Reinforced Cement Composites Research Articles

Influence of internal composition of fiber reinforced cement composites on resistance to near field blast

This paper describes the influence of internal composition of fiber reinforced cement composites on resistance to near field blast. The influence of multiple basalt meshes and dispersed fibers on a damage induced by a near-field blast is studied and numerically evaluated. Experimental measurements performed in the Boletice military area in 2014, 2015 and 2016 are evaluated by numerical simulations. The evaluation of the results is mainly focused on the stress in the cement composite, propagation of the overpressure caused by the blast and velocity of the ejected parts from the specimen. The influence of velocity of ejected parts coming out of the specimen, originally caused by the impact of a steel plate which bears TNT charges, is examined. And last, but not least, the influence of presence and position of basalt meshes in the specimen on its damage induced by delamination is also examined.

A Study on the Drying Shrinkage and Mechanical Properties of Fiber Reinforced Cement Composites Using Cellulose Nanocrystals

As part of the research on cement composites using cellulose nanocrystal (CNC) aqueous solution instead of general water, this study produced high-toughness cement composites reinforced with flax and steel fibers to improve the tensile deformation capacity, assessing the isothermal conduction calorimetry analysis, drying shrinkage, and strength characteristics. The mixing amount of CNCs was 0.4, 0.8, and 1.2 vol.% by volume of cement, and an aqueous solution was prepared using the ultrasonication dispersion method. When comparing the results of the experiment according to the CNC mixing ratio, CNCs at 0.8 vol.% led to an improvement in the shrinkage rate and mechanical performance compared with the plain specimen.

Experimental study and benchmarking of 3D textile reinforced cement composites

Textile Reinforced Cement composites (TRCs) have become a key research topic when it comes to lightweight alternative construction materials for traditional concrete industry. While most of the research performed on TRCs combines a cementitious matrix material with 2D textile fabrics, this paper investigates the mechanical behaviour of TRCs reinforced with 3D textile fabrics. The main goal is to investigate the influence of the transversal fibre that is connecting the fibre layers and is typical for 3D textiles, on the tensile and flexural properties of the TRC. Therefore two textile fabric architectures were compared, firstly an unaltered 3D textile fabric and secondly a tensile-equivalent 2D textile fabrics with equal in-plane textile reinforcement. An experimental campaign in tension and bending was performed on four different TRC layups. When comparing the bending behaviour of the unaltered 3D-TRCs with the 2D alternatives, an increase in stiffness in the post-cracking stage was observed, while no influence was observed in tension. The experimental results were also compared with numerical predictions of the 2D-TRCs to put in evidence the influence of the 3D architecture.

Value-added reuse of scrap tire polymeric fibers in cement-based structural applications

Presently, scrap tire polymeric fibers (STF) have limited reuse value in most countries of the world, hence it is largely land filled or used as an eco-unfriendly tire derived fuel (TDF). Unfortunately, toxic gases and acids could be released from these aforementioned STF management strategies. Therefore, in this study, an alternative reuse approach for the STF was explored; the possibility that it could enhance the flexural post-crack residual strength and wear resistance of cement composites were examined. Furthermore, the likelihood of improving the aforementioned properties through the hybridization of the STF with commercial macro fibers such as steel hook-end (HE) and polypropylene (PP) fibers was also evaluated. The cement composites investigated consist of a set of 0.50 water-to-cement (w/c) ratio mortar and two sets of concrete batches corresponding to 0.50 and 0.40 w/c ratios. Results indicate that the post-crack residual strengths of mortar and concrete mixtures singly reinforced with the STF was about 0.10 MPa and 0.10 – 0.20 MPa, respectively. Hence, these STF reinforced cement composites have no useful structural application value. However, with the hybridization of 0.35% STF with 0.2 – 0.5% macro fibers, mortar mixtures with post-crack residual strengths ranging from 1.4 to 3.1 MPa were attained as a result of the positive synergy between the STF and the HE fibers. Hybrid 0.35% STF and 0.35% HE fiber reinforcement of concrete also led to a positive synergy and improvement in post-crack residual strength capacity, especially for the 0.50 w/c ratio mixture. Relative to the plain concrete, 0.35% STF or hybrid combination of 0.35% STF and 0.35% PP had no impact on concrete abrasion resistance. Conversely, cumulative volume loss of concrete reinforced with hybrid 0.35% STF and 0.35% HE fibers decreased by approximately 8.9% and 16.1% for 0.50 and 0.40 w/c ratio concrete mixtures, respectively. All-in-all, these results suggest that in lieu of its present use as a TDF, the STF hybridized with HE fibers could actually be used as a sustainable, discrete fiber reinforcement for cement-based repair applications where slightly enhanced flexural post-crack performance and resistance to abrasive wear are desired.

