Fiber-reinforced Concrete Pavement Research Articles

Effect of adding additional Carbon Fiber on Piezoresistive Properties of Fiber Reinforced Concrete Pavements under Impact Load

Multifunctional Cementitious Composite (MCC) characteristics are directly related to the type and dosage of the Electrically Conductive Materials (ECMs) reinforcing the relevant concrete matrices. This study investigated the electro-mechanical capacities of fiber reinforced concrete pavement (FRCP) with and without the addition of micro scale-carbon fiber (CF). The impact energy of FRCP under compacted load was evaluated initially; then, the effects of 0.5% and 1% content by volume of CF on the piezoresistivity capacities of FRCP were investigated under applied impact load. This type of load is the most common force causing long-term rigid pavement deterioration. Obtained results showed that the use of a hybrid fiber (micro-scale carbon fiber 0.5% and macro-scale steel fiber 1% by volume) enhanced the impact strength (impact energy) due to CF’s resistance to micro-cracks. The developed FRCP showed good results in terms of self-sensing under compact load with both 0.5 and 1.0% by volume of CF.

Analysis of Flexural Capacity of Fiber Reinforced Concrete Pavements

Analysis of Flexural Capacity of Fiber Reinforced Concrete Pavements

Fiber Effect on Interfacial Bond Between Concrete and Fiber-Reinforced Mortar

Field overlay and bridge deck studies have suggested that vertical curling deflections and debonding can be reduced when the overlay contains fiber reinforcement. This study investigates the tensile and shear bond between aged concrete and fiber-reinforced mortar. Three macrofibers commonly used in fiber-reinforced concrete pavement overlays or bridge decks were investigated. The macrofibers were a stretched synthetic, a textured synthetic, and a hooked-end steel fiber. The tensile fracture energy within the fiber-reinforced mortar material and an interfacial tensile bond energy between the fiber-reinforced mortar cast against the aged and sandblasted concrete were all higher than that of plain unreinforced mortar. The peak loads associated with tensile or shear bond failure were not statistically affected with the addition of fibers in the overlay mixture. Overall, the interfacial tensile bond energy did improve as the fiber volume content increased, especially because some of the fracture path occurred through the mortar layer and was bridged by the fibers near the interface surface.

Laboratory Fatigue and Toughness Evaluation of Fiber-Reinforced Concrete

Concrete pavement design is currently centered on steel reinforcement: whether in the form of dowel bars, as in jointed plain concrete pavement, or in the form of continuous rebar reinforcement, as in continuously reinforced concrete pavement. The use of steel in concrete pavements presents durability problems because of the corrodibility of steel. This study evaluated the use of polypropylene fibrillated fibers, polypropylene macrofibers, and carbon fibers as primary reinforcement in concrete pavements for the Louisiana Department of Transportation and Development. Results showed that fiber reinforcement can be used to improve both the fatigue and toughness performance of concrete. When post-cracked strength or toughness was the concern, concrete containing more fibers and fibers with a high tensile strength was desirable. Carbon fibers maintained greater load-carrying capacity at lower deflections than did the steel fibers, which produced the greatest ductility. However, toughness and fatigue performance did not correlate for small deflections; this result suggests that polypropylene macrofibers may be adequate for repeated, low-stress loading. This study also found that when repeated low deflections were a concern, such as with pavements, there had to be sufficient fibers across a crack to maintain a tight crack. Conversely, too many fibers prevented adequate consolidation and aggregate interlock and negatively influenced performance. The resultant pavement design, continuously fiber-reinforced concrete pavement, will provide an alternative to jointed plain concrete pavement and continuously reinforced concrete pavement in highway pavement design that is not susceptible to durability problems associated with corrosion of reinforcement.

Application of the Maximum Undamaged Defect Size (d max) Concept in Fiber-Reinforced Concrete Pavements

Many fiber types are used in fiber-reinforced concrete (FRC) pavements. The maximum undamaged defect size (d max) concept has been applied to predict notch-based fracture in different types of concrete. The present paper applies this concept to different types of FRC pavement, namely, glass fiber-reinforced concrete pavement and steel fiber-reinforced concrete pavement. Due to the quasi-brittle manner of concrete, various fracture models have been developed to study the crack propagation in the pavement structures. The fracture energy was determined based on the recommendation of the RILEM Committee 50-FMC. An experimental study was carried out to investigate the effect of adding short fiber, steel or glass, in controlling the fracture energy of concrete. The analysis was invoked for constant fiber length of 25mm. The flexure test of single-edge notched and unnotched specimens was performed using three-point bending configuration. Four different values of crack-depth ratios were considered, mainly, 0.00, 0.10, 0.25, and 0.40. Experimental results showed that the calculated d max based on RILEM Committee 50-FMC is greater than the maximum aggregate size (MAZ). This means that there is no compatibility between the flexural strength of FRC and its fracture energy calculated based on RILEM Committee 50-FMC. Therefore, a modified calculation of the area of load-deflection curve was suggested to improve the reliability of fracture energy measured based on RILEM Committee 50-FMC. It is found based on this modification that d max is less than 0.7 MAZ.

Effect of nano-particles on durability of fiber-reinforced concrete pavement

In this study frost resistance and mechanical properties of fiber-reinforced concrete pavement containing nano-particles are studied. Nano-particles are employed to be as substitute of a portion of cement. For comparison the frost resistance and mechanical properties of plain concrete (control concrete), concrete containing nano-particles (without fibers) and concrete containing polypropylene fibers are also experimentally studied separately in this work. The specimens were subjected to cycles of freezing and thawing in water according to ASTM C666A. Experimental results show that using 5% nano-silica (by the weight of cementitious materials) improves the compressive strength and frost resistance of concrete as much as 30% and 83% respectively. Substitution 3% of cement by nano-alumina particles can improve compressive strength and frost durability of concrete as much as 8% and 81% respectively. Experimental results also show that polypropylene fibers can slightly affect the frost durability and compressive strength of concrete. As a general result it can be concluded that using nano-particles incorporating polypropylene fibers enhances frost resistance and compressive strength of concrete pavement because of that the permeability and porosity of concrete are reduced due to the use of nano-particles and also the tensile strength of concrete is enhanced due to the use of polypropylene fibers.

