Next-Gen Geopolymer Concrete: Optimizing Strength and Durability with Fibers

Geopolymer is an inorganic alumino-silicate product that shows good bonding properties. Geopolymer binders are used together with aggregates to produce geopolymer concrete which is an ideal building material for infrastructures. A by-product material such as fly ash is mixed together with an alkali to produce geopolymer. Current research on geopolymer concrete has shown potential of the material for construction of reinforced concrete structures. Structural performance of reinforced concrete depends on the bond between concrete and the reinforcing steel. Design provisions of reinforced concrete as a composite material are based on the bond strength between concrete and steel. Since geopolymer binder is chemically different from Ordinary Portland Cement (OPC) binder, it is necessary to understand the bond strength between geopolymer concrete and steel reinforcement for its application to reinforced concrete structures. Pull out test is commonly used to evaluate the bond strength between concrete and reinforcing steel. This paper describes the results of the pull out tests carried out to investigate the bond strength between fly ash based geopolymer concrete and steel reinforcing bars. Beam end specimens in accordance with the ASTM Standard A944 were used for the tests. In the experimental program, 24 geopolymer concrete and 24 OPC concrete specimens were tested for pull out. The concrete compressive strength varied from 25 to 55 MPa. The other test parameters were concrete cover and bar diameter. The reinforcing steel was 500 MPa steel deformed bars of 20 mm and 24 mm diameter. The concrete cover to bar diameter ratio varied from 1.71 to 3.62. It was found from the test results that the failure occurred by splitting of concrete in the region bonded with the steel bar, in both geopolymer and OPC concrete specimens. Comparison of the test results shows that geopolymer concrete has higher bond strength than OPC concrete. This suggests that the existing design equations for bond strength of OPC concrete with steel reinforcing bars can be conservatively used for calculation of bond strength of geopolymer concrete.

Environmental impact assessment of fly ash and silica fume based geopolymer concrete

A fractal dimension-modified stochastic damage model for bond-slip responses of corroded steel rebar embedded in different types of geopolymer concrete

Rapid urbanization and modern construction approach create an impervious island in urban and semi-urban areas, which leads to make a situation of artificial flooding. The major reason for making impervious islands is due to the use of cement-based concrete pavement in and around the urban areas. As a result, stormwater runoff is promptly collected and discharged to various receiving main drains, rivers, and, eventually, the sea. This leads to decrease infiltration and depletes the water table. To overcome these problems, pervious concrete is very essential to be laid down in the parking areas, low volume road pavement, sidewalks, driveways, tennis courts etc. in place of normal cement concrete. Normal porous concrete is a special type of cement concrete with high porosity, allowing water to percolate into the sub-grade. But cement is said to be the most unsustainable material requiring huge energy, emitting huge carbon dioxide and consuming huge natural resources during its production. On the other hand, alkali-activated alumina-silica rich waste material made geo-polymer concrete is said to be a sustainable alternative to cement concrete. This paper reports on the preparation and properties of an eco-friendly geo-polymer self-compacting pervious concrete mix using fly ash under the sun curing. Various laboratory tests like compressive strength, flexural strength and permeability of prepared geo-polymer concrete were taken up. The laboratory results of sun-cured geo-polymer concrete were compared to water-cured normal concrete and found more or less nearer to each other. To establish the structural performance of prepared geo-polymer pervious concrete, a pilot study was taken up using the prepared material as shoulder material. Rebound hammer tests were conducted at the field and compared to laboratory results and found consistent. The compressive strength obtained was found more than 15 MPa for which it can be used also used for applications with low traffic volume. The location of the pilot project: Lat 20°21'10.58"N, Long: 85°54'54.78"E village-Aradiapada, Cuttack Odisha India.

This paper describes the research on bond behavior of plain reinforcing bars in geopolymer and normal concrete. The geopolymer concrete in this research was made of class F fly ash taken from Tanjung Jati Electric Steam Power Plant (PLTU) with Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) as alkaline activator, added in the mixture. The effect of bar size was studied by varying the bar diameter in range 10 mm to 19 mm. Each bar was casted in the center of concrete blocks made of geopolymer as well as normal concrete. Pull-out tests were carried out to the specimens that have reached 28 days of age. The test results show that the bond behavior of geopolymer concrete differs substantially from normal concrete, where geopolymer concrete has a higher bond strength when compared to normal concrete with identical concrete strengths.

