Publications

Abstract This study experimentally examines the effect of rubber aggregate size on the static and dynamic behavior of rubberized concrete. Rubberized concrete specimens were prepared with different maximum rubber aggregate sizes ranging from 1 to 3 mm to 3 to 5 mm while the rubber content was kept constant at 15% by volume. The dynamic compressive behavior of rubberized concrete was investigated by using split Hopkinson pressure bar (SHPB) tests. The experimental results have shown that rubberized concrete with smaller rubber aggregates showed higher static compressive strength as compared to that with larger rubber aggregates. Meanwhile, the rubber aggregate size did not considerably affect the density of rubberized concrete. The use of smaller rubber aggregate size mitigated the slump reduction of rubberized concrete. Rubberized concrete exhibited obvious sensitivity to strain rate and those with larger rubber aggregates showed higher strain rate sensitivity. The progressive damage of rubberized concrete showed more ductile behavior with bulging failure, which was different from the typical concrete under compression. In general, the use of smaller rubber aggregate size was beneficial to the static compressive strength but less effective to the dynamic compressive strength of rubberized concrete as compared to those with larger rubber aggregates.

Abstract The optical response of the Gyricon display to addressing voltages is discussed, with special emphasis on the image storage behavior.

Abstract This study investigated the effects of fabrication technique on the tensile properties of fiber reinforced polymer (FRP) flat coupon tests. A total of 20 FRP flat coupons were prepared by two different techniques, which were tested in tension until failure. The first technique of preparing the FRP coupons was based on the recommendation of ASTM D7565/D7565M-10, named the “Cutting Technique,” while the second technique, named the “Folding Technique,” was proposed by this study. Experimental results from this study indicated that preparing FRP coupons using the Cutting Technique resulted in a reduction in the tensile properties as compared to coupons prepared by the proposed Folding Technique. Most notably, the tensile force per unit width obtained by the FRP flat coupons prepared using the Folding Technique was up to 8 % higher than that obtained by coupons prepared using the Cutting Technique. In addition, the effect of the % bending on the tensile properties was also studied. It was found that the % bending about the thickness plane was greater than that of the % bending about the width plane. Furthermore, the tensile properties of the FRP coupons were not sensitive to its % bending.

Basalt fiber-reinforced polymer (BFRP) has been applied for strengthening concrete structures. However, studies on reinforced concrete (RC) slabs strengthened by BFRP strips under impact loads are limited in open literature. This study investigates the efficiency of using BFRP strips with various strengthening layouts and anchoring schemes on the impact resistance of RC slabs. A total of 11 two-way square slabs were prepared and tested, including one reference specimen without strengthening and ten slabs strengthened with BFRP strips and/or anchors. The RC slabs were impacted by a drop weight with increasing height until slab failure. The observed failure modes include punching shear failure, BFRP sheet debonding and reinforcement fracture. The failure modes and the effects of using various strengthening schemes on the impact resistant capacity of RC slabs were examined. The quantitative measurements, such as impact velocity, indentation depth and diameter, were compared and discussed. In addition, numerical studies were carried out by using LS-DYNA to simulate the impact tests of RC slabs with and without BFRP strengthening. With the calibrated numerical model, the impact behavior of slabs with various dimensions and strengthening layouts under different impact intensities can be predicted with good accuracy.

Moulded flexible polyurethane foam using hot-cure moulding technology with TDI as the isocyanate component was developed in the mid 1950's. The authors trace the development in the mid 1960's of HR or cold-cure foams which used TDI/MDI blends and more reactive polyether polyols. The logical next step was the introduction of All-MDI based, cold-cure flexible foams in the late 1970's. Much progress has been made since then, and the changes in processability which have led to better durability and greater comfort in seat cushions – both in the automotive industry and the high quality upholstered-furniture market are reviewed. Comfort properties are defined in terms of persons-sitting experience, and the load-bearing and hardness qualities required are defined to achieve good comfort levels. Environmental considerations are discussed with respect to the lower vapour pressures at normal processing temperatures given by MDI as compared with TDI. The current concern regarding the effect of CFC's on the atmosphere is discussed and ways in which the levels are being reduced in the All-MDI based foam moulding process are indicated. Cushions with dual and multiple hardness and pour-in-place techniques are discussed and the commercial experiences with the total range of All-MDI based foam systems – worldwide – is reviewed.