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Conventional reparation and maintenance method of mortars and buildings have adverse side effects on their surrounding environmental and aesthetic value. This study reported the impact of a locally isolated bacterium, Bacillus sp. strain SKC on the parameters affecting the properties of mortar. The abiotic control and bacteria-modified mortars were investigated to determine the differences in their properties. The compressive strength of the bacteria-modified mortar was successfully enhanced which was twofold higher than that of the abiotic control mortar, thus increasing the density. Calcium carbonate crystal deposition on bacteria-modified mortar reduced the porosity and permeability. The bacterial deposition of calcium carbonate was confirmed by SEM images and XRD analysis.

Beton Geopolimer merupakan beton yang tersusun dari campuran agregat kasar dan halus tanpa pengikat semen Portland (OPC). Sebagai penggantinya, digunakan pengikat dari bahan yang banyak mengandung silica dan alumina seperti fly ash. Analog dengan beton yang berbasis semen Portland, beton geopolimer juga menjadi kurang sempurna jika campuran beton segar mempunyai konsistensi yang tinggi dan bersifat kental (kaku) sehingga sulit untuk dikerjakan (workabilitas rendah). Penambahan Superplastisizer manjadi salah satu cara untuk meningkatkan workabilitasnya. Dalam makalah ini digunakan superplastisizer yang berbasis naphthalene dengan dosis 0%, 1.5%, dan 2 %. Molaritas larutan NaOH yang digunakan sebagai aktivator alkalin adalah 8 M, 10 M, 12 M, dan 14 M dengan rasio Na2SiO3/NaOH = 1.5. Dari hasil pengujian diketahui bahwa pengaruh superplastisizer yang berbasis naphthalene cukup efektif untuk memperbaiki workabilitas beton geopolymer. Beton segar menjadi lebih encer dan mudah dilakukan pemadatan saat di tuang ke dalam cetakan. Superplastisizer juga mampu meningkatkan kekuatan beton geopolymer namun besaran hanya mencapai 5.42%. Dosis Superplastisizer akan optimum pada persentase 1.5% terhadap berat fly ash dengan kuat tekan mencapai 31.63 MPa dan nilai slump antara 8-10 cm. Molaritas larutan NaOH yang baik untuk rasio Na2SiO3/NaOH = 1.5 adalah 8 M.

Many empirical confinement models for normal and high strength concrete have been developed. Nevertheless, reported studies in the term of confinement of fiber reinforced concrete are limited. Whereas, the use of fiber reinforced concrete in structural elements has become the subject of the research and has indicated positive experiences. Since the stress-strain relationship of concrete in compression is required for analysis of structural members, the study of the stress-strain relationship for synthetic fiber reinforced concrete is substantial. The aim of the study is to examine the capabilities of the various models available in the literature to predict the actual experimental behavior of synthetic fiber reinforced high-strength concrete columns. The experimental data used are the results of the circular column specimens with the spiral spacing and the volume fraction of synthetic fiber as the test variables. The axial stress-strain curves from the tests are then compared with the various models of confinement from the literature. The performance index of each model is measured by using the coefficient of variation (COV) concept of stress and strain behavior parameter. Among the confinement models, Cusson model shows the closest valid value of the coefficient of variation.

