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This study aims to assess the effect of sodium chloride attack on the mechanical and durability properties of high-performance concrete (HPC) based on fibers and natural pozzolans. The resistance of specimens against chemical attack is determined by the unit weight, compressive strength, splitting-tensile strength, chloride ion permeability, apparent gas permeability, and visual inspection after 28, 90, 180, and 365 days of testing. A total of three types of concrete are assessed: reference concrete (RC), HPC, and high-performance fiber-reinforced concrete (HPFRC) stored in tap water and aggressive water (i.e., a 10% NaCl solution). The test results demonstrate that the presence of fibers negatively affects the permeability of HPC. However, HPC and HPFRC remain stable and are not influenced by the NaCl solution compared to RC. The natural pozzolans attenuate the side effect of fibers by occupying voids (i.e., the filler effect) and generating denser products (i.e., the pozzolanic reaction) in the cement matrix.

Perlite, a natural glassy volcanic rock could be used as supplementary cementitious material to reduce environmental pollution and the consumption of precious natural resources in the concrete industries. The aim of this work is to assess natural perlite used as 50% aggregates substitution by volume (sand or gravel) and as 10%, 15%, 20% cement substitution in self-compacting concrete. Workability characteristics and mechanical properties were analysed. Results showed that replacing 50% of natural aggregates with 50% of perlite aggregates or substituting cement with 10% of perlite powder generated the best workability characteristics and improved compressive, flexural strength, and elastic modulus of concrete at 28 days. Moreover, the results were combined to develop correlations that prove to be good between mechanical properties of self-compacting. Using perlite as aggregates offers a new source of supply and saves natural aggregates. Also, perlite used as cement substitution helps to reduce PC consumption, cost, and CO2 emission.

In this paper, influence of heat treatment on evolution of mechanical strengths at early age, less than 24hours of self-compacting concretes containing limestone powder and silica fume as fine materials was investigated experimentally. Two compositions of self-compacting concrete have been studied; the first is elaborated with silica fume addition and the second with limestone powder, each mixture were prepared with a constant water/binder ratio of 0.39. Concrete samples were either cured in water at (23±1°C), or steam cured at 65°C maximum temperature over six hours (6h) curing period. Tests of mechanical strengths were performed on specimens cooled down slowly to room temperature after heating.The obtained results show that all self-compacting mixtures exhibited satisfying fresh properties and check EFNARC specifications of self-compacting concrete (slump flow diameter higher than 650mm, L-box ratio higher than 80% and sieve stability less than 17%).Mechanical strengths of concrete containing limestone addition are slightly lower than those of concrete based on silica fume at all ages. Moreover, heat treatment generates an improvement of compressive and flexural strength. Interesting compressive strengths are obtained. At 24 hours, after heat treatment, the strengths are already greater than 35 MPa. The values ​​are 37 MPa and 40 MPa for self-compacting concrete containing limestone powder and silica fume respectively compared to 40 MPa and 46 MPa obtained at 7 days for the corresponding non-heat treated concretes. Compressive strength gain of SCCs mixtures with limestone powder and with silica fume, undergoing heat treatment at the age of 24hours is 85% and 75% respectively compared to SCCs mixtures cured in water.

This paper presents the results of an experimental study that investigates the compression behavior of concrete and evaluates the effect of hybrid reinforcement by multiple geometries, and total and partial confinement, using CFRP and GFRP composite materials. A total of nine (09) variants of concrete cylindrical specimens, including one (01) variant of unconfined concrete and eight (08) variants of confined concrete with different geometries were subjected to axial load compression. The objectives of this study were to verify the applicability and effectiveness of partial and total confinement to improve the behavior of concrete, evaluate the effect of the hybrid confinement used, and obtain a typical reinforced model. The results obtained clearly show the effectiveness of the hybrid confinement and partially confined concrete in improving the compressive strength and deformation of the concrete, so it is possible to replace CFRP total confinement by partially confined concrete with two CFRP layers or by a hybrid confinement with a CFRP layer in the central zone and GFRP layers on the top and bottom of the specimen.

