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Optimization and characterization of sustainable geopolymer mortars based on palygorskite clay, water glass, and sodium hydroxide

  • Samer Hamid EMAIL logo , Izwan Johari and Nadras Othman
Published/Copyright: February 13, 2024
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Open Engineering
From the journal Open Engineering Volume 14 Issue 1

Abstract

The synthesis of ambient-cured sustainable geopolymer mortars (GMs) was studied throughout this work. To reduce carbon dioxide emissions, new materials must be used in the production of sustainable concrete and mortars. Many types of binders are used in the synthesis of GM and concrete (GPC), especially clay minerals. These clay minerals are considered sources of alumina and silica in GM and concrete. The geopolymerization process relies on the alkaline solution activating the alumino-silicate to produce geopolymer gel products. The palygorskite (PA) clay mineral, sodium hydroxide (NaOH), and sodium silicates (Na2SiO3) were chosen as a binder (solid material) and alkaline activator solution to synthesize GM at ambient temperature. PA was thermally treated at 550, 650, 700, and 750°C, respectively, to convert into high-reactive PA (HRP) HRP550, HRP650, HRP700, and HRP750, respectively. The characteristics of PA clay, HRP powders, and HRP-based GM were evaluated using compressive strength (CS) testing, X-ray fluorescence analysis, carbon footprint analysis, X-ray diffraction (XRD) diffractograms, Fourier transform infrared spectroscopy (FTIR) spectroscopy, scanning electron microscopy (SEM) images, and energy-dispersive X-ray spectroscopy (EDS) analysis. The maximum CS of 25.1 MPa was acquired for geopolymer synthesis utilizing HRP700-based GM cured at 30°C for 28 days. FTIR spectroscopy demonstrated that HRP-based GM showed the presence of Si–O, Al–O, and O–C–O bonds stretching vibrations in the alumino-silicate network. The results showed that the CO2 emissions had a reduction in the HRP-based GM compared with the reference mix of ordinary Portland cement mortar (OPM). The percentage of reductions was 14.1, 13.7, 13.1, and 12.4 for HRP550, HRP650, HRP700, and HRP750, respectively, compared with the OPM mixture. SEM images/EDS analysis and XRD diffractograms confirmed the presence of sodium alumino-silicate hydrates, magnesium silicate hydrate, and calcium silicate hydrate gels with high quantities particularly in the HRP700-based GM than that in HRP550, HRP650, and HRP750, respectively. The results indicate the suitability of HRP calcined at 700°C (HRP700) in the synthesis of the GM.

Keywords: sustainable material; alkaline solution; calcination temperatures; carbon footprint; high-reactive palygorskite

1 Introduction

Ordinary Portland cement (OPC) is regarded as the primary component in construction projects because of its durability and mechanical characteristics. Environmental pollution and excessive energy consumption associated with manufacturing of OPC have been increasing considerably. The cement sector contributes around 8% of global carbon dioxide (CO2) emissions [1]. To reduce CO2 emissions, reducing cement percentage in concrete or exploring alternative materials is important for environmental protection. The average amount of carbon dioxide in the atmosphere increased by 0.64% from 2018 to a record-breaking 410.5 ppm in 2019 [2]. Because of the expanding global population and the corresponding requirement for infrastructure, the output of fossil fuels and Portland cement (PC) will increase dramatically [3]. Limiting the usage of cement products in the concrete and mortars mixes is another efficient way to minimize pollution and obtain clean air due to the significant quantity of carbon dioxide (CO2) emissions produced during the cement production process [4]. However, among the alternative sustainable materials are the clay minerals, such as kaolin, attapulgite, and montmorillonite. Clay minerals are alumino-silicate hydrates found in nature that contain varying concentrations of alkali metals, alkaline earths, iron, and magnesium [5]. Numerous clay minerals can be utilized to partially substitute PC or produce other types of concrete, such as geopolymer concrete. One of these clay minerals is palygorskite (PA). PA is the major mineral present in attapulgite, a form of fibrous, rod-shaped clay. PA is an alumino-silicate mineral that contains magnesium in abundance and has a chain-layered structure. The chemical formula of PA is (Mg,Al)2Si4O10(OH)·4(H2O). The geopolymer is formed by alkali activation of alumino-silicate in the binder materials, such as clay minerals, blast furnace slag, and coal fly ash [6]. Kaolin is the clay type that has received considerable attention for geopolymer production. Kaolin changes into metakaolin during thermal processing, which is an excellent source of silica (SiO2) and alumina (Al2O3) [7]. The geopolymer is produced by combining binders high in silica and alumina with potent alkaline activators. The type, quantity, and proportion of the raw components, as well as the temperature and curing time, must all be considered when creating formulas for geopolymer concrete or mortar [8]. With better performance than conventional concretes, geopolymers are a highly promising option [9]. However, PA has only been used in a few studies as a binder material in geopolymer mortar (GM) and concrete. The current study prioritizes the direct use of PA in GM to determine the optimum calcination temperature of the raw material powder. PA clay-based GM research mainly includes a raw material burning program, chemical composition analyses, mechanical properties assessment, and morphology analysis. Understanding the impact of various variables on the characteristics of a GM based on PA calcined at different temperatures for creating a good GM is crucial.

1.1 Alumino-silicate

PA is considered a good source of silica and alumina in GM. According to ASTM C618-01 [10], PA can be classified based on its chemical composition and sulfur trioxide (SO3) content as a class N pozzolan [11]. PA can be considered a source of CaO because it has large amount of CaO in its chemical composition. The presence of CaO in the PA results in a higher compressive strength (CS) of GM because of the volume of hydration products, such as calcium silicate hydrate (CSH) [12]. Alkali-activated systems are divided into two primary groups. In the first model, products that mostly include Si and Ca are somewhat alkalinized to activate it. A gel of CSH is the result of this process. The CSH gel hydration products are similar to the CSH obtained through hydration of PC, however, comprising of a lower Ca/Si ratio. In the second model, alkaline solution is used to activate a substance that primarily includes Si and Al. Owing to this reaction, the polymerization process produces an inorganic binder [13].

1.2 Alkaline solution

The most common alkaline solutions used to activate alumino-silicate or calcium silicate in the solid material are sodium hydroxide (NaOH) or potassium hydroxide (KOH), sodium silicate (Na2SiO3), or potassium silicate (K2SiO3).

The alkaline solution activators play a significant role in dissolving Al3+ and Si4+ ions from the alumino-silicate source, which improves CS by generating sodium alumino-silicate hydrates (NASH), CASH, or CSH gels. The combination of NaOH and Na2SiO3 results in higher CS compared to using only NaOH [14]. An important issue is the ratio of Na2SiO3 to NaOH [15]. As NaOH dissolves more Al3+ and Si4+ ions than KOH, using NaOH as an alkaline activator in GM is better than using KOH [16].

1.3 Added water

The workability of fresh GM is affected by many factors, such as the quantity of water to binder ratio, fineness of the clay mineral, and viscosity of the Na2SiO3 activator. As fresh GM has no water, it has poor workability compared to the fresh PC mortar, adversely affecting the workability of GM and CS. Additional water can be added to the mixture to improve workability; however, this reduces its CS [17].

