the hydration procedure of OPC to shape the calcium–silicate–hydrate (C–S–H) gel. The improvement use of high-volume fly ash, which empowered the substitution of OPC up to 60–65% by mass [1], had been considered as a big step in this attempt. Davidovits explained the polymerization process as a significantly rapid chemical response in extremely alkaline condition on Si–Al mineral deposits, causing a triple dimension polymeric sequence as well as ring construction having Si–O–Al–O chains [2]. The proposed technique consists of the process of dissoluting Si in addition to Al atoms from the source materials by the action of hydroxide ions, orienting precursor ions into monomers, and then setting them into polymeric structure [2].

Many researches showed that the geopolymer is created via a reaction of the alkaline solution with sodium plus alumina in addtion to fly ash, getting a binder material which shows excellent mechanical properties and durability in aggressive environments [3, 4]. When fly ash are alkali activated, a chemical procedure started to permit to allow the user to transform glassy structures partially or totally amorphous into very compact well-cemented composites [5].

 Fly ash is appropriate to be utilized as a geopolymer original substance since this powder is comprised for the most part of polished, empty, and circular particles [6]. Fly ash geopolymer concrete has been utilized broadly, due to its features, lower creep [7], lower shrinking [8], better flame and acid resistance [9], and protection from sulfate assault [10], which have been superior properties to these of typical concrete. Lightweight concrete is in demand these days, which can be produced in several ways: injection of air or neglecting the finer size of the aggregate or substituting these by pore ones. Most standards mention that the density of light concrete could be ranged as 300–1800 kg/m3 [11], while the density of typical concrete can be about 2400 kg/m3 .

Light aggregate concrete is comprised of light aggregate (extended shale, mud, or slate substance that has been burnt in a rotational furnace to grow a pored construction) which could be utilized as a substitution for normal aggregate, for example, pounded stone or sand [11]. In our study we produce geopolymer artificial lightweight aggregate concrete (GPALWAC) for the first time in Iraq [12], using local artificial lightweight aggregate [13]. Yet, the purpose of this research is to study some additional properties.

#### **2. Experimental work**

The aim of this study is to investigate the drying shrinkage and permeability of GPALWAC, as these properties have not been taken much care of in researches that deal with geopolymer lightweight aggregate concrete.

#### **2.1 Materials**

The substances utilized to make GPALWAC are fly powder type F (low-calcium), artificial local course lightweight aggregate, naturalistic typical weight fine aggregates (sand), alkaline solution, steel fiber, and water. The fly ash utilized was imported from Turkey as by-product of coal combustion from ISKENment-Turkey power station during production of electricity. The tests show that the fly ash fulfills the demands of ASTM C 618 [14], as shown in **Table 1** and **Figure 1**.

Sodium silicate (Na2SiO3) in addition to sodium hydroxide (NaOH) sols that make the alkali-activated solution and sodium silicate solution chemical composition and properties were shown in **Table 2**.

 Sodium hydroxides are, as flakes (NaOH with 98% virtue), produced in Iraq. The sol was readied, a day before blending so as to be cooled; later it was blended with sodium silicate sol in a weight extent of 1, 2.5 sodium hydroxide, sodium silicate, and it was blended with the fly powder. Al-Ekhaider characteristic ordinary sand with greatest volume of 4.75 mm had been utilized


**Table 1.**  *Chemical analysis of fly ash.*  *Drying Shrinkage and Permeability of Geopolymer Lightweight Aggregate Concrete DOI: http://dx.doi.org/10.5772/intechopen.87836* 

#### **Figure 1.**

*Fly ash: ALWCA used in GPALWAC.* 


#### **Table 2.**

*Chemical composition and properties of sodium silicate.* 

 as fine aggregate; its physical characteristics meet the demands of the Iraqi Specification No. 45/1984. Its degree is in zone (2). Synthetic light aggregates, which are created by bentonite mud and water glass (sodium silicate) [13, 15], had been utilized as coarse with most extreme volume of 19 mm and fine aggregates as an incomplete substitution by volume of the normal sand in some mixes made in the research as shown in **Figure 1**. **Table 3** shows the properties of artificial lightweight fine aggregate (ALWFa), and artificial lightweight coarse aggregate (ALWC) that is used in this investigation was prepared as the requirements of ASTM C330-03 [16].

High-malleable steel snare-end fibers had been used, having length and distance across of 30 mm and 0.5 mm individually and proportion (l/d) of 60 with modulus of elasticity (E) of 210 GPa as indicated by the maker organization (BASF) as appeared in **Figure 2**. A high water-reducing admixture DARACEM 19CFMQ had been utilized in the current investigation with 1.9% by weight of binder.


