Properties Of Ultra-high Performance Concrete Research Articles

The influences of cooling regimes on fire resistance of ultra-high performance concrete under static-dynamic coupled loads

Cooling regimes have a significant effect on the mechanical properties of ultra-high performance concrete (UHPC) after exposure to elevated temperatures. Load-bearing structures are easily subjected to the coupling action of static and dynamic loads in the fire. This study investigated the dynamic behavior and failure characteristics of UHPC after exposure to heating-cooling treatments. The variations in the P-wave velocities, compressive strengths, elastic modulus and dynamic increase factor (DIF) of the specimens in terms of the different cooling regimes (natural cooling, water cooling) were analyzed. The experimental results indicated that as compared to natural cooling, water cooling caused significant losses in the P-wave velocities, quasi-static and dynamic compressive strength, and dynamic elastic modulus due to the thermal shock induced by water cooling. As the target temperature increased from 250 to above 500 °C, the difference of mechanical property losses varied from small to large, indicating that the thermal shock induced by water cooling caused insignificant damage to the specimen at 250 °C, whereas considerable damage was induced to the specimen above 500 °C. Water cooling enhanced the DIF values of the specimens below 500 °C, but reduced the DIF values at 750 °C. Axial static-pressure loading improved the mechanical properties of the specimen when UHPC was in the elastic phase, which could be attributed to the initial microcracks and pores closed and compacted by the axial static-pressure. However, when the axial static-pressure exceeded the elastic limit of UHPC, microcracks were prone to expansion under impact loads and the mechanical properties of the specimens deteriorated rapidly. Likewise, the failure pattern of the specimen under a given impact load was mainly determined by the heating temperature and cooling regime, whereas the axial static-pressure loading could only affect the fragment size.

Research progress on the dynamic compressive properties of ultra-high performance concrete under high strain rates

Ultra-high performance concrete (UHPC) has been accepted rapidly attributed to its superior mechanical performance and the split Hopkinson pressure bar (SHPB) is being widely utilized to evaluate the dynamic compressive properties of UHPC. Numerous studies have been performed on the dynamic behaviour of UHPC, however, a systematic summary and analysis on the dynamic compressive properties of UHPC tested by SHPB is still missing. The review starts by introducing the advantages, deficiencies and improvement methods of SHPB system. Dynamic compressive properties including dynamic compressive strength, peak strain, stress-strain relationship and dynamic elastic modulus are analyzed. The effects of steel fiber (content, type, orientations and hybrid), temperature condition, coarse aggregate, nanomaterials, size effect and loading rate on the dynamic characteristics of UHPC are comprehensively discussed. Dynamic increase factor, energy absorption characteristics and their models are summarized. Then, the dynamic constitutive model and the dynamic failure pattern are evaluated. Based on the analysis, prediction models of dynamic strength and energy absorption are proposed by considering the strain rate and volume of steel fiber, further, a new failure mechanism of UHPC under different strain rates is proposed. Finally, the topics requiring further study are highlighted. It is expected that this paper can provide references for prospective research on dynamic characteristics of UHPC.

Effect of different steel fiber types on mechanical properties of ultra-high performance concrete

The influence of steel fiber on the mechanical properties of ultra-high performance concrete (UHPC) were studied through slump, compressive strength, flexural strength test. The experimental results showed that the incorporation of steel fiber had an influence on the working performance of UHPC, and the slump and expansion degree of UHPC were inversely proportional to the volume content and length-diameter ratio of steel fiber. The steel fiber significantly improved the compressive and flexural strength of UHPC. The mechanical property of UHPC was the best when the steel fiber content was 4%, with 28 day compressive strength up to 163.2MPa and flexural strength up to 45.9MPa. UHPC showed a trend of gradual decrease of compressive strength and gradual increase of flexural strength with the increase of aspect ratio of steel fiber on the condition of constant volume content of steel fiber. The addition of special-shaped steel fiber can improve the compressive and flexural strength of UHPC effectively.

