Structural Behavior of Light Weight Ferrocement Columns

This paper presents the results of the behavior of reinforced ferrocement light weight columns by permanent precast lightweight ferrocement hollow blocks. For this objective, an experimental program was carried out extensively and finite element models with ANSYS 14.5 were conducted. The program of the experimental constructed and testing of sixteen columns of total dimensions 450×650×250 mm consisting of 3 permanent precast lightweight ferrocement hollow blocks having the dimensions of200×400×200 mm filled with core material. Two types of light weight ferrocemnet hollow blocks were used to construct the columns. Two types of single layer welded steel mesh and glass fiber mesh were used as a horizontal connection between the permanent precast lightweight ferrocement hollow blocks. The core material was investigated: one layer of welded steel mesh embedded in the matrix. Welded steel mesh with single and double layers was used to reinforce the plastering layer as a bonding layers forms; namely welded steel mesh. Shear connections between the permanent precast hollow blocks and the core material were investigated called; shear connector. The columns were tested under uniform load. The behavior of the columns was compared. The results showed that an improvement in the cracks resistance, serviceability loads, ultimate loads, and energy absorption. Theses results were verifies the validity of the proposed model. Good agreement was found compared with the experimental results. Out of this research, this paper presents applications of  using light weight ferrocement  units in construction of low-cost housing which are very useful for developed and developing countries alike with great economic advantages.

Reinforced Concrete Corrosion and Protection

This paper reports result of a study conducted to assess the effect of some locally produced materials on the protection of reinforcing steel against corrosion. Also the effect of period and the main consequences on mechanical properties of steel and concrete are evaluated. Reinforcing steel bars, 10 mm in diameter, that were corroded in reinforced concrete specimens were removed and tested in tension. Twenty seven concrete cylinders with dimensions (15 × 30 cm) provided with central steel bar were cast and tested after 28 days to demonstrate the effect of the protective materials on the bond strength. A total of ten reinforced concrete beams (10 × 15 × 100 cm) were cast using a self-compacted concrete mix. All beams were tested in flexure. The results of the tested beams are analyzed in terms of; cracking pattern, load deflection, ductility. The failure mode of each specimen was recorded. The tests recommended determining the mechanical properties of mix were; the compressive test, the splitting tensile test, and flexural strength test. Results cleared that with increasing duration of exposure to a corrosive environment, the steel mass loss increases appreciably. This leads to a significant increase of the applied stress. In addition, a reduction of the tensile ductility of the material was observed. The main result from the accelerated corrosion tests in bare steel bars, that the important ductility property of the elongation to failure is very sensitive to mass loss due to corrosion, it is valid and in real structures. Coating with epoxy resin increases the protective from the corrosion more cement-based resin by 15 %

Effect of freezing-thawing on concrete behavior

This study aims to determine the effect of change of temperature (freezing-thawing cycles) on the behavior of the mortar and the concrete. Also, the evaluation of the effect of air entering for improving the durability of the mortar and concrete was discussed. 23 mixes were cast to evaluate the purpose of this study. Cement types (Portland cement and limestone cement), aggregate types (dolomite and gravel), dosages of air entering 0.01, 0.1, 0.15 and 0.2% of cement weight and freezing thawing cycles (50, 100, 150, 200, 300 and 400 cycles) were considered. Relative dynamic modules of elasticity which is illustrated the internal cracks growth, durability factor and losses of weight were evaluated. Empirical correlations were formulated. The results showed that; 0.15% air entrained of cement weight improve the durability in term of freezing-thawing; where the durability factor for the mixes was ≥ 85% that exposed to freezing-thawing cycles in range 0-200. Up to 200 cycles of freezing-thawing cycles did not effect on the compressive strength of the mixes and the durability of the mortar and the concrete. It is recommended that more than 300 freezing-thawing cycles must be avoided