2 Materials and experimental methods

2.1 Materials

The PA clay raw material (density [d] = 2.34 g/cm3) was supplied with the assistance of the (State Company of Geological Survey and Mining, Baghdad, Iraq). The chemical composition of PA was established by X-ray fluorescence (XRF) analysis as shown in Table 1. Alkaline activator solution used in this study was NaOH pellets (d = 2.12 g/cm3) and Na2SiO3 solution (d = 1.55 g/cm3) purchased from QREC (ASIA) SDN, BHD, Selangor, Malaysia. The fine aggregate (sand) used in this study was natural river sand acquired from Nibong Tebal, Penang, Malaysia.

Table 1

Chemical composition of palygorskite (PA) and high-reactive palygorskite (HRP) at different calcination temperatures

Oxides Percentage compositions (wt%)
PA HRP550 HRP650 HRP700 HRP750
SiO2 47.9 46.7 51.1 49.9 49.4
Al2O3 10.8 12.7 14.8 11.6 11.8
Fe2O3 10.7 12.4 10.5 10.9 11.3
CaO 12.1 14.5 11.9 13.6 13.5
MgO 3.2 4.3 3.9 3.7 4.1
TiO2 1.2 1.4 0.9 1.1 1.3
K2O 2.4 3.5 3.1 3.5 3.5
P2O5 1.2 1.4 1.8 1.5 1.6
SO3 0.8 0.7 0.6 0.9 0.8
LOI 8.9 1.4 1.1 1.6 1.3

2.2 Experimental methods

2.2.1 Particle size and fineness

The particle size of fine aggregate was examined using mechanical sieving in this study. It was retained on a 150 μm sieve and passed through a 1.18 mm. The PA and high-reactive palygorskite (HRP) characteristics, such as the specific surface area and particle size, were determined using the laser diffraction particle size analyzer (Mastersizer/E).

2.2.2 Preparation of HRP

The PA raw material was burned in electrical-operated furnace (having a maximum temperature of 1100°C). Subsequently, the calcination process began with various burning temperatures (550, 650, 700, and 750°C) to produce: HRP550, HRP650, HRP700, and HRP750. The average rate of temperature rise was 10°C/min. After the calcination process was complete, the samples were left inside the furnace to cool down. Before 500°C, the activation of PA does not exist. On the other hand, in the X-ray diffraction (XRD) analysis, PA showed a high-range decrease in intensity until it disappeared at 800°C [18]. This played a significant role in selecting 550, 650, 700, and 750°C to test the calcination temperature in PA clay. Chemical composition of HRP550, HRP650, HRP700, and HRP750 was established by XRF analysis as shown in Table 1. HRP samples burned at various temperatures are shown in Figure 1.

Figure 1 Samples of HRP burned at 550, 650, 700, and 750°C.
Figure 1

Samples of HRP burned at 550, 650, 700, and 750°C.

2.2.3 CS test

Using 50 mm × 50 mm × 50 mm cubes of steel molds, the CS test was performed according to ASTM C109 [19]. A common standard testing device with a 2,000 kN capacity was used to evaluate the CS of cubes. The rate of loading was 0.8 kN/s. For each age testing group, an average of three samples were taken.

2.2.4 XRF

The compositions of the elements were quantitatively determined using the XRF. The BS EN ISO 12677 standard was followed during this analysis. Using the Rigaku X-Ray Spectrometer69, an elemental analysis was performed, specifically the RIX 3000 operated at 50 kV voltage and 50 mA current.

2.2.5 XRD

The X-ray diffractograms (XRD) were utilized to identify the phase composition in powders and GM samples to ascertain the mineral phase component of PA and HRP. Using Bruker (D8) Advance XRD equipment with Cu K radiation (1.5406) between 10° and 90° of 2θ, the analysis was performed. Subsequently, Expert High Score Plus software was used to evaluate the diffraction patterns.

2.2.6 Chemical bonding, Fourier transform infrared spectroscopy (FTIR)

The FTIR test determined the various types of chemical bonds that were present in the materials. The (Perkin-Elmer) Spectrum1 was the apparatus used for FTIR. Using an agate mortar and pestle, 5 mg of the powdered combination was combined with 95 mg of the potassium bromide (KBr). The transparent pellets were created by hydraulically crushing the powder for 2 min at 2.758 MPa before it was placed inside the infrared spectrometer. The wave number of spectra was captured between 4,000 and 500 cm−1.

2.2.7 Scanning electron microscopy (SEM) test and EDS analysis

The morphology and microstructure samples were evaluated using SEM. SEM (Zeiss Supra 35V) was used to measure the variations in the physical characteristics and chemical compositions of materials as well as to assess the morphologies of the microstructure.

2.2.8 Carbon footprint analysis

The environmental impacts of alkaline-activated GMs were evaluated by comparing the CO2 emissions of GM to Portland cement mortar-based binder as a reference mixture. Based on the combined emissions of CO2, CH4, NO2, and synthetic gases produced during each activity, as well as the types of gases produced and their respective global warming potentials (GWP) when the fuel is fully burned, CO2-e was calculated. The CO2-e emissions were calculated by the following equation:

(1) CO 2 -e = Q × EC × GWP,

where Q is the weight of fuel used to complete the given assignment (kg), EC is the energy content of the specific fuel used to complete the task (J/kg), and total GWP is the sum of the emissions of each gas that contributes to global warming, including carbon dioxide, methane, nitrous dioxide, and synthetic gases (kg CO2-e/J).

The 2012 National Greenhouse Accounts Factors were the basis for the EC and GWP [20]. This methodology takes into account global standards guiding the computation of national greenhouse gas inventories, such as the US EPA Mandatory Greenhouse Gas Reporting Rule [21], and the EU Guidelines for the Monitoring and Reporting of Greenhouse Gas Emissions [22].

The value for the carbon footprint of PA was based on 1.5 h of grinding in a 12 kg ball mill in the laboratory and the use of an electrical kiln to produce HRP550, HRP650, HRP700, and HRP750. On the other hand, the emission factor calculated due to the following equation [21,22]:

(2) Emission factor [23,24] = CO 2 emission ( kg CO 2 / m 3 ) / Compressive strength at 28 days .

3 Design of mixtures and preparation of GMs

3.1 Mix design

The four mixtures of GM and cement paste prepared for this study is shown in Table 2. Each mixture of GM contains fine aggregate, binder material, and an alkaline activator with a limited percentage of added water. The binder material comprised of HRP550, HRP650, HRP700, and HRP750. The additional amount of binders to GM increases the CS; however, it reduces the setting time and workability [25]. Alkaline activators were used to activate the silica and alumina in HRP550, HRP650, HRP700, and HRP750 using Na2SiO3 having a silica modulus (Ms) of 3.3 and a concentration of 10 M NaOH.

Table 2

Mix proportions of HRP-based geopolymer mortar

Mix Binder material (kg) Sand (kg) Alkaline activator
Na2SiO3 (kg) NaOH (kg) Added water (kg)
HRP550 0.96 1.44 0.56 0.22 0.10
HRP650 0.96 1.44 0.56 0.22 0.10
HRP700 0.96 1.44 0.56 0.22 0.10
HRP750 0.96 1.44 0.56 0.22 0.10

The ratio of alkaline activator to binder material was set at 0.8 for all mixes, as referenced from prior work, and the ratio of Na2SiO3/NaOH was established at 2.5 as previous research shows that this ratio leads to the highest CS results in alkaline activator GM [26]. For each mixture, the amount of added water was 9.6% of the weight of binder materials (HRP550, HRP650, HRP700, and HRP750) determined according to the percentage of alkaline-activated pastes [27]. Based on the previous studies, all GM mixes were prepared with a sand-to-binder material ratio of 1.5 [28]. Table 2 shows the mixture proportions (binders, alkaline solutions, sand, and added water) for GM based on the absolute volume method. On the other hand, the mix design of ordinary Portland cement mortar (OPM) is shown in Table 3.