Influence of Glass Powder on Rheological Properties of Ultra-High Performance Concrete Paste

Replacing cement and silica fume with glass powder to prepare ultra-high performance concrete (UHPC) is beneficial to solve the ecological problem in the field of civil engineering, but the technologies of preparation, transportation, pumping, and hardening of UHPC mainly relate to its rheological property. Therefore, this paper studied the influence of glass powder on the rheological properties of UHPC paste by performing the flow and the rheological test. Experimental results showed that when the cement and silica fume partially replaced by glass powder, the UHPC paste appears shear thickening, yield stress, plastic viscosity, and area of hysteresis loop decrease. This means that mixing glass powder can somehow inhibit the problems of segregation and bleeding of UHPC during pumping. In this manner, the dosage of the superplasticizer in UHPC is appropriately reduced, the filling capacity of UHPC during pouring is improved, and the energy required for UHPC in the pumping process is weakened. Compared with replacing cement, replacing silica fume with glass powder significantly increases the shear thickening and fluidity of UHPC paste, and at the same, reduces its yield stress and plastic viscosity. This indicates that the construction performance of UHPC is greatly improved with the replacement of silica fume. The fluidity and yield stress of UHPC paste satisfy the quadratic polynomial function relationship, and the replacement of cement and silica fume with glass powder should be less than 33% and 50%, respectively. Under this condition, the rheological properties of the UHPC paste are greatly improved and result in little negative impact on the mechanical properties of UHPC.

Properties of ultra-high performance concrete using optimization of traditional aggregates and pozzolans

The properties of ultra-high performance concretes (UHPCs) made with traditional fine aggregates, different cementitious materials types and combinations, and varying steel fiber contents and shapes were studied. In the first phase, a total of 78 UHPCs were used to assess their compressive and splitting-tensile strengths, and drying shrinkage, which led to identifying 40 optimized mixtures for the second phase of the investigation for which their compressive, splitting-tensile, and flexural strength, modulus of elasticity, load–deflection response, and drying shrinkage properties were obtained. The outcome of this study revealed that the optimized UHPCs displayed excellent bulk properties and dimensional stability. Amongst the utilized cementitious materials combinations, UHPCs made with the combined silica fume and class F fly ash, as a partial replacement of cement, performed the best, whereas the companion mixtures incorporating only class F fly ash exhibited the contrary. A clear strain hardening and softening was observed in the load–deflection response of steel fiber-reinforced UHPCs. Due to better steel to concrete surface adhesion, straight steel fibers had a more positive influence on the mechanical properties and dimensional stability of the studied UHPCs when compared to those of the hooked fibers. Overall, this experimental study supports that, with proper gradations and proportioning, traditional fine aggregates can be used as an effective substitute for the expensive filler materials used for production of the proprietary UHPCs without compromising their mechanical properties and dimensional stability.

Secondary curing effect on the hydration of ultra-high performance concrete

Once the dense microstructure has been formulated, the external water supply has been generally regarded as ineffective for enhancing the material properties of ultra-high performance concrete (UHPC). Two days of high temperature curing is typically required after one day curing at ambient conditions to facilitate UHPC production. In this study, the curing process was divided into 1 day ambient curing, 1 day curing at 90–180 °C, 1 day water curing, and a subsequent 1 day curing at 90 °C. The UHPC hydration process, including consumption of silica fume and production of C-S-H, was quantitatively analyzed by the X-ray diffraction-based partial- or no-known crystal structure (PONKCS) method. The obtained strength was almost proportional to the initially applied temperature, and the secondary curing program (i.e., water curing and subsequent curing at 90 °C) showed an advantage for the later strength development of UHPC by promoting the reformation of C-S-H and the pozzolanic reaction. On the other hand, the partial decomposition of C-S-H at temperatures of 120–180 °C was observed from the diffraction and thermal analyses, but had a negligible effect on the development of material properties at that moment of the modification. Meanwhile, the decomposed C-S-H was efficiently reformed once the secondary curing was applied, which has a positive effect on structural properties. Although UHPC has an early formation of a dense microstructure, this study confirmed that secondary supplied water could sufficiently penetrate the matrix of UHPC, which can be used to enhance the long-term properties by reformulating C-S-H and enhancing pozzolanic reaction.