A Study on the Shrinkage Control of Fiber Reinforced Concrete Pavement

Cement concrete pavement provides durable service life and remarkable applicability for heavy traffic. Its purchase being easier than asphalt, cement concrete pavement offers excellent advantages in terms of durability and economic efficiency. However, adequate repair of this pavement is harder than asphalt concrete in case of degradation or damage. Cracking in the concrete pavement is the major cause of such disadvantages and the demand of repair on road sites is growing every day. This emphasizes the urgency to secure technologies for the control of early and longterm cracking. Accordingly, this study evaluates the drying and autogenous shrinkage strains regard to fiber reinforcement in order to reduce cracking of the concrete pavement mix so as to control the damage of the pavement by means of fiber reinforcement. The results show that the drying shrinkage strain can be significantly reduced to about 1/4 through the admixing of 0.2% volume ratio of NY fiber compared to the non-reinforced plain concrete, and that the hybrid fiber reinforcement mix H-N1-ST1 can realize remarkable reduction of the autogenous shrinkage.

Design Aspects on Steel Fiber-Reinforced Concrete Pavements

A numerical study on the fracture behavior of steel fiber-reinforced concrete (SFRC) slabs on grade for industrial pavements is presented. Finite element analyses have been carried out by using a commercial finite element code where user subroutines based on nonlinear fracture mechanics have been implemented to describe the progressive cracking behavior of SFRC. The model is capable of simulating both primary and secondary cracks when they occur in concrete and it has been validated by comparing numerical predictions with experimental observations of full-scale tests on slabs on elastic subgrade under point loads in different positions. A real pavement with contraction or construction joints has been numerically simulated to investigate the stress and the strain fields for the most significant positions of point loads.

Simplified method for concrete pavement design with discrete structural fibers

The addition of discrete macro fibers to plain concrete increased the flexural capacity of concrete slabs supported on ground. Flexural strength tests (i.e., ASTM C78) did not capture the added toughening mechanisms fibers imparted to concrete slabs. Based on the results of small and large-scale testing, the equivalent flexural strength ratio ( R e,3) was used to quantify the increased flexural capacity of synthetic and steel-fiber reinforced concrete slabs over plain concrete slabs. An effective flexural strength approach was proposed for the design of fiber-reinforced concrete pavements. The method applied a percentage increase to the modulus of rupture (MOR) of plain concrete based on the measured R e,3 value for the fiber-reinforced concrete mixture. The effective MOR accounts for the contribution of fibers to the added slab flexural capacity and fits into existing linear elastic-based design guidelines for concrete pavement. Large-scale test results verified the proposed design approach for fiber-reinforced concrete pavements. The proposed method is applicable for concrete mixtures reinforced with relatively low volume fractions of fibers that produce R e,3 values between 20% and 50%. Such fiber concrete mixtures are practically and economically attractive as they can be mixed, placed, and compacted with normal paving techniques.

Responses of Plain and Steel Fiber-Reinforced Concrete Beams to Temperature and Mechanical Loads: Experimental Study

To study the structural responses of plain and steel fiber-reinforced concrete pavements under combined mechanical and thermal loads, two test series have been conducted with plain and steel fiber-reinforced concrete beams. The magnitude and duration of the differences in the induced stresses caused by traffic load and a positive nonlinear temperature gradient (the top surface was warmer than the bottom surface during the day) may lead to some relaxation of thermal stresses and subsequently increase the load-carrying capacity. Considering the loss of support contact in the interior part of the concrete pavement, the experimental study of combined loading with restrained concrete beams may provide some insight and an indication of whether the superposition of stresses is a proper approach. The beams were subjected to solely thermal, solely mechanical, and combined thermal and mechanical loads while the rotation of the beam at supports was prevented. The results of tests conducted with both plain and steel fiber-reinforced beams showed that the superposition of stresses under combined loading before cracking gave a satisfactory estimation of the load-carrying capacities. The results also showed that the effect of relaxation of stresses due to short-term thermal loads was not noticeable in the load-carrying capacity achieved in tests with combined thermal and mechanical loads. On the contrary, a tendency for reduction of the load-carrying capacity was observed at higher thermal gradients. In addition, the overall structural responses of steel fiber-reinforced concrete beams under mechanical load and a nonlinear temperature gradient combined were similar to the responses of plain concrete beams up to the cracking stage. However, the release of thermal stresses due to cracking and the considerable residual load-carrying capacity after cracking were the most important observations for steel fiber-reinforced concrete beams.

黒磯バイパスにおける鋼繊維補強コンクリート舗装

本文は国道4号線黒磯バイパス建設工事において行われた鋼繊維補強コンクリート試験舗装の中間報告書である。1975～1978年にかけて, 現場で通常使用されているセット・ホーム型の舗設機械を用いて, 鋼繊維補強コンクリートの実用試験舗装が行われた。4種類の設計の舗装が施工され, コンクリート舗装版の長さについても検討が行われた。本文には鋼繊維補強コンクリートの曲げ強度, 繊維の配向・分散, コンクリートの密度, コンクリート版の動向, すべり抵抗などについての試験結果が述べられている。