Pre- and Post-Fire Strength Assessment of Ferrocement beams

The results of an experimental investigation on the behavior of ferrocement beams after exposed to fire are presented in this paper. Different types of steel meshes are used compared with conventional reinforcement. The experimental program comprised casting and testing of eighteen beams having the dimensions of 100mm×100mm×1000mm. Three beams were reinforced as a conventional reinforcement. Each control beam was reinforced with two steel bars of diameter 8 mm in tension, two steel bar of diameter 6mm in compression and stirrups of 6 mm diameter placed at 200 mm intervals. The ferrocement beams were reinforced with steel meshes without any stirrups. Two types of steel meshes were used to reinforce the ferrocement laminate. These types are: square welded wire fabric, and expanded wire mesh. Single layer, double layers and three layers of square welded wire mesh were employed. Single layer and double layers of expanded wire mesh were employed. The experimental program was classified into three groups. First group was tested without exposure to fire, the second group was tested after exposure to fire for six hours and the last group was tested after exposure to fire under loading. All specimens were tested under 4-points flexural loadings. The performance of the test beams in terms of strength, stiffness, cracking behavior and energy absorption was investigated. The results showed that high serviceability and ultimate loads, crack resistance control, and better deformation characteristics could be achieved by using the proposed ferrocement forms

Bond Strength of Concrete Containing Different Recycled Coarse Aggregates

Some of the remnants of construction demolition wastes could be used after recycling as coarse aggregate in concrete industry. Among these wastes are ceramics, shale bricks and hardened concrete. This research was carried out to determine the effect of using such recycled aggregate (RA) as total or partial replacement of the natural dolomite coarse aggregate in concrete mixes on their compressive and bond strength with steel bars. Two types of concrete were investigated in this research which included normal concrete and self-compacted concrete. The main variables taken into consideration wee, the type of concrete, the type and percentage of the recycled aggregate and the age of testing. The consistency of the normal fresh concrete was measured by the slump test. However, the workability and flowability of the self-compacted fresh concrete were measured using slump test, V-funnel test. Out of the experimental test results, equations were predicted which correlated between the concrete compressive strength and bond strength of both the recycled aggregate ordinary concrete and the recycled aggregate self-compacted concrete. These equations were completely different than that of the steel-concrete bond equation of concrete with natural aggregate. Out of this research results, the recycled aggregate concrete could be used in both non structural applications and in some structural applications with special precautions

Feasibility of using self-compacting concrete in civil engineering applications

This research aimed to investigate the feasibility of using self-compacting concrete in civil engineering applications as a producing a precast hollow unit. The behavior of the hollow sections cast with self-compacted concrete beneath line-load was evaluated. An experimental work was carried out and a finite element model with ANSYS (version 15) was adopted. A total of fourteen hollow beams were cast and tested. The most variables taken into thought were; the types of reinforcement (reinforced steel bar and steel wire meshes), the types of steel wire meshes (expanded and welded steel wire mesh), number of layers of steel meshes (one layer and two layers), cross section thickness of concrete (40 mm and 60mm), concrete cover thickness (15mm and 20 mm) and also the shapes of cross section (square or circular). Special attention to initial cracking load, ultimate load, deflection, cracking pattern, energy absorption and ductility index were investigated. Good agreement was found compared with the experimental results. Out of this research; this paper presents applications of self-compacted concrete for casting skinny structural hollow members. These members can be used as precast units within the construction of the tunnel to decrease the problems in highway roads due to the difficulty of using crossing bridges particularly for kids and old people which are very useful for developing countries with great economic advantages

Behavior improvement of self-compacting concrete in hot weather

The main aim of this research is studying the effect of hot weather on the properties of self-compacting concrete and conventional concrete in both fresh and hardened state. Also, this research extends to improve the behavior of self-compacting concrete in hot weather. The main parameters were surrounding weather temperature (5°C, 20°C and 35°C), concrete materials temperatures’ (25°C, 50°C), curing temperatures (25°C and 50°C) and admixtures (using a retarder). Two stages were carried out to achieve the research aim. The behavior of self-compacting concrete compared to conventional concrete was evaluated in the first stage. Based on the first stage, attempts to enhance the concrete properties were evaluated in the second stage. Precautions on mixing and placing concrete in these climates are considered. Results are a drive in terms of; workability tests, compressive strength, splitting tensile strength, and flexural strength. Test results showed that self-compacting concrete behavior and strengths were better than conventional concrete. Slump test, J-ring and V-funnel test were used to evaluate the fresh properties of the self-compacting concrete. Drying shrinkage of self-compacting concrete in hot weather were also evaluated

