Concrete Composites

This paper reports the study carried out to examine the thermal properties of lightweight foamed concrete (LFC) integrating various additives. Various densities of LFC samples ranging from 600, 1000 and 1400 kg/m3 with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45 were produced. Fly ash, lime and polypropylene fiber with different percentages were used as additives. The main purpose of this study is to explore the effect and divergence of reaction on each additive that influences the thermal properties of LFC. Detail experiments were setup to study the behavior and reaction of additives which is expected to give different results on thermal properties of LFC. Each additive has different properties and reaction which will impinge on the thermal properties of LFC. The reaction during the hydration process is significant to be examined seeing that it will create complex particle that results in different microstructure formation. Detail observation by using scanning electron microscopy (SEM) will provide better understanding on thermal properties that is influenced by microstructure formation, moisture content and porosity of LFC. Experimental results show that lower density LFC translates to lower thermal conductivity. The density of LFC is controlled by the porosity where lower density LFC indicates greater porosity thus thermal conductivity changes significantly with the porosity of LFC because air is the poorest conductor compared to solid and liquid due to its molecular structure.

In this research work, Artificial Neural Network Model(ANN) for the composite circular steel tubes- with re-cycled concrete infill with three different grades of concrete(M20,M40 and M60) are tested for ultimate load capacity and axial shortening , under axial monotonic loading for compression has been developed. Steel tubes are compared for different lengths, cross sections and thickness, and specimens were tested separately. In this paper, authors have developed a suitable artificial neural network model using feed forward back propagation network having verified it for 11 hidden layers as per Kolmogorov’s theorem. The developed ANN model has been verified with the experimental results conducted on composite steel columns (axial load) using Tagauchi’s model. Being a flexible building method, the ANN is an ideal tool to construct the complex relationship between the input and the output parameters accurately. The ANN technique is used to predict the crushing behavior of axial shortening and ultimate axial load in composite circular steel columns. Effects of parameters such as network architecture and number of hidden layer neurons are considered. Predictions are compared to experimental results and are shown to be in good agreement.

Normal concrete was prepared with a water-cement ratio of 0.50. cube specimens were cast for testing the compressive strength at 7 and 28 days of curing respectively using three curing methods namely immersion, sprinkling and Plastic sheeting, curing to cure the cube specimens until the day of testing. Test results indicates that water curing (WAC) as well as sprinkling (spraying) curing provided much better results than membrane (Plastic Sheeting) method of curing. The rate of drying was significant when the specimens were subjected to membrane (Plastic sheeting) method of curing. This thus hampered the hydration process and thus affected the compressive strength property of the hardened concrete. The overall finding of this study suggests that concrete should be cured by water curing to achieve a better compressive strength.

High Performance Concrete (HPC) is that concrete which meets special performance and uniformity requirements that cannot always be achieved by conventional materials, normal mixing, placing and curing practices. The grade of concrete selected was control mix (CM) of M80. Investigation was carried out on mixes of partial replacement of cement with metakaolin (MK) 10% and silica fume (SF) 15%. Regression analysis equations were developed for each type of curing based on compressive strength and age of concrete (7, 14, 28 and 56 days). In this study the effect of various curing conditions on compressive strength of HPC were studied. The various curing conditions adopted were normal curing (NC), wet cover curing (WCC), membrane curing (MC) and accelerated curing (AC). Normal water curing includes immersion of concrete cubes in water. Wet cover curing includes covering concrete with burlap. Membrane curing includes application of wax coating on concrete cubes. Accelerated curing includes application of heat at ordinary pressure. The overall finding of this study suggests that concrete should be cured by water curing to achieve a better compressive strength.

This paper focusses on the flow behavior of quaternary blended HPC using modified slump cone test. 49 HPC mixes including control mix were developed incorporating mineral admixture combinations of metkaolin, slag and fly ash up to 92.5% replacement levels. Semi-empirical models were proposed for yield stress and plastic viscosity as the function of the slump and slump time. It was found that the fluidity of concrete increased moderately and the plastic viscosity and yield stress decreased noticeably, when mineral admixture combinations were substituted partially for cement. Out of 49 HPC mixes, the quaternary HPC mix developed with 57.5% cement, 7.5% metakaolin, 25% slag, and 10% fly ash, gives a minimum yield stress of 878 Pa and plastic viscosity of 179 Pa.s.

This study presents an experimental investigation on self-compacting concrete with two mineral admixtures such as silica fume and fly ash. With low water-binder ratio, we had achieved higher grade of self-compacting concrete. The water-binder ratio was maintained to 0.36 for all the SCC mixes. This research includes the following studies: (i) Develop a suitable design mix for SCC that would satisfies all the acceptance criteria of EFNARC (ii) A study has been made for the rheology properties of SCC.The main requirements of fresh properties of SCC are filling ability, passing ability, and high segregation resistance, which can be investigated by slump flow, T50 slump flow, J ring, V-funnel, L box test. (iii) concrete samples were casted and tested for its compressive strength and Young’s modulus. The results show that SCC with 10% of SF gives higher values of compressive strength than those with 15% of FA.

The State of the art of concrete filled steel tubular columns is presented in this paper. Experimental data has been collected and compiled in a comprehensive format listing parameters involved in the study. Areas of further research are presented and results of ongoing experimental and numerical investigations are also shown.

The purpose of this research is to investigate the use using steel chips and steel fibre in concrete to enhance its electric conductivity. The objective of this study is to determine and to do the comparative study of the properties of concrete with steel chips only, containing steel fibre only and containing both steel chips and steel fibres. This investigation was carried out using several tests. Workability and surface finishability were used as primary evaluation criteria. Effect on Humans due to flow of current through concrete was also considered.

The behaviour of self-consolidating fibre reinforced high strength concrete (SCFRHSC) filled hollow structural steel (HSS) columns subjected to an axial load was investigated experimentally. A total of 45 specimens were tested. The main parameters varied in the tests are: (1) % of fibre (2) tube diameter or width to wall thickness ratio (D/t from 15 to 25) (3) L/d ratio from 2.97 to 7.04 The results from prediction were compared with the experimental data. Validation to the experimental results was made.

The State of the art of Double Skinned concrete filled steel tubular columns is presented in this paper. Experimental data has been collected and compiled in a comprehensive format listing Parameters involved in the study. Areas of further research are presented . Also, results of ongoing experimental and numerical investigations by various authors including us are presented in this paper.