Characterization of Titanium Nanotube Reinforced Cementitious Composites: Mechanical Properties, Microstructure, and Hydration.

In recent years, nano-reinforcing technologies for cementitious materials have attracted considerable interest as a viable solution for compensating the poor cracking resistance of these materials. In this study, for the first time, titanium nanotubes (TNTs) were incorporated in cement pastes and their effect on the mechanical properties, microstructure, and early-age hydration kinetics was investigated. Experimental results showed that both compressive (~12%) and flexural strength (~23%) were enhanced with the addition of 0.5 wt.% of TNTs relative to plain cement paste at 28 days of curing. Moreover, it was found that, while TNTs accelerated the hydration kinetics of the pure cement clinker phase (C3S) in the early age of the reaction (within 24 h), there was no significant effect from adding TNTs on the hydration of ordinary Portland cement. TNTs appeared to compress the microstructure by filling the cement paste pore of sizes ranging from 10 to 100 nm. Furthermore, it could be clearly observed that the TNTs bridged the microcracks of cement paste. These results suggested that TNTs could be a great potential candidate since nano-reinforcing agents complement the shortcomings of cementitious materials.

Comparison of commercially available 25OHD and 1,25(OH)2D assays: Experience of pediatric hospital laboratory participating in DEQAS proficiency testing

Textile Reinforced Cement composites (TRCs) have become a key research topic when it comes to lightweight alternative construction materials for traditional concrete industry. While most of the research performed on TRCs combines a cementitious matrix material with 2D textile fabrics, this paper investigates the mechanical behaviour of TRCs reinforced with 3D textile fabrics. The main goal is to investigate the influence of the transversal fibre that is connecting the fibre layers and is typical for 3D textiles, on the tensile and flexural properties of the TRC. Therefore two textile fabric architectures were compared, firstly an unaltered 3D textile fabric and secondly a tensile-equivalent 2D textile fabrics with equal in-plane textile reinforcement. An experimental campaign in tension and bending was performed on four different TRC layups. When comparing the bending behaviour of the unaltered 3D-TRCs with the 2D alternatives, an increase in stiffness in the post-cracking stage was observed, while no influence was observed in tension. The experimental results were also compared with numerical predictions of the 2D-TRCs to put in evidence the influence of the 3D architecture.

Experimental Investigation on Compressive Toughness of the PVA-Steel Hybrid Fiber Reinforced Cementitious Composites

In order to achieve the whole process control of crack formation of engineered cementitious composites (ECC) under loading and improve the mechanical properties of ECC, PVA-steel hybrid fiber reinforced cementitious composites (HyFRCC) was proposed by mixing steel fibers with traditional ECC. And the key parameters to affect the HyFRCC performance are PVA fiber content, steel fiber content and aspect ratio of steel fiber. In order to investigate the mechanical properties of PVA-steel HyFRCC such as the compressive toughness, 15 PVA-steel HyFRCC specimens with different volume fraction of steel fiber and PVA fiber, together with 1 non-fibrous cementitious composites specimen and 3 ECC specimens with PVA fiber only for comparison were designed and uniaxial compression tests were conducted. Furthermore, the effect of fiber content, fiber type and fiber geometrical characteristic on the compressive toughness of HyFRCC were analyzed. The results show that PVA fiber content, steel fiber content and aspect ratio of steel fiber have little impact on the uniaxial compressive strength of the PVA-steel HyFRCC, while the peak strain, compressive toughness and the post-peak ductility of PVA-steel HyFRCC are improved significantly due to fiber hybridization. The formation of large scale cracks of ECC specimens after post-peak loading is restrained effectively with the addition of steel fiber. The mixture of PVA and steel fiber has a remarkable effect on the improvement of ECC compression toughness and crack control. It indicates that the energy dissipation and damage control capacity of the structural component with PVA-steel HyFRCC under seismic loading will be enhanced.