Makalah ini menampilkan hasil penelitian eksperimental terhadap 3 buah benda uji struktur flat slab beton mutu sangat tinggi dengan campuran beton bubuk reaktif dibawah kombinasi beban gravitasi dan beban lateral siklis. Pengujian dilakukan dengan sistem sub assemblage hubungan pelat dan kolom dari struktur flat slab. Benda uji terdiri dari pelat dengan rasio tulangan tarik relatif rendah (0,65%) dan relatif tinggi (1,8%) yang diaplikasikan untuk bentang pelat 3,00 m sedangkan untuk pelat dengan bentang 2,00 m rasio tulangan yang dipakai hanya 1,8%. Beban gravitasi sebesar 8,45 kN/m2 diaplikasikan konstan, sedangkan beban lateral siklis diberikan dalam bentuk displacement control. Pembebanan siklis dilakukan melebihi ketentuan drift ACI 374.1-05 yaitu sampai dengan drift ± 5,00%. Pada drift 5%, perilaku non linear struktur menunjukkan respon histeresis yang daktail tanpa mengalami penurunan kekuatan yang signifikan baik untuk rasio tulangan tinggi maupun rendah. Meskipun demikian, penurunan kekakuan masih terjadi. Pengaruh rasio tulangan tarik lebih signifikan dibanding bentang pelat terhadap respon kekuatan dan kekakuan pelat terutama pada fase inelastis. Pelat bentang 3,0 m dengan rasio tulangan tarik rendah mempunyai rasio daktilitas perpindahan paling tinggi sedangkan pelat dengan bentang 3,0 m dengan rasio tulangan tarik tinggi mempunyai rasio daktilitas perpindahan paling rendah dibanding yang lain. Abstract . This paper presents the result of the experimental study on three very high strength concrete flat slab structures constructed with reactive powder concrete under combined gravity and cyclic lateral loads. The tests were conducted on slab-column connection sub assemblages of the flat slab structure. Two specimens had slab span of 3.00 m with relatively low and high tension steel reinforcement ratios of 0.65% and 1.8%, respectively. The other specimen had slab span of 2.00 m with tension steel reinforcoment ratio of 1.8%. The specimens were subjected to constant gravity load of 8.45 kN/m2 and the lateral cyclic load using displacement control close to 5% drift ratio. The drift was set up larger than as required in ACI 374.1-05. At 5% drift, nonlinear behavior of the structures showed ductile hysteresis responses without a significant decrease in strength both for lower and higher tension steel reinforcement ratio. However, a stiffness degradation still occurred for all specimens. Effect of tension steel reinforcement ratio was more significant than that of slab span on stiffness and strength responses particularly at inelastic ranges. Slab with span of 3.00 m and low tension steel reinforcement ratio showed the largest displacement ductility ratio while the slab with same span but higher tension steel reinforcement ratio resulted the lowest displacement ductility ratio compared to the other specimens.

Experimental work on four specimens of reinforced concrete slab- column connection sub-assemblages using reactive powder concrete (RPC) was conducted. The specimens were subjected to a combination of gravity and cyclic loading. The gravity loading was represented by a number of concrete cubes hung on the slab bottom surface and the cyclic lateral loading was applied on the upper end of the columns. The specimens consisted of two variables, i.e tensile flexural reinforcement ratio (0.65% and 1.8%) and slab span (2.0 m and 3.0 m). Shear reinforcement was not used in the slab. The displacement history consisted of three repeated cycles, starting from 0.07 to 5.00 percent drift ratio, covering the elastic and the inelastic response of the specimens. The RPC mixture proportion for the specimen’s material was developed using local materials and normal concrete technology methods. The average RPC compression tests results were 136.0 MPa at 28 days and 141.0 MPa at the time of the first specimen, tested at 56 days. The tests results showed that up to 5.0 percent drift all specimens had stable hysteresis loops without any significant degradation of strength and stiffness. The specimen with a larger tensile flexural reinforcement ratio developed more strength, stiffness and energy dissipation.

Keywords: High Performance Concrete, mix proportions, compressive strength , and durability Abstract. The use of concrete materials to date, remain a key ingredient in such construction work on the construction of building, bridges and infrastructure. One indicator is the increased production of readymix concrete which is nearly 16 billion tons in 2010. But the increased used of concrete, apparently bring the impact of environmental damage. This is due to the fact that production of raw materials contributes greatly to CO2 in the air. One effort to reduce such impact is to use of high performance concretes. Mix proportion of High Performance Concrete are strongly determined by the quality and availablity of local materials. The implications of research result from other countries can‘t be directly used. Therefore is need to the research on development of High Performance Concrete mix using locally available materials. In this research the mix proportions for f’c : 60 and 80 MPa are developed using local materials that are commonly used by readymix producers. The high Performance Concrete is developed based on compressive strength and durability. The result is expected to be applied to readymix industry particularly for construction use in Indonesia.

