Mechanical Properties Of Geopolymer Concrete Research Articles

Microstructure and Mechanical Properties of Ambiently-Cured Blended Coal Ash-Based Geopolymer Concrete

This paper presents the results of an experimental study on the behavior of fly ash-, bottom ash-, and blended fly and bottom ash-based geopolymer concrete (GPC) cured at ambient temperature. Four bathes of GPC were manufactured to investigate the influence of the fly ash-to-bottom ash mass ratio on the microstructure, compressive strength and elastic modulus of GPC. All the results indicate that the mass ratio of fly ash-to-bottom ash significantly affects the microstructure and mechanical properties of GPCs

Production of geopolymer concrete using natural pozzolan: A parametric study

An experimental investigation was undertaken to study the mechanical properties of geopolymer concrete (GPC), produced with Jordanian natural pozzolan (JNP) as base material and commercially available alkaline solution made of sodium silicate (NS) and sodium hydroxide (NH). GPC mixtures with limestone aggregates were proportioned considering various ratios of NSNH-to-JNP, and NS-to-NH, and concentrations of NH then tested for fresh and hardened properties using the technology currently used for conventional concrete. The compressive strength was determined over time for specimens that were either cured in laboratory air or dry cured in an oven for 24 or 48h at three different curing temperatures (40, 80, and 120°C) after 24h of casting. Scanning Electron Microscopy (SEM) images were also taken for samples representing various GPC specimens and dry curing temperatures. The parameters considered in proportioning various GPC mixtures had significantly impacted strength; confirming the behavior observed in literature; with optimal mixtures achieving matured compressive strengths in excess of 30MPa. Dry curing of GPC in an oven at 40°C and 80°C for less than 48h imparted significant increase in compressive strength at 25% and 32% of that obtained at normal curing in laboratory air, respectively. Extending dry curing period at the present temperatures beyond the first day after casting has resulted in a limited increase in compressive strength at 28days. The present GPC mixtures demonstrated high early strength development exceeding 70% of ultimate strength at three days of dry curing. SEM pictures confirmed the behaviors noticed for compressive strength for GPC mixtures, prepared at various proportions or heat cured at various temperatures.

Structural Behaviour and Design of Geopolymer Concrete Members

The worldwide production of concrete is on the increase in order to meet the increasing rate of construction. Since cement production contributes to the greenhouse gas emission, it is vital to develop alternative low-emission binders to reduce the carbon footprint of concrete. Fly ash based geopolymer is an alternative binder that has potential to reduce the CO2 emission of concrete production. It has been shown in different studies that the mechanical properties of geopolymer concrete are comparable to those of ordinary Portland cement (OPC) concrete. This paper describes the behaviour and design aspects of geopolymer concrete structural members. The design aspects presented in this paper are bond of reinforcing steel in pull-out and spliced bars in beams, beams in shear and flexure, and columns in uniaxial and biaxial bending. It is shown that the current provisions for OPC concrete can be conservatively used for design of reinforced geopolymer concrete members.

Mechanical properties of geopolymer concrete exposed to dynamic compression under elevated temperatures

Through adoption of a self-designed high temperature SHPB apparatus herein, an experimental study is made on the mechanical properties of geopolymer concrete (GC) exposed to dynamic compression under elevated temperatures. As the results have turned out, the weight loss is remarkable within temperature ranges from room temperature to 200°C as well as from 600°C to 800°C. The dynamic compressive strength of GC grows higher at 200°C than at room temperature, but suffers a dramatic drop at 800°C. The critical strain is higher at elevated temperature than that at room temperature. At 200°C and 600°C, respectively, its energy absorption property is superior to that at room temperature. However, at 400°C and 800°C, respectively, it is inferior to that at room temperature. The strain rate effect of the dynamic increase factor (DIF) obtained from test data can reflect the inherent nature of GC. The DIF assumes a linear relationship with the logarithm of strain rate.