Response of coir fibre reinforced cement composites to water repellent chemical additive and microwave accelerated curing

The present investigation deals with performance of coir fibre reinforced cement boards subjected to matrix modification by silane-based water repellent chemical additive and microwave accelerated curing (MC). The fibre-cement boards were tested for water absorption, modulus of rupture (MOR) and modulus of elasticity (MOE). Scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to characterize the composite samples. 84% reduction in water penetration was achieved through the use of the water repellent additive while MC samples had higher MOR and MOE values than the water cured samples. SEM characterization showed that MC provided good interfacial adhesion between the matrix and the reinforcement while the chemical additive reduced the occurrence of voids and pores on the surface. FTIR indicated prominent bands at 3423, 1425.44 and 875.41 cm−1 which are indicative of O–H stretching of the portlandite, C-H denoting the lignin deformation with aromatic ring stretching and C-O representing bend of carbonates. Therefore, MC and use of water repellent additive are recommended to improve the performance of cellulose fibre cement based applications.

Fatigue Behaviour of Textile Reinforced Cementitious Composites and Their Application in Sandwich Elements

Using large lightweight insulating sandwich panels with cement composite faces offers great possibilities for the renovation of existing dwellings. During their lifetime, these panels are subjected to wind loading, which is equivalent to a repeated loading. To guarantee the structural performance of these panels during their entire lifetime, it is necessary to quantify the impact of these loading conditions on the long term. The fatigue behaviour was, therefore, examined in this paper both at the material level of the faces and at the element level as well. plain textile reinforced cementitious composite (TRC) specimens were subjected to 100,000 loading cycles by means of a uniaxial tensile test, while sandwich beams were loaded 100.000 times with a four-point bending test. Results show that the residual behaviour is strongly dependent on the occurrence of cracks. The formation of cracks leads to a reduction of the initial stiffness. The ultimate strength is only affected in a minor way by the preloading history.

Study on Behaviour of Hybrid Fibre Reinforced Cementitious Composites

Study on Behaviour of Hybrid Fibre Reinforced Cementitious Composites

Experimental and numerical analysis of interfacial bonding strength of polyoxymethylene reinforced cement composites

Abstract The objective of this paper is to investigate the interfacial bonding strength of polyoxymethylene (POM) reinforced cement composites through pull-out tests and finite element model (FEM). As comparison with usual materials, the pull-out tests of polypropylene (PP) reinforced cement composites and polyethylene terephthalate (PET) reinforced cement composites are also performed. The pull-out tests are performed in forms of fiber reinforced cement and woven fabric reinforced cement. The woven fabrics contain three different structures, i.e. plain, twill and hybrid. Compared with PP and PET, the results show that POM could form a much stronger interface bonding with cement irrespective of reinforcement form (fiber or woven fabric). Besides, the interfacial bonding strength of woven fabric reinforced cement composite presents a significant structural dependency. The FEM of woven fabric reinforced cement composite is established and the internal mechanism for the structural effect is analysed. Woven fabric comprises two different yarn segments: curved segment and straight segment. During the pull-out process, the curved segment rotates and distorts the weft yarn. Owing to the rotational deformation, the cement surrounding the curved segments damages more seriously. Therefore, a woven fabric with more straight segments could form a stronger interface bonding with cement.

Thermomechanical Behavior of Textile Reinforced Cementitious Composites Subjected to Fire

The mechanical behavior of textile reinforced cementitious composites (TRC) has been a topic of wide investigation during the past 30 years. However, most of the investigation is focused on the behavior under ambient temperatures, while only a few studies about the behavior under high temperatures have been conducted thus far. This paper focused on the thermomechanical behavior of TRC after exposure to fire and the residual capacity was examined. The parameters that were considered were the fiber material, the thickness of the concrete cover, the moisture content and the temperature of exposure. The specimens were exposed to fire only from one side and the residual strength was measured by means of flexural capacity. The results showed that the critical factor that affects the residual strength was the coating of the textiles and the law of the coating mass loss with respect to temperature. The effect of the other parameters was not quantified. The degradation of the compressive strength of TRC was quantified with respect to temperature. It was also concluded that a highly asymmetrical design scheme might lead to premature failure.

