High Strength Fly Ash Concrete Research Articles

Short-Term Gradation Loading Creep Properties and Failure Characteristics of High-Strength Fly Ash Concrete for Underground Engineering

In order to study the short-term creep deformation of high-strength concrete with varying fly ash replacement ratios, concrete samples with 0, 20, 35, and 50 wt% fly ash were tested using an electrohydraulic servocontrolled creep testing system and characterized using scanning electron microscopy after fracturing. Three different creep deformation behaviors were observed over time under different stress levels, namely, decelerating, isokinetic, and accelerating creep, where the creep rate increased with increasing stress. Failure of the samples occurred once isokinetic creep was achieved. The peak stress of the concrete samples exhibited a parabolic trend with increasing fly ash content, where the peak stress in the 0, 20, 35, and 50 wt% samples during short-term gradation loading creep testing was 13.08%, 7.94%, 15.14%, and 14.50% lower, respectively, than the peak stress measured in conventional uniaxial compression testing. The accumulated creep of the samples was reported and can be used as a reference for future studies on the long-term creep characteristics of concrete. The macro- and microscopic failure modes of the fly ash concrete during short-term gradation loading creep under uniaxial compression were brittle cleavage fracturing.

Strength Prediction Model of High Strength Fly Ash Concrete Based On Mixed Kernel Function

In this paper, the proportion of fly ash in cementitious material, the amount of cementitious material and the ratio of water to cement are selected, and the rough set theory is used to process the data. A mixed kernel function support vector machine prediction model with conditional attribute as input and decision attribute as output is established to explore the influence of three factors on the strength of high strength fly ash concrete. The prediction model with high prediction accuracy is selected for optimization. According to the existing test data, the variation law of concrete strength with proportioning parameters is summarized.

The effects of steel fiber waste tyre on properties of high strength fly ash concrete

The utilization of steel fiber from waste tyres can be an alternative to reduce waste tyres due to the increase of tyre production in Indonesia annually. Steel fiber from waste tyre can be added to concrete mix to improve the concrete properties. In this study, the effects of steel fiber waste tyre (SFWT) on high strength concrete containing fly ash was investigated experimentally. The content of fly ash in the high strength concrete is 30% of being partially replaced the cement weight. Steel fiber waste tyres are obtained from extracting the steel wire of the waste tyres and then cut into 4 cm long. The addition of SFWT on the high strength fly ash concrete is 0.5%, 1.0%, 1.5%, and 2% by concrete volume. The mechanical properties of concrete such as compressive strength, tensile strength, and flexural strength are tested at day 28. The test results show that the addition of 2 % SFWT on high strength fly ash concrete increase the compressive strength, tensile strength, and flexural strength of the concrete by around 9.99 %, 63.75 %, 18.18 %, respectively.

High Temperature Mechanical Properties of High-Strength Fly Ash Concrete with and without Fibers

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Experimental Study on Sustainable Concrete with the Mixture of Low Calcium Fly Ash and Lime as a Partial Replacement of Cement

Even though the use of fly ash in concrete is nowadays a common practice, its relatively slow pozzolanic reactivity hinders its greater utilization; hence efficient methods of activation are on demand. This study was carried out to evaluate the influence of lime as a chemical activator on the mechanical and durability properties of high strength fly ash concrete. Mixtures were made with 0, 30, 40, and 50% of cement replaced by low calcium fly ash. Corresponding mixtures were also made with the same amount of fly ash and addition of 10% of lime to each mixture. For each concrete mixture, slump, compressive strength, water absorption, sorptivity, apparent volume of permeable voids, and resistance to chloride-ion penetration were measured. The results obtained showed that addition of lime improved the compressive strength significantly at all ages. The strength of all the fly ash mixtures containing lime surpassed that of the corresponding Portland cement mix at 60 days. Addition of lime also improved the sorptivity and resistance to chloride-ion penetration of the fly ash concrete. It however increases the water absorption and the volume of permeable voids of the fly ash concrete.

Crack Resistance Evaluating of HSC Based on Thermal Stress Testing

In order to evaluate the crack resistance of high strength fly ash concrete, concretes with different contents of silica fume and fly ash were compared with same strength grade by adjusting water to binder ratio. Compared with the concrete with 5% silica fume plus 35% fly ash，concrete with 40% fly ash has same mechanical properties and tensile strain as well as lower drying shrinkage. Complex crack resistance of high strength fly ash concretes were evaluated by Temperature Stress Testing Machine (TSTM). The results show that fly ash concretes have outstanding crack resistance because of higher allowable temperature differential and lower cracking temperature.

Chloride induced reinforcement corrosion in lightweight aggregate high-strength fly ash concrete

Reinforced lightweight aggregate high-strength concrete slabs that incorporated fly ash were exposed to 2% chloride solution for over 15 months. Chloride ion ingress, corrosion potentials, corrosion current density and electrical resistivity were determined. These slabs were compared with slabs from normal weight concrete of medium and high-strength. The results indicated that lightweight high-strength concrete slabs with fly ash in the concrete mixture showed the least amount of chloride concentration. Values of corrosion current density were very low and values of electrical resistivity were very high and indicative of extremely low corrosion current. The dense matrix of the lightweight high-strength concrete is believed to restrict continuous pores that may carry chloride ions. The effect of fly ash in lowering the chloride diffusivity further contributed to reduce harmful chloride ions. In addition, the porous sintered fly ash aggregates are believed to have acted as buffer reservoirs for the chloride laden solution and thus prevented the chloride ions from reaching the steel surface.

Flexural behavior of high strength fly ash concrete beams

Abstract The minimum void concept was used to proportion high strength fly ash concrete. Numerous trial batches were made to determine the optimum mix proportion. Nine beams were cast from optimum mix to investigate the flexural behavior of this type of concrete. The requirements specified in current ACI 318 for modulus of elasticity of concrete, modulus of rupture of concrete, flexural strength of beam sections, effective moment of inertia of flexural members, maximum tension reinforcement ratio and minimum tension reinforcement for seismic design were examined for their application to high strength fly ash concrete.