#### **Table 3.**

*The properties of artificial coarse and fine aggregate (material test is carried out by constructing labs and research center).* 

**Figure 2.**  *Steel fiber used in GPALWAC.* 

#### **2.2 Mixing, casting, and curing of geopolymer lightweight concrete**

 The production of GPALWAC was described briefly in previous researches [21, 22], after casting in molds. Samples are left in ambient conditions for a period of 24 hours; after that the samples had been demolded and restored in a broiler for 48 hours at 90°C. These samples had been removed and left at surrounding condition with a normal temperature of 28°C until the testing period. **Figure 3** shows the steps of preparing the GPALWAC.

 GPALWAC reference mix (MR) was carried out after many trial mixes [21]. Four mixes were produced using (25, 50, 75, and 100%) contents of artificial fine lightweight aggregates as a volumetric substitution to naturalistic ordinary weight fine aggregates. Two percentages of steel fiber (0.25, 0.5) were added to the (MR) mix to enhance the mechanical properties. The details of mixes are shown in **Table 4**. The specimen notation listed in **Table 4** refers to the volume content of lightweight fine artificial aggregate and steel fiber content.

It should note that:


**Figure 3.**  *Production of geopolymer lightweight artificial aggregate concrete.* 

*Drying Shrinkage and Permeability of Geopolymer Lightweight Aggregate Concrete DOI: http://dx.doi.org/10.5772/intechopen.87836* 


#### **Table 4.**

*Details of GPALWAC mixes.* 

• The GPALWAC mixes have a mixing ratio of 1:1.1:1.5 (fly ash/ALWCa/ sand) by weight, alkali activator ratio to fly ash = 0.4, and molarity of alkali activator = 16.

#### **2.3 Experimental tests**

**Table 5** shows the experimental tests, their standard specifications, their specimen dimension, and their ages that have been carried out in this research on the GPALWAC as in **Figures 4** and **5**:


#### **Table 5.**  *Tests of GPALWAC.*

**Figure 4.**  *Drying shrinkage of GPALWAC.* 

**Figure 5.**  *Permeability test for GPALWAC.* 

### **3. Results and discussion**

#### **3.1 Properties of fresh GPALWAC**

 Fly ash geopolymer lightweight aggregate concrete made in the current work shows excellent feasibility having slump amount of 245 mm plus density of 1951 kg/ m3 for the reference mixture (MR). On the contrary, GPALWAC mixtures that include ALWFa experience a loose in workability state. Such behavior can be attributed to various specified gravity of the ALWFa relative to natural sand. The added steel fiber causes an increase in density of GPALWAC mixtures in comparison with the plain GPALWAC mixture. This can be attributed to the large specified gravity of steel fiber as shown in **Figure 6**.

#### **3.2 Properties of hardened GPALWAC**

#### *3.2.1 Oven-dry density*

The reference GPALWAC (MR) produced in this investigation satisfied the requirements of lightweight concrete [16] . Due to the low density of the ALWFa, furnace-dried density of GPALWAC having various contents of this aggregate shows a slight decrease, but 100% substance shows a great reduction of about 10.6%

**Figure 6.** 

*Fresh density, oven-dry density, and slump of GPALWAC.* 

relative to the reference mix, while the density of GPALWAC mixes containing steel fiber (0.5%) is higher than that for reference mix of about 4.63% due to the high specific gravity of steel fiber.

#### *3.2.2 Compressive strength*

As ordinary concrete, the compressive strength increments when the age increments in GPALWAC. The rates of increment are in the scope of 6.3–12.6 and 12.2–19.1% at the age of 28 and 56 days separately, with respect to the age of 7 days. This is because of the constant geopolymerization process.

 The quick geopolymerization procedure under heat cure makes early strength improvement at the age of 7 days in the range of 86–94% of that at the age of 28 days for all geopolymer concrete that has or has no fiber. The compressive strength outcomes of 28-day age show that the reference GPALWAC (MR) obtained strength of 35.8 MPa which means, based on ACI 213R-14 [29], a structural lightweight concrete. **Figure 7** shows opposite outcomes in the compressive strength of GPALWAC, as the increase in the percentage content of ALWFa causes a decrease in the compressive strength of GPALWAC (the variety in relation to reference mixture at the age of 28 days ranging from −8.93 to −19.74%) because the ALWFa had low strength relative to natural sand. Using steel fibers led to slight increment in the compressive force which belongs to GPALWAC (the variety in relation to reference mixture at the age of 28 days ranged from +0.86 to +4.46%), as the steel fibers had large stiffness and big surface area, which improves the bond-resisting ability, besides restricting the crack propagation as in **Figure 7**.

