Effects of isothermal microwave curing on steel fibre-reinforced reactive powder concrete: Strength, microstructure and hydration products

Results of investigations of reactive powder concrete (RPC) are presented in the paper. Optimization of the concrete composition was performed to achieve the highest degree of grains packing based on the optimal graining curve according to Funk for dmax = 1000 μm and dmin = 0.1 μm. Cement, silica fume, quartz and sand powder were considered in the composition. Steel fibers addition of 25% by mass was applied. A very low water–to–binder ratio, amounting to 0.2, was reached applying novel generation of superplasticizers based on polycarboxylates. The RPC mixture remained fluid during 1 hour. The diameter of slump flow according to PN-EN standard amounted to 250 mm after 60 minutes. The hardened concrete RPC displayed high strength and durability. Compressive strength reached 145 MPa after 2 days and about 200 MPa after 28 days; the bending strength exceeded 50 MPa after 28 days. After 56 freezing/defrosting cycles in the deicing salt solution, the concrete has shown minimal salt scaling of only 0.0007 kg/m2. Therefore, frost resistance of the concrete studied can be rated as very good according to PN-EN standard. The SEM pictures proved the amorphous phase of hydrated calcium silicates (C-S-H) is the dominant phase within the RPC microstructure. Usually, the C-S-H phase tightly covers the quartz grains and is in close contact with the unreacted cement grains. Crystallites of the monosulphate (AFm) were also found. The concrete microstructure was compact; pores of a few micrometers were rarely observed. The RPC porosity was measured using the mercury porosimetry. Porosity reduction by almost twice (from 10.9% down to 4.4%) was found after the RPC curing from 2 to 28 days. In the same period, a fraction of small mezopores (diameter below 20 nm) increased from 39.8% to 77.1%. Based on the research results data, presented the RPC concrete can be regarded as an interesting alternative to other construction materials of enhanced explosion resistance. Key words: Reactive Powder Concrete, strength, durability, explosion resistance

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THE INFLUENCE OF STEEL FIBRE CONTENT AND CURING CONDITIONS ON MECHANICAL PROPERTIES AND DEFORMABILITY OF REACTIVE POWDER CONCRETE AT BENDING

Brittle Matrix Composites 9 ◽

10.1533/9781845697754.33 ◽

2009 ◽

pp. 33-42 ◽

Cited By ~ 2

Author(s):

Tomasz ZDEB ◽

Jacek ŚLIWIŃSKI

Keyword(s):

Mechanical Properties ◽

Steel Fibre ◽

Fibre Content ◽

Reactive Powder Concrete ◽

Curing Conditions ◽

Reactive Powder

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Strength of Reinforced Reactive Powder Concrete Hollow Beams

Tikrit Journal of Engineering Sciences ◽

10.25130/tjes.26.2.03 ◽

2019 ◽

Vol 26 (2) ◽

pp. 15-22

Author(s):

Mazin Abdulrahman ◽

Saba Mahmood

Keyword(s):

Concrete Strength ◽

Reactive Powder Concrete ◽

Load Carrying Capacity ◽

Hollow Section ◽

Hollow Beam ◽

Strength Capacity ◽

Load Carrying ◽

Concentrated Loading ◽

Reactive Powder ◽

Hollow Beams

The main objective of this research is to investigate the structural behavior and strength of reinforced reactive powder concrete beams with a hollow section subjected under two point concentrated loading. The experimental work consist of ten beams with dimensions (150mm width×200mm height×1000 mm length), eight of them are hollow beams and two solid beams were cast and tested up to failure. The major parameters adopted in the current research includes the hollowness ratio (10% and15%), hollow location (at top or at bottom), and hollow shape (circle or square). The amount of longitudinal and transverse reinforcement, concrete strength and the other parameters were kept constant for all the specimens. The comparisons between all specimens (hollow and solid) are based on the load carrying capacity, deflection, crack pattern and mode of failures. Results showed that the strength capacity of hollow beam when the hollow lies in the bottom is much higher than for top hollow, and the square hollow will lead to more decrease in the beam strength compared with the circular hollow and this is more evident when the hollowness ratio increases from (10% to 15%).

