Review of mechanical properties of short fibre reinforced geopolymer composites

A “fracture testing” based approach to assess crack healing of concrete with and without crystalline admixtures

This paper presents mechanical and durability properties of geopolymer concrete containing recycled coarse aggregate (RCA). The RCA is sourced from local construction and demolition (C&D) waste in Perth, Australia. The RCA is used as a partial replacement of natural coarse aggregate (NCA) in geopolymer concrete at 15%, 30% and 50% by wt. which corresponds to series two, three and four, respectively, while the geopolymer concrete containing 100% NCA is control and is considered as the first series. Class F fly ash is used as the source material for the geopolymer and 8 M sodium hydroxide and sodium silicate alkali activators are used to synthesise the fly ash geopolymer in this study. In all four series a constant alkali activator to fly ash ratio is used. Compressive strength, indirect tensile strength and elastic modulus of above geopolymer concrete are measured at 7 and 28 days, while sorptivity, immersed water absorption and volume of permeable voids of above geopolymer concrete are measured at 28 days. Relevant Australian standards are used to measure all the above properties except the sorptivity which is measured according to ASTM standard. Results show that the compressive strength, indirect tensile strength and elastic modulus of geopolymer concrete decrease with an increase in RCA contents, which is also true for both 7 and 28 days. Excellent correlations of compressive strength with indirect tensile strength and elastic modulus are also observed in geopolymer concrete containing RCA. Existing empirical models for cement concrete and geopolymer concrete containing NCA underestimate and overestimate the indirect tensile strength and elastic modulus, respectively of geopolymer concrete containing RCA. The measured durability properties such as sorptivity, water absorption and volume of permeable voids of geopolymer concrete were also adversely affected by the incorporation of RCA and these properties increase with an increase in RCA contents. The effects of RCA on the measured mechanical and durability properties of geopolymer concrete follow similar trend in cement concrete. Very good correlations of compressive strength with volume of permeable voids and water absorption of geopolymer concrete containing RCA are also observed, while the correlation between the compressive strength and the sorptivity is not that strong.

https://cyberleninka.org/article/n/529951.pdf

Mechanical and durability properties of fly ash geopolymer concrete containing recycled coarse aggregates

Hybrid short fiber reinforcement system in concrete: A review

Concretes containing mixed recycled aggregate (RA) have a larger number of coarse aggregate/paste interfacial transition zones (ITZs) than conventional concretes, due to the various component materials present in recycled aggregate. This study investigated the properties of various RA/paste ITZs in concrete using nanoindentation and scanning electron microscopy (SEM) and analysed the possible impact of the properties of the ITZs on the macro-mechanical performance of recycled concrete. It was found that the elastic modulus of the ITZ varies with the type of constituent materials present in recycled aggregate, with ITZs associated with organic components (e.g. wood, plastic and asphalt) exhibiting lower minimum elastic modulus values. The impact of ITZ properties on macro-mechanical properties of concrete depends on the relative content of different constituent materials present in the recycled aggregate and the micro-mechanical properties of the ITZs involved.

https://myresearchspace.uws.ac.uk/ws/files/1191453/1_s2.0_S0958946517304006_main.pdf

Properties of interfacial transition zones (ITZs) in concrete containing recycled mixed aggregate

Experimental results on the strain hardening and multiple cracking behaviors of polyvinyl alcohol (PVA) fiber reinforced cementitious composites under bending are reported in this paper Different hybrid combinations of PVA fibers with different lengths and volume fractions are considered to reinforce the mortar matrix Among different hybrid combinations, the composite containing 2% thicker PVA fibers of 12 mm length and 1% thinner PVA fibers of 6 mm length and the composite containing 2% thicker PVA fibers of 24 mm length and 1% thinner PVA fibers of 6 mm length showed the best performance in terms of highest ultimate load, largest CMOD (crack mouth opening displacement) at peak load and multiple cracking behavior The effects of four types of light weight sands on the strain hardening and multiple cracking behavior of hybrid fiber composites are also evaluated in this study It has been observed that the ultimate load and CMOD at peak load for all light weight hybrid fiber composites are almost the same irrespective of volume fractions of light weight sand The composites containing finer light weight sands exhibited higher ultimate load than those containing coarser light weight sands It is also observed that the hybrid fiber composite containing normal silica sand exhibited higher ultimate load than the composites with light weight sands

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Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites

For the purpose of global sustainability the long life of structures is essential and the durability performance of reinforced concrete structures is one of the key issues to be resolved. This paper reports the results of a series of long term corrosion tests on fiber reinforced cementitious composites containing polyethylene (PE) alone and hybrid steel cord (SC) and PE fibers. The results are also compared with ordinary mortar. The specimens are subjected to accelerated corrosion for one year by applying external potential to the steel bar anode and a cathode made out of a steel wire mesh placed outside the concrete. Durability performances of the specimens are examined through regular monitoring of the time to initiate corrosion, the corrosion area ratio, corrosion depth, and the amount of steel loss. Results show that the hybrid fiber reinforced cementitious composites (HFRCC) containing hybrid SC and PE fibers exhibited excellent performance compared to mortar and fiber reinforced cementitious composites (FRCC) containing PE fiber. The order of the durability performance is HFRCC, FRCC, and Mortar. It is observed that the sacrificial corrosion of some of the SC fibers in the HFRCC specimen played an important role in the significant reduction of steel bar corrosion in the specimen.