Table 3

Mix proportions of OPM

Mix Unit Cement Sand Water w/c
Ordinary Portland cement mortar (OPM) Kg/m 328 781 190 0.58

3.2 Preparation of alkaline activators

In this study, mixtures of NaOH and Na2SiO3 solution were used as alkaline activators with additional water. A comparable amount of NaOH pellets was dissolved in distilled water to produce 1 l of solution, which served as the percentage of aqueous NaOH. The equivalent mass was 404.0 g for 10 M. As the addition of NaOH pellet to water resulted in an exothermic reaction, the solution was produced and allowed to settle for 24 h in a laboratory setting before use.

3.3 Workability requirements

The workability of fresh GM is affected by many factors, such as the quantity of water to binder ratio, finesse of the clay mineral, and viscosity of the Na2SiO3 activator. As the study used a new binder material, the requirements of the fresh mixture’s workability depend on the previous studies were done with nearest binder material, such as metakaolin and trail mixes, to match these results.

The ratio of alkaline activator to binder material was set at 0.8 for all mixes, and the ratio of Na2SiO3/NaOH was established at 2.5 as referenced from prior works [26]. For each mixture, the amount of added water was 9.6% of the weight of binder materials (HRP550, HRP650, HRP700, and HRP750) determined according to the percentage of alkaline-activated pastes [27].

3.4 Mixing, casting, and curing of GM

The GM samples were mixed with a 4.73-l capacity (Hobart bench) style mixer. First, the dry mixture of solid materials (HRP and sand) was mixed for 2 min. The alkaline activator was prepared 24 h prior to it being added to the solid materials. They were mixed and blended for 10 min to synthesize the GM. The casting of fresh GM was done by two layers into cubes of oil-coated steel molds with dimensions of 50 mm × 50 mm × 50 mm. A vibrating table was used to apply 15 s of vibration to each layer.

The molded samples were then left at temperature 25 ± 3°C and 75 ± 5% relative humidity (RH) for 12 h. The specimens were demolded and then wrapped in heat-resistant vinyl bags to reduce moisture loss. Subsequently, a 24 h curing procedure was done in a drying oven set at 75°C. The specimens were maintained in the laboratory at a temperature of 25 ± 3°C and 75 ± 5% RH prior to testing [29].

4 Results and discussion

4.1 Particle size distributions and fineness of solid materials

According to ASTM C136, the fineness modulus estimated for the fine aggregate was 2.7 [30], and specific gravity was 2.63 evaluated according to ASTM C128 [31]. The specific gravity of PA was 2.68.

The specific surface area, average particle size distribution, and color of the PA and HRP burning at various temperatures are shown in Table 4.

Table 4

Average particle size, specific surface area, and color of Pa and HRP at different calcination temperatures

Sample Calcination temperature (°C) Average particle size (μm) Specific surface area (m2/g) Color
PA — 5.13 1.75 Green (clear) gray
HRP550 550 4.09 1.82 Gray yellow
HRP650 650 4.15 1.79 Yellow orange
HRP700 700 3.94 1.93 Orange
HRP750 750 3.98 1.91 Orange (dark)

The average particle size of HRP increased when the calcination temperature increased from 550 to 650°C (4.09 and 4.15 μm for HRP550 and HRP650, respectively), and then, it decreased at 700°C [32]. The specific surface areas were 1.82, 1.79, 1.93, and 1.91 m2/g for HRP550, HRP650, HRP700, and HRP750, respectively. These results support the findings of previous studies, which state that when particle size decreases. The surface area increases due to the reaction of the particles itself, which produces new compounds [32].

4.2 CS

The results of CS for OPM and HRP-based GM are shown in Table 5. It is noticeable that the oxide ratios (which were adjusted according to the calcination temperatures) and curing age have an effect on the CS of the mixtures. In the mixture (HRP550), the CS increased from 18.8 MPa after 3 days of curing age to 20.9 MPa after 28 days. The CS of the mixture (HRP650) was 19.1 MPa after 3 days and increased to 21.6 MPa after 28 days. In the mixture (HRP700), the CS was 22.1 MPa after 3 days which increased to 25.1 MPa at 28 days However, the CS of HRP750 began at 21.6 MPa and increased to 23.8 MPa after 28 days. The results of the CS of GMs using HRP treated at different calcination temperatures are shown in Table 5. The gradual progress of strength of HRP-based GM depends on the SiO2/Al2O3 ratio. As seen in Table 5, the mixture of HRP700 has a higher strength than that of HRP550, HRP650, and HRP750. In the early ages of all mixes, the CS gained more than 80% from the total strength at 28 days. The early age strength is related to Al2O3, which reacted faster than SiO2, this increased bond formation between silicate and aluminates more than that of silicate alone, resulting in the initial increase in CS [33]. During the geopolymerization process, the SiO2/Al2O3 ratio cannot be constant because it increases at various stages [34].

Table 5

Results of CS of OPM and geopolymer mortars using HRP treated with different calcination temperatures 550, 650, 700 and 750°C

Mix Compressive strength (MPa)
3 days 7 days 14 days 28 days
HRP550 18.8 19.8 21.1 20.9
HRP650 19.1 20.3 21.8 21.6
HRP700 22.1 23.4 23.7 25.1
HRP750 21.6 22.2 22.4 23.8
OPM 16.3 17.1 20.2 20.7

4.3 Chemical compositions of HRP treated with different calcination temperatures

The chemical composition of PA and HRP (HRP550, HRP650, HRP700, and HRP750) was established by XRF analysis as shown in Table 1.

The SiO2 + Al2O3 + Fe2O3 in the HRP powders were 71.8, 76.4, 72.4, and 72.5% for HRP550, HRP650, HRP700, and HRP750, respectively, from the results. The molar ratios of SiO2:Al2O3 were 3.68, 3.45, 4.31, and 4.11 for HRP550, HRP650, HRP700, and HRP750, respectively. The molar ratio was anticipated to increase with the increase in the calcination temperature of activated clay [35]. However, in this study, the molar ratio decreased when the temperature increased between 550 and 650°C. The molar ratio increased at 700°C. The molar ratio; however, decreased slightly at 750°C.

The presence of CaO in the chemical composition of PA and HRP at various calcination temperatures is contrary to some other clay minerals, such as metakaolin, where the percentage of CaO is absent.

The percentage of CaO was 12.1% in PA, and 14.5, 11.9, 13.6, and 13.5% for HRP550, HRP650, HRP700, and HRP750, respectively. The formation of CASH and/or CSH may be significantly influenced by the presence of CaO. However, the higher content of CaO in the composition of clay minerals or natural pozzolan results in higher CS due to the amount of CSH gel formation [9,16]. SiO2 exists in the mineral as a quartz and tridyamite, while the presence of CaO and MgO refers to dolomite in the row material.

