An extensive experimental study on various characteristics of Reactive Powder Concrete (RPC) cured in normal conditions is investigated. An attempt is made to investigate the influence of the ingredients of RPC on the compressive strength of RPC using 112 mixes. The study extends to understand the effects of variation in silica fume, found to be most influential ingredient, on other mechanical properties such as flexural strength, shear strength and bond strength. Of the various mixes studied, the ideal mix proportion giving suitable performance is used to conduct further tests to determine the water absorption, water permeability, sorptivity, chloride permeability, resistance against fire, sulphate attack, acid attack, alkaline attack and abrasion of RPC. Overall results highlighted the enhanced mechanical and durability properties of RPC and its compatibility with conventional concrete.
This paper discusses the comparison of the flexural toughness parameters of fibre reinforced concrete (FRC) obtained from unnotched and notched beam tests. Results obtained from tests on a 40 MPa strength concrete reinforced with different dosages of hooked-ended steel, polypropylene and glass fibres have been used to correlate toughness parameters obtained from the two test methods. It was observed that for steel and polymer fibre reinforced concrete, good correlation existed between the unnotched beam test parameters (fe,150 and fe,300) and notched beam test parameters (fR1 and fR3). This enables the use of the fib Model Code 2010 for the design of FRC structural elements at both serviceability and ultimate limit states, even when only unnotched beam test data is available.
Analyses of chemical constituents in sand were undertaken after these sand samples were collected from different sources, including river sand and manufactured sand from all over India, ensuring a fair representation. Indian subcontinent is home to 20% of the worlds’ population. X-Ray Fluorescence (XRF) results along with data from X Ray diffraction suggested that Indian sand is not necessarily pure silica based sand but all most always has calcium carbonate as a constituent. Its content varied from a few percent to majority fraction of the sand at certain locations. This can chemically react with acidic ground water (hard water) and make any exposed concrete porous and susceptible to further degradation based on capillary action. As calcium salts like carbonate was present in non-negligible amounts, such sand samples need to be leached with dilute acids and such content removed to make the sand chemically more stable before mixing with cement for production of reinforced concrete, for better durability even in slightly acidic environments with nonpotable ground water or in areas close to the sea coast or areas with tidal effects.
In the present study, four numbers of two-layered ANN models were used to predict the compressive strength of geopolymer concrete. The differences in the models were the number of neurons in the hidden layer and the method of termination of training. Eight input parameters were employed which included curing time, Na2SiO3 / NaOH ratio, alkaline liquid/fly ash ratio, plasticizer, rest period, water content, NaOH concentration and curing temperature. There was one output parameter that was a compressive strength. A total number of 51 datasets were utilized among which 35 were used for training, eight were applied for validation, and the remaining eight were employed for testing. It was detected that as the number of neurons in the hidden layer increased, there was an improvement in the result and errors decreased. Also, the termination state affects the results. ANN III and ANN IV were found to exhibit the best results.
Sustainability in the construction industry can be accomplished by adapting sustainable practices ensuring ecological harmony. Using recycled aggregates and fly ash has been emerging as one of the sustainable practice for responsible consumption of waste and converting it into wealth by utilising them in producing concrete. Deterioration of concrete members exposed to aggressive acid environments is a key durability issue that affects the life cycle performance and economy of civil infrastructures. Groundwater, chemical waste, sulphate and chloride bearing compounds in earthfill, acid rain in industrial zones and biogenic acid in sewer systems are the main sources of acid affecting concrete structures. Addressing these concerns, this present study aims at exploring the effects of Recycled Coarse Aggregate (RCA) and fly ash on durability characteristics of concretes, when exposed to severe acidic environment. The parameters considered were weight loss and strength loss, when exposed to 5% concentrated HCl acid and 5% concentrated H2SO4 acid. It was found that replacement of Natural Coarse Aggregate (NCA) with RCA and cement with fly ash showed a way of considering economy and environmental effects as criteria, given a little bit of compromise towards strength and durability but still falling well within an acceptable limit. The RCA used in this study was unprocessed, washed with water to remove impurities.
The study presents an experimental investigation on the properties of Self-Compacting Concrete (SCC) containing ultra-fine Ground Granulated Blast furnace Slag (GGBS) as a Super-Pozzolanic Material (SPM) in combination with class-F fly ash. Portland cement was replaced by weight with ultrafine GGBS in the varying proportion from 0% to 10% at the rate of 2.5% whereas the fly ash was nominally fixed at 20% by weight of the total powder content in all the SCC mixtures. The properties studied include fresh state behaviour, compressive strength, ultrasonic pulse velocity, water absorption, pH of the concrete, chloride and sulfate resistance of the SCC. Results showed that the incorporation of ultra-fine GGBS positively affect the fresh, the hardened and the durability performance of the considered SCC. An increase of about 32% was observed in
the compressive strength for the ternary blended SCC mixture with 10% GGBS content; when compared to the binary blended control SCC mixture. Water absorption values of the SCC showed a decreasing trend with increase in the GGBS content. Durability performance of the SCC in terms of chloride and sulfate resistance improved with addition of this ultra-fine GGBS at the later ages.
Marble is widely used in structures, it increases the amount of waste powder obtained. As marble powder is a waste product obtained during the process of sawing and shaping of marble by marble rocks which contains heavy metals that makes the water unfit for use. Since marble powder has cementing property it can be used in concrete as partial replacement of cement. In this study, waste marble powder has been collected from the industry and its effect on the concrete mix has been investigated by incorporating marble dust as partial replacement of cement as 10%, 15% and 20%. Steel fibres in different proportion such as 0%, 0.5% and 1% were added by volume of concrete. Mechanical properties such as compressive strength, splitting tensile strength and flexural strength were determined for all the combinations of marble powder and steel fibre. Durability properties such as drying shrinkage and sorptivity were determined and the obtained results were compared with control concrete. Further, using Taguchi based grey relational analysis optimisation of marble powder and steel fibre was carried out.
The present study investigates different replacement percentages of metakaolin (MK) in ternary blends of ordinary portland cement (OPC), fly ash (FA) and MK for achieving high early strengths in cement concrete. OPC is replaced by 10%, 13% and 16 % MK while 15% FA is uniformly used in all the mixtures. The tests for compressive strength, splitting tensile strength and flexural strength at 7 days and 28 days periods reveal that 7 days strengths at par with the control concrete can be achieved in OPC-FA mix by MK addition. The mix with 10% MK gives highest 7 days compressive strength.