Influence of steel fiber size, shape, and strength on the quasi-static properties of ultra-high performance concrete: Experimental investigation and numerical modeling

This investigation focused on identifying the impact of various types of steel fibers on the quasi-static mechanical behavior of ultra-high performance concrete (UHPC) through different laboratory experiments as well as their numerical modeling. UHPC specimens were fabricated with four steel fiber types: ZP305, Nycon type V, OL 10mm, and OL 6mm. Fiber shape and size had little impact on quasi-static properties of UHPC in compression, while they showed significant impact on flexural and tensile properties. The main benefits offered by the smaller fibers occurred prior to reaching the ultimate load carrying capacity. Once the ultimate strength was reached, larger fibers were more effective in bridging larger cracks. Numerical modeling of the presented experiments were performed using the Lattice Discrete Particle Model (LDPM) enriched with fibers effect. LDPM is a meso-scale model simulating concrete at the scale of coarse aggregate pieces, and it has been extensively used for the simulation of concrete mechanical behavior under various loading and environmental conditions. The extension of this model, the so-called LDPM-F, developed for the simulation of fiber-reinforced concrete, is employed in this research to verify and better understand the experimental observations.

An Enhanced UHPC-Grout Shear Connection for Steel-Concrete Composite Bridges with Precast Decks

This article develops an enhanced UHPC-grout shear connection for steel-concrete composite bridges with precast decks. The primary improvement is the use of ultra-high performance concrete (UHPC) as the connection grout. To validate the constructability and the mechanical performance of the new connection, two series of experimental tests (including grouting tests and push-out tests) were conducted. Results from the grouting tests show that both the pressure grouting method and the self-levelling grouting method are applicable to inject the UHPC grout into the channel void of the connection. Results from the push-out tests indicate that the advanced properties of UHPC allow for a significant improvement of the shear resistance of the adhesive connection over traditional cementitious grouts. The ultimate shear capacity of the adhesive connection is controlled by the interface shear strength between the embossed steel and the UHPC grout, with a cohesion value of approximately 5.87 MPa. Meanwhile, the residual frictional resistance can be taken as approximately one-half of the ultimate resistance. The results of the finite-element analysis show that the trilinear model is reasonable to simulate the shear-slip laws of the embossed steel-grout interface and the rough concrete-grout interface.

Contribution of fiber orientation to enhancing dynamic properties of UHPC under impact loading

This paper investigates the contribution of fiber orientation to enhancing dynamic properties of ultra-high performance concrete (UHPC) under impact loading. Dynamic properties of 27 cylindrical core samples taken from prisms that have predominantly perpendicular, random, and parallel fiber orientations relative to the loading direction were tested. The Spilt Hopkinson Pressure Bar test method was used with strain rates of 160–290 s−1. Fiber orientation of samples after impact was evaluated using computed tomography scan. Test results indicated that the dynamic compressive strength, peak strain, and energy absorption capacity increased by up to 65%, 105%, and 295%, respectively, with the increase in strain rate. For a given strain rate, samples with predominant fiber orientations perpendicular and parallel to the loading direction showed the highest and lowest dynamic properties, respectively. Such spread in dynamic compressive strength, peak strain, and energy absorption capacity due to fiber orientation was up to 40%, 90%, and 135%, respectively. Fiber orientation coefficients along the direction of tensile stress were around 0.7 and less than 0.3 for samples with predominantly perpendicular and parallel fiber orientations, respectively. Good relationships were established to estimate the dynamic properties of UHPC given the quasi-static compressive strength, strain rate, and fiber orientation. A constitutive model to estimate the stress-strain curves of UHPC subjected to impact loading was developed. The model considers the influence of fiber orientation and strain rate. The model was successfully validated using the experimental data and was found to provide accurate prediction of the ascending portions of the stress-strain curves of UHPC under impact loading. The maximum spread between predicted and experimental dynamic compressive strength was limited to 10%.

Influence of fiber alignment and length on flexural properties of UHPC

This paper investigates the influence of fiber alignment induced during casting on flexural properties of ultra-high performance concrete (UHPC). Straight steel fibers with different lengths of 6, 13, and 20 mm were used at 2% volume ratio. Pullout load and energy of fibers with different lengths were evaluated. Flexural strength and toughness were determined for prismatic samples cast using a flow-induced device that can improve fiber orientation during placement. The horizontal outlet height of the device was adjusted to 10, 20, and 30 mm in order to secure different degrees of fiber orientation. Test results indicate that the longest fiber had approximately 5- and 27-time greater pullout load and pullout energy than those of the shortest fiber. Compared to UHPC made with the shortest fiber, UHPC cast with the longest fiber had approximately 75% and 245% higher flexural strength and toughness, respectively. The fiber dispersion and orientation improved when the horizontal outlet height decreased, resulting in greater flexural strength and toughness. Such enhancement was up to 75% and 100%, respectively, compared to similar UHPC cast using the conventional method that can result in random fiber orientation. Synergistic improvement exceeding 130% in flexural strength was obtained for samples cast with fiber length of 13 mm and horizontal outlet height of 10 mm, compared to samples cast with shorter fiber of 6 mm using the conventional casting method. The smoothed particle hydrodynamics simulation indicated that the ratio between fiber length and horizontal outlet height of 1.1 was more efficient to improve flexural properties of UHPC, compared to the ratios of 0.6 and 1.6 where the highest value led to blockage.

