Annual Book Of Astm Standards

Confinement of high-strength concrete (HSC) columns with fiber reinforced polymer (FRP) composites has been receiving increasing research attention due to the advantageous engineering properties offered by the composite system. The use of silica fume as a concrete additive is a widely accepted practice in producing HSC. However, the influence of the presence and amount of silica fume on the efficiency of FRP confinement is not clearly understood. This paper presents the results of an experimental study on the influence of silica fume on the compressive behavior of FRP-confined HSC. 30 FRP-confined and 30 unconfined concrete cylinders containing different amounts of silica fume were tested under axial compression in two phases. In the first phase of the study, specimens with a constant water–cementitious binder ratio were tested. The results of this phase indicate that for a given water–cementitious binder ratio, the compressive strength of unconfined concrete increases with an increase in the amount of silica fume. It is found that this increase in strength leads to an increased concrete brittleness, which adversely affects the effectiveness of FRP confinement. In the second phase, water–cementitious binder ratios of the specimens were adjusted to attain a constant unconfined concrete strength for specimens containing different amounts of silica fume. The results of these tests indicate that for a given unconfined concrete strength, strength enhancement ratios of FRP-confined HSC specimens are not influenced by the silica fume content of the concrete mix. On the other hand, it is found that the silica fume content influences the axial strain enhancement ratios of these specimens. In addition, the transition zones of the stress–strain curves of FRP-confined HSC are observed to be sensitive to the amount of silica fume used in the mix.

https://researchbank.swinburne.edu.au/file/880c7328-3959-4ad6-8ae1-f240cd40229a/1/PDF (Published version).pdf

Influence of silica fume on stress-strain behavior of FRP-confined HSC

A scientometric review of waste material utilization in concrete for sustainable construction

For the efficient and durable design of concrete, the role of fiber-reinforcements with mineral admixtures needs to be properly investigated considering various factors such as contents of fibers and potential supplementary cementitious material. Interactive effects of fibers and mineral admixtures are also needed to be appropriately studied. In this paper, properties of concrete were investigated with individual and combined incorporation of steel fiber (SF) and micro-silica (MS). SF was used at six different levels i.e., low fiber volume (0.05% and 0.1%), medium fiber volume (0.25% and 0.5%) and high fiber volume (1% and 2%). Each volume fraction of SF was investigated with 0%, 5% and 10% MS as by volume of binder. All concrete mixtures were assessed based on the results of important mechanical and permeability tests. The results revealed that varying fiber dosage showed mixed effects on the compressive (compressive strength and elastic modulus) and permeability (water absorption and chloride ion penetration) properties of concrete. Generally, low to medium volume fractions of fibers were useful in advancing the compressive strength and elastic modulus of concrete, whereas high fiber fractions showed detrimental effects on compressive strength and permeability resistance. The addition of MS with SF is not only beneficial to boost the strength properties, but it also improves the interaction between fibers and binder matrix. MS minimizes the negative effects of high fiber doses on the properties of concrete.

Effect of Varying Steel Fiber Content on Strength and Permeability Characteristics of High Strength Concrete with Micro Silica.

The casting and testing specimens for determining the mechanical properties of concrete is a time-consuming activity. This study employed supervised machine learning techniques, bagging, AdaBoost, gene expression programming, and decision tree to estimate the compressive strength of concrete containing supplementary cementitious materials (fly ash and blast furnace slag). The performance of the models was compared and assessed using the coefficient of determination (R2), mean absolute error, mean square error, and root mean square error. The performance of the model was further validated using the k-fold cross-validation approach. Compared to the other employed approaches, the bagging model was more effective in predicting results, with an R2 value of 0.92. A sensitivity analysis was also prepared to determine the level of contribution of each parameter utilized to run the models. The use of machine learning (ML) techniques to predict the mechanical properties of concrete will be beneficial to the field of civil engineering because it will save time, effort, and resources. The proposed techniques are efficient to forecast the strength properties of concrete containing supplementary cementitious materials (SCM) and pave the way towards the intelligent design of concrete elements and structures.

Application of Advanced Machine Learning Approaches to Predict the Compressive Strength of Concrete Containing Supplementary Cementitious Materials.

Recently, the addition of natural fibers to high strength concrete (HSC) has been of great interest in the field of construction materials. Compared to artificial fibers, natural fibers are cheap and locally available. Among all natural fibers, coconut fibers have the greatest known toughness. In this work, the mechanical properties of coconut fiber reinforced high strength concrete (CFR-HSC) are explored. Silica fume (10% by mass) and super plasticizer (1% by mass) are also added to the CFR-HSC. The influence of 25 mm-, 50 mm-, and 75 mm-long coconut fibers and 0.5%, 1%, 1.5%, and 2% contents by mass is investigated. The microstructure of CFR-HSC is studied using scanning electron microscopy (SEM). The experimental results revealed that CFR-HSC has improved compressive, splitting-tensile, and flexural strengths, and energy absorption and toughness indices compared to HSC. The overall best results are obtained for the CFR-HSC having 50 mm long coconut fibers with 1.5% content by cement mass.

https://www.mdpi.com/1996-1944/13/5/1075/pdf

Hisham Al Abduljabbar

Papers

Effect of Coconut Fiber Length and Content on Properties of High Strength Concrete.