This paper presents an experimental and numerical investigation of reinforced concrete beams strengthening by means of different combinations of externally bonded hybrid fabrics-reinforced polymer composite: Carbon and glass fabric–reinforced polymer composite and another fabric-reinforced polymer composite based on vegetable fiber it is the jute fiber. The objective of this study is the conjugation of the properties of each type of fiber fabric to increase the load capacity, rigidity, and ductility of reinforced concrete beams and obtaining a typical model of reinforcement beams, which provides both these three desired mechanical properties. Three control beams and 27 beams strengthened in flexural–shear with Carbon, glass, and jute fabric–reinforced polymer composite and hybrid fiber fabrics were conducted and tested under three points bending. The load–deflection response, ductility, and associated failure modes of the tested specimens have been recorded and analyzed. In addition to the experimental investigations, numerical simulation using ABAQUS was developed to predict the load–deflection response and the failure modes, the results were compared with the corresponding experimental results, a good correlation was obtained.

This work aims to investigate the effect of metakaolin represented by calcined clay of Djbel Debbagh quality 3 (DD) as a pozzolan addition on physical mechanical properties and the durability of Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC), compared to the silica fume (SF). Within the scope of this study, durability tests, such as chloride penetration resistance of various mixtures of UHPFRC based on steel fibres, have been investigated besides mechanical properties. The comparison of thermal stability of these mixtures, with two other formulations based on SF and calcined clay DD with polypropylene fibers is studied. The experimental results showed that the substitution of SF by calcined clay DD, makes it possible to produce UHPFRC with equivalent mechanical performance and a good resistance to penetration of chloride ions, this calcined clay has a high pozzolanic reactivity and can be used as fireclay addition which contributes to improve thermal behaviour of concrete. The specimens contain...

This paper presents the fresh and hardened properties of self-compacting concrete (SCC) containing plastic bag waste fibers (PBWF). Fibers were prepared by recycling waste material such as, plastic bag. Fourteen mixtures of SCC with 0.40 of water/cement ratio were studied, twelve SCC mixtures with plastic bag waste fiber (WFSCC) by varying the length of fibers (2, 4 and 6 cm) with different levels of incorporation (1, 3, 5 and 7 kg/m3) and two other mixtures, one with 1 kg/m3 of polypropylene fibers (PFSCC) and another without fiber as reference (RSCC). Slump flow, L-box, and sieve stability were performed to assess the fresh properties of the prepared mixtures. Compressive strength, splitting tensile strength and flexural strength of the concrete were determined for the hardened properties Test results show that mixtures based on PBWF with a length of 2 cm, met the criteria of self-compactability (evaluated by slump flow diameter, L-box and sieve stability test) regardless of the fibers content. The obtained results are very interesting, suggesting a possible use of PBWF for structural reinforcement of SCC, the presence of this fibers in concrete delaying the location of microcracks. Although, the incorporation of PBWF has not a significant effect on the compressive and flexural strengths, it has a important effect on the split tensile strength value at 28 days. The improvement varies from 4% to 74%, it depends on the amount of fibers, and it is not affected by the length of PBWF.

In recent years, fiber-reinforced polymers (FRPs) materials have shown great potential as materials for repair and reinforced concrete structures such as beams or columns by externally bonding FRP sheet(s) onto the surface of substrate concrete structures. However, the performance of FRP systems exposed to fire is a serious concern due to the combustibility of FRPs. This study introduces the results of an experimental investigation on the behavior of the circular columns of concrete under a load of axial compression, confined by an envelope of composite materials (carbon fiber and glass fiber) and protected by a layer of mortar cement or plaster coating, after they have been subjected at various temperature (23, 120, and 350 °C). The specific objectives of this study are verifying the applicability and the effectiveness of the proposed technique to improve the behavior of concrete in fire resistance and evaluate the effect of composite materials and the layer coating type used. The results indicated that ...

This paper summarizes the experimental results from a comprehensive research program to study the fundamental stress–strain behavior of damaged concrete repaired by two techniques: increased concre...

This paper presents the results of an experimental study which investigates the effect of the use of marble powder (MP), as partial cement substitution, on the fresh and hardened properties of fibre-reinforced self-compacting concrete (FRSCC) of non-uniform size (length) and aspect ratio of fibres used. For each length of steel fibre (25, 30 and 50 mm), three percentages (.5, .8 and 1%) were used to improve the performance of FRSCC. All mixtures of concrete specimens prepared with 30% of MP were evaluated. Slump flow time and diameter, sieve stability and L-Box were performed to assess the fresh properties of the (FRSCC). Compressive strength, splitting tensile strength, flexural strength and ultrasonic pulse velocity of the FRSCC and self-compacting concrete (SCC) were determined for the hardened properties. The results were compared with ordinary concrete (without steel fibre) containing 30% of MP (SCC). The results suggest that the incorporation of steel fibre in the SCC requires the use of high volume...