Bauxite tailing waste or commonly known as red mud is considered to be a very hazardous material. The using of red mud to make alternative building material has been widely studied for many years. Geopolymer as one of the breakthrough in the searching of ordinary portland cement/concrete substitution provides many options and possibilities of using different types of pozzolanic or alumina-silica materials. In this study, the using of red mud in metakaoline-based geopolymer paste has been studied in three different curing conditions for 7 days of sample age. Each sample then characterized both, macroscopically and microscopically including compressive strength testing, SEM photograph, XRD and FTIR spectroscopy

Based on data from Indonesian Directorate General of Mineral and Coal Technology, popular sources of silica sand in Indonesia can be found: Bangka Belitung, Pangkal Pinang,South Sumatra, Lampung, West Kalimantan, South Kalimantan, West Java, and East Java. Unfortunately, the use of silica sand in concrete mix is still limited as filler material. The challenge is then to explore the use of such silica sand, for instance in the form of nano silica. This research work explores silica sand from: Bangka Belitung, Pangkal Pinang, Lampung, West Java, East Java, West Kalimantan and South Kalimantan. The selected silica sand are then processed by the novel method developed by Indonesia Center for Ceramics using Polishing Liquid Milling Technology. The result is expected to contribute in the development of increased added value of locally available silica sand and to advancing application of nano silica for concrete.

One of the important requirements for earthquake resistant building related to confinement is the use of seismic hooks in the hoop or confining reinforcement of reinforced-concrete column elements. However, installation of a confining reinforcement with a 135-degree hook is not easy. Therefore, in practice, many construction workers apply a confining reinforcement with a 90-degree hook (non-code compliant). Based on research and records of recent earthquakes in Indonesia, the use of a non-code compliant confining reinforcement for concrete columns produces structures with poor seismic performance. This paper presents a study that introduces an additional element that is expected to improve the effectiveness of concrete columns confined with a non-code compliant confining reinforcement. The additional element, named a pen-binder, is used to keep the non-code compliant confining reinforcement in place. The effectiveness of this element under pure axial concentric loading was investigatedcomprehensively.The specimens tested in this study were 18 concrete columns,with a cross-section of 170 mm x 170 mm and a height of 480 mm. The main test variables were the material type of the pen-binder, the angle of the hook, and the confining reinforcement configuration.The test results indicate that adding pen -binders can effectively improve the strength and ductility of the column specimens confined with a non-code compliant confining reinforcement.

Geopolymer concrete is a new material made by activating the raw materials which contain many elements of silica and alumina. Compressive strength of geopolymer concrete produced was influenced by the concentration of the activator solution. This paper presents an experimental investigation into fly ash-based geopolymer concrete. Research objective was to investigate the effects of alkaline activator solution (AAS) molarity on compressive strength of geopolymer concrete. Variable of the test were a solution to sodium hydroxide was chosen as the activator solution. Concentration of sodium hydroxide solution used was 10 M, 12 M and 14 M with ambient curing. The specimen is made of concrete cylinder with diameter 10 cm and height 20 cm as many as 9 pieces each variable. Compressive strength tests is performed when the concrete is 7, 14, and 28 days old. Results of the test are indicated that the increasing of sodium hydroxide (NaOH) solution concentration leads to improve the compressive strength of geopolymer concrete. The optimal compressive strength of geopolymer concrete was achieved at a concentration of sodium hydroxide solution (NaOH) of 12 M. Geopolymer concretes compressive strength only achieves around 50-60% of the planned.

Age dependent mechanical and kinetic properties including Young's modulus, early-age creep, autogeneous and thermal deformations, and heat of hydration were investigated for concrete made of blended cements. These are among the key properties that control the early-age cracking behavior in hydrating concrete members. Among the main goals of the investigation were to provide the experimental data and to study the effect of adding mineral additives such as fly ash (FA), ground granulated blast furnace slag (GGBF), and silica fume (SF) on the aforementioned properties. The age-dependent behavior of Young's modulus, creep compliance, and autogeneous shrinkage as functions of heat of hydration were modeled. We emphasized on mathematical modeling the viscoelastic properties of concrete. The equations obtained can be used as inputs needed to calculate the early-age stress development in concrete members.