4.4 XRD analysis and FTIR spectrum

4.4.1 XRD analysis of PA and HRP at different calcination temperatures

Figure 2(a) shows the X-ray diffractograms of the PA. The diffractogram of the sample indicates a composition dominated by quartz (SiO2) (ICSD No. 00-046-1045), dolomite (CaMg(CO3)2) (ICSD No. 00-036-0426), tridymite (ICSD No. 00-033-1161), hematite (Fe2O3) (ICSD No. 00-024-0072), and feldspar (K2O.Al2O3.6SiO2).

Figure 2 XRD of (a) PA and (b) HRP treated at different calcination temperatures (HRP550, HRP650, HRP700, and HRP750).
Figure 2

XRD of (a) PA and (b) HRP treated at different calcination temperatures (HRP550, HRP650, HRP700, and HRP750).

Figure 2(b) shows the X-ray diffractograms of the HRP treated at different calcination temperatures, HRP550, HRP650, HRP700, and HRP750, respectively. The diffractogram of the HRP550 and HRP650 samples indicates a composition dominated by quartz (SiO2) (ICSD No. 00-046-1045), dolomite (CaMg(CO3)2) (ICSD No. 00-036-0426), tridymite (ICSD No. 00-033-1161), hematite (Fe2O3) (ICSD No. 00-024-0072), and feldspar (K2O·Al2O3 6SiO2). While the diffractogram of the HRP700 and HRP750 samples indicates a composition dominated by quartz (SiO2) (ICSD No. 00-046-1045), tridymite (ICSD No. 00-033-1161), hematite (Fe2O3) (ICSD No. 00-024-0072), feldspar (K2O.Al2O3.6SiO2), periclase (MgO) (ICSD No 9006747), and calcite (CaCO3) (ICSD No. 01-085-1108).

The four HRP samples have peaks between 2-theta angles of 20–29°, while the PA has peaks between 18° and 29°, whereas the other peaks appeared from 30° to 80° (2-theta angles). Considering the intensity level, the higher peak of quartz and the presence of high sharpness are due to the high crystalline surface of quartz. This causes a high reflection in the XRD diffractogram [36].

Alpha quartz (α-SiO2) of tridymite phase diffraction peak intensity is still stable as the calcination temperature rises from 550 to 750°C [37]. However, tridymite begins to transform into a stable shape cristobalite after the calcination temperature passes 1,000°C. The XRD test results found hematite (Fe2O3), which confirmed the experimental conclusions inferred above in addition to the distinct presence of the feldspar phase at different calcination temperatures.

4.4.2 FTIR spectrum of PA and HRP at different calcination temperatures

The primary functional groups of PA and HRP calcination at different temperatures were identified using the Fourier transform infrared analysis. The infrared spectra of PA and HRP calcination at various temperatures are shown in Figure 3(a) and (b).

Figure 3 FTIR spectra of (a) PA and (b) HRP treated at different calcination temperatures (HRP550, HRP650, HRP700, and HRP750).
Figure 3

FTIR spectra of (a) PA and (b) HRP treated at different calcination temperatures (HRP550, HRP650, HRP700, and HRP750).

The raw material PA spectrum indicates a stretch band at 3547.9 cm−1 attributed to two hydroxyl groups on their exterior surfaces O–H stretching modes [38]. In addition, 1651.6 cm−1 matched with the inner surface hydroxyl O–H. The band at 978.7 cm−1 was compatible with the Al–OH curvature vibration, hydroxyl group linked with the Al. Si–O stretching was observed at 778.3 and 646.8 cm−1 indicating the presence of quartz phase, which is the main phase in the PA clay [39]. The deformation band at 558.9 cm−1 is compatible with Si–O of the quartz phase and the bending vibration band at 873.1 cm−1 refers to Si–C (silicon compounds).

PA was converted to HRP after the material underwent heat treatment. The O–H stretching band 3398.2 cm−1 of HRP550 decreased to 3388.4 cm−1 in HRP650, with more stretch, and then decreased to 3387.9 and 3387.6 cm−1 in HRP700 and HRP750, respectively. On the other hand, the stretching broadened the band as the inner surface of hydroxyl O–H was compatible with 1647.5 cm−1 in HRP550, 1646.9 cm−1 in HRP650, 1635.1 cm−1 in HRP700, and 1638.1 cm−1 in HRP750, respectively. The C–O bond has a presence at bands 1420.1 cm−1 in HRP550, 1420.6 cm−1 in HRP650, 1419.3 cm−1 in HRP700, and 1420.1 cm−1 in HRP750, respectively, confirmed in XRD by decarbonation of dolomite.

The Al–OH bond has a presence at band 976.5 cm−1 in HRP550, 995.6 cm−1 in HRP650, 979.8 cm−1 in HRP700, and 989.4 cm−1 in HRP750. After the calcination process, HRP at different calcination temperatures still maintains the quartz and amorphous silica at the bands 777.9 and 649.9 cm−1 in HRP550, 783.7 and 667.8 cm−1 in HRP650, 776.9 and 649.9 cm−1 in HRP700, and 795.2 and 648.2 cm−1 in HRP750, respectively [40]. The Si–O bond represented by Alpha quartz (α-SiO2) has a presence at the deformation peaks of 558.4 cm−1 in HRP550, 559.1 cm−1 in HRP650, 554.7 cm−1 in HRP700, and 559.4 cm−1 in HRP750, respectively.

4.4.3 XRD analysis of HRP-based GM

According to the XRD analysis of the HRP-based GM mixes (HRP550, HRP650, HRP700, and HRP750) shown in Figure 4. The diffractogram of the HRP550 and HRP650 samples indicates a composition dominated by quartz (SiO2) (ICSD No. 00-046-1045), dolomite (CaMg(CO3)2) (ICSD No. 00-036-0426), tridymite (ICSD No. 00-033-1161), and microcline (KAlSi3O8) (ICSD No. 01-003-4789). While the diffractogram of the HRP700 and HRP750 samples indicates a composition dominated by quartz (SiO2) (ICSD No. 00-046-1045), tridymite (ICSD No. 00-033-1161), microcline (KAlSi3O8) (ICSD No. 01-003-4789), periclase (MgO) (ICSD No 9006747), and calcite (CaCO3) (ICSD No. 01-085-1108).

Figure 4 XRD of alkaline activated mortar for HRP550, HRP650, HRP700, and HRP750 at 28 days.
Figure 4

XRD of alkaline activated mortar for HRP550, HRP650, HRP700, and HRP750 at 28 days.

Microcline is a type of alkali feldspar (KAlSi3O8) (followed by the alumino-silicates family). Microcline appears between 2-theta angles of 33–45°. It has a high Si:Al ratio; therefore, it forms stronger geopolymer structures [41]. However, microcline is more stable in an alkaline environment than feldspar.

According to the quantification XRD (QXRD) results for the HRP-based GM mixes are shown in Table 6. The amount of reacted quartz plays a significant role in the final reaction of gel products of alkaline-activated mortar. Quartz phase amount increased to 39.3% in HRP700 compared with HRP550 (34.1%), HRP650 (38.5%), and HRP750 (32.4%), respectively, while the amount of microcline phase dropped from 20.1% in HRP550 to 16.6% in HRP650, then increased at HRP700 to 19.2%, and HRP750 to 21.6%, respectively.

