Recycling demolition waste materials as construction materials offers environmental as well as economic benefits by protecting virgin materials and reducing overall costs of project. This paper presents an experimental investigation on flexural behavior of reinforced concrete beams made with coarse aggregate fully 100 % or partially 50 % replaced by crushed concrete or crushed bricks as waste materials in full or half depth of beams. Nine beams are tested over a simply supported span, one with full natural aggregate as reference and the others with waste aggregate in different ratios and depths (four with crushed concrete and four with crushed bricks). Results show that the structural behavior of beams with waste aggregates is similar to the reference beam with strength reduction of 3 – 20 %. Crushed concrete beams show higher strength and stiffer behavior (in general) than crushed bricks. Also, increasing replacement ratio from 50 % to 100 % or replacement depth from half to full reduced strength by about 10 % only which encourage utilizing maximum quantity of waste construction materials in concrete structures.
One of the most serious problems of reinforced concrete structures is corrosion of embedded reinforcing steel bars especially in aggressive environments. To control steel corrosion, several approaches have been followed but do not introduce 100% corrosion resistance and guaranteed longterm performance. Glass Fiber Reinforced Polymer (GFRP) bars are considered to be an ideal alternative to overcome corrosion problem in steel bars because of their high corrosion resistance. This paper discusses the main topics related to the use of GFRP bars as reinforcement in structural reinforced concrete applications and presents an overview to the available literature especially in GFRP bond behavior. The main conclusions are: standardizing the manufacturing process of GFRP bars are needed in order to limit the contradictory results of their performances due to the high differences in the products characteristics, and that the available design guidelines have much conservative equations, so they are recommended to be revised to be more practical.
In this paper, the ABAQUS / CAE 6.13.1 program is used to study the effect of several variables on the efficiency of the load transfer through an expansion joint in plain concrete pavement system under the influence of the static wheel load. The variables that have been addressed are the diameter of dowel bar (12, 16 and 20 mm), subgrade soil type (A-6) and (A-7-5), concrete type (normal strength concrete and high strength concrete), joint width (10, 20 and 30 mm), thickness of the concrete slab (125, 175 and 250 mm), position of static wheel load (corner load, internal load and edge load) and the effect of soil damage. The results showed, the load transfer efficiency (LTE) and joint effectiveness (E) are enhanced from 69.82% to 89.73% and from 82.23% to 94.59%, respectively as dowel diameter increases from 12 mm to 20 mm, from 60.48% to 79.64% and from 75.37% to 88.66, respectively as joint width decreases from 30 mm to 10 mm, from 64.24% to 89.73% and from 78.23% to 94.59%, respectively as slab thickness decreases from 250 mm to 125 mm and from 69.81% to 79.64% and 82.22% to 88.66%, respectively when CBR value of subgrade soil increases from 5% to 7%, while approximately the same LTE (about 80%) and E (about 89%) are resulted as the concrete compressive strength increases from 27 MPa to 43 MPa. Corner load reduces LTE and E from 84% to 70.49% and from 91.3 to 82.7, respectively as compared to internal load. Presence of weak or gap in subgrade soil reduces LTE and E from about 79% to 59% and 88% to 74%, respectively.
This paper presents an experimental investigation on stress-strain behavior of normal and high strength self-compacting concrete with two different maximum aggregate sizes. Eight mixes are adopted for this purpose with nominal compressive strength ranging from 20 to 80 MPa and maximum aggregate size of 10 and 20 mm. Results show that the ascending parts of the stress-strain curves become steeper as the compressive strength increases and maximum aggregate size decreases. Strain at failure increases with the increase in compressive strength and maximum aggregate size. Also, changing maximum aggregate size from 10 to 20 mm, generally, increases compressive strength (up to 13.97% for cylinders and 17.24% for cubes) and modulus of elasticity (up to 19.27%).
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