Influence of recycled concrete aggregates on the flexural properties of reinforced alkali activated slag concrete

Alkali-activated concretes are a novel invention for substituting conventional construction materials; their main variation from conventional Portland cement concretes is utilizing comparatively alkali-rich, clinker-free binder matrix namely alkali-activated slag or geopolymer. Alkali-activated concrete is an environmental friendly and possibly considered to be a part of the sustainable development. Since, aggregates constitutes the major part of the concrete, there is a need to reduce the use of natural aggregate thereby reducing the exploitation of natural resources. This paper explains the influence of recycled concrete aggregates derived from the demolished concrete waste on the mechanical properties of geopolymer concrete (GPC). Since, very few studies been conducted using recycled aggregates in geopolymer concrete under ambient curing, an experimental work was carried out involving mixes with varying proportion of recycled aggregates and their influence on the physical, mechanical and flexural characteristics of geopolymer concrete. The results infer that the inclusion of recycled aggregate improves the strength characteristics of geopolymer concrete.

Dynamic mechanical properties of geopolymer concrete after water immersion

This paper aims to investigate the influence of water immersion on dynamic mechanical properties of geopolymer concrete (GC). Dynamic compressive tests on specimens placed indoors (GCN) and specimens with water immersion (GCW) were conducted by a split Hopkinson pressure bar system. The results indicate that the dynamic strength and impact toughness of GCN and GCW display an increasing trend as strain rate increases, while the elastic modulus is not rate-sensitive since no obvious trends can be observed with strain rate. The quasi-static strength of GC decreases after water immersion. Under impact loading, however, water immersion exhibits a strengthening and stiffening effect on GC as confirmed by the higher dynamic strength and higher dynamic elastic modulus of GCW. And the absorbed water within specimen also improves the rate sensitivity of GC׳s strength performance. Besides, water immersion has a minor influence on the impact toughness of GC. However, as compared with GCN, GCW dissipate less impact energy prior to the peak load and have a lower average deformation during the impact procedure. In general, the impact damage of GCW is less serious than that of GCN at approximately the same strain rate. The fragment size of GCW distributes in the coarser grained side.

Effect of Alkaline Activator Ratio to Mechanical Properties of Geopolymer Concrete with Trass as Filler

This paper describes the effect of alkaline activator ratio (Na2SiO3/NaOH) to mechanical properties of geopolymer concrete. The mechanical properties of geopolymer concrete were assessed by setting time, split tensile strength and porosity. Fly ash was used as a cement substitute, and trass used as filler. While, Natrium hydroxide (NaOH) and Sodium Silicate (Na2SiO3) was applied as alkaline activator. In this study, NaOH concentration eight and ten molar with an alkaline activator ratio Na2SiO3/ NaOH by mass: 0.5, 1, 1.5, 2 and 2.5 were used. The test result showed that setting time, porosity and split tensile strength of geopolymer concrete were hardly influenced by NaOH concentration and the alkaline activator ratio. The alkaline activator ratio of Na2SiO3/NaOH has an optimum value at 2 and 2.5. Test result showed that the fastest setting time was 25 minute, the highest amount of closed porosity was 9.035 % and the highest split tensile strength was 2.86 MPa.

MECHANICAL PROPERTIES OF FLY ASH BASED GEOPOLYMER CONCRETE WITH ADDITION OF GGBS

Concrete plays an important role in the construction industry worldwide. New technology has made for easier development of new types of construction and alternative materials in the concrete area. Cement is the major component in the production of concrete, but its manufacture causes environmental issues and thus there is a need for alternative materials. Geopolymer concrete is a new type of material with that potential, commonly formed by alkali activation of industrial alumina silicate byproducts, such as fly ash and ground granulated blast furnace slag (GGBS). For this paper, mechanical properties of geopolymer concrete with fly ash and GGBS cured under ambient temperatures were studied. Five different grades of concrete were considered. The results were encouraging: The workability of the geopolymer concrete was similar to that of conventional concrete. Experimental results of flexural and splitting tensile strength revealed insignificant variation compared to conventional concrete. The mechanical properties of fly ash and GGBS-based geopolymer concrete were comparable with conventional concrete.

English

The objective of this project is to study the effect of class fly ash (FA) and ground granulated blast furnace slag (GGBS) on the mechanical properties of geopolymer concrete (GPC) at different replacement levels (FA0-GGBS100, FA25-GGBS75, FA50-GGBS50; FA75-GGBS25, FA100, GGBS0). Sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solution have been used as alkaline activators. In the present investigation, it is proposed to study the mechanical properties viz. compressive strength, split tensile strength of low calcium fly ash and GGBS based geopolymer concrete. These properties have been determined at different curing periods like 7, 28, 56 and 90 days and at ambient room temperature.