Development of Infilled Cementitious Composites (ICC)

Infilled cementitious composites (ICC) are a new class of fiber composite materials featured by high sustainability and overall high performance. Successful mix design of ICC involves fiber-particle packing optimization, paste volume control and ultra-high performance concrete (UHPC) technology, which are not easy so far. In this research, fiber-aggregate skeletons (FAS) were first manufactured utilizing four types of steel fibers at four fiber volumes blended with different sizes of coarse aggregates. Then, UHPC with a low water to cementitious materials (W/CM) ratio of 0.20 were prepared and infilled into the FAS to produce a total of 34 ICC mixes. The packing density of the FAS, the properties of UHPC and the ICC were systematically scrutinized and modeled for the first time.. Tests results demonstrate the feasibility and superiority of ICC over traditional UHPC, as evidenced by the reduced cost and embodied CO2 and the enhanced performance. The ICC should be a milestone in the development of fiber reinforced concrete with an overall ultra-high performance for both civil and military construction such as large-scale dams and shielding structures.

Tensile and Flexural Behavior of Ultra-High Performance Concrete (UHPC) under Impact Loading

The rate-sensitive properties of ultra-high performance concrete (UHPC) subjected to flexural and direct tensile loads were investigated. Dynamic flexural tests were performed by means of a drop hammer impact machine, whereas a servo-hydraulic system was utilized to conduct direct tension tests. The absorbed energy of the UHPC specimens under flexure increased from 0.74 to 4.49 J as the input energy varied from 6.7 to 67 J. The load-bearing capacity and maximum flexural deformation exhibited identical trends as the input energy increased. The high-speed tensile properties, including strength, ductility, and energy dissipation capacity, improved upon increasing the strain rate up to 100 s-1. A nonuniform distribution of the deformation of UHPC specimens under high-speed tension was observed by identifying the zones of strain localization (near crack), uniform strain (far field), and shear lag (transition zone in between) using digital image correlation. The full-field data of displacement, strain, and strain rates were obtained and quantitatively evaluated. The results indicated that multiple mechanisms were involved in the rate-dependent behavior of the UHPC specimens.

The Role of Supplementary Cementitious Materials (SCMs) in Ultra High Performance Concrete (UHPC): A Review.

Although ultra high-performance concrete (UHPC) has great performance in strength and durability, it has a disadvantage in the environmental aspect; it contains a large amount of cement that is responsible for a high amount of CO2 emissions from UHPC. Supplementary cementitious materials (SCMs), industrial by-products or naturally occurring materials can help relieve the environmental burden by reducing the amount of cement in UHPC. This paper reviews the effect of SCMs on the properties of UHPC in the aspects of material properties and environmental impacts. It was found that various kinds of SCMs have been used in UHPC in the literature and they can be classified as slag, fly ash, limestone powder, metakaolin, and others. The effects of each SCM are discussed mainly on the early age compressive strength, the late age compressive strength, the workability, and the shrinkage of UHPC. It can be concluded that various forms of SCMs were successfully applied to UHPC possessing the material requirement of UHPC such as compressive strength. Finally, the analysis on the environmental impact of the UHPC mix designs with the SCMs is provided using embodied CO2 generated during the material production.

Mechanisms underlying the strength enhancement of UHPC modified with nano-SiO2 and nano-CaCO3