#### *3.2.3 Drying shrinkage*

 This shrinking can be defined as the middling variation in length of the sample per unit length because of the lost in free water under ordinary condition. A huge amount of drying shrinkage took place at an early age because of speedy dampness lost out of the sample surface due to heating as shown during the test of specimens, whereas the final result of heat-cured fly ash GPALWAC suffers very low drying shrinkage. **Table 6** outlines the drying shrinkage value which exhibits a lower amount than ordinary cement. This is because of the heating curing that limits the moisture in the pores; this is concurred with different scholars [30, 31]. Test outcomes demonstrate that the drying shrinkage strain of steel fiber mixes was equivalent to the reference GPALWAC. This implies that the impact of fiber in restricting the free drying shrinkage strain was observed to be immaterial.

**Figure 7.**  *Compressive strength of GPALWAC.* 


#### **Table 6.**

*Drying shrinkage of GPALWAC.* 

The drying shrinkage of GPALWAC against age is shown in **Table 6**. The incomplete and complete substitutions of normal sand by ALWFa increased the drying shrinkage amounts for GPALWAC. The amount of increment in drying shrinkage at the age of 180 days was 15% for MF100 concrete samples, compared with MR mixture. Such result can be credited to the lower modulus of elasticity of fine artificial aggregates than normal sand which influences the limitation to shrinking. In addition, the increase of artificial fine aggregates increased the water needed to have reasonable workability, and thus this would prompt more shrinking strains.

#### *3.2.4 Permeability*

 The test had been conducted by examining the depth of penetration of water under pressure, and the samples are then broken to measure the deepness of the waterfront. The water might be connected to the outside of the test sample from either the base or the head [28]. The consequences of porousness testing of all GPALWAC can be seen in **Figure 8**.

 The specimens of GPALWAC containing ALWFa as a substitution for natural fine aggregates illustrate more water penetration than MR mix. The proportions of increasing water penetration are 25.0, 32.3, 61.7, and 64.7% for samples with 25–100% ALWFa, respectively, relative to reference GPALWAC specimens.

**Figure 8.**  *Penetration depth of GPALWAC.* 

*Drying Shrinkage and Permeability of Geopolymer Lightweight Aggregate Concrete DOI: http://dx.doi.org/10.5772/intechopen.87836* 

### **4. Conclusions**


#### **Author details**

Ibtesam F. Nasser1 \*, Wasan I. Khalil2 and Waleed A. Abbas2

 1 Institute of Technology, Middle Technical University, Baghdad, Iraq

2 Civil Engineering Department, University of Technology, Baghdad, Iraq

\*Address all correspondence to: ibtesamhabbaba@yahoo.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Drying Shrinkage and Permeability of Geopolymer Lightweight Aggregate Concrete DOI: http://dx.doi.org/10.5772/intechopen.87836* 

#### **References**

[1] Hardjito D, Wallah SE, Rangan BV. Research into engineering properties of geopolymer concrete. In: Lukey GC, editor. Geopolymers. 2002 International Conference, Siloxo, Melbourne, Australia. 2002

[2] Davidovits J. Chemistry of geopolymeric systems terminology. In: Proceedings of Geopolymer International Conference; France. 1999

[3] Davidovits J. High-Alkali Cements for 21st Century Concretes. Special Publication. 1994;**144**

[4] Sofi M, van Deventer JSJ, Mendis PA, Lukey GC. Engineering properties of inorganic polymer concretes. Cement and Concrete Research. 2007;**37**(2):251-257

 [5] Palomo A, Grutzeck MW, Blanco MT. Alkali-activated fly ashes. A cement for the future. Cement and Concrete Research. 1999;**29**(8):1323-1329

[6] Kumar S, Kumar R, Alex TC, Bandyopadhyay A, Mehrotra SP. Effect of mechanically activated fly ash on the properties of geopolymer cement. In: Proceedings of the 4th World Congress on Geopolymer, Saint-Quentin, France. 2005. pp. 113-116

[7] SE W. Creep behaviour of fly ash-based geopolymer concrete. Civil Engineering Dimension. 2010;**12**:73-78

[8] Hardjito DW, Wallah SE, Sumajouw DMJ, Rangan BV. On the development of fly ash based geopolymer concrete. ACI Materials Journal. 2004;**101**:467-472

[9] Guo X, Shi H, Dick WA. Compressive strength and microstructural characteristic of class C fly ash geopolymer. Cement and Concrete Composites. 2010;**32**:142-147

[10] Wallah SE, Hardjito DW, Sumajouw DMJ, Rangan BV. Sulfate and acid resistance of fly ash-based geopolymer concrete. In: Proceedings of the Australian Structural Engineering Conference; Newcastle, Australia. 2005