Electrochemical Characterization and Inhibiting Mechanism on Calcium Leaching of Graphene Oxide Reinforced Cement Composites.

Calcium leaching is a degradation progress inside hardened cement composites, where Ca2+ ions in cement pore solution can migrate into the aggressive solution. In this work, calcium leaching of graphene oxide (GO) reinforced cement composites was effectively characterized by combined techniques of electrochemical impedance spectroscopy (EIS) and scanning electron microscope (SEM). Inhibiting mechanism of GO on calcium leaching of the composites was also examined. The obtained results show that the diameter of the semi-circle of the Nyquist curves of leached samples with GO addition decreased less than that of controlled samples. After leaching for 35 days, loss rate of model impedance RCCP of leached samples with 0, 0.05, 0.1, 0.15, and 0.2 wt.% GO addition was 94.85%, 84.07%, 79.66%, 75.34%, and 68.75%, respectively. Therefore, GO addition can significantly mitigate calcium leaching of cement composites, since it can absorb Ca2+ ions in cement pore solution, as well as improve the microstructure of the composites. In addition, coupling leaching depth and compressive strength loss were accurately predicted by using the impedance RCCP.

High performance fibre reinforced cementitious composites: Six memos for the XXI century societal and economical challenges of civil engineering

Worldwide increasing consciousness for sustainable use of natural resources has made “overcoming the apparent contradictory requirements of cost and performance effectiveness a challenging task” as well as a major concern. High Performance Fibre Reinforced Cementitious Composites, by providing tailored and multiple functionalized performance can represent an asset for the construction industry to face the challenges imposed by the needs of our continuously and fast evolving society. The paper, moving from a parallel with “Six memos from the next millennium” by Italo Calvino, the author will provide his own perspective on the current state on the topic, trying to highlight the benefits achievable through a reliable and consistent incorporation into a design and construction practice for both new and existing buildings and structures.

Uniaxial compression mechanical properties and fracture characteristics of brucite fiber reinforced cement-based composites

In this work, the mechanical properties, stress-strain behaviors, and microstructure of brucite fiber reinforced cement-based composites are determined. The results reveal that the incorporation of brucite fiber limits the compressive strength reinforcement of cement-based composite but leads to a significant increase of tensile strength by 136% and flexural strength by 73%. The employment of brucite fiber increases the fracture toughness KIcS and KIcQ of the cement-based composite by 450% and 98%. The incorporation of brucite fiber increases the linear elastic fracture toughness energy GF by 455% and elastic-plastic fracture toughness energy JC by 279%. The constitutive model of brucite fiber reinforced cement paste is also established. The diameter of the brucite fiber bundle is 1.5–16.3 μm, and the diameter of the single dispersed fiber is around 45–110 nm. There are about 15–363 single fibers in a bundle. Due to the brucite fiber possesses an intrinsic fibrous anisotropy, and network topology, the brucite fiber reinforced cement composites exhibit advantages of greater bending strength and crack bridging, as well as better crack resistance properties.

Physical and Chemical Modifications of Plant Fibres for Reinforcement in Cementitious Composites

This paper highlights the physical and chemical surface modifications of plant fibre (PF) for attaining suitable properties as reinforcements in cementitious composites. Untreated PF faces insufficient adhesion between the fibres and matrix due to high levels of moisture absorption and poor wettability. These conditions accelerate degradation of the fibre in the composite. It is also essential to reduce the risk of hydrophilic PF conditions with surface modification, to enhance the mechanical properties of the fibres. Fibres that undergo chemical and physical modifications had been proven to exhibit improved fibre‐matrix interfacial adhesion in the composite and contribute to better composite mechanical properties. This paper also gives some recommendations for future research on chemical and physical modifications of PF.

