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

BEHAVIOUR OF HIGH STRENGTH CONCRETE COMPOSITE SLABS WITH DIFFERENT END ANCHORAGES

This study is performed to investigate experimentally the behaviour of steel deck composite slabs with different end anchorages. End anchorage as a type of shear connection for composite slabs plays an important role to prevent relative slip between concrete and steel deck. The presented composite slab specimens are made of high strength concrete and loaded at a specific shear span. Objectives of this study is to evaluate experimentally load carrying capacity, end slip, mode of failure, shear bond capacity, and the end anchorage contribution to the whole composite slab behaviour. Research also presents a comparison between the experimental results and the theoretical results derived according to m-k and partial shear connection methods included in these standards (BS 5950-4:1994, CSSBI S3-2003, and EC4 EN 1994-1-1:2004)

BEHAVIOR OF REINFORCED CONCRETE CONTINUOUS BEAMS STRENGHENED WITH NEAR SURFACE MOUNTED REINFORCEMENT

Using Near Surface Mounted (NSM) technique for flexural strengthening of reinforced concrete continuous beams became particularly attractive for researchers and applicators. Due to the existence of carbon fiber reinforced polymer (CFRP)laminates as external strengthening it is subjected to severe damage resulting from mechanical and environmental conditions. There is limited experimental work investigating the behavior of reinforced concrete continuous beams strengthened using NSM technique.This paper presents an experimental investigation of the behavior of reinforced concrete continuous beams strengthened with near surface mounted (NSM) technique in the hogging and sagging moment region. The main variable was changing the lengths of the NSM strips within the negative and positive moment region. The effect of the change in lengths of the NSM strips on the failure load, mid-span deflection, strain on reinforcement, slippage of CFRP strips and crack widths were investigated. The study revealed that the NSM technique can enhance crack and failure loads and controls crack widths

Structure and stress of Re(11%21); chiral terraces at a racemic surface

The surface structure and morphology of the clean Re(11%21) surface has been investigated through combined low energy electron diffraction intensity analysis of data taken at multiple angles of incidence, scanning tunneling microscopy, and first-principles density functional calculations. The results show how this globally racemic surface terminates in two chirally distinct terraces, which show largescale out-of-plane atomic relaxations and in-plane lateral movement of the uppermost atoms. We further identify and discuss the initial stages of step bunching upon adsorption of oxygen that leads ultimately to the large-scale faceting of the surface. Finally, we present calculations of surface stress and the response to applied surface strain, which suggest routes to the exertion of control over the expression of chirality at the surface

Built Environment, Physical Activity, and Frailty Among Older Persons

Stimulating physical activity is a promising strategy to prevent frailty and disabilities in daily life. Besides offering facilitated physical activity (such as via sport clubs), it is also possible to be physically active in an unorganized setting such as walking in the built environment. This thesis provides insights and recommendations for research, policy, and practice with regard to the frailty development process and the role of the built environment and physical activity programs for physical activity and disability among older persons

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