The unique physical and chemical properties of nano-particles can enhance the nature of cement-based materials at the micro-scale and nano-scale levels, leading to improved properties. To uncover the strengthening mechanism associated with various types of nano-particles, a laboratory investigation was undertaken to evaluate and compare the influence of nano-SiO2 and nano-CaCO3 on mechanical properties of ultra-high performance concrete (UHPC) made with 2% steel fibers. Each type of nano-particle was incorporated at four contents, and the mini-slump flow of the UHPC was maintained at 240–260 mm. The microstructure of the matrix and the fiber-matrix interface of UHPC, as well as the features of hydration products were characterized using advanced techniques, such as electron microscopy (SEM), X-ray diffraction (XRD), differential thermal gravimetric (DTG) analyses, 3D micro-tomography, and mercury intrusion porosimetry (MIP). Test results indicate that both the fiber-matrix strength and mechanical strength of UHPC increased with the increase of nano-SiO2 and nano-CaCO3 until threshold limits of 1% and 3.2%, respectively. The 28-d fiber-matrix bond, compressive, and flexural strengths of the optimal UHPC mixtures made with 3.2% nano-CaCO3 were approximately 40%, 10%, and 20%, respectively, greater than those of the reference mixture. These strength values were higher than those of UHPC made with 1% nano-SiO2. When used below these optimal nano-material contents, the filler and nucleation effects related of the nano-SiO2 and nano-CaCO3 promoted the strength development through improved density and homogeneity with optimized structure of hydration products, as indicated by SEM observation and DTG analysis. Beyond these limits, additional use of nano-materials resulted in increased volume of air voids and capillary pores and weak interfacial zones due to the agglomeration of nano-particles, which hindered strength development.

Contribution of fiber alignment on flexural properties of UHPC and prediction using the Composite Theory

This paper investigates the effect of fiber alignment on the flexural properties of ultra-high performance concrete (UHPC) made with different steel fiber lengths (6, 13, and 20 mm) and volumes (1%, 2%, and 3%). Fiber alignment of prismatic samples was secured using a flow-induced casting method. Test results indicated that prismatic samples cast using the flow-induced method can enable 35% greater fiber orientation compared to those prepared using a conventional casting method that results in random fiber orientation. Such improvement in fiber orientation led to 60% and 80% higher flexural strength and toughness, respectively. At a fiber volume of 2%, the increase in fiber length from 6 to 20 mm can result in 45% and 195% greater flexural strength and toughness, respectively, for samples with flow-induced fiber alignment. With the increase in fiber volume from 1% to 3% for 13-mm long fibers, such enhancements were 55% and 40%, respectively. Similar flexural properties can be obtained for UHPC made with 1% of the longer fibers when the flow-induced casting method is employed compared to those prepared using the conventional casting method at 3% of the shorter fibers. The flexural-to-tensile strength ratio of UHPC increased with the increase in fiber length, volume, and orientation. For a given fiber length and volume, the flexural-to-tensile strength ratio increased linearly with the increase in fiber orientation. When the variations in flexural-to-tensile strength ratios are considered as a function of fiber length, volume, and orientation, flexural strength of UHPC can be predicted with a maximum spread of 15% using the Composite Theory.

Influence of steel fiber corrosion on tensile properties and cracking mechanism of ultra-high performance concrete in an electrochemical corrosion environment

In this paper, the mechanisms by which the tensile mechanical properties of ultra-high performance concrete (UHPC) are influenced by the degree of steel fiber corrosion are investigated via accelerated electrochemical corrosion, direct tensile testing, and acoustic emission (AE) analysis. The elastic modulus is shown to decrease, while the ultimate tensile strength initially increases and subsequently decreases, with increasing corrosion time. Further, an increased degree of corrosion is shown to decrease the crack control capability of the UHPC such that crack widths rapidly increase and a large amount of AE energy is generated. Concurrently, the cracking behavior due to corrosion of the steel fiber network is examined by X-ray computed tomography (X-ray CT), revealing that corrosion cracking and cambium spalling are facilitated by concentration of the steel fibers. In the case of a small amount of corrosion, the chloride ions permeation is found to be small, and the corrosion only occurs on the surface of the specimens. With increased corrosion time, however, chloride ions gradually penetrate into the interior of the specimen, thus increasing the degree of corrosion. Finally, a formula is established for predicting the time of corrosion cracking in the concrete cover, and a parametric analysis is performed.