Table 6

The quantification XRD (QXRD) results for the HRP-based GM mixes

Phase Mix
HRP550 (%) HRP650 (%) HRP700 (%) HRP750 (%)
Quartz 34.1 38.5 39.3 32.4
Tridymite 20.0 20.1 25.1 30.1
Microcline 20.1 16.6 19.2 21.6
Dolomite 25.0 24.8 — —
Calcite — — 10.1 10.5
Perclase — — 5.2 4.4

The QXRD shows the amounts of reacted dolomite at HRP550 (25.0%) and HRP650 (24.8%). The CS results matched the QXRD analysis in the development of gel binder at 28 days. The presence of calcite and perclase in HRP700 and HRP750 correlates with the decarbonation of dolomite after 700°C and this gives an index to form CSH.

The primary components that increased the CS of hardened alkaline-activated mortars were CSH or CASH crystals, which were produced when Ca(OH)2 interacted with SiO2 and Al2O3 in HRP during pozzolanic reactions, where Ca(OH)2 reacted with SiO2 to produce CSH gel [42].

According to the previously discussed results, the HRP700 alkaline-activated mortar had superior geopolymer binder structure properties. However, the quantity of unreacted quartz phase significantly contributed to the mechanical characteristics, particularly of the CS.

4.4.4 FTIR spectrum of HRP-based GM using PA calcined at Different Temperatures

Figure 5 shows the FTIR results for the alkaline activator mortars of the mixes HRP550, HRP650, HRP700, and HRP750 after 28 days of curing. Between 4,000 and 500 cm−1 wave numbers, the different functional groups were identified using the FTIR spectra. Owing to the stretching bands of 3386.1, 3387.9, 3388.9, and 3388.8 cm−1 in HRP550, HRP650, HRP700, and HRP750, respectively, it is located at the hydroxyl group O–H, and there is a bending vibration H–O–H related to the geopolymerization process and its products [43]. The H–O–H bond gives an index of presence to the H2O at this stage. On the other hand, the stretching bands 1652.4 cm−1 in HRP550, 1637.1 cm−1 in HRP650, 1647.1 cm−1 in HRP700, and 1647.3 cm−1 in HRP750 show the inner surface of hydroxyl O–H, while the stretching bands 1420.1 cm−1 in HRP550, 1420.0 cm−1 in HRP650, 1417.4 cm−1 in HRP700, and 1419.5 cm−1 in HRP750 show the stretching vibrations O–C–O in the carbonate groups [44].

Figure 5 FTIR spectra of alkaline activated mortars for HRP550, HRP650, HRP700, and HRP750 at 28 days.
Figure 5

FTIR spectra of alkaline activated mortars for HRP550, HRP650, HRP700, and HRP750 at 28 days.

The increase in main vibration bands (982.5, 990.3, 989.3, and 999.4 cm−1 in HRP550, HRP650, HRP700, and HRP750, respectively) reflects positively on the bond Al–O in the tetrahedral system of AlO4 [45]. The bands between 667 and 730 cm−1 in HRP550, HRP650, HRP700, and HRP750, respectively, are related to the double quartz band (group of Si–O stretching) [40]. The Si–O bond represented by Alpha quartz (α-SiO2) is located at the bands 559.5 cm−1 in HRP550, 568.2 cm−1 in HRP650, 558.5 cm−1 in HRP700, and 564.9 cm−1 in HRP750. The increase of these bonds reflects the formation of NASH gel in the binary systems of the geopolymer products [46].

4.5 SEM analysis

4.5.1 SEM analysis of PA and HRP at different calcination temperatures

The characteristics of PA powder sample were illustrated using the SEM image as shown in Figure 6.

Figure 6 SEM result of PA raw material powder.
Figure 6

SEM result of PA raw material powder.

The uniform distribution of the PA particles can be seen in the image at magnifications of 1,000. The fine grinding of particles makes the surface area look bigger and more homogenous. On the other hand, PA particles are characterized by their needle shapes [6].

In Figure 7(a)–(d), the morphological characteristics of HRP at various calcination temperatures were illustrated using SEM images. The effect of the increasing temperature (550, 650, 700, and 750°C) can be seen on the surface area of the particles.

Figure 7 SEM results of HRP powders (a) HRP550, (b) HRP650, (c) HRP700, and (d) HRP750.
Figure 7

SEM results of HRP powders (a) HRP550, (b) HRP650, (c) HRP700, and (d) HRP750.

4.5.2 SEM/EDS analysis of HRP-based GM using PA calcined at different temperatures

In Figure 8(a)–(d), morphological characteristics of HRP-based GM using PA calcined at different temperatures are shown by SEM and EDS. In the cross-sections shown in SEM of Figure 8, the reacted and unreacted particles of HRP as well as the visible tiny pores in the microstructure can be seen. As shown in Figure 8(c), when compared to HRP550, HRP650, and HRP750, the SEM micrograph of the HRP700 alkaline-activated binder exhibits a better appearance with a denser and more discretely uniform cross-section because of the larger surface area-to-volume ratio. The existence of silica gel is demonstrated by the EDS analysis of HRP550 and HRP650 in Figure 8(a) and (b), which revealed the presence of the same peaks of Si and Na with a low quantity of Ca and Al. On the other hand, In Figure 8(c) and (d), the EDS analysis of HRP700 and HRP750 revealed the phase of Si and Na with little Ca and Al, and there is an amount of unreacted Mg. The presence of Mg in these mixtures refers to unreacted perclase. While the results indicated the possible formation of CSH, NASH, and magnesium silicate hydrate (MSH) gels [47]. However, there are more NASH gel products than HRP550, HRP650, and HRP750 alkaline-activated binders, which reflect the results of CS.

Figure 8 SEM and EDS results of HRP-based GM (a) HRP550, (b) HRP650, (c) HRP700, and (d) HRP750 at 28 days.
Figure 8

SEM and EDS results of HRP-based GM (a) HRP550, (b) HRP650, (c) HRP700, and (d) HRP750 at 28 days.

4.6 Carbon footprint analysis

Tables 7 and 8 demonstrate the CO2 emissions of OPM and HRP-based GM that have been calcined at 550, 650, 700, and 750°C. As it shown in those tables, from obtaining raw materials through producing and constructing 1 m3 of concrete, each activity’s contribution to CO2-e was summarized. The results showed that the CO2 emissions had a reduction in the HRP-based GM compared with the reference mix of OPM. The percentage of reductions was 14.1, 13.7, 13.1, and 12.4% for HRP550, HRP650, HRP700, and HRP750, respectively, compared with the OPM mixture. The emission factors of HRP550, HRP650, HRP700, HRP750, and OPM are shown in Table 9.

Table 7

The CO2 emissions of HRP-based GM mix

Engaged resources CO2 emissions (kg CO2/m3)
HRP550 HRP650 HRP700 HRP750
Batching 3 3 3 3
Transport 8 8 8 8
Placement 9 9 9 9
Curing* 38 38 38 38
Fine Aggregate 10 10 10 10
Sodium silicate 154 154 154 154
Sodium hydroxide 32 32 32 32
**Palygoriskite 9 10 12 14
Total 263 264 266 268

*Curing time of HRP mixtures done at 70°C for 24 h.