Strength Prediction and Correlation of Cement Composites: A Cross-Disciplinary Approach

We present a cross-disciplinary approach applied to the strength prediction and correlation of cement composites in this paper. The empirical models for predicting flexural and compressive strengths of a kind of fiber reinforced cement composites, known as engineered cementitious composites (ECCs), were first developed. Nonlinear regressions were applied to the measurement data of a destructive compression test and four-point bending test. Each of these tests was conducted on 36 specimens at growing ages (3, 7, 14, and 28 days), wherein three mixes of ECC (PE1, PE2, and PE3) were prepared for each test. Each mix had different water-to-binder (w/b) ratios of 0.20, 0.255, and 0.30 whereas the total volume of each mix remained the same. The correlations among flexural strength, compressive strength, and electrical conductance of ECCs were then developed based on the early-age measurement using the microwave non-destructive test (mDNT). The primary objective of this research is to study the relations between flexural strength and compressive strength of ECC specimens under the influence of small deviations in w/b ratio. The secondary objective is to predict the strength growth of ECCs with the microwave effective conductance. The correlation results show that the flexural strength behaves as a quasi-linear function with increasing compressive strength, which has been verified by using direct measurement data. This cross-disciplinary approach highlights the effectiveness of the mDNT in predicting the mature strengths of ECCs at early ages.

Effect of nano silica addition on enhancing the performance of cement composites reinforced with nano cellulose fibers

The utilization of cellulose nano fibers (NCell) as reinforcement to cement composites may account for enhancing particle packing and decreasing the crack growth at the nano level. Besides that, their high specific surface area can improve the bond between the cement hydration products. nano silica particles can also influence the performance of fiber reinforced cement composites through increasing the calcium-silicate-hydrate gel content, as well as enhancing the fiber to matrix interface cohesion. The aim of this investigation is to evaluate the effects of different contents of nano silica particles (0, 1, 1.5, and 2% by weight of cement) on the mechanical properties, and microstructure of cement composites reinforced with various contents of nano cellulose fibers (0, 0.35, 0.55, and 0.75% by weight of cement). The results out of studying such nano systems revealed that the addition of the NCell particles separately, helped in improving the tensile strength by about twice the value of the control mix when appropriate content of NCell was incorporated (0.35%). Moreover, the microstructural analyses demonstrated the effectiveness of nano silica particles to modify the transition zone between the nano cellulose fiber and the cementitious matrix and subsequently allowing greater reinforcement efficiency especially when external compression or tensile forces were transferred to the composite.

Flexural performance of RC columns with FRCC jacketing

A new repair technique consisting on a light jacketing with Fibre Reinforced Cementitious Composites (FRCC) for existing reinforced concrete (RC) buildings has been recently proposed to reduce durability problems of RC members and enhance their capacity. In this work, the effects of FRCC jacketing on the flexural capacity of existing RC columns, with and without a pre-damage, has been evaluated of full-scale specimens under cyclic loading. Digital Imagine Correlation (DIC) was also adopted for understanding the strain distribution in the FRCC jacket. The results shown that the FRCC jacket without a proper anchorage slightly enhanced the flexural capacity of the column. The strengthened column experienced a low damage with respect to control column, but occurrence of premature failures did not allow the achievement of high levels of deformation capacity and ductility.

"Flexural Performance of Hybrid Fiber Reinforced Cement Composites Under Elevated Temperatures"

"Historically, the flexural behavior of hybrid fiber cement composites is not completely understood using the traditional test methods. This research presents the results of an experimental investigations on a high performance cement composites (HPCC) containing both micro steel fibers (SF) and micro polypropylene fibers (PP) before and after elevated temperature exposure. The experimental program was developed to study the flexural performance (flexural strength, toughness and stiffness) under high temperature using mono and hybrid (SF) and (SF + PP) fibers. Mixtures were divided into eight different groups, with constant w/c of 0.28 and different fibers content. Based on the results of this research, the replacing of micro (SF) in high performance cement composites by 15 % of micro (PP) fibers is recommended at high temperature exposure due to the fact that all hybrid fiber HPCC specimens show slight decreasing in flexural behavior compared to samples reinforced with 1% volume fraction of mono steel fibers after high temperature exposure."