/pdf/corrosion-of-reinforcing-steel-in-fiber-reinforced-3tpqfcrq46.pdf

Corrosion of Reinforcing Steel in Fiber Reinforced Cementitious Composites

This paper reports the properties of concrete containing recycled coarse aggregate (RCA) sources from local construction and demolition (C&D) wastes and fly ash (FA) sourced from Western Australia (WA). The RCA is used as 25, 50, 75, and 100% (by weight) replacement of natural coarse aggregate (NCA). In addition, the effect of 40% (by weight) class F fly ash as partial replacement of cement on the properties of recycled aggregate concrete is also evaluated. The properties of concrete evaluated are the compressive strength, indirect tensile strength, flexural strength, and water absorption. All properties are measured at 7, 28, 56, and 91 days. The results show that better compressive, tensile, and flexural strength of concrete containing 25% RCA as partial replacement of NCA can be obtained in recycled aggregate concrete. However, in the case of recycled aggregate concretes containing 40% fly ash, the compressive strength at later ages, such as at 56 and 91 days is increased but the indirect tensile and flexural strengths are decreased at all ages. It is observed that the water absorption is decreased as RCA content increased. It is also observed that the water absorption is decreased significantly in recycled aggregate concretes containing 40% fly ash at all ages.

/pdf/properties-of-concrete-containing-construction-and-2h9o81j8oi.pdf

Properties of Concrete Containing Construction and Demolition Wastes and Fly Ash

Repair and restoration work of reinforced-concrete (RC) structures is increasing because of the deterioration of aging infrastructures worldwide. Generally, plain mortar and polymer-modified mortar are widely used as repair materials for RC structures. In this study the effect of the combined use of polymers with supplementary cementitious materials (SCMs) on certain mechanical and durability properties (such as compressive and flexural strengths, water absorption, carbonation, and chloride penetration) of modified mortars is evaluated experimentally. The experimental program consists of two parts. In Part I, the effect of SCM slag and silica fume (SF) on the mechanical and durability properties of mortars is evaluated. On the basis of the best performance among different slag and SF contents, Part II of the experimental program is designed, in which the combined effect of polymers and slag/SF on the mechanical and durability properties of modified mortar is evaluated. Results show that the combined slag/SF and polymer-modified mortars (PMMs) exhibited better results than polymer-modified mortar alone. Between the combined polymers and SF/slag-modified mortars, the polymer-modified mortar containing 10% SF exhibited the highest compressive and flexural strengths and the lowest chloride penetration resistance compared to those containing 40% slag. Interestingly, the combined polymer and 40% slag-modified mortars exhibited better performance in water absorption and carbonation resistance than polymer-modified mortar containing 10% SF.

Mechanical and Durability Properties of Mortars Modified with Combined Polymer and Supplementary Cementitious Materials

Concrete is a composite material consisting of mortar and coarse aggregates. The use of recycled aggregates in concrete is increasing gradually. Recycled coarse aggregates are highly porous and often contain microcracks and weak interfacial transition zone (ITZ). Therefore, the recycled aggregates are weaker than natural coarse aggregate and their modulus of elasticity (E) is expected to be lower than that of natural coarse aggregate. This paper examines and presents the existence of dividing strength in concrete containing recycled coarse aggregate. In this study 192 concrete cylinders (100ϕ×200  mm) and 192 mortar cubes (50×50×50  mm) were cast and tested at 28 days for compressive strengths of natural aggregate concretes (NAC) and recycled aggregate concretes (RAC). In the case of NAC, the linear relationship between the compressive strength of concrete and that of mortar is observed. However, in the case of RAC, a distinct two-stage relationship between concrete strength and mortar strength is...

Shaikh Faiz Uddin Ahmed

Papers

Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites

Corrosion of Reinforcing Steel in Fiber Reinforced Cementitious Composites

Properties of Concrete Containing Construction and Demolition Wastes and Fly Ash

Mechanical and Durability Properties of Mortars Modified with Combined Polymer and Supplementary Cementitious Materials

Existence of Dividing Strength in Concrete Containing Recycled Coarse Aggregate