**Palygorskite burnt at 550, 650, 700, and 750°C, respectively.

Table 8

The CO2 emissions of OPM

Engaged resources CO2 emissions (kg CO2/m3) of OPM
Batching 3
Transport 8
Placement 9
Curing 1
Fine aggregate 12
Cement 273
Total 306
Table 9

Emission factor of OPM and HRP-based GM mixes

Specify HRP550 HRP650 HRP700 HRP750 OPM
Emission factor 12.5 12.2 10.6 11.2 14.8

In the OPM mixtures, the most significant source of emissions, responsible for 89.2% of CO2-e in OPM mortar, was by far PC. On the other hand, the alkaline-activated GM consumes a lot of energy during production, and the geopolymer binder’s contribution (PA + sodium silicate + sodium hydroxide) is 196 kg CO2-e/m3 as compared to OPC’s 273 kg CO2-e/m3. The differences between factors such as raw materials, energy/fuel types, geopolymer mixture compositions, and production processes for the alkali activators play a significant role in the variety of carbon dioxide emissions. However, the range of estimates for CO2-e due to the substitution of OPM with GM ranges from 80 to 20% [46–49].

5 Conclusions

The main findings of this study are:

  1. The higher CS was synthesized with HRP700-based GM.

  2. The higher molar ratio SiO2:Al2O3 was 4.31 for HRP700, compared to the lower ratios of 3.68, 3.45, and 4.11 for HRP550, HRP650, and HRP750, respectively.

  3. The XRD diffractograms show the main phases of PA clay and HRP calcined at 550 and 650°C were quartz, hematite, tridymite, dolomite, and feldspar. While the HRP calcined at 700 and 750°C were quartz, calcite, perclase, tridymite, hematite, and feldspar. The main phases of HRP550 and HRP650-based GM mixtures were quartz, tridymite, dolomite, and microcline. While the phases of HRP700 and HRP750-based GM mixtures were quartz, tridymite, calcite, perclase, and microcline.

  4. The presence of main bonds in the structure of the atoms of PA clay and HRP calcined at 550, 650, 700, and 750°C were hydroxyl bond O–H, Al–OH bond, Si–O bond, C–O bond, and Si–C bond. The presence of aluminum hydroxide bonds and silicate bonds was compatible with the composition of powders as concluded in the XRF analysis. On the other hand, the main bonds in HRP-based geopolymer were hydroxyl O–H and water H–O–H, carbonate O–C–O, the Al–O bond in the tetrahedral system of AlO4, Si–O (double quartz) and the alkaline-activated alumino-silicate N–A–S–H (in the binary system of geopolymer products).

  5. The morphology analysis by SEM images and EDS analysis of the HRP-based GMs calcined at different temperatures showed the presence of CSH, MSH, and NASH gel products. The HRP700-based GM showed higher amount of NASH compared to the lower amounts in HRP550, HRP650, and HRP750, respectively. This reflects the progress of the geopolymerization process in HRP700 more than in other mixes.

  6. The results showed that the CO2 emissions had a reduction in the HRP-based GM compared with the reference mix of OPM. The percentage of reductions was 14.1, 13.7, 13.1, and 12.4% for HRP550, HRP650, HRP700, and HRP750, respectively, compared with OPM mixture.

  1. Funding information: I declare that the manuscript was done depending on the personal effort of the author, and there is no funding effort from any side or organization.

  2. Conflict of interest: The authors state no conflict of interest.

  3. Data availability statement: Most datasets generated and analyzed in this study are comprised in this submitted article.

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Received: 2023-09-10
Revised: 2023-10-19
Accepted: 2023-10-30
Published Online: 2024-02-13

© 2024 the author(s), published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 International License.

