This research aims to experimentally evaluate the behaviour of multi-layered fibrous cementitious composites with intermediate Glass Fibre Meshes (GFM) under repeated projectile load. The impact load was subjected through a convex edge projectile needle at a low velocity on cylindrical specimens of three-layered fibrous cementitious composites, which have two different steel fibre distributions. In series A mixtures, a constant steel fibre dosage of 2.5% by volume was used. On the other hand, the fibre dosage of the outer layers was 3.0%; while it was 1.5% in the middle layer of series B mixtures. The number of intermediate GFM was the variable that distinguishes the mixtures of each series. The resistance to projectile impacts was evaluated on the basis of penetration depth, near surface distortion, weight loss, damage ratio and failure pattern. The test results showed that due to the combined effect of steel fibre and GFM, significantly lower weight losses were recorded for series A and B specimens compared with reference specimens. However, the different fibre distributions (series B) led to lower penetration depths and weight losses with less surface distortion compared with the fixed fibre distribution (series A). The reduction in the destroyed front surface area of series A specimens compared with reference specimens ranged from 27.8 to 38.1%; while that of series B specimens ranged from 34.8 to 53.4%. In addition, a simplified analytical model was introduced to predict the ejected composite mass. The model predictions were found to be in good agreement with the experimental masses. arabic 9 English 71
Hakim S. Abdelgader (1-2021)

Although several studies have been conducted to evaluate the impact response of concrete using the American Concrete Institute (ACI) 544-2R falling mass impact test, the variations in test results are the main drawback of this testing method. This study aims to reduce the variations in experimental impact test results by introducing two simple test setup modifications; (1) using coarse or fine aggregate bed- ding as an alternative to the steel base plate, (2) the use of line or cross-notched specimens with a line or cross-load distributing steel plate. One hundred thirty-five cylindrical discs were prepared with Preplaced Aggregate Fibrous Concrete (PAFC) and Slurry Infiltrated Fibrous Concrete (SIFCON), tested in nine groups to assess the proposed modified techniques. Steel hooked-end (2.5%) and macro polypropylene (8.0%) fibers were used to develop PAFC and SIFCON, respectively. The research findings revealed that using aggregate bedding increased the impact resistance by 38 to 429% for no-notch spec- imens and up to 283% for notched specimens. The presence of notches reduced the total energy absorbed by the bedding material. For instance, the specimens with a line notch and sand bedding exhibited 15 to 51% lower failure impact numbers than their corresponding no-notch specimens. Considering surface- notched specimens and aggregate bedding led to a lower scattering of the impact test results, while the line-notched specimens exhibited lower average scattering than the cross and no-notched specimens. In general, a percentage decrease in the coefficient of variation of 30 to 74% was attained for specimens with bedding and/or surface notch compared to reference specimens. arabic 16 English 111
Hakim Salem Abdelgader Abdelgader (9-2021)

Two-layered Grouted Aggregates Fibrous Concrete Composite (TGAFCC) is a new category concrete which became popular recently and attracted the attention of researchers globally. Recent studies indicated that TGAFCC has notable improvement in mechanical properties, which has been sufficiently documented. However, the impact behaviour of TGAFCC when combined with Glass Fibre Mesh (GFM) and Textile Fibre Mesh (TFM) is still unexplored. The research objective is to study the effect of GFM and TFM inser- tion in TGAFCC against the drop hammer impact. Twenty one TGAFCC mixtures were prepared and divided into two series; non-fibrous concrete and fibrous concrete. The combined action of GFM and TFM of various diameters were inserted between the two layers and tested experimentally against drop mass impact. Additionally, all fibrous specimens were reinforced with a constant 3% dosage of 5D hooked end fibre. All specimens were tested under repeated drop mass impact as per ACI Committee 544. The impacts number or number of blows till the first visible crack and failure, impact energy at the first vis- ible crack and failure, impact ductility index and cracking configuration were examined. Besides, Weibull distribution was used to examine the variations in the test results, where impact numbers were pre- sented using the reliability function. The research findings indicate that inserting GFM and TFM between the two layers combined with 5D hooked end steel fibres, provided high impact resistance, higher absorbed energy and prolonged failure duration. Increasing the diameters of the GFM and TFM insertions, in both non-fibrous and fibrous concrete resulted in increasing the impact numbers till the first visible crack and failure. The experimental findings confirm that the major contribution of impact resistance comes from the 5D hooked end steel fibres, while the share of the intermediate meshes was significantly lower. arabic 13 English 88
Hakim S. Abdelgader (12-2020)