Optimum design of alkali activated slag concretes for the low oxygen/chloride ion permeability and thermal conductivity

Balçıkanlı, Müzeyyen; Özbay, Erdoğan

doi:10.1016/j.compositesb.2016.01.047

Cited by 59 publications

(19 citation statements)

References 44 publications

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“…This issue might be solved by numerous approaches, e.g. careful selection of raw materials [57], adjustment of mix proportions [18], addition of nano-materials [67], change of activator usage and type [68].…”

Section: )mentioning

confidence: 99%

“…In order to reduce water sorptivity of AAS, a range of techniques have been applied, e.g. changing mix designs and curing conditions [18], adding inert mineral admixtures [19], adding steel fiber [20]. Using these techniques can decrease the water transport rates of AAS, while the sorptivity is still higher than that of the corresponding PC specimens.…”

Section: Introductionmentioning

confidence: 99%

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An alternative admixture to reduce sorptivity of alkali-activated slag cement by optimising pore structure and introducing hydrophobic film

Yang

2019

Cement and Concrete Composites

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The high water absorption rate of alkali-activated slag (AAS) cement, which causes concerns to designers and constructors as "long-term" durability comes into question, was addressed using an alternative admixture, calcium stearate (CaSt). The macro-and micro-performance of AAS cement with two levels of CaSt dosage (4 wt%, 8 wt% of slag) were characterised under the water to binder ratio (W/B) ranging from 0.35 to 0.45 and benchmarked against corresponding Portland cement (PC) samples by sorptivity along with compressive strength, porosity, electrical resistivity, pore connectivity, pore size distribution and pore geometries. The interpretation of results showed that CaSt played an instrumental role in pore structure features of AAS and the use of CaSt could significantly reduce its sorptivity, even lower than the corresponding PC samples. It is also found that the recommended usage of CaSt is 4% of slag, beyond which no significant variation in sorptivity can be detected. The performance improvement was caused by two main mechanisms, optimising the pore structure (more entrained pores, less pore connectivity factor and less microcracks) and introduce of the hydrophobic film on the pore surface. One limitation of using CaSt was noted as well. That is, the strength development of AAS can be affected and it can be avoided through modifying mix proportions according to practical requirements. Therefore, CaSt can be used as a chemical admixture for AAS to solve the concern on its high sorptivity behaviour.

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Section: )mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An alternative admixture to reduce sorptivity of alkali-activated slag cement by optimising pore structure and introducing hydrophobic film

Yang

2019

Cement and Concrete Composites

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“…By increasing the density of activator within the geopolymer mixture, up to a certain degree, an increase in the compressive strength of the geopolymer is observed [17]. The most important aspect in mixing NaOH and nSiO2Na2O at certain ratios is the tuning of the SiO2/Na2O ratio, called the silica modulus (Ms) [19]. Increasing the Ms ratio by a certain amount increases the endurance; however, the ability to process it decreases due to the geopolymer structure formed [20].…”

Section: Introduction mentioning

confidence: 99%

Behaviour of Geopolymer Mortars after Exposure to Elevated Temperatures

Kaya

Uysal²,

Yılmaz

et al. 2018

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In this study it was investigated the behavior of class F fly ash based geopolymer mortars subjected to elevated temperatures. Geopolimer composites were prepared with CEN-sand, water, fly ash as the binder, nSiO2Na2O and NaOH mixture combination as alkali activator. After mixing fresh geopolymer mixture, prismatic specimens were prepared using 40 mm × 40 mm × 160 mm prism molds. After molding, fresh geopolymer mortar samples with their mold were subjected to heat curing at 50 °C, 60 °C, 70 °C, 80 °C, 90 °C and 100 °C temperature for 48 hours in an oven. After 48 hours initial heat curing, the hardened samples were taken out of their mold. Then, they were further cured by leaving them in laboratory environment at about 22 ± 2 °C temperature, until 28 days together with heat curing duration. At the end of 28 days, geopolymer mortar samples developed flexural strength values between 2,9 MPa and 8,51 MPa. Geopolymer mortar samples developed compressive strength values between 7,63 MPa and 50,64 MPa. High temperature experiments were conducted to observe behaviour of geopolymer mortars at elevated temperatures. The control cement mortar mixtures were also prepared and subjected to high temperature exposure in comparison to geopolymer mortar mixtures. Control cement mortars were cured at laboratory environment for 28 days without initial temperature curing. Control cement mortar mixtures and geopolymer mortar mixtures were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C and 800 °C temperature. The unit weight, ultrasonic pulse velocity, flexural and compressive strength of all mixtures were measured before and after high temperature exposure. Scanning electron microscope (SEM) images of the mixtures were taken and X-ray fluorescence (XRF) spectrometer analyses were carried out. It was observed that there was an increase in the flexural and compressive strengths of some geopolymer mortars after high temperature exposure. In general, geopolymer mortars exhibited better performance at elevated temperatures in comparison to control cement mortar mixture.

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“…Geopolymers, as inorganic cementitious materials, have received much attraction in recent years due to their high strength, acid corrosion resistance, high temperature resistance, fire resistance, eco-friendliness, and good durability [1][2][3]. The formed three-dimensional networks of geopolymers exhibit the properties of organic thermoset polymers via dissolving aluminosilicate oxides to produce silicon tetrahedral (Si(OH) 4 -) and aluminum tetrahedral(Al(OH) 4 -) monomers, followed by linking the two tetrahedras alternately with oxygen atoms to form polysialate chains [4][5]. Geopolymers not only show similar mechanical properties to Ordinary Portland Cement (OPC), but the CO 2 emission in the manufacture process is also significantly reduced by at least 80% [6].…”

Section: Introductionmentioning

confidence: 99%

Microstructure and compressive properties of silicon carbide reinforced geopolymer

Xie

Zhang

et al. 2016

Composites Part B: Engineering

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Geopolymers (GPs) have emerged as a promising alternative to ordinary cement due to its attractive physical and thermal properties. The typical compressive strength of geopolymers and their composites is usually limited to around 80 MPa, therefore they should be further strengthened for wider applications, such as ultrahigh strength concrete, and bone replacement. This paper presents a facile method of enhancing the compressive strength by incorporating silicon carbide particles (SiC p) and silicon carbide whiskers (SiC w) into the geopolymer matrix via the geopolymerization of metakaolin (MK). The effects of the reinforcement of SiC p and SiC w on the microstructure, thermal properties and compressive properties of the composites were investigated. The SEM images showed that both SiC p and SiC w were well dispersed in the geopolymer matrix. Due to the bridging effect among the SiC w particles, SiC w /GP composites possessed higher porosity and lower density, and thus lower thermal stability and thermal conductivity as compared with SiC p /GP. The mechanical tests showed that the compressive strength of SiC p /GP composites increased with the increase of SiC p concentration. With an optimum concentration of 10 wt. % of SiC p , the compressive strength of the composite was enhanced to 155 MPa, corresponding to a 100% increase as compared with the unfilled geopolymer.

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Optimum design of alkali activated slag concretes for the low oxygen/chloride ion permeability and thermal conductivity

Cited by 59 publications

References 44 publications

An alternative admixture to reduce sorptivity of alkali-activated slag cement by optimising pore structure and introducing hydrophobic film

An alternative admixture to reduce sorptivity of alkali-activated slag cement by optimising pore structure and introducing hydrophobic film

Behaviour of Geopolymer Mortars after Exposure to Elevated Temperatures

Microstructure and compressive properties of silicon carbide reinforced geopolymer

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