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  83. Role of individual component failure in the performance of a 1-out-of-3 cold standby system: A Markov model approach
  84. Implementation for the cases (5, 4) and (5, 4)/(2, 0)
  85. Center group actions and related concepts
  86. Experimental investigation of the effect of horizontal construction joints on the behavior of deep beams
  87. Deletion of a vertex in even sum domination
  88. Deep learning techniques in concrete powder mix designing
  89. Effect of loading type in concrete deep beam with strut reinforcement
  90. Studying the effect of using CFRP warping on strength of husk rice concrete columns
  91. Parametric analysis of the influence of climatic factors on the formation of traditional buildings in the city of Al Najaf
  92. Suitability location for landfill using a fuzzy-GIS model: A case study in Hillah, Iraq
  93. Hybrid approach for cost estimation of sustainable building projects using artificial neural networks
  94. Assessment of indirect tensile stress and tensile–strength ratio and creep compliance in HMA mixes with micro-silica and PMB
  95. Density functional theory to study stopping power of proton in water, lung, bladder, and intestine
  96. A review of single flow, flow boiling, and coating microchannel studies
  97. Effect of GFRP bar length on the flexural behavior of hybrid concrete beams strengthened with NSM bars
  98. Exploring the impact of parameters on flow boiling heat transfer in microchannels and coated microtubes: A comprehensive review
  99. Crumb rubber modification for enhanced rutting resistance in asphalt mixtures
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  102. Forecasting empirical formula for suspended sediment load prediction at upstream of Al-Kufa barrage, Kufa City, Iraq
  103. Optimization and characterization of sustainable geopolymer mortars based on palygorskite clay, water glass, and sodium hydroxide
  104. Sediment transport modelling upstream of Al Kufa Barrage
  105. Study of energy loss, range, and stopping time for proton in germanium and copper materials
  106. Effect of internal and external recycle ratios on the nutrient removal efficiency of anaerobic/anoxic/oxic (VIP) wastewater treatment plant
  107. Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars
  108. Sustainable road paving: Enhancing concrete paver blocks with zeolite-enhanced cement
  109. Evaluation of the operational performance of Karbala waste water treatment plant under variable flow using GPS-X model
  110. Design and simulation of photonic crystal fiber for highly sensitive chemical sensing applications
  111. Optimization and design of a new column sequencing for crude oil distillation at Basrah refinery
  112. Inductive 3D numerical modelling of the tibia bone using MRI to examine von Mises stress and overall deformation
  113. An image encryption method based on modified elliptic curve Diffie-Hellman key exchange protocol and Hill Cipher
  114. Experimental investigation of generating superheated steam using a parabolic dish with a cylindrical cavity receiver: A case study
  115. Effect of surface roughness on the interface behavior of clayey soils
  116. Investigated of the optical properties for SiO2 by using Lorentz model
  117. Measurements of induced vibrations due to steel pipe pile driving in Al-Fao soil: Effect of partial end closure
  118. Experimental and numerical studies of ballistic resistance of hybrid sandwich composite body armor
  119. Evaluation of clay layer presence on shallow foundation settlement in dry sand under an earthquake
  120. Optimal design of mechanical performances of asphalt mixtures comprising nano-clay additives
  121. Advancing seismic performance: Isolators, TMDs, and multi-level strategies in reinforced concrete buildings
  122. Predicted evaporation in Basrah using artificial neural networks
  123. Energy management system for a small town to enhance quality of life
  124. Numerical study on entropy minimization in pipes with helical airfoil and CuO nanoparticle integration
  125. Equations and methodologies of inlet drainage system discharge coefficients: A review
  126. Thermal buckling analysis for hybrid and composite laminated plate by using new displacement function
  127. Investigation into the mechanical and thermal properties of lightweight mortar using commercial beads or recycled expanded polystyrene
  128. Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site
  129. The impact of incorporating waste materials on the mechanical and physical characteristics of tile adhesive materials
  130. Seismic resilience: Innovations in structural engineering for earthquake-prone areas
  131. Automatic human identification using fingerprint images based on Gabor filter and SIFT features fusion
  132. Performance of GRKM-method for solving classes of ordinary and partial differential equations of sixth-orders
  133. Visible light-boosted photodegradation activity of Ag–AgVO3/Zn0.5Mn0.5Fe2O4 supported heterojunctions for effective degradation of organic contaminates
  134. Production of sustainable concrete with treated cement kiln dust and iron slag waste aggregate
  135. Key effects on the structural behavior of fiber-reinforced lightweight concrete-ribbed slabs: A review
  136. A comparative analysis of the energy dissipation efficiency of various piano key weir types
  137. Special Issue: Transport 2022 - Part II
  138. Variability in road surface temperature in urban road network – A case study making use of mobile measurements
  139. Special Issue: BCEE5-2023
  140. Evaluation of reclaimed asphalt mixtures rejuvenated with waste engine oil to resist rutting deformation
  141. Assessment of potential resistance to moisture damage and fatigue cracks of asphalt mixture modified with ground granulated blast furnace slag
  142. Investigating seismic response in adjacent structures: A study on the impact of buildings’ orientation and distance considering soil–structure interaction
  143. Improvement of porosity of mortar using polyethylene glycol pre-polymer-impregnated mortar
  144. Three-dimensional analysis of steel beam-column bolted connections
  145. Assessment of agricultural drought in Iraq employing Landsat and MODIS imagery
  146. Performance evaluation of grouted porous asphalt concrete
  147. Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method
  148. Effect of waste tire products on some characteristics of roller-compacted concrete
  149. Studying the lateral displacement of retaining wall supporting sandy soil under dynamic loads
  150. Seismic performance evaluation of concrete buttress dram (Dynamic linear analysis)
  151. Behavior of soil reinforced with micropiles
  152. Possibility of production high strength lightweight concrete containing organic waste aggregate and recycled steel fibers
  153. An investigation of self-sensing and mechanical properties of smart engineered cementitious composites reinforced with functional materials
  154. Forecasting changes in precipitation and temperatures of a regional watershed in Northern Iraq using LARS-WG model
  155. Experimental investigation of dynamic soil properties for modeling energy-absorbing layers
  156. Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams
  157. An experimental study on the tensile properties of reinforced asphalt pavement
  158. Self-sensing behavior of hot asphalt mixture with steel fiber-based additive
  159. Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers
  160. Optimizing asphalt binder performance with various PET types
  161. Investigation of the hydraulic characteristics and homogeneity of the microstructure of the air voids in the sustainable rigid pavement
  162. Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study
  163. Special Issue: AESMT-7 - Part I
  164. Preparation and investigation of cobalt nanoparticles by laser ablation: Structure, linear, and nonlinear optical properties
  165. Seismic analysis of RC building with plan irregularity in Baghdad/Iraq to obtain the optimal behavior
  166. The effect of urban environment on large-scale path loss model’s main parameters for mmWave 5G mobile network in Iraq
  167. Formatting a questionnaire for the quality control of river bank roads
  168. Vibration suppression of smart composite beam using model predictive controller
  169. Machine learning-based compressive strength estimation in nanomaterial-modified lightweight concrete
  170. In-depth analysis of critical factors affecting Iraqi construction projects performance
  171. Behavior of container berth structure under the influence of environmental and operational loads
  172. Energy absorption and impact response of ballistic resistance laminate
  173. Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs
  174. Effect of surface roughness on interface shear strength parameters of sandy soils
  175. Evaluating the interaction for embedded H-steel section in normal concrete under monotonic and repeated loads
  176. Estimation of the settlement of pile head using ANN and multivariate linear regression based on the results of load transfer method
  177. Enhancing communication: Deep learning for Arabic sign language translation
  178. A review of recent studies of both heat pipe and evaporative cooling in passive heat recovery
  179. Effect of nano-silica on the mechanical properties of LWC
  180. An experimental study of some mechanical properties and absorption for polymer-modified cement mortar modified with superplasticizer
  181. Digital beamforming enhancement with LSTM-based deep learning for millimeter wave transmission
  182. Developing an efficient planning process for heritage buildings maintenance in Iraq
  183. Design and optimization of two-stage controller for three-phase multi-converter/multi-machine electric vehicle
  184. Evaluation of microstructure and mechanical properties of Al1050/Al2O3/Gr composite processed by forming operation ECAP
  185. Calculations of mass stopping power and range of protons in organic compounds (CH3OH, CH2O, and CO2) at energy range of 0.01–1,000 MeV
  186. Investigation of in vitro behavior of composite coating hydroxyapatite-nano silver on 316L stainless steel substrate by electrophoretic technic for biomedical tools
  187. A review: Enhancing tribological properties of journal bearings composite materials
  188. Improvements in the randomness and security of digital currency using the photon sponge hash function through Maiorana–McFarland S-box replacement
  189. Design a new scheme for image security using a deep learning technique of hierarchical parameters
  190. Special Issue: ICES 2023
  191. Comparative geotechnical analysis for ultimate bearing capacity of precast concrete piles using cone resistance measurements
  192. Visualizing sustainable rainwater harvesting: A case study of Karbala Province
  193. Geogrid reinforcement for improving bearing capacity and stability of square foundations
  194. Evaluation of the effluent concentrations of Karbala wastewater treatment plant using reliability analysis
  195. Adsorbent made with inexpensive, local resources
  196. Effect of drain pipes on seepage and slope stability through a zoned earth dam
  197. Sediment accumulation in an 8 inch sewer pipe for a sample of various particles obtained from the streets of Karbala city, Iraq
  198. Special Issue: IETAS 2024 - Part I
  199. Analyzing the impact of transfer learning on explanation accuracy in deep learning-based ECG recognition systems
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  201. Improving multi-object detection and tracking with deep learning, DeepSORT, and frame cancellation techniques
  202. The impact of using prestressed CFRP bars on the development of flexural strength
  203. Assessment of surface hardness and impact strength of denture base resins reinforced with silver–titanium dioxide and silver–zirconium dioxide nanoparticles: In vitro study
  204. A data augmentation approach to enhance breast cancer detection using generative adversarial and artificial neural networks
  205. Modification of the 5D Lorenz chaotic map with fuzzy numbers for video encryption in cloud computing
  206. Special Issue: 51st KKBN - Part I
  207. Evaluation of static bending caused damage of glass-fiber composite structure using terahertz inspection
https://doi.org/10.1515/eng-2022-0546
Keywords for this article
sustainable material; alkaline solution; calcination temperatures; carbon footprint; high-reactive palygorskite
Creative Commons
BY 4.0