The Influence of Alkali Activator Concentration to Mechanical Properties of Geopolymer Concrete with Trass as a Filler

This paper describes one of the varying factors influencing the mechanical properties of geopolymer concrete. Fly ash and volcanic material called trass was used as raw materials, while sodium Hydroxide (NaOH) and Sodium silicate (Na2SiO3) was applied as an alkali activator. Mechanical properties were assessed by compressive test, the concentration of NaOH used in this study was eight and ten Molars, and ratio of Na2SiO3to NaOH by mass was 0.5, 1, 1.5, 2, and 2.5. Test results indicated that the strength of geopolymer concrete and binder were hardly influenced by concentration of NaOH in solution and the activator ratio. Binder with activator ratio of 2.5 has the highest compressive strength both in 8M and 10M NaOH system. However, in concrete, there are a few difference, concretes made with 8M NaOH and activators ratio of 2 have the highest compressive strength. This result might due to the low workability of fresh geopolymer concrete. On the other hand, binder and concrete made with 10M NaOH, showed the highest compressive strength when they were made with the activator ratio of 2,5.

PERFORMANCE OF ALKALINE SOLUTIONS ON GRADES OF GEOPOLYMER CONCRETE

Geopolymer is a class of aluminosilicate binding materials synthesized by thermal activation of solid aluminosilicate base materials such as fly ash, metakaolin, GGBS etc., with an alkali metal hydroxide and silicate solution. The geopolymer was activated with sodium hydroxide, sodium silicate and heat. This paper presents the experimental investigation done on the variation of alkaline solution on mechanical properties of geopolymer concrete. The grades chosen for the investigation were M-30, M-40, M-50 and M60, the mixes were designed for 8 molarity. The alkaline solution used for present study was the combination of sodium silicate and sodium hydroxide solution with the varying ratio of 2, 2.50, 3 and 3.50. The test specimens were 150x150x150 mm cubes and 100x200 mm cylinders heat-cured at 60°C in an oven. The results revealed that the workable flow of geopolymer concrete was in the range of 85 to 145 and was dependent on the ratio by mass of sodium silicate and sodium hydroxide solution. The freshly prepared geopolymer mixes were cohesive and their workability increased with the increase in the ratio of alkaline solution. The strength of geopolymer concrete can be improved by decreasing the water/binding and aggregate/binding ratios. The curing period improves the polymerization process resulting in higher compressive strength. The geopolymer concrete do not have any Portland cement, they can be considered as less energy interactive. It utilizes the industrial wastes such as fly ash for producing the binding system in concrete. The obtained compressive strength and split tensile strength were in the range of 20.64 – 60 N/mm 2 and 3 – 4.9 N/mm 2 . The optimum dosage for alkaline solution can be considered as 2.5, because for this ratio the GPC specimens of any grade produced maximum strength in compression and tension.

Research on Mechanical Properties of Geopolymer Concrete under early Stage Curing System

Mechanical properties of geopolymer concrete under early stage curing system were studied. The results showed that at the early stage of curing time, compressive strength was improved significantly with the increasing of curing temperature and curing time. The compressive strength decreased and was close to that of standard curing condition at the age of 28d as the curing age increased. In addition, prolonging the storage time at room temperature before the step of high temperature curing could increase the long-term strength.

Mechanical Properties of Fly-Ash-Based Geopolymer Concrete

The mechanical properties of fly-ash-based geopolymer concrete (GPC) were studied. Experimentally measured values of the static elastic modulus, Poisson’s ratio, compressive strength, and flexural strength of GPC specimens made from 25 fly ash (FA) stockpiles from different sources were recorded and analyzed. The results were studied using regression analysis to identify tendencies and correlations within the mechanical properties of GPC. It was found that the mechanical behavior of GPC is similar to that of ordinary portland cement (OPC) concrete, suggesting that equations, akin to those given by ACI 318-08, could be applied for GPC to determine its flexural strength and static elastic modulus. The validity of an equation to determine the density of GPC as a function of FA fineness was also put forward.