Applied Mechanics and Materials Vols. 754-755

Abstract: Concrete waste from construction site such as pile waste and tested concrete cubes waste is quite a problem for the contractor to dispose of. This waste is currently being buried or dumped illegally at a certain area, which lead to environmental pollution issue and waste of construction materials. In this study, concrete cubes waste from a concrete testing laboratory is crushed and recycled as natural coarse aggregate (NA) replacement (0% - control, 30% and 50% by mass) in grade 15, 25 and 40 concrete. The recycled concrete waste aggregate (RCWA) was tested for grading, specific gravity, percent absorption and impact and crushing (% crushed). For the fresh concrete mix, slump and compaction factor test were carried out. Concrete samples are wet cured and tested at 7 and 28 days for compressive strength. Results show that the workability of RCWA concrete reduce as the content of RCWA increase in the mix as the water absorption of RCWA is higher than the NA. The compressive strength of the RCWA concrete is acceptable at all RCWA replacement for grade 15 and 25 concrete with strengths higher than the design values of 15 and 25 MPa. For grade 40 concrete, the optimum RCWA replacement is at 30% and at 50% replacement, the compressive strength of the RCWA concrete is lower than the design value of 40 MPa. 50% replacement of NA with RCWA works well for grade 15 and 25 concrete, but for higher concrete grade (C40), the limiting value of replacement is 30%.

Abstract: This research presents the results of an investigation on the influence of thermally activated alum sludge ash (AASA) as a partial cement replacement on the near-surface characteristics of binary and ternary blended binder (TBB) concretes incorporating silica fume (SF), ground granulated blast furnace slag (GGBS), and palm oil fuel ash (POFA). All of the mixtures were prepared with a water/binder ratio and total binder content of 0.30 and 493 kg/m³, respectively. Initial surface absorption (ISAT) and sorptivity tests were conducted at the age of 28 days. Results indicate decrease in the ISAT and sorptivity values of binary blended binders with 15% AASA cement replacement compared with the control and 20% AASA concretes. A higher replacement level of 20% AASA did not help improve inner core durability but improved surface durability characteristics. All TBB concretes performed better than the binary blends with AASA at the same replacement levels.

Abstract: Usage of waste materials as concrete mixture can reduce the waste management crisis in the world. Used tyres were widely researched as an alternative source of aggregates replacement in concrete mixture. This research is to study the behaviour of concrete incorporating rubber tyre crumb as fine aggregate replacement. The workability, compression strength and water absorption of this concrete will be determined and then compared to normal concrete. Motorcycle inner tube will be used as rubber source and it will be shredded to crumbs. Three samples of concrete with rubber as fine aggregates were prepared. Rubber crumbs will be used to replace fine aggregates in 2.5, 5.0 and 7.5% in mass. Normal concrete were prepared separately as control for comparison. Concrete mixture of 1:2:4 and 0.5 of water cement ratio were used. Slump test were done to test the workability of each mix. Twelve sample cubes from (150mm x 150mm x 150mm) each mix were prepared and cured for 7, 14 and 28 days. Compression tests were performed for each mix cube at age 7, 14 and 28 days. Water absorption test were done at age 28 days. Results revealed that rubberized concrete has better workability than normal concrete. They also have smaller compressive value and higher water absorption compared to normal concrete.

Abstract: When reinforced concrete (RC) beams are found deficient in flexure, and fails in shear capacity after shear strengthening, the need to use new technique for flexure strengthening become important. Over the years, there are many experimental studies had been carried out with this technique of strengthening, and finding from other researchers have proved to be effective and successful. In this study, the behavior of flexure in RC beams strengthened with carbon fiber reinforced polymer (CFRP) were investigated. ANSYS11 software package of finite element method was use to simulate two models of RC beams with different parametric study such as (i) effect of grade of concrete, (ii) number of layers of CFRP strips, (iii) effect of steel stirrups and CFRP strips and (iv) longitudinal reinforcement yield stress. The results show that for beams strengthened with CFRP has increased in capacity load up to 32.8%. In general, good agreement between the FE solution and the available experimental results has been obtained.