A procedure for calculating the early-age stress development in concrete incorporating the aging viscoelastic effects is presented in this paper. The important features of the present procedure are the use of tensile creep and inclusion of heat of hydration. The latter is used as an aging parameter and incorporates the effect of temperature on age-dependent material parameters. To validate stress predictions, experiments to measure early-age stress development in concrete mixes made of blended cements were conducted. The predictions were found to be accurate and could be improved when the effect of temperature was included. Effects of using mineral additives (fly ash, slag, and silica fume) appeared to be beneficial in reducing the risk of cracking at early ages. The effect of temperature gradient was also studied when the stress calculation was applied to pavement or foundation slabs resting on a very stiff subgrade.

The performance of one and two-dimensional ferroelectric memory capacitors characterized by the hysteresis of applied electric field versus the surface charge density is investigated using the finite element method. Sensitivity of the electrical hysteresis of the 2D capacitor constrained by compliant layers to selected geometrical variables is explored. The remnant polarization and the coercive filed are compared with those of a free-standing film and a film fully constrained by the substrate. The aspect ratio can significantly influence the clamping behavior and thus the remnant polarization of the capacitor.

Alkali activated fly ash material (AAFAM) has become the most promising material to substitute materials based on ordinary Portland cement (OPC). However, there is no available nomogram for AAFAM mixtures. In contrast, there are many rational methods available in the literature to make paste, mortar and concrete with OPC based materials, such as Monteiro-Helene’s nomogram, which uses Abram’s law, Lyse’s law and Molinari’s law. This paper presents a study to construct such a nomogram for AAFAM mixtures by first conducting experiments on the paste and mortar phases. The procedure of Monteiro-Helene’s nomogram was adopted in this formulation. The first step in this direction was to find a close relationship between the strength and paste composition of the material that can be used as a substitute for Abram’s law. The second step was to construct the equivalent of Lyse’s and Molinari’s relationships by varying the sand and fly ash contents. The results show that it is possible to make a nomogram for AAFAM mixtures such as the one for OPC based materials. Class F fly ash and its mortar phase were used to construct the nomogram. In addition, the mortar samples that were used to build the nomogram had similar solidification products according to their microscopic characteristics.

Surface and subsurface responses during frictionless indentation of elasto-plastic solids are investigated. Cases of monotonic and repeated loading are considered. It is shown that the role of plasticity parameters on indentation behavior cannot be well described in terms of surface response alone. It must be tied with subsurface response. In particular, the difference between the materials exhibiting isotropic hardening and that exhibiting kinematic hardening is less apparent when the force-displacement response and the deformed surface from the two are compared. Yet, it is quite apparent when subsurface response such as plastic strain, residual stress and plastic zone dimension are compared. An attempt has been made to characterize such surface and subsurface responses, for different plastic behavior, and to compare them with estimations obtained from analytical solutions.

Simulations of spherical indentation of a substrate coated with a protective layer have been performed in the elastic deformation range. They provide key responses that can be used to examine the load resistance of a coated substrate. The key responses result in diagrams indicating whether yielding or fracture occurs first. In this kind of diagram, the ratio of coating fracture strength to substrate yield is related to the contact radius in indentation. As it is difficult to determine the contact radius experimentally, the latter has been found numerically and has also been approximated analytically. The analytical approximation plays an important role as it identifies the general loading condition for various sphere radii. This approximation can be extended to predicting the unloading curve which allows the elastic properties of a coated substrate to be determined.

Hydration of portland cement pastes containing three types of mineral additive; fly ash, ground-granulated slag, and silica fume was investigated using differential thermal analysis, thermogravimetric analysis (DTA/TGA) and isothermal calorimetry. It was shown that the chemically bound water obtained using DTA/TGA was proportional to heat of hydration and could be used as a measure of hydration. The weight loss due to Ca(OH) 2 decomposition of hydration products by DTA/TGA could be used to quantify the pozzolan reaction. A new method based on the composition of a hydrating cement was proposed and used to determine the degree of hydration of blended cements and the degree of pozzolan reaction. The results obtained suggested that the reactions of blended cements were slower than portland cement, and that silica fume reacted earlier than fly ash and slag.

