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This study deals with a proposed mix design method for SCC utilizing different properties of coarse aggregate. The work was conducted in three phases, i.e. paste, mortar and concrete to facilitate the mix design process. Initial investigation on cement paste determined the basis for water cement ratio and superplasticizer dosage for the concrete. For the study on mortar, metakaolin (MK) as pozzolan was used at replacement levels of 5%, 10%, 15%, and 20% by weight of cement. Self compactability of mortars was obtained by adding suitable materials such as mineral admixtures and superplasticizer which provided a sufficient balance between flowability and viscosity of the mix. The optimum MK replacement level for cement was 10% from the viewpoint of workability and strength. Flowability of mortar decreased with the use of metakaolin. Moreover, strength of mortar increased when the optimum replacement level of pozzolan was used. Different fresh concrete tests were adopted. The results obtained for fresh concrete properties showed that flowability of concrete increased with increase flowability of mortar. The mixes which contained coarse aggregate with lower volume, small size, and continuous grading affected positively the fresh properties of SCC. Finally, the mix design method used was successful in producing SCC with different coarse aggregate properties.

This article attempts to explain the effect of composite action in reinforced concrete (RC) elements on the natural frequencies. Natural frequencies are governed by the relationship between the physical properties of RC elements and its composite action. The softening of concrete in tension, compression, and pre- and post-yielding steel behavior are considered. The bonding action between steel and concrete under loading and unloading conditions is also taken into account. The assumption of the increase in stiffness of RC elements in tension due to bond action is investigated by tests on two RC beams. Both static and modal testing were carried out after inducing different levels of damage in the beams. Results show the validity of the assumption made due to composite action. Mode 1 can be an indicator for bond action behavior and for predicting the yield state of steel in the RC beams. Mode 2 behavior is governed by the amount of steel reinforcement, where for maximum steel ratio it will be affected by con...

In this paper, fly ash and metakaolin as pozzolan while limestone powder and kaolin as filler material were used at replacement levels of 5%, 10%, 15%, and 20% by weight of cement and sand, respectively. The effects of these powders on the fresh property of mortar mixes were studied and reported. Superplasticizer dosages were determined from flow test on cement paste and mortar with different powder content. A total of 33 mixes were prepared, mixed, and tested. The mini slump cone and mini V-funnel box tests were used to assess the flowability of the fresh mortar. In addition, the effect of mineral admixture on setting time of the mixes was also evaluated. In this study, the optimum dosage of superplasticizer was determined based on the desired flowability for self compactability. Superplasticizer at higher dosages than optimum reduced the stability due to bleeding. The results confirmed the role of the mineral powders in determining the desired stability and the flowability of mortar mixes which is crucial for self compacting concrete.

A steel beam compressive strain sensor using single-mode-multimode-single-mode (SMS) fiber structure is demonstrated. Parallel measurements are made using an electrical resistance (ER) strain gauge along with the SMS to sense the compressive strain on the steel beam. The ER strain gauge result shows that the steel beam has an elastic limit at a compressive load of 42 kN, as predicted via calculation. On the other hand, the SMS sensor is capable to detect the elastic limit by its significant increase in the slope of the peak center wavelength from compressive strain of 0.000261–0.001986 mm/mm. Moreover, the SMS sensor exhibits compressive strain sensitivity of −1411.2 nm/(mm/mm) from the initial load until it reaches the beam elastic limit.

The strengthened effectiveness and the performance capacity of repaired Reinforced Concrete (RC) structures with Carbon Fibre Reinforced Polymer (CFRP) sheets is dependent on the properties of the adhesive interface layer. Adhesive material requires a specific setting time to achieve the maximum design capacity. Adhesive producer provides technical data which demonstrates the increase with time of the capacity, up to the maximum. The aim of this study is to investigate the effect of the adhesive setting time on the modal parameters as an indication of the effectiveness of CFRP on repaired RC beams. Firstly, datum modal parameters were determined on the undamaged beam and subsequently the parameters were obtained when damaged was induced on the RC beam by application of load until the appearance of the first crack. Finally, the RC beam is repaired with externally bonded CFRP sheets, and modal parameters are once again applied after 0.5, 1, 2, 3, 5, 8, 11, 15 and 18 days. The comparison is made with the data based on half day results in order to monitor the change in the modal parameters corresponding to the adhesive setting time. The modal parameters where used as indicators for the effectiveness of CFRP are affected by the adhesive time as shown in this study. Results are compared with the adhesive technical data provided by the adhesive producer.