Abstract: This study investigates the axial load behavior of an existing composite wall consists of a double-skinned profiled steel sheet in-filled with normal concrete. Three different composite walls in three-dimensional finite element models were developed, i.e. profiled steel sheet (PSS), core concrete, and the full composite wall system. The models were simulated and compared with the experimental results published by other researchers. Studies are then carried out on different effect of varying the PSS thicknesses, an embedded octagon cold-formed steel (CFS) thickness, and an embedded octagon CFS supported by two stiffeners with different shapes. As a result, the ultimate axial load of the composite wall was increased by approximately 3.3% when PSS thickness changed from 0.8 mm to 1.0mm. Meanwhile, the ultimate axial load was also increased by 17% and 55% when an embedded octagon CFS with thicknesses of 0.8 mm and 1.0 mm were used. Lastly, the ultimate axial load was raised by 54% and 78% when an L-shaped and a T-shaped stiffener were added.

Abstract: Patch repair materials made from unsaturated polyester resin (UPR)-mortar have been investigated to determine their bond strength characteristic by slant shear test method. The relative mechanical properties of UPR-mortar and substrate concrete for composing the specimens are: lower modular and high strength ratio. The experimental results show that the combination of materials causes the observed bond strength are dictated by failure of substrate concrete. The actual bond strength could be higher as most of the specimens fail without separation of the UPR-mortar and substrate concrete at the bond plane.

Abstract: Self-compacting concrete has been produced incorporating fly ash as cement replacement. The hardened properties of this concrete in term of compressive strength and porosity are investigated. The main goal of this investigation is to observe the effect of fly ash on those properties. The range of fly ash replacement level is 50%-70% by weight of the total binder. The compressive strength self-compacting concrete is reduced when fly ash replacement level is increased. The decrease in strength is more distinctive at 28 days of age compared to that of earlier or later age. Porosity as measured by vacuum saturation method tends to increase as fly ash replacement level is increased. A good correlation exists between porosity and compressive strength.

Abstract: This paper offers a review on production of fly ash-based geopolymer bricks.Bricks are the world’s most versatile, durable and reliable construction material.Conventional bricks are produced from clay with high temperature kiln firing or from ordinary Portland cement (OPC) concrete,and thus contain high embodied energy and have large carbon footprint. In many areas of the world,there is already a shortage of natural source material for production of the conventional bricks. For environmentalprotection and sustainable development, extensive research has been conducted on productionof bricks from waste materials.Fly ash is a waste material of coal firing thermal plants and its accumulation near power plants causes severe pollution problems. Therefore, its utilization as a raw material for brick making will be a very beneficial solution in terms of economic and environmental aspects.

Abstract: This research is aimed to investigate the flexural behaviour of patched reinforced concrete beam with patching material made from unsaturated polyester resin mortar. The variable studied is the dimension of patching zone as compared to the control beam (without patching). Based on the load-deflection observation of the beam under a four-point bending loading, it is confirmed that the flexural behaviour of the patched reinforced concrete beam is similar to that of control beam at a loading up to about peak load. After this load the patched reinforced concrete beam tends to behave more ductile. The patched reinforced concrete beam show less cracking density compared to control concrete.

Abstract: Slope stability is very important on designing a safe slope. If this were to be taken lightly by the engineer, major disaster will occur that results in lost of lives. Each engineer is responsible to evaluate all aspects of design, especially when designing a slope gradient on the surface of soft clay. Soft clay containing high water content and if not planned properly, water from the soft clay will seep into the slope and causes reduction in soil strength. The purpose of this research was to investigate the effect of water absorption of soft clay on the stability of the slope. The objectives of this study were to analyze the soil strength when the soil were soaked in water to a set of different time range and to analyze slope stability on soft clay based on the infiltration of water from underground using PLAXIS software. In this study, soil samples were taken and laboratory experiments were carried out to obtain the unit weight, cohesion, and friction angle of the soil samples. The experiments involved were grain size analysis test and unconfined compression test. Data from the experiments will be used in PLAXIS software to obtain the factor of safety.