[11] National Ready Mixed Concrete Association (NRMCA). Structural Lightweight Concrete. Silver Spring MD, USA: NRMCA; 2003

[12] Khalil WI, Abbas WAA, Nasser IF. Geopolymer Lightweight Aggregate Concrete, patent. Iraq; 2018

[13] Khalil WI, Ahmed HK, Hussein ZM. Properties of artificial and sustainable lightweight aggregate. 17th International Conference Berlin, Germany. Vol. 17, No. 9. 2015

[14] C618 A. Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete American Society for Testing and Materials. 2008

[15] Khalil WI, Ahmed HK, Hussein ZM. Inventor Properties of Artificial and Sustainable Lightweight Aggregate. Iraq; 2015

[16] C330-03 A. Standard Specification for Lightweight Aggregates for Structural Concrete Annual Book of ASTM Standards Concrete and Aggregates, United States. Vol. 04-02. 2003

[17] ASTM C127 Standard Test Method for Density Relative Density (Specific Gravity) and Adsorption of Coarse Aggregate. Annual Book of ASTM Standards. Vol. 04, No. 02. 2004. pp. 68-73

[18] ASTM C29/C29M Standard Test Method for Bulk Density (Unit Weight) and Voids in Aggregate American Society for Testing and Materials.

Annual Book of ASTM Standards. Vol. 04.02. 2004. pp. 1-4

[19] BS 812. Part 110 Method for Determination of Aggregate Crushing Value (ACV). British Standards Institution; 1990. p. 8

[20] BS 3797. Specification for Lightweight Aggregates for Masonry Units and Structural Concrete. British Standards Institution. Manchester, United Kingdom: AZO build; 1990. p. 2

[21] Khalil WI, Abbas WAA, Nasser IF. Production of Lightweight Geopolymer Concrete Using Artificial Local Lightweight Aggregate 3rd International Conference; Sharem Alshakh-Eyjpt. 2017

[22] Nasser IF. Some Properties of Geopolymer Lightweight Aggregate Concrete [PhD thesis]. Baghdad, Iraq: University of Technology; 2018

[23] ASTM C143 Standard Test Method for Slump-Cement International. Annual Book of ASTM Standards: American Society for Testing and Materials. Vol. 04-02, United States; 2004

[24] ASTM C138 Standard Test Method for Density (Unit Weight), Yield, and Air Content (Gravimetric) of Concrete. Annual Book of Standards. Vol. 0402. American Society for Testing and Materials; 2015

[25] ASTM C642-97 Standard Test Method of Specific Gravity, Absorption and Voids in Hardened Concrete. Annual Book of ASTM Standards. Vol. 04-02. 1997

[26] BS 1881-Part 116. Method for Determination of Compressive Strength of Concrete Cubes. British Standards Institution; 1989

[27] ASTM C490. Standard Practice for Use of Apparatus for the Determination of Length Change of Hardened Cement Paste, Mortar and Concrete. Annual Book of ASTM Standards. Vol. 04.02. 2009. pp. 266-270

[28] BS EN 12390-8:2009. Part 8: Depth of Penetration of Water Under Pressure. British Standards Institution; 1881

[29] ACI 213R-03. Guide for Structural Lightweight Aggregate Concrete ACI Manual of Concrete Practice, Part 1: Materials and General Properties of Concrete. 2004

[30] Wallah SE. Drying shrinkage of heat-cured fly ash-based geopolymer concrete. Modern Applied Science. 2009;**3**(12):14

[31] Rangan BV. Fly Ash-Based Geopolymer Concrete Proceedings of the International Workshop on Geopolymer Cement and Concrete. Mumbai, India: Allied Publishers Private Limited; 2010

#### **Chapter 28**

### Microstructure Properties of Sulfate-Effected Blast Furnace Slag Reinforced Restoration Mortars

*Rüya Kılıç Demircan and Gökhan Kaplan* 

#### **Abstract**

 In this study, the sulfate resistance was investigated in lime mortars, which are used in restoration works, by adding artificial pozzolana and fiber. Instead of lime, ground granulated blast furnace slag (GGBFS) was used at the rate of 25, 50, and 75%. Moreover, basalt fiber (BF) was also added to the mortars at the rate of 0.5 and 1% according to their binder contents. It was determined that the most appropriate BFS ratio was 50% for the non-fiber mortar production. When fiber was added to the mixtures, the compressive strength of the mortars decreased. As per the sulfate resistance, an increase in the BF rate could cause an increase in the expansion of the mortars. As was in the compressive strength, a 50% BFS content increased the sulfate resistance. It was determined in the microstructure analyses that ettringite structures were generally observed in the mortar contents. It was determined that chemical and mineralogical properties should also be considered while choosing the material to be used in repair works of historical structures.