This article reports the results of an investigation on the engineering properties of concrete containing black sugar palm fiber. Three fiber lengths of 15, 25, and 35 mm in four volume fractions, namely 0.2%, 0.4%, 0.6%, and 0.8%, were utilized in this investigation. The values of compressive, flexural, toughness, first crack deflection, first crack toughness, and toughness indices are reported for ages up to 90 days. It was observed that the addition of palm fibers slightly increased the flexural strength of concrete. The incorporation of the fibers had no significant effect on the compressive strength. The mix with 0.8% volume fraction and 35 mm length fiber gave higher toughness and ductility compared to other mixes.

Self Compacting Concrete (SCC) is new type of concrete that posse's property of high flow ability, passing ability and stability. To achieve SCC, many factors must be investigated. Coarse aggregate is one of these factors that have a significant influence on SCC. This paper presents the coarse aggregate properties such as maximum size, texture and type of coarse aggregate that have a direct effect on achieving SCC. Three types of coarse aggregate are used, namely crush gravel, uncrushed gravel and crush limestone. To determine the workability, different test methods are adopted such as slump flow, V-funnel, L-box and U-box test. It was found that by increasing the maximum size of coarse aggregate, flowability and passing ability reduced. In addition it was observed that when uncrushed gravel was used in the concrete mixture, flow ability, passing ability and segregation resistance increased as compared to concrete with crushed gravel. Furthermore, the inclusion of 10% HRM as a partial replacement by weight of cement leads to reduce flow ability and increase viscosity. The compressive and flexural strengths and modulus of elasticity was measured. It was noticed that concrete mixes prepared with crushed limestone showed higher strengths and modulus of elasticity than concrete mixes prepared with crushed and uncrushed gravel. In addition, lower maximum size of coarse aggregate leads to higher strengths compared to higher maximum size of coarse aggregate in SCC mixes.

Investigation of the influence of the differences in the support conditions on the dynamic parameters are presented in this study. Bridge girders are usually supported by elastic bearings and suffer deterioration during the service life of the bridge. Early stages of deterioration of the elastic bearing occur with decrease in its stiffness. Advance stages of deterioration causes total damage of the elastic bearing, whereby the bridge girder will be supported directly on the structural element below it. The deterioration can occur on one or both sides of the supports. In order to study the effect of this phenomenon, experiments were conducted on a simply supported beam supported on elastic rubber pads with different stiffness as well as on steel supports. The undamaged support condition was simulated by using new rubber pads with stiffness of 10MN/m. The damage support conditions were represented by using old rubber pads with stiffness of 3 MN/m and using steel supports to simulate the case of total deterioration of the rubber bearing pads. Natural frequencies and mode shapes were obtained from modal testing and compared using of Modal Assurance Criteria MAC. The results showed a direct relationship between the support stiffness and the natural frequencies and mode shape. The first bending mode was most sensitive to the changes in support stiffness followed by Mode 2. It was also observed that the other modes had similar but lower sensitivity to the state of deterioartion of the supports.

The rising cost of construction in developing countries like Malaysia has led concrete experts to explore alternative materials such as coconut shells which are renewable and possess high potential to be used as construction material. Coconut shell powder in varying percentages of1%, 3% and 5% was used as filler material in concrete grade 30 and evaluated after a curing period of 7 days and 28days respectively. Compressive strength, water absorption and carbonation tests were conducted to evaluate the strength and durability of CSP concrete in comparison with normal concrete. The test results revealed that 1%, 3% and 5% of CSP concrete achieved a compressive strength of 47.65MPa, 45.6MPa and 40.55% respectively. The rate of water absorption of CSP concrete was recorded as 3.21%, 2.47%, and 2.73% for 1%, 3% and 5% of CSP concrete respectively. Although CSP contained a carbon composition of 47%, the carbonation test showed that CSP no signs of carbon were detected inside the concrete. To conclude, CSP offers great prospects as it demonstrated relatively high durability as a construction material.