Concrete usage around the world is second only to water. Ordinary Portland Cement (OPC) is conventionally used as the primary binder to produce concrete. But the amount of carbon dioxide released during the manufacture of OPC due to the calcinations of lime stone and combustion of fossil fuel is in the order of 600 kg for every ton of OPC produced. In addition, the extent of energy requires to produce OPC is only next to steel and aluminum. On the other hand, the abundant availability of fly ash worldwide creates opportunity to utilize (by ‐ product of burning coal, regarded as a waste material) as substitute for OPC to manufacture concrete. Binders could be produced by polymeric reaction of alkali liquids with the silicon and the aluminum in the source materials such as fly ash and rice husk ash and these binders are termed as Geopolymer. In Geopolymer Concrete, fly ash and aggregates are mixed with alkaline liquids such as a combination of Sodium Silicate and Sodium Hydroxide. United Nation’s Intergovernmental panel on Climate Change (IPCC) prepared a report on global warming during April 2007 which enlists various methods of reduction of CO2 emissions into atmosphere. As per that report, unmindful pumping of CO2 into the atmosphere is the main culprit for the climate change. Large volume of fly ash is being produced by thermal power stations and part of the fly ash produced is used in concrete industry, low laying area fill, roads and embankment, brick manufacturing etc. The balance amount of fly ash is being stored in fly ash ponds. Hence it is imperative on the part of Scientists and Engineers to devise suitable methodologies for the disposal of fly ash. Disposal of fly ash has the objective of saving vast amount of land meant for ash pond to store fly ash. Further, use of fly ash as a value added material as in the case of geopolymer concrete, reduces the consumption of cement. Reduction of cement usage will reduce the production of cement which in turn cut the CO2 emissions. Many researchers have worked on the development of geopolymer cement and concrete for the past ten years. The time has come for the review of progress made in the field of development of geopolymer concrete. Consequently 102 papers pertaining to the ingredients and technology of geopolymer concrete have been reviewed in this state of the art paper.

Comparison on the properties of ITZs in fly ash-based geopolymer and Portland cement concretes with equivalent flowability

The reliability of the Rapid Chloride Permeability Test (RCPT), ASTM C1202, for geopolymer concrete (GPC) is often debated, particularly due to the use of 60 V and the lack of a standardised rating scale tailored to GPC. Although prior studies have noted problems with RCPT in GPC and proposed partial remedies, a fully validated framework tailored to GPC is still lacking. Standardised testing conditions and clear links between RCPT results and chloride transport behaviour remain undeveloped. To this end, this study examines the effect of applied voltage on RCPT results and recommends a modified methodology to establish a suitable rating scale for GPC. Sixty GPC mixtures, characterised by varying mix designs and strengths, were assessed, and their key properties – compressive strength, conductivity, formation factor, and charge passed – were analysed in relation to chloride diffusion coefficients. The formation factor was incorporated to normalise pore solution conductivity, thereby enabling assessment of microstructural transport behaviour. Findings confirm that voltages above 10 V often cause premature test termination; therefore, 10 V is identified as the recommended upper operating voltage for reliable RCPT testing in GPC under the investigated conditions. Following these results, performance criteria for the modified RCPT and formation factor are proposed, providing a reliable basis for assessing chloride permeability in GPC. Additionally, prescriptive requirements are outlined to guide the selection of suitable GPC mixtures for specific applications. This study delivers a validated framework for reliable RCPT use in GPC, defining voltage, rating scale, and formation factor limits to enable standardisation and adoption in design codes. • Validated guidelines established for voltage selection in RCPT tailored to GPC • RCPT performance-based testing framework developed and validated for GPC • Introduced formation factor from pore conductivity as durability indicator • Proven OPC pore chemistry–RCPT relation inapplicable to GPC

Incorporating crumb rubber in slag-based geopolymer: Experimental work and predictive modelling

Durability performance of low calcium Flyash-Based geopolymer concrete

Evaluation of freeze-thaw resistance of geopolymer concrete incorporating GFRP waste powder