**Keywords:** blast furnace slag, basalt fiber, cultural sustainability, restoration, durability

#### **1. Introduction**

Historical structures are important fingerprints reflecting the society of their time in the history or the culture of this society. Protection of this culture and handing it down to the next generations are among the most important responsibilities of countries. Historical structures are damaged due to reasons emerging from environment-climate, human beings, and time. Some parts of these structures are destroyed due to the damage sustained, and some other parts need repairs. This repair should be appropriate to the historic fabric of the structure and its genuine condition should be protected. The applied repairs and reinforcements should physically and chemically comply with the structure, without affecting its stability.

 From past to present, numerous research studies have been conducted about the mortars used in the repair of historical structures. Studies are intensely conducted in a quest for finding the mortar with the quality suitable for the lime mortar, which had been used as a binder before the cement was not discovered. With the

development of technology, it is now possible to simply detect the physical, chemical, mineralogical, and microstructure characteristics of the mortar of the time. Under the light of these pieces of information, mortars are produced in compliance with the structure.

In our world, where the nonrenewable energy resources are rapidly running out, sustainability has gained an important place and due consideration is given to the conscience about the use of sustainable material in the construction sector. Considered as a sustainable material, the blast furnace slag, which is also known as the artificial pozzolana, has been used in many fields of the construction sector as well as in the contents of the repair mortars. Some research studies on this issue in the literature can be summarized as follows.

Altun et al. [1] produced mortars with hydraulic lime using polypropylene fiber and examined some properties of the mortars such as compressive-flexion strength, water absorption capacity, and drying shrinkage. They prepared three different sets of mortar mixtures as fibrous and non-fibrous including hydraulic lime as the binder and limestone aggregate as the aggregate. In order to increase the strength and decrease the drying shrinkage, they added polypropylene fiber as much as 0.5 and 1.0% of the total volume to the mortar mixtures. They determined the compressive-flexion strength values of the mortar mixtures at the 1st, 3rd, 7th, and 28th days, and the water absorption and drying shrinkage values at the 28th day. According to the results, it was determined that there was not a significant improvement in strength, water absorption, and shrinkage values.

Aktürk et al. [2] produced two kinds of mortars to be used as plaster and activated with sodium hydroxide and sodium silicate, not-including cement, and based on blast furnace slag and hydraulic lime. Certain mechanical properties of the mortars were determined such as flexion-compressive-adhesional strength, as well as other characteristics such as sulfate effect and freeze-thaw stability. The performances of the plasters, which were produced from materials activated with alkalies, were compared with lime-based plasters, thus, their usability in historical structures was evaluated. Considering the strength and durability characteristics of the mortar, which was blast-furnace-slag-based and activated with sodium hydroxide, they reported that it could be a second alternative to be used in the plaster and repair of historical structures.

Tesch and Middendorf [3] developed gypsum-based lime mortar resistant to the adverse weather conditions to be used in the restoration works of historical structures. They observed the formation of thaumasite due to hydraulic and carbonate components. They prepared mixtures with different amounts of hydraulic components. At the end of the 90-day curing period, the mortars were investigated through physical, mechanical, and chemical-mineralogical techniques. As the conclusion, it was reported that the cause of thaumasite formation and expansion was the raw material components of the lime, the thaumasite formation was at a low level and it did not influence the mechanical properties. Böke and Akkurt [4] took a sample of lime mortar-brick from a historical Ottoman Turkish-Bath. While the first type of plaster was original and structurally sturdy, the second type of plaster taken from the same place was deteriorated. The motive behind this difference was investigated through comparison of the pozzolanic activity and raw material composition. As a result, ettringite crystals were determined in the XRD, SEM-EDS, and FT-IR analyses. An expansion occurred due to the enlargement of the ettringite crystals of the repair plaster mortar, and it was reported to cause the mortar to lose its original status.

Makhloufi et al. [5] examined the magnesium sulfate resistance of lime mortars containing limestone filling material, blast furnace slag, and natural pozzolana.

*Microstructure Properties of Sulfate-Effected Blast Furnace Slag Reinforced Restoration Mortars DOI: http://dx.doi.org/10.5772/intechopen.87836* 

 Certain properties of the samples such as weight and height change, and compressive strength values were measured at the 30th, 60th, 90th, 120th, and 160th days and they were evaluated. The X-ray method was used in order to determine different mineral phases.