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  2. Methodology of automated quality management
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  18. Improved correlation of soil modulus with SPT N values
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  37. Applications of nanotechnology and nanoproduction techniques
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  42. Erratum to “Effect of short heat treatment on mechanical properties and shape memory properties of Cu–Al–Ni shape memory alloy”
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  53. Special Issue: AESMT-5 - Part II
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  58. Asphalt binder modified with recycled tyre rubber
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  80. Experimental investigation of RC beams strengthened with externally bonded BFRP composites
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  88. Deep learning techniques in concrete powder mix designing
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  90. Studying the effect of using CFRP warping on strength of husk rice concrete columns
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  103. Optimization and characterization of sustainable geopolymer mortars based on palygorskite clay, water glass, and sodium hydroxide
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  107. Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars
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  111. Optimization and design of a new column sequencing for crude oil distillation at Basrah refinery
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  121. Advancing seismic performance: Isolators, TMDs, and multi-level strategies in reinforced concrete buildings
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  125. Equations and methodologies of inlet drainage system discharge coefficients: A review
  126. Thermal buckling analysis for hybrid and composite laminated plate by using new displacement function
  127. Investigation into the mechanical and thermal properties of lightweight mortar using commercial beads or recycled expanded polystyrene
  128. Experimental and theoretical analysis of single-jet column and concrete column using double-jet grouting technique applied at Al-Rashdia site
  129. The impact of incorporating waste materials on the mechanical and physical characteristics of tile adhesive materials
  130. Seismic resilience: Innovations in structural engineering for earthquake-prone areas
  131. Automatic human identification using fingerprint images based on Gabor filter and SIFT features fusion
  132. Performance of GRKM-method for solving classes of ordinary and partial differential equations of sixth-orders
  133. Visible light-boosted photodegradation activity of Ag–AgVO3/Zn0.5Mn0.5Fe2O4 supported heterojunctions for effective degradation of organic contaminates
  134. Production of sustainable concrete with treated cement kiln dust and iron slag waste aggregate
  135. Key effects on the structural behavior of fiber-reinforced lightweight concrete-ribbed slabs: A review
  136. A comparative analysis of the energy dissipation efficiency of various piano key weir types
  137. Special Issue: Transport 2022 - Part II
  138. Variability in road surface temperature in urban road network – A case study making use of mobile measurements
  139. Special Issue: BCEE5-2023
  140. Evaluation of reclaimed asphalt mixtures rejuvenated with waste engine oil to resist rutting deformation
  141. Assessment of potential resistance to moisture damage and fatigue cracks of asphalt mixture modified with ground granulated blast furnace slag
  142. Investigating seismic response in adjacent structures: A study on the impact of buildings’ orientation and distance considering soil–structure interaction
  143. Improvement of porosity of mortar using polyethylene glycol pre-polymer-impregnated mortar
  144. Three-dimensional analysis of steel beam-column bolted connections
  145. Assessment of agricultural drought in Iraq employing Landsat and MODIS imagery
  146. Performance evaluation of grouted porous asphalt concrete
  147. Optimization of local modified metakaolin-based geopolymer concrete by Taguchi method
  148. Effect of waste tire products on some characteristics of roller-compacted concrete
  149. Studying the lateral displacement of retaining wall supporting sandy soil under dynamic loads
  150. Seismic performance evaluation of concrete buttress dram (Dynamic linear analysis)
  151. Behavior of soil reinforced with micropiles
  152. Possibility of production high strength lightweight concrete containing organic waste aggregate and recycled steel fibers
  153. An investigation of self-sensing and mechanical properties of smart engineered cementitious composites reinforced with functional materials
  154. Forecasting changes in precipitation and temperatures of a regional watershed in Northern Iraq using LARS-WG model
  155. Experimental investigation of dynamic soil properties for modeling energy-absorbing layers
  156. Numerical investigation of the effect of longitudinal steel reinforcement ratio on the ductility of concrete beams
  157. An experimental study on the tensile properties of reinforced asphalt pavement
  158. Self-sensing behavior of hot asphalt mixture with steel fiber-based additive
  159. Behavior of ultra-high-performance concrete deep beams reinforced by basalt fibers
  160. Optimizing asphalt binder performance with various PET types
  161. Investigation of the hydraulic characteristics and homogeneity of the microstructure of the air voids in the sustainable rigid pavement
  162. Enhanced biogas production from municipal solid waste via digestion with cow manure: A case study
  163. Special Issue: AESMT-7 - Part I
  164. Preparation and investigation of cobalt nanoparticles by laser ablation: Structure, linear, and nonlinear optical properties
  165. Seismic analysis of RC building with plan irregularity in Baghdad/Iraq to obtain the optimal behavior
  166. The effect of urban environment on large-scale path loss model’s main parameters for mmWave 5G mobile network in Iraq
  167. Formatting a questionnaire for the quality control of river bank roads
  168. Vibration suppression of smart composite beam using model predictive controller
  169. Machine learning-based compressive strength estimation in nanomaterial-modified lightweight concrete
  170. In-depth analysis of critical factors affecting Iraqi construction projects performance
  171. Behavior of container berth structure under the influence of environmental and operational loads
  172. Energy absorption and impact response of ballistic resistance laminate
  173. Effect of water-absorbent polymer balls in internal curing on punching shear behavior of bubble slabs
  174. Effect of surface roughness on interface shear strength parameters of sandy soils
  175. Evaluating the interaction for embedded H-steel section in normal concrete under monotonic and repeated loads
  176. Estimation of the settlement of pile head using ANN and multivariate linear regression based on the results of load transfer method
  177. Enhancing communication: Deep learning for Arabic sign language translation
  178. A review of recent studies of both heat pipe and evaporative cooling in passive heat recovery
  179. Effect of nano-silica on the mechanical properties of LWC
  180. An experimental study of some mechanical properties and absorption for polymer-modified cement mortar modified with superplasticizer
  181. Digital beamforming enhancement with LSTM-based deep learning for millimeter wave transmission
  182. Developing an efficient planning process for heritage buildings maintenance in Iraq
  183. Design and optimization of two-stage controller for three-phase multi-converter/multi-machine electric vehicle
  184. Evaluation of microstructure and mechanical properties of Al1050/Al2O3/Gr composite processed by forming operation ECAP
  185. Calculations of mass stopping power and range of protons in organic compounds (CH3OH, CH2O, and CO2) at energy range of 0.01–1,000 MeV
  186. Investigation of in vitro behavior of composite coating hydroxyapatite-nano silver on 316L stainless steel substrate by electrophoretic technic for biomedical tools
  187. A review: Enhancing tribological properties of journal bearings composite materials
  188. Improvements in the randomness and security of digital currency using the photon sponge hash function through Maiorana–McFarland S-box replacement
  189. Design a new scheme for image security using a deep learning technique of hierarchical parameters
  190. Special Issue: ICES 2023
  191. Comparative geotechnical analysis for ultimate bearing capacity of precast concrete piles using cone resistance measurements
  192. Visualizing sustainable rainwater harvesting: A case study of Karbala Province
  193. Geogrid reinforcement for improving bearing capacity and stability of square foundations
  194. Evaluation of the effluent concentrations of Karbala wastewater treatment plant using reliability analysis
  195. Adsorbent made with inexpensive, local resources
  196. Effect of drain pipes on seepage and slope stability through a zoned earth dam
  197. Sediment accumulation in an 8 inch sewer pipe for a sample of various particles obtained from the streets of Karbala city, Iraq
  198. Special Issue: IETAS 2024 - Part I
  199. Analyzing the impact of transfer learning on explanation accuracy in deep learning-based ECG recognition systems
  200. Effect of scale factor on the dynamic response of frame foundations
  201. Improving multi-object detection and tracking with deep learning, DeepSORT, and frame cancellation techniques
  202. The impact of using prestressed CFRP bars on the development of flexural strength
  203. Assessment of surface hardness and impact strength of denture base resins reinforced with silver–titanium dioxide and silver–zirconium dioxide nanoparticles: In vitro study
  204. A data augmentation approach to enhance breast cancer detection using generative adversarial and artificial neural networks
  205. Modification of the 5D Lorenz chaotic map with fuzzy numbers for video encryption in cloud computing
  206. Special Issue: 51st KKBN - Part I
  207. Evaluation of static bending caused damage of glass-fiber composite structure using terahertz inspection
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