The concept of efficiency can be used for comparing the relative performance of various pozzolans when incorporated into concrete. In this paper, an alternative approach for the evaluation of efficiency factor k of a pozzolanic material has been introduced. The method, developed following Abrams strength-W/C ratio rule, calculates efficiency in terms of relative strength and cementitious materials content. The advantage of this method is that only two mixtures are required to determine the k factor of a specific mixture. A laboratory investigation on silica fume (SF) and metakaolin (MK) concrete found that the computed efficiency factors varied with pozzolan type, replacement level and age. At 28 days, the k values ranged from 1.6 to 2.3 for MK and 2.1 to 3.1 for SF mixtures, while at 180 days, the k values varied from 1.8 to 4.0 for MK and 2.4 to 3.3 for SF mixtures. Generally, the k factors increased with age but declined with higher pozzolanic content. It was also observed that change in W/CM ratio from 0.33 to 0.27 did not significantly affect the resultant efficiency factors. © 2004 Elsevier Ltd. All rights reserved.

A mathematical model is presented for estimating compressive strength of high-strength concrete incorporating pozzolanic materials, based on the strength of a control ordinary Portland cement (OPC) concrete made with similar mixture characteristics and curing history. In this study, metakaolin (MK) and silica fume (SF) were used as cement replacement materials at 5%, 10%, and 15% by mass. Water/cementitious materials (w/cm) ratios varied from 0.27 to 0.33, and strength testing was conducted up to an age of 180 days. It was found that the strength of a pozzolanic mixture could be related to the strength of its equivalent control by a linear function. Key parameters involved in the model are the pozzolanic and dilution factors, which can be correlated to the pozzolan content in the mixture. The study concludes that the accuracy of the model increases with concrete age. At ages 28 days and above, 97% of the estimated strengths are within ±5% of the actual value. © 2004 Elsevier Ltd. All rights reserved.

This paper presents the results of an investigation on the use of metakaolin and silica fume as supplementary cementing materials in enhancing the near surface properties of concrete. Metakaolin and silica fume mixtures, each with 10% replacement, were prepared and tested for initial surface absorption, water absorption and sorptivity. Metakaolin and silica fume were found to enhance the overall near surface characteristics of the concrete. The inclusion of metakaolin and silica fume greatly reduced the initial surface absorption, water absorption and sorptivity of concrete in varying magnitudes. Generally, the curing method adopted had significant effects on the near surface properties of concrete incorporating metakaolin or silica fume.

The weatherability of PTFE- and PVC-coated fabrics under tropical climate was evaluated based on outdoor exposure test for a period of 2 years. This study is confined to the examination of the surface characteristics of 10 different types of fabric which include dirt repellency, discolouration and coating condition. The results indicate that the dirt repellency of PTFE-coated fabrics is generally more superior. However, the surface treatment for some of the PVC-coated fabrics, do provide excellent dirt repellency as well. Morphological examinations using the scanning electron microscope revealed that cracking and peeling of the coating were more evident on the PVC-coated as compared to the PTFE-coated fabrics. The hot and humid conditions prevalent in a tropical environment were very conducive for the growth of fungi, which adhered on the surface of some of the PVC-coated fabrics. Generally the degree of surface degradation on all the fabrics was more severe due to the much harsher tropical climate in comparison with other exposure tests conducted in the past.

An experimental investigation to study the effect of general corrosion on the modal parameters of reinforced concrete beams was conducted. The full scale beams were subjected to reinforcement corrosion until an appreciable amount of steel corrosion damage was introduced. The states of damage in the test beams were assessed through measurement of crack width and spalling. Modal tests were performed on the test beams after corrosion damage and the modal parameters extracted were compared against that from a control beam. The results obtained showed changes in the modal parameters especially natural frequencies and damping ratio. The trend in the measured natural frequencies was sensitive to the deterioration state of the beams. Changes in modal damping ratio for the transfer function method and the normal mode method were also observed. However, the changes were inconsistent with the changes in natural frequencies, as concluded by previous researchers, but a trend was observed which was rather mode dependent. Furthermore, the load carrying capacity of the beams was determined through static load test and the results were correlated with the state of corrosion damage and changes in the modal parameters. This investigation provides further insight on the use of modal parameters to detect damage in structural concrete elements which can be useful for structural appraisal and assessment purposes when applied to full scale structures.