A bifurcation analysis was carried out for a class of layered materials whose constitutive behavior were described by the model of Christoffersen and Jensen, 1996. The problem was solved in uniaxial plane strain compression for compressible materials without volumetric plastic strain. The elastic–plastic response of the constituent materials is described by J 2 -deformation theory and J 2 -flow theory. Results indicate that bifurcation stresses vary smoothly with wavelength and are sensitive to the moduli ratio between constituent materials and the volume fractions. The results show that there is a transition in the bifurcation mode from an Euler type elastic bifurcation of a slender column made of a composite material to a surface bifurcation mode in the plastic regime for a wide plate. Furthermore, effects of residual stress were also incorporated and studied.

The main objective is to investigate key properties that influence the stress development in concrete at early ages and the effect of using blended cements. Mineral additives and amount by weight of total binder used in the blended cements are fly ash (25%), ground granulated blast furnace slag (25%), and silica fume (10%). The properties investigated include tensile creep, elastic modulus, split tensile strength, and autogenous shrinkage. The relaxation modulus used for stress prediction was obtained from the creep data fitted using a log-power creep function. These findings show that tensile creep and stress relaxation are important properties of Portland cement concrete. These properties however are reduced in concretes containing blended cements. Blended cements affect the early age strength and elastic modulus moderately but significantly alter the autogenous deformation. Water/cement ratio (w/c), type and dosage of mineral additives were found to influence the magnitude of autogenous deformation. This deformation was found to be significant in low water-cement ratio concretes and should be included in early age stress calculations.

A three-dimensional (3D) finite element (FE) model is developed to investigate whether the condition of plane sections remaining plane exists in concrete pavements subjected to nonlinear temperature gradients. This model is utilized to validate the analytical method proposed by Mohamed and Hansen. The 3D brick element is chosen so that the plane section condition is not imposed in the model, as compared with the model using the flat plate element. Furthermore, the possibility of loss of contact between the pavement slab and the subgrade is studied. The condition of full contact is investigated for a nonlinear temperature gradient that produces the maximum tensile stress in the slab according to the data used. Two slab lengths and two radii of relative stiffness are considered. It is found that plane sections remain plane for the entire slab except for a region very close to the free edges, which also establishes the boundary where solutions by Mohamed and Hansen are applicable. In both cases of the contact condition, the 3D FE model predicts no loss of contact between the slab and the subgrade.

The influence of mechanical constraint imposed by device geometry upon the switching response of a ferroelectric thin film memory capacitor is investigated. The memory capacitor was represented by two-dimensional ferroelectric islands of different aspect ratio, mechanically constrained by surrounding materials. Its ferroelectric non-linear behaviour was modeled by a crystal plasticity constitutive law and calculated using the finite element method. The switching response of the device, in terms of remnant charge storage, was determined as a function of geometry and constraint. The switching response under applied in-plane tensile stress and hydrostatic pressure was also studied experimentally. Our results showed that (1) the capacitor's aspect ratio could significantly affect the clamping behaviour and thus the remnant polarization, (2) it was possible to maximise the switching charge through the optimisation of the device geometry, and (3) it is possible to find a critical switching stress at zero electric field and a critical coercive field at zero residual stress.

The role of mechanical constraint upon the switching response of a ferroelectric thin film memory capacitor is explored. The memory capacitor is represented by a two dimensional ferroelectric island whose non-linear behaviour is modelled by a crystal plasticity constitutive law within the finite element method. The switching response of the device, in terms of remnant charge storage, is determined as a function of geometry and constraint. Various types of constraint on the ferroelectric capacitor are considered, including the presence of a silicon dioxide passivation layer, a silicon substrate and metallic electrodes. The effect of the relative resistance to 90 degree switching and 180 degree switching is also explored in a tetragonal ferroelectric device. Throughout the study, the finite element calculations are compared with the behaviour of a material element subjected to various degrees of mechanical constraint.