Effect of self-curing admixture on concrete properties in hot climate conditions

Hot climates prevail in many regions of the globe. The average summer temperature of hot arid areas is in the range of 40-50°C with temperatures exceeding these values under direct solar radiation. Curing concrete in these regions may be challenging due to limited availability of suitable water for curing and/or rapid loss of curing water by evaporation. For many years self-curing admixtures were recommended as an alternative to water curing, however, limited studies have been conducted on their performance in hot weather conditions. In this investigation, the effects of a hot climate on the fresh and hardened properties of self-curing (SC) concrete and normal conventional concrete (NC) in hot weather were studied. A water- soluble polymer self-curing agent, polyethylene glycol (PEG 400), was added to the SC mixes. The testing parametersOwere concrete dry materials (25 or 50OC) and/or mix water temperatures (5, 20 or 35 C) at the time of mixing. NC samples were continuously water cured at 25 or 50 OC, whereas the SC ones were air cured at the same temperatures. The tested properties were workability, compressive strength, splitting tensile strength, and flexural strength. It was found that SC outperformed NC under varying conditions. The results could not be simply attributed to the retention of mix water by the self-curing admixture. A more comprehensive explanation for the observations is proposed

Evaluation of the lightweight foamed concrete characteristics

The purpose of this paper is to assess the properties of light weight foamed concrete. In this research, two phases are investigated. The first stage explored the characteristics of fresh and hardened foamed concrete using a foaming agent. The following parameters were employed in this study: foaming agent used as a volume of concrete mix by 10, 20, and 40%, fly ash used as a replacement of cement content by 10, 25, and 50%, and polypropylene fiber used with varied volume fractions of 0.5, 0.75, and 1.0%. Slump values are applied to evaluate the fresh properties. To evaluate the hardened concrete, the dry density and compressive strength at 7 and 28 days are computed. Furthermore, the 28-day tensile splitting strength and flexural strength are studied. The effect of a high temperature was evaluated. The second stage investigated the effects of polypropylene fiber on both fresh and hardened concrete. It was observed that foaming agents improve fresh characteristics while decreasing compressive strengths and dry density. Furthermore, utilizing fly ash improves the characteristics of both fresh and hardened foamed concrete. The fiber reduces the fresh characteristics while enhancing the toughened properties. Because of its low density, foamed concrete is being used for structural applications because of this study. Such as those utilized for thermal insulation, acoustic impedance, and fire breaks. Also used to create road foundations for roads built on soft soil

Structural behavior of ferrocement composite hollow-cored panels for roof construction

The main objective of the following work is to study the effect of using different types of metallic and non-metallic mesh reinforcement materials on the flexural behavior of ferrocement hollow-cored panels as a viable alternative for conventional reinforced concrete roofs. The proposed panels are lighter in weight relative to the conventional reinforced concrete panels. Three types of the steel meshes were used to reinforce the ferrocement skin layers. Namely: welded wire mesh, expanded metal mesh, and tenax mesh with various numbers of layers. Experimental investigation was conducted on the proposed panels. A total of ten slabs having the total dimensions of 2000 mm length, 500 mm width and 120 mm thickness were cast and tested under flexural loadings until failure. The deformation characteristics and cracking behavior were recorded and observed for each panel at all stages of loadings. The results showed that high ultimate and serviceability loads, crack resistance control, high ductility, and good energy absorption properties could be achieved by using the proposed panels. This could be of true construction merits for both developed and developing countries alike. The experimental results were then compared to analytical models using (ABAQUS/Explicit) programs. The finite element (FE) simulations achieved better results in comparison with the experimental results