In the realm of environmentally friendly building materials, geopolymer concrete stands out as a viable substitute for traditional concrete made of cement. This literature review explores recent developments and innovations in geopolymer concrete, with an emphasis on optimizing its properties through the use of various supplementary materials. The aim is to enhance both the mechanical strength and geopolymer concrete's microstructural properties, while also investigating the cost efficiency of these enhancements. The review systematically examines different combinations of supplementary cementitious materials, analyzing their impact on mechanical stability and long-term performance. Additionally, the study delves into the creation of precise Artificial Neural Network models using mixed synthetic data to accurately predict geopolymer concrete properties. Microstructural properties of geopolymer concrete are evaluated through XRD and SEM analyses, providing valuable insights into its structural integrity. Furthermore, a comparative analysis of the cost parameters between traditional concrete and geopolymer concrete is conducted, shedding light on the economic viability of GPC in construction projects. This thorough evaluation aims to support ongoing research and development in the field of geopolymer concrete, offering valuable insights for engineers, researchers, and industry professionals seeking sustainable and efficient construction materials. Incorporating supplementary cementitious materials, such as fly ash, slag, and metakaolin, significantly enhances the mechanical strength and durability of geopolymer concrete (GPC), providing superior resistance to environmental degradation, such as sulfate attack, compared to traditional Portland cement concrete. The application of artificial intelligence, specifically ANN modeling with mixed synthetic datasets, demonstrates a high degree of accuracy in predicting the compressive strength and long-term performance of GPC. This facilitates the development of optimized and reliable mix designs tailored to diverse construction needs. A detailed cost analysis highlights the economic and environmental viability of GPC. While its initial production costs may be higher due to specialized materials, its long-term cost-effectiveness is evident through enhanced durability and reduced maintenance. Its lower carbon footprint makes GPC a sustainable alternative for future projects while using industrial by-products promotes a circular economy. Major Findings: Geopolymer Concrete (GPC) can significantly enhance mechanical strength and microstructural properties through various supplementary cementitious materials. Advanced techniques like Artificial Neural Networks (ANN) and microstructural analyses (XRD, SEM) provide deeper insights into GPC's stability and performance. Additionally, GPC demonstrates economic viability compared to traditional concrete, offering sustainable benefits for construction projects.

In recent years, Geopolymer concrete (GPC) stands as a promising alternative to traditional Portland cement-based concrete in the quest for eco-friendly and sustainable construction materials. However, the practical application of GPC remains limited due to the need for controlled high-temperature curing environments. Furthermore, accurately predicting GPC properties has become an urgent issue to reduce the time and cost associated with laboratory experiments. This study aims to investigate how different curing methods, for both on-site and precast application, impact the fracture energy of GPC. Three curing methods at varying temperatures, room temperature (25 °C), mobile dryer (50 °C), and heating cabinet (80 °C), were considered. A comprehensive dataset comprising 194 fracture test results was compiled to propose diverse machine learning models capable of forecasting GPC fracture energy, both without and with various fibers (Steel, Polypropylene, Basalt, Polyvinyl alcohol…). The findings revealed that GPC fracture energy increased by 89% when the curing temperature rose from 25 to 50 °C. A further increase in temperature from 50 to 80 °C resulted in an additional 11% increase in fracture energy. Interestingly, GPC exhibited slightly higher (up to 8%) fracture energy than Portland cement concrete when their compressive strengths were comparable. The developed machine learning models exhibited correlation coefficient values above 0.95 and root mean squared error values within 10% of the average actual values, indicating their exceptional accuracy in predicting GPC fracture energy, regardless of fiber presence. Additionally, sensitivity analysis highlighted the significance of fiber volume content as the primary factor influencing fracture energy in GPC, while in GPC without fibers, the notch depth ratio emerged as the determining factor, accounting for 78% predictive importance.

Water and chemical penetration characteristics of graded geopolymer concrete

Developing sustainable construction products has been showing a rising trend recently. Geopolymer composites are remarkable binding materials fabricated based on recycling and sustainability. In this paper, an experimental investigation was conducted to study some mechanical and durability characteristics of steel fiber-reinforced fly ash/slag-based geopolymer concrete (GPC) with different proportions of recycled coarse aggregate. Steel fiber-reinforced geopolymer concrete mixtures incorporating recycled coarse aggregates of up to 40% at the interval of 10% were prepared, and the mixtures without recycled coarse aggregate were used as reference samples. The steel fiber ratio of 0.3% and 0.6% were used and the combined effect of steel fiber and recycled coarse aggregate on the geopolymer composites’ behavior regarding strength properties, sulfate resistance, elevated temperature resistance, abrasion resistance, and freezing-thawing resistance was addressed. A significant improvement in strength properties was observed in steel fiber reinforced recycled aggregate geopolymer concrete with increasing fiber content; however, the strength properties of geopolymer concrete were decreased with the increase of recycled coarse aggregate amount. Also, the properties such as abrasion resistance, resistance to elevated temperature, sulfate resistance, and freeze-thaw resistance were improved with the addition of steel fiber. It indicates that the synergetic effect of steel fiber and recycled aggregate helps to produce ecologically sound geopolymer concrete with good engineering properties and durability characteristics that will bring sustainability to the concrete sector. Generally, the results show that the recycled coarse aggregate ratio of up to 30% and 0.6% of steel fiber can be considered an ideal combination to make geopolymer concrete with better overall properties.