No abstract

No abstract

Construction materials made of renewable resources have promising potential given their low cost, availability, and environmental friendliness. Although hemp fibers are the most extensively used fiber in the eco-friendly building sector, their unavailability hinders their application in Iraq. This study aimed to overcome the absence of hemp fiber in Iraq and develop a new sustainable construction material, strawcrete, by using wheat straw and traditional lime as the base binder. A comparable method of developing hempcrete was established. The experimental program adopted novel Mixing Sequence Techniques (MSTs), which depended on changing the sequence of mixed material with fixed proportions. The orientation of the applied load and the specimen’s aspect ratio were also studied. The mixing proportion was 4:1:1 (fiber/binder/water) by volume. Results showed that the developed strawcrete had a dry unit weight ranging from 645 kg/m3 to 734 kg/m3 and a compressive strength ranging from 1.8 MPa to 3.8 MPa. The enhanced physical and strength properties varied with the MST and loading orientation. The properties of the developed hempcrete were compared with those of strawcrete.

An experimental investigation of PVC-concrete columns is presented to assess the efficiency of using PVC tube for enhancing strength and ductility of PVC-concrete columns. Study was conducted to assess provided PVC casing confinement mechanism efficiency for enhancing strength and ductility of considered PVC- concrete columns. To investigate the composite mechanism and confining mechanism of the PVC tube, fabricated specimens are tested under uniaxial compression loading in two modes of load application; composite mode and confining mode. The results showed that the composite mode columns exhibit more strength improving than those of confining mode. The upgrading rate in sustained loading resistance of composite mode columns varied from 2.25 to 1.56, while it was 2.07 to 1.55 for confining mode columns. The same comparison is entirely reversed in scope of ductility, where confining mode columns exhibited more axial and lateral deformations than the corresponding composite mode columns. The results are normalized in term of radial stress (fr ) and concrete compressive strength (f’ e ), determined enhanced confined concrete strength (f’ ee ) could be used to predicate plastic capacity of columns of different mechanism.

The structural behaviour of hybrid reinforced concrete beams of trapezoidal section was investigated in this work. The main aim of study was to investigate the interaction effect of hybrid concrete compressive strength–section geometry variations on beam strength characteristics. The experimental programme included fourteen simply supported reinforced concrete deep beams being prepared and examined under a four-point load setting protocol. All specimens were of 1,000 mm length and of equal cross-sectional area. The specimens were divided into groups according to section shape variations and hybrid compressive strength considerations. Various concrete compressive strengths (70, 50, and 25) MPa were considered, and three different trapezoidal geometries of different alignment side angles (75°, 80°, and 85°) were also adopted, along with two steel rebar ratios (0.008617 and 0.01508). Generally, the experimental results showed that the shear strength capacity increased with increases in the area of high-strength concrete in the compression zone in increments, with improvements ranging from 3.66% to 8.63% as compared to reference specimens of uniform section (rectangular section); the diagonal crack load decreased, however. It was also observed that the hybrid concrete created high ductile behaviour, and the significant failure mode was shear mode without slippage of the hybrid concrete layers. A comparison of results with the hybrid strength reduction index (Ψ=f’cb/f’ct ) showed that as Ψ decreased from 0.714 to 0.357, the average rating varied between 1.15 and 1.22 with respect to rectangular specimens and from 1.07 to 1.13 with respect to trapezoidal sections of uniform strength. An optimum alignment side angle for trapezoidal configuration also appears to be indicated, with the best results for all hybrid strength-trapezoidal sections in specimens where Ө=80°.