This paper presents results of an experimental study which investigates the effect of four pozzolan additions made from various by-product materials on physical and mechanical properties of ultra-high performance fibre-reinforced concrete (UHPFRC) compared with the silica fume (SF): waste bricks (WB) and three types of metakaolin (MK) as calcined clays at 750 °C: calcined clay of Djbel Debbagh quality 3 (DD), calcined sludge incineration at the manufacture of paper (PS) and calcined silt of dams (SD) having median particle sizes less than 45 μm are used as addition. For each addition, five percentages of steel fibres (1, 1.5, 2, 2.5 and 3%) were used to improve the performance of concrete. The results suggest that the use of WB, PS and SD has no significant effect on the compressive strength as compared with SF concretes. Calcined clay DD can be used as pozzolanic materials in making UHPFRC. This MK competes with the SF, after 28 days of curing, the concrete containing 25% of DD and 2.5% steel fibre prese...

This study introduces the results of an experimental investigation on the behavior of the circular columns of concrete under a load of axial compression, confined by an envelope of composite materials (carbon fiber and glass fiber). The composite used is a FRP glued in surface with epoxy resin. The specific objectives of this study are: verifying the applicability of this method of reinforcement of the columns to improve the behavior of concrete from the point of view strength and ductility, seeing the influence of composite materials type used, and confronting the experimental results acquired with different models developed on one hand and on the other hand with empirical formulas developed by other researches. Two models were developed to represent the structural behavior of the tested samples based on the calibration of the experimental results and criterion of Mohr—Coulomb failure. The validity of the results acquired numerically is based on a comparison with experimental results as well as with empirical formulas developed.

This study exhibits the experimental results of axial compression tests on concrete cylinders, circumferentially confined by the set-up of the composite grids arranged inside the cylinder, according to several combinations of circumscribed grids. The main aim is to verify the applicability of this method and then to quantify the contribution to strength improvement due to confinement as well as its influence on the rupture mode under axial compression. The test results of loading carried out on cylindrical concrete specimens, confined by alveolus composite grids arranged inside the section, show that it is possible to substantially increase the ductility of the columns, and in certain cases, their strength. It is also noted that the rupture of confined concrete is highly influenced by the presence of the grids depending on the configuration and the shape of the cells (rhombus or hexagonal) constituting the composite grid. The experimental results are compared with the theoretical model data.

The strength development of self-compacting mortars (SCM) containing calcined silt (CS) and ground brick waste (GWB) was investigated. The variables are the nature of addition (CS and GWB) in the binder and the heat curing at different temperatures (20 ºC and 60 ºC) at 7 and 14 days of curing. Two temperatures 20 and 60 ºC were applied to samples with intermediate levels (depending on the drying method applied to precast) for 18 hours in total. In this study, a Portland cement (CEMII), Calcined silt (750 ºC for 5 hours), ground waste brick, were used in the binders of SCM. The results show that the compressive strength to 14 days of mortars, increases with annealing (60 ºC) compared to that measured at 20 ºC. Also, values of compressive strength of mortars at 14 days that are close to those obtained without 28 days curing treatment. Indeed, a strength gain of about 20.5% and 27.3% was obtained respectively for the SCM with GWB and the SCM with CS. However, a small change in mass recorded for both types of mortars.

In this research, we will try to understand the mechanisms involved in the introduction of calcined clays in substitution for a portion of cement in the manufacture of mortars. This experimental work focuses on the recovery of a clay type haloysite quality three, from eastern Algeria. This clay comes from a region called Djbel Debbagh hence its name (DD3). The main objective of this study is to see the influence of the activated clay by calcination with different percentages of 5, 10, 15 and 20% in substitution of cement, on thephysical-mechanical properties and behaviour of mortars towards chemical attacks. The study of pozzolanic activity allows to optimize a calcinations temperature of about 750°C, the study of its mechanical performance has shown an improvement of strength. Finally, the results of the durability test showed a good performance in different environments. Key words: Valorization, clay, mortar, temperature, pozzolanic activity, durability.

This paper presents results of an experimental study which investigates the effect of industrial pozzolan made from calcined silt of dam at 750 °C for 5 h, on mechanical properties and durability of ordinary mortar, compared to the silica fume. Mortar specimens prepared with 5, 10 and 15 % of calcined silt to substitute cement were evaluated for their compressive and flexural strength, sulfate, acid and penetration of chloride ions resistance. The results were compared with ordinary mortar (without addition) and mortar containing 10 % of silica fume. The results obtained showed that the calcined silt of dam has a high potential to be used as a pozzolanic material, it improves the strength and the durability of mortar and compete the silica fume.