This paper discussed the effects of modified metakaolin (MK) with nano-silica (NS) on the mechanical properties and durability of concrete. In the first phase, trial mixes of concrete were prepared for achieving the desired value of the 28 days compressive strength, and the charge passed in rapid chloride permeability test (RCPT). In the second phase, statistical analysis was performed on the experimental results using the response surface method (RSM). The RSM