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Mechanism Analysis of the Influence of Delay Period on Mechanical Properties of Reactive Powder Concrete

Frontiers in Materials ◽

10.3389/fmats.2020.563234 ◽

2021 ◽

Vol 7 ◽

Author(s):

Xiaohui Wang ◽

Qingxin Zhao ◽

Xiaojun He ◽

Shuang Zhang

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Delay Period ◽

Reactive Powder Concrete ◽

Hydration Products ◽

X Ray ◽

Significant Difference ◽

Calcium Silicon ◽

Reactive Powder

In order to analyze the influence mechanism of delay period on the mechanical properties of reactive powder concrete (RPC), the compressive strength of RPC with delay periods of 18, 24, and 30 h was tested at the age of 7, 28, and 90 days, respectively. The results show that compared with the RPC with delay period of 18 h, the compressive strength of the RPC with delay periods of 24 and 30 h increases by 3.2 and 4.2%, respectively, and the long-term strength reduction ratio decreases by 22.8 and 71.9%, respectively. The constitutive model curves of RPC under different delay period show that the initial elastic modulus E increases with the delay period and the strength and rigidity of RPC increase with the extension of delay period. According to the non-evaporation water quantity test, it could be speculated that the quantities of hydration products of the RPC with delay periods of 24 and 30 h slightly increase compared with the RPC with delay period of 18 h. X-ray diffraction (XRD) analysis show that the delay periods of 24 and 30 h consume more 3CaO·SiO2 (C3S) and 2CaO·SiO2 (C2S) compared with delay period of 18 h. Seen from the scanning electron microscope (SEM) image, the structures of the three groups of samples are relatively dense and have no significant difference. Through energy dispersive X-ray spectroscopy (EDS) analysis, the calcium-silicon ratios of hydration products of the RPC with delay periods of 18, 24, and 30 h are 1.81, 1.56, and 1.54, respectively. The existence of C-S-H gel and Ca(OH)2 in hydration products is confirmed by thermogravimetric-differential scanning calorimetry (DSC-TG) analysis. An appropriate delay period (30 h in this paper) generates more hydration products, then improves the compactness of the internal structure and reduces the calcium-silicon ratio of hydration products, and it is conducive to the growth of RPC compressive strength and the stability of long-term compressive strength.

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Reactive Powder Concrete with Steel, Glass and Polypropylene Fibers as a Repair Material

Civil Engineering Journal ◽

10.28991/cej-2019-03091422 ◽

2019 ◽

Vol 5 (11) ◽

pp. 2441-2449 ◽

Cited By ~ 3

Author(s):

Lamyaa Gh. Salim ◽

Haider M. Al-Baghdadi ◽

Haitham H. Muteb

Keyword(s):

Flexural Strength ◽

Glass Fibre ◽

Steel Fibre ◽

Polypropylene Fibre ◽

Reactive Powder Concrete ◽

Repair Material ◽

Normal Strength Concrete ◽

Repair Materials ◽

Normal Strength ◽

Reactive Powder

Repairing of reinforced concrete structures is currently a major challenge in the construction industry and is being put back into operation with a slight loss in load carrying capacity. Damage occurs due to many factors that reduce the strength of concrete structures and their durability. The aim of this paper is study the compatibility between three types of reactive powder concrete with (steel fibre, glass fibre and polypropylene fibre) as a repair materials and normal strength concrete as a substrate concrete. Compatibility was investigated in three steps. First: individual properties for substrate concrete were studied, these are (slump test, compressive strength, splitting strength, and flexural strength) also, for repair material these are (compressive strength and flexural strength) were determined by using standard ASTM test methods. Second: bond strength of composite cylinder for substrate concrete with different repair materials were evaluated by using slant shear test. Third: compatibility was investigated by using composite prisms of substrate concrete with different repair materials under two-point loading (flexural strength test). From the experimental results concluded, bond strength between reactive powder concrete with glass fibre as a repair material and normal strength concrete as a substrate layer is higher (17.38Mpa) compared with RPC with steel fibre (13.13Mpa) and polypropylene fibre (14.31MPa). Also, it is more compatible due to flexural strength for composite prisms (having higher flexural strength (8.13MPa). Compared with steel fibre (7.44MPa) and polypropylene fibre (6.47MPa). These results due to RPC with glass fibre have good workability with suitable flowability and glass fibre have higher tensile strength compare with other fibre.

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