Fracture Toughness and Impact Strength of High-Volume Class-F Fly Ash Concrete Reinforced with Natural San Fibres
Results of experimental investigation carried out to study the effects of addition of natural san fibres on the fracture toughness and impact strength of high-volume fly ash concrete are presented in this paper. San fibres belong to the category of ‘Natural Bast Fibres’, also known as ‘Sunn Hemp’. Its scientific (botanical) name is Crotalaria Juncea. It is mostly grown in the Indian Sub-Continent, Brazil, Eastern and Southern Africa, and in some parts of the U.S.A. Initially, a control mixture without fly ash was designed. Then, cement was replaced with three percentages (30, 40 and 50%) of low-calcium (Class F) fly ash. Three percentages of san fibres (0.30, 0.60 and 0.90%), having 25 mm length, were used. Tests were performed for compressive strength, fracture toughness, and impact strength at the ages of 28 and 91 days. The test results indicated that the replacement of cement with fly ash decreased the compressive strength and fracture toughness, and had no significant effect on the impact strength of plain (control) concrete. Addition of san fibres did not affect significantly the compressive strength, increased the fracture toughness and impact strength of high-volume fly ash concrete as the percentage of fibres increased.
Experimental study on shear performance of plain construction joints integrated with ultra-high performance concrete (UHPC)
Abstract As a part of an ongoing research to develop construction joints using ultra-high performance concrete (UHPC) and reinforcements, shear performance of plain concrete construction joints is experimentally examined with push-off tests. Two different sets, namely, a combined set of UHPC (180 MPa) and a set of UHPC (180 MPa) and NSC (normal strength concrete, 30 MPa) were considered, each of which had five cases of interface treatment including use of water jet, vertical joint, and three cases of a grooved joint. In addition, cases without any construction joint were also considered as a reference. Key factors affecting shear performance of individual construction joint were investigated in terms of shear strength, failure mechanism, and displacement responses. Experimental results show that steel fibers and grooved geometry greatly affect shear performance for the combined set of UHPC, while interlocking mechanism of coarse aggregates is crucial for the set of UHPC and NSC.
InTlP — a proposed infrared detector material
In1−xTlxP is proposed as a promising material for infrared detectors. A number of key optical and structural properties are studied within local density‐functional theory. In1−xTlxP at x=0.67 and In1−xTlxAs at x=0.15 are estimated to have a gap of 0.1 eV. Their binding energies are larger than that of InSb, and they are found to form stable zinc‐blende alloys for all x. In1−xTlxP nearly lattice matches to InP, and offers the potential to integrate detector array and read‐out circuit.