Multi-level micromechanical analysis of elastic properties of ultra-high performance concrete at high temperatures: Effects of imperfect interface and inclusion size

Ultra-high performance concrete (UHPC), as a typical multi-phase composite material, is vulnerable to mechanical degradation and explosive spalling at high temperatures. In this work, the temperature-dependent elastic modulus of UHPC is estimated through the step-by-step homogenization from gel matrix level to ultra-high performance fiber-reinforced concrete level. Totally three forms of C-S-H gels are considered to determine the elastic properties of the initial matrix, and the phase transformation and volume fractions of individual phases at high temperatures are calculated based on the hydration and dehydration kinetics models. Moreover, the effects of imperfect interface and inclusion size are taken into account by introducing the spring-layer interface model and log-normal size distribution function to the homogenization scheme. The predicted elastic moduli are validated by analytical and experimental results, showing that accurate predictions can be obtained at up to 800°C. Interestingly, the imperfect interface matters when high-modulus inclusions are embedded in the low-modulus matrix, and the effect of imperfect interface on effective elastic modulus varies a lot at different microscopic levels. The findings highlight the synergistic effects of imperfect interface and inclusion size on the elastic properties, which is helpful to the mechanical design of UHPC at high temperatures.

A review study on sustainable development of ultra high-performance concrete

<abstract> <p>A systematic literature review was undertaken in this report to illustrate the development concepts and properties of ultra-high performance concrete (UHPC). UHPC's affluent development relies on its compositional content, water–binder (w/b) ratio, and design mix approach, which contributes to denser and comparatively more homogeneous packaging of particles. Numerous research studies from around the world were used to compile a database on UHPC mechanical and durability properties. Moreover, the results of this study reveal that the curing conditions, aggregates, fibre dosage and characteristics, and curing time are the most important elements in determining the mechanical and durability qualities of UHPC. Furthermore, due to its ultra-high-strength features, superior fatigue behavior, and extremely low porosity, UHPC is considered a practical and long-term alternative for improved sustainable building, resulting in increased resilience to hostile environments. Besides that, attempts are being taken to resolve existing challenges (such as high initial costs, a lack of skills, and a lack of design code) and their solutions to their widespread economic use. This study aims to help architects, builders, and other construction stakeholders better grasp UHPC's basic features and capacities, which will help to understand this durable and long-lasting building material.</p> </abstract>

Physical-mechanical properties and durability of ultra-high performance concrete (UHPC)

This paper presents the results of the authors' laboratory testing of physical, mechanical and durability properties of Ultra-high Performance Concrete (UHPC). The short history of development and application of UHPC concrete is presented in the first part of this paper while the second part deals with the experimental investigation, presenting the results of material characterization obtained from physical-mechanical and durability tests. Based on the results shown in the paper, the mean value of compressive strength obtained at 28 days is 114 MPa, with the average density of 2270 kg/m3 in hardened state. The results showed that tested UHPC belongs to the highest class of water impermeability V-III, as well as the highest class MS0 (without visible damage) in a simulated freeze-thaw environment and de-icing salt attack test. Also, the highest class XM3 for abrasion resistance was achieved. Additional tests showed that the tested concrete fulfils the requirements for the highest exposure classes XC4 and XD4, in terms of resistance to carbonation and the penetration of chloride ions. Conclusions and recommendations for further development and possible application of UHPC are presented at the end of paper.

Mechanical Properties of Ultra-high Performance Concrete Reinforced by Glass Fibers under Accelerated Agin

Ultra-High Performance Concrete (UHPC) is a cementitious composite with fine aggregates and a homogeneous matrix with high compressive strength and excellent durability against aggressive agents. It is common to use short steel fibers in the UHPC. Besides, using steel fibers considerably increases the flexural ductility, durability and energy absorption. Using glass fibers in UHPC is a novel technique which improves its mechanical properties and it has the benefit of being lighter, and cheaper than steel fibers. Furthermore, glass fibers can be used for thin concrete plates for aesthetic purposes. However, glass fibers reinforced concrete is incompatible with the hydration reaction in the alkaline environment of concrete as it can damage glass fibers, so the mechanical properties of the concrete are decreased over long periods. The mechanical properties of UHPC containing glass fibers (GF-UHPC) was investigated under three regimes of normal curing, autoclave curing, and autoclave curing plus being in hot water for 50 days (accelerated aging). Besides, the substitution of silica fume by Metakaolin in GF-UHPC was studied to understand its mechanical properties after thermal curing. The results showed that after accelerated aging, the behavior of specimens become more brittle and the modulus of rupture and toughness indices of all prismatic specimens decreased, the modulus of rupture for samples containing glass fibers was 40% lower than autoclave curing results. However, the compressive strength under accelerated aging increased at least 4% in comparison to the normal curing. Replacement of silica fume with Metakaolin slightly increased the toughness with regard to flexural strength.