Borges et al. [6] took samples of lime mortars under the sea water influence from two historically important castles on the shore of Portugal-Lisbon region and conducted analyses on them. Physico-chemical and micro-structural characterization techniques, optic and SEM images, XRD analysis, DTA-TG analysis, chemical analysis, mercuric porosimeter, and water absorption experiments were conducted to determine the properties of the mortars. Gökdemir et al. [7] examined materials properties of Kastamonu Castle's and made suggestions for restorations. They determined SEM-EDS properties of samples, and according to their result, they made suggestions about lime mortar.

In this study, restoration mortars were prepared that were produced from blast furnace slag, among the artificial pozzolanas, which have recently started to be used as a sustainable construction material, replacing lime. In preparation of the restoration mortars, blast furnace slag and basalt fiber were used in different ratios and certain properties were examined such as physical, mechanic, sulfate resistance, and dimensional stability. Dimensional changes and microstructural analyses of the samples in 365 days were explained through the SEM images.

#### **2. Material and methods**

#### **2.1 Materials**

In the production of the mortars, aggregate, lime, blast furnace slag (as the artificial pozzolana), water, and basalt fiber were used. Sub-chemical and physical properties of the materials are explained below.

#### *2.1.1 Lime*

 CL 70-S class, slacked calcium lime, which complies with the TS EN 459-1 standard, was used as the binder material in the preparation of the mortars. Chemical and physical properties about the slacked calcium lime are explained in **Table 1**.

#### *2.1.2 Blast furnace slag (BFS)*

 In the preparation of the mortars, the granulated blast furnace slag was used, which was the waste of the Edremit Iron and Steel Plant and which was granulated until 4400 cm<sup>2</sup> /gr fineness value. 28-day activity index of the BFS used in the mortars is approximately 90%, according to the ASTM C 989 Standard. Chemical and physical properties concerning the BFS are given in **Table 2**.


**Table 1.**  *Properties of lime.* 


#### **Table 2.**

*Properties of the blast furnace slag (BFS).* 

#### *2.1.3 Aggregate*

In the production of the BFS added lime mortars, the silica aggregate was used as the fine aggregate. The gradation of the silica aggregate and other properties are given in **Table 3**.

#### *2.1.4 Basalt fiber (BF)*

Basalt fiber was used for the dimensional stability in the production of the BFS added mortars. The properties of the basalt fiber are given in **Table 4**.

#### **2.2 Mixture properties**

In this study, nine different mortars were prepared. The total binder content in the mortars was determined as 900 gr. Instead of lime, the BFS was substituted at the rates of 25, 50, and 100%. The water/binder (w/b) ratio and the aggregate/ binder (a/b) ratios of the mixtures were fixed between 0.50 and 1.00. BF was added to the mixture as much as 0.5 and 1% of the binder content. The ratio and material contents of the mixtures are given in **Table 5**.


#### **Table 3.**

*Gradation of the silica aggregate (gradation properties).* 


#### **Table 4.**

*Properties of the basalt fiber (BF).* 

*Microstructure Properties of Sulfate-Effected Blast Furnace Slag Reinforced Restoration Mortars DOI: http://dx.doi.org/10.5772/intechopen.87836* 


#### **Table 5.**

*Mortar mix proportions.* 

#### **2.3 Preparation of the mortars and the cure conditions**

 In the preparation of the mortars, initially, dry aggregate, lime, and BFS were mixed in a mixer for 0.5 minutes with 140 rpm speed. Adding water inside the mixture, it was mixed for 1 minute with 140 rpm speed and 1 minute with 285 rpm speed. Lastly, BF was added to the mixture and it was mixed for 1.5 minutes in 285 rpm speed. Total mixing duration was 4 minutes in the preparation of the mortars. At the end of the mixing procedure, the mortars were placed as two layers into steel containers with 40×40×160 and 25×25×285 mm3 sizes. Each layer was pressed with a mechanical vibration for 1 minute. The mortars, which were dismantled from the containers 1 day later, were placed into plastic containers including a certain amount of water. Closing the lids of the plastic containers, they were kept under room conditions with 18–23°C of until the experiment day. The mortars were placed into the plastic containers without contacting the water. The lids of the plastic containers were kept open for 1 hour each day until the 28th day. The water inside the plastic containers was checked and refilled if needed against vaporization. The cut view of the cure conditions prepared for the lime mortars is given in **Figure 1**.

#### **2.4 Hardened mortar experiments**

 For hardened mortar samples, 5% Na2SO4 sulfate solutions were prepared for the sulfate resistance of the BFS-added mortars. The mortar samples, which were

**Figure 1.**  *Cure conditions prepared for the lime mortars.* 

exposed to cure procedure for 28 days in a humid environment, were subsequently placed into 5% Na2SO4 solutions. Determining the height changes of the mortars with 25 × 25 × 285 mm3 arris at the 0, 30, 60, 90, 120, 150, 180, 210, 240, 270, and 365 days, the sulfate resistance was investigated. The 5% sodium sulfate solution was refilled in every 30 days. SEM images were taken in order to examine the microstructure in the mortars being exposed to Na2SO4 effect for 365 days. The SEM analyses were conducted in the Department of Material and Metallurgical Engineering, Gazi University, through the Jeol JEM 6060 LV scanning electron microscope.