In metal forming, failure of coated tools often indicate problems related to sliding contact, fretting, and substrate plasticity. To date, failure prediction of tools subjected to sliding and fretting contact has been largely based on elastic analysis if not empirical. As an effort to understand the issue and specifically, to investigate the role of plasticity, a finite element‐based analysis of plane strain contact of brittle coating is performed. The problem consists of cyclically loading a rounded‐edge punch in normal and tangential directions to a coated substrate. The results are presented for the maximum principal stress in the coating indicative of brittle failure and the evolution of plastic deformation in the substrate. These quantities are analyzed as functions of substrate’s plasticity parameters, coating’s elastic modulus, friction, and loading parameters. A combined isotropic‐kinematic hardening plasticity law is considered. The prediction of the tool’s service life based on the above failure conditions is also discussed.

This paper presents the development of an analytical procedure to determine the heat and degree of hydration due to nonisothermal temperature history using a 3-parameter model. The procedure can also be applied to concrete mechanical properties if they are strongly related to the degree of hydration. To demonstrate this, experiments were conducted to obtain the heat of hydration, chemically bound water, compressive strength, split tensile strength, and Young's modulus of concrete. Experimental results in the literature were also used. It was found that the measured degree of hydration relates uniquely to measured concrete properties. The analytical procedure was then extended to determine a generalized hydration or aging time. Results from the literature were used to confirm the predictive capability of the proposed aging relation. The proposed maturity relation was found to relate uniquely to mechanical properties such as compressive strength and fracture energy.

Previous studies have shown that fiber reinforced concretes can improve post-peak behaviour, ductility and energy-dissipation ability of concrete elements under flexure, shear and axial load. Ductile behaviour is one of the essential characteristics that have to be possessed by structures located in moderate to high seismic regions. This paper presents an experimental investigation of a series of nine macro synthetic fiber-reinforced concrete (MSNFRC) circular columns. The objective of the studies was to investigate the effects of the macro synthetic fibers on strength and ductility of the columns. The test parameters were the spacing of the spiral reinforcement and the volume fraction of the macro synthetic fibers. In two-thirds of the specimens, when macro synthetic fibers were added to the specimens, spiral reinforcement was reduced. The remaining specimens were detailed in accordance with the code minimum requirement for spiral reinforcement in order to examine the influence of the fibers on strength and ductility. A concentric axial compression load was applied monotically on the column specimens. The results show that the addition of macro synthetic fibers leads to improved ductility and strength. Furthermore, based on this study, the code required spiral reinforcement can be reduced whenever MSNFRC is used.

The last three decades have been marked by remarkable growth of high strength concrete applications in building and bridges. Both types of construction will benefit from the positif effetcs such as reductions in member sizes and amount of reinforcement, when using high strength concrete. However, bridges are often made with long spans resulting in significant dead weight which combined with the creep and shrinkage properties of concrete, leads to significant deformation and loss of prestressing force in the long term. In this study, the effects of creep and shrinkage of high strength concrete used for prestressed concrete bridge girder is investigated. The aim is to quantify the loss of prestress in high strength concrete bridge and to find justfications on increasing usage of high strength concrete for bridges. A continuous-span bridge built using span by span method (movable scaffold system) is chosen as a case study. Three grades of concrete strength are investigated, 40 MPa, 80 MPa, and 100 MPa, each representing normal, moderately high and high strength concrete. These are grades that can be routinely produced by concrete industry without significant alteration in current production/process technology. As part of this study, a literature survey has also been conducted. It suggests that high strength concrete requires modification of current creep and shrinkage code (applicable only for normal concrete). Thus, the initial part of this study deals with determination of proper creep and shrinkage code. Then, a finite element analysis of the bridge case is performed. The result indicates that reduction in girder size and amount of prestressing is not simply governed by concrete strength, but by the comlplex effects of strength, creep and shrinkage behavior of high strength concrete.

The finite element method is used to investigate the performance of a ferroelectric random access memory as a function of its geometry. Performance is characterised by the charge versus electric field relation, and the sensitivity of performance to geometry is explored. The primary geometric variables are the dimensions of a prismatic two-dimensional (2D) island of ferroelectric material, and the edge inclination angle caused by the etching process along the sides of the island. The performance of the two-dimensional ferroelectric device is compared to those of an unsupported ferroelectric thin film and of a ferroelectric film bonded to a substrate.