This paper presents the results of both analytical and experimental study on the repair effectiveness of Carbon Fibre Reinforced Polymer (CFRP) sheets for RC beams with different levels of pre-repair damage severity. It highlights the effect of fixing CFRP sheets to damaged beams on the load capacity, mid-span deflection, the steel strain and the CFRP strain and failure modes. The analytical study was based on a Finite Element (FE) model of the beam using brick and embedded bar elements for the concrete and steel reinforcement, respectively. The CFRP sheets and adhesive interface were modelled using shell elements with orthotropic material properties and incorporating the ultimate adhesive strain obtained experimentally to define the limit for debonding. In order to validate the analytical model, the FE results were compared with the results obtained from laboratory tests conducted on a control beam and three other beams subjected to different damage loads prior to repair with CFRP sheets. The results obtained showed good agreement, and this study verified the adopted approach of modelling the adhesive interface between the RC beam and the CFRP sheets using the ultimate adhesive strains obtained experimentally.

Wire bond has been an important tool in the world of microelectronic interconnections. The effect of Reactive Ion Etching (RIE) on the successful rate of thermosonic bonding using gold wire on aluminium pad is studied. Surface morphology images from Atomic Force Microscopy (AFM) are used as correlation comparison. In this work wire bonding adhesion is studied on two different surface conditions, which are treated with RIE and the other without RIE treatment. In this experiment only the bonding time was varied for each set of experiments. Results of the wire bond from both samples, with and without RIE were compared. The RIE treated surfaces yield better adhesion results in this work.

The main objective of this investigation is to determine the effect of palm diesel on concrete under accelerated laboratory conditions. Mortar samples of ordinary Portland cement (OPC), modified OPC with natural rubber latex, magnesium phosphate cement and epoxy-coated OPC were soaked in palm diesel. Samples were p prepared under different curing regimes and soaked in palm diesel for a definite period. Both visual and microscopic examinations were then made to ascertain the nature of the attack. The change in weight of the specimens was also recorded to quantify the degree of deterioration. The mortar samples containing OPC exhibited the highest degree of deterioration, whilst the epoxy-coated and magnesium phosphate samples were least affected. The degree of deterioration was also dependent on the curing regime. The principal cause of the deterioration was attributed to saponification by the free lime present in the set cement, forming a calcium soap. It can be concluded from the results of this preliminary investigation that surface treatment with epoxy or other suitable materials chemically resistant to palm diesel may inhibit the deterioration on the concrete. Furthermore, by using a different kind of cement that contains a substantially smaller amount of calcium than OPC, the attack of the palm diesel may be reduced or prevented.

Publisher Summary A laboratory investigation to study the effect of general corrosion on the modal parameters of reinforced concrete beams is conducted in this chapter. Full-scale beams are subjected to reinforcement corrosion until an appreciable amount of steel corrosion damage is introduced using an accelerated technique—namely, galvanostatic method. The states of damage in the test beams are assessed through measurement of crack width, loss of area, and half-cell potential. Modal tests are performed on the test beams after corrosion damage and the modal parameters extracted are compared against that from control beams. The results obtained show changes in the modal parameters especially, natural frequencies and mode shapes. The intensity of the drop in the measured natural frequencies is sensitive to the deterioration state of the beams. Changes in natural frequencies could be established as a damage indicator, which relates to the loss in flexural stiffness of the corroded beams. Using modal assurance techniques to perform orthogonality checks on sets of mode shape from the control and corroded beams, changes can be visualized, which are dependent on the degree of corrosion damage induced. Finally, the load carrying capacity of the beams is determined through static load test and the results are correlated with the state of corrosion damage and changes in the modal parameters. This investigation provides further insights into the use of modal parameters to detect and assess damage in structural concrete elements.

High strength concrete mixtures containing 10% metakaolin replacement and 10% metakaolin addition, water/cementitious material ratio of 0.3 and 1% superplasticizer were studied. Similar mixtures incorporating silica fume were also prepared. The effect of mineral admixtures on the fresh and hardened properties of concrete was investigated. Mixtures with mineral admixture exhibited lower workability, less bleeding, and slightly lower air content. Metakaolin resulted in a higher loss of workability compared with silica fume. Mixtures incorporating mineral admixture developed greater compressive strength and elastic modulus at all ages. The enhancement was more pronounced at early ages and in the addition mixtures. The study concludes that the performance of metakaolin is equivalent to silica fume in terms of contribution to the enhancement of strength and elastic modulus. The metakaolin addition mixture attained 70% and 50% strength improvement while the metakaolin replacement mixture achieved 67% and 39% strength increment at the respective ages of 3 and 28 days.