#### **3. Findings**

#### **3.1 Mechanical properties of the mortars**

The effect of BFS (25, 50, and 75%) and BF (0, 0.5, and 1.0%) used in different ratios on the 7th and 28th day compressive strength is given in **Figure 2**.

It is seen in **Figure 3a** that BFS addition to non-fiber mixtures increases the compressive strength in the 7th and 28th days. In the 7-day lime mortars including 50% BFS, the compressive strength increases by 70.9%. If the BFS ratios are 75%, the increase rate is 42.9%. In the 28-day non-fiber lime mortars with 50% BFS ratio, the compressive strength value increases by 109.6%. In case the BFS substitution ratio is 75%, the increase in the compressive strength is 88.7%. When the ratio of the BFS is 75%, there is a neglectable amount of compressive strength loss compared to the mortars with 50% BFS content. When the cure duration increases, as expected, the compressive strength values increase as well.

 In the mortars with 0.5% BF, 25 and 50% BFS, the 7-day compressive strength values decreased compared to the non-fiber mixtures. In the mortars with 0.5% BF and 50% BFS, increases were observed in the compressive strength values in the 7th day compared to the non-fiber mixtures. Use of 0.5% BF, 25 and 50% BFS caused workability loss, and as a result of this, decreases were observed in the compressive strength values. However, in the mixtures with 0.5% BF and 75% BFS,

**Figure 2.**  *The effect of BFS and BF on compressive strength.* 

*Microstructure Properties of Sulfate-Effected Blast Furnace Slag Reinforced Restoration Mortars DOI: http://dx.doi.org/10.5772/intechopen.87836* 

**Figure 3.**  *7th and 28th-day compressive strength values of the BFS and BF added mortars.* 

the workability increased compared to the non-fiber mixtures and as a result of decreasing porosity, the compressive strength increased. The 28th-day compressive strength values of the mortars with 0.5% BF were detected to be similar to those of the 7th-day compressive strength values. As a result of increasing BFS content, the compressive strength values increased. Use of 75% BFS in the mixtures with 0.5% BF increased the compressive strength values by 117.6% at the 7th day, and by 128% at the 28th day. That the compressive strength increases together with the increase in the BFS content are explained by the pozzolanic activity.

 In **Figure 3a**, it is observed that the 7th-day compressive strength values of the mixtures with 1% BF were similar to those of non-fiber mixtures. With a 50% BFS ratio, the compressive strength value was obtained as 3.85 MPa at the 7th day, while it was determined as 3.44 MPa in the mixtures with 75% BFS. Use of 75% BFS at the 28th day in the mixture with 1% BF decreased the compressive strength to a large extent. Use of 1% BF in the mixtures with 75% BFS decreased the compressive strength by approximately 14.6%. However, the compressive strength of these mixtures doubled compared to the 7th-day mortar mixtures. The 28th-day compressive strength values of the mixtures with 1% BF and 50% BFS increased approximately 2.9 times compared to that of the 7th day. The changes in the compressive strength values of the BFS and BF added mortars at the 7th and 28th days are given in **Figure 3a**.

 As is seen in **Figure 3b**, the highest compressive strength (>4.25 MPa) value in the 7th-day mortar samples was determined in the mixture with 0% BF and 50% BFS. Moreover, when the BF ratio was 0.5%, having the BFS ratio at 75% increased the compressive strength. Increasing the BFS content ratio in the 7th-day mortar mixtures generally increased the compressive strength. As per the 28th-day compressive strength values, the highest value (>13.2 MPa) was obtained when 0.5% BF was added to the mixture with 50–75% BFS content. In the 28th-day mortar mixtures, the use of BFS generally increased the compressive strength values. The most appropriate content ratio for the 7th and 28th-day compressive strength values were observed to be 75% BFS and 0.5% BF. Concerning the mechanical properties of the mortars, an increase in the BFS ratio made a positive contribution to the compressive strength value. The motive behind this can be explained by the Ca/Si ratio in the mortar structures. It is considered that due to the SiO2 content of the BFS, the Ca/Si ratio decreases. In previous studies, it was reported that a decrease in the Ca/Si ratio caused an increase in the compressive strength. The molar volumes of the C-S-H gels decrease with the decrease of the Ca/Si ratio, accordingly, higher surface areas are obtained and compressive strength increases [8]. Additionally, the compressive strength values increase with the effect of precipitated silica and pozzolanic activity incorporated in the BFS.

 Since fibers such as BF have the water retention characteristic, decreases are generally observed in the workability. In previous studies, it was determined that workability decreased as a result of increasing BF ratio [9]. Therefore, it was determined that the most appropriate BF ratio was 0.5%. An increase in the BFS ratio in the mixtures with 0.5% BF increased the compressive strength. This effect was explained by the strengthening fiber-matrix interface because of mineral additives.

#### **3.2 Sulfate resistance**

The BFS added lime mortars were placed into the 5% Na2SO4 solution following a 28-day cure process. The sulfate mixtures were kept in the Na2SO4 solution for 360 days (approximately 1 year). The temporal expansion of the mortars kept in the Na2SO4 solution for 360 days is given in **Figure 4**.

 As is seen in **Figure 4**, the lowest expansion value was determined in the non-fiber mortars (0B50C) with 50% BFS content, and the highest value was determined in the mortars (1B25C) with 1% BF and 25% BFS contents. In general, higher expansion values were obtained from the mixtures with 1% BF content. This case can be explained by that workability negatively influenced the increase of BF content. As a result of decreasing workability, it becomes more difficult to place the mortars into molds, and therefore, the porosity values can increase. It is considered that the sulfate ions influenced the microstructure more as a result of increasing porosity. The 50% BFS used in the mortar with 0B50C code, in which the lowest expansion value was obtained, made contributions to its sulfate resistance.

 Fibers such as BF, which has the water retention characteristic, have negative effects on workability. This, in return, causes an increase in porosity, ultimately decreasing the resistance. Therefore, due diligence should be given to the fiber preference for the lime mortars to be used in the restoration works. It was observed that the BFS, which is used as a mineral additive, increased the sulfate resistance, even a little. Since the C2S content of the BFS increases the Ca(OH)2 content, it did not cause the expected enhancement for the sulfate resistance. However, the mineral additive preferences should also be carefully decided for the mortars that are exposed to sulfate effect. Shrinkage is generally observed in the first 30 days in the mortars with 75% BFS content. This is explained by that the sulfate ions activate the BFS. The deteriorations in the mortars exposed to Na2SO4 effect for 360 days are given in **Figure 5**.

**Figure 4.**  *Temporal expansion values of the BFS-added lime mortars exposed to the Na2SO4 effect.* 

*Microstructure Properties of Sulfate-Effected Blast Furnace Slag Reinforced Restoration Mortars DOI: http://dx.doi.org/10.5772/intechopen.87836* 

**Figure 5.**  *Physical deteriorations in the mortars exposed to Na2SO4 effect.* 

#### **3.3 Microstructure examinations**

Microstructure examinations were conducted on mortars exposed to Na2SO4 effect for 360 days. The SEM images of the microstructures are given in **Figure 5–7**. The SEM images of the non-fiber mixtures are seen in **Figure 6**.

As is seen in **Figure 6**, it was determined in the SEM images that C–S–H gels were formed as well as ettringite was detected due to the sulfate effect. The SEM images of the mortars with 0.5% BF are given in **Figure 6**.

 In the SEM images of the mortars with 0.5% BF in **Figure 5**, C–S–H gels, ettringite, and CH formations were observed. An intense ettringite formation was detected in the mortars with 50% BFS. As per the mortars with 75% BFS, reaction outputs were observed similar to the hemihydrate calcium sulfate (basanite) structure. The SEM images of the mortars with 1% BF are given in **Figure 7**.

As seen in **Figure 8**, ettringite structures were observed in the microstructures of the mortars. Similarly, basalt fiber was observed in the microstructures of the mortars with 75% BFS.

**Figure 6.**  *The SEM images of the non-fiber mixtures.* 

**Figure 7.**  *The SEM images of the mortars with 0.5% BF.* 

**Figure 8.**  *The SEM images of the mortars with 1% BF.* 

#### **4. Conclusion**

In this study, the effect of the use of BFS and BF in the production of lime mortars to be used in restoration works on the sulfate resistance was investigated. The results obtained from this experimental study are summarized below.


### **Author details**

Rüya Kılıç Demircan1 \* and Gökhan Kaplan<sup>2</sup>

1 Department of Civil Engineering, Gazi University, Ankara, Turkey

2 Department of Civil Engineering, Kastamonu University, Kastamonu, Turkey

\*Address all correspondence to: ruyakilic86@gmail.com

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Microstructure Properties of Sulfate-Effected Blast Furnace Slag Reinforced Restoration Mortars DOI: http://dx.doi.org/10.5772/intechopen.87836* 

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Section 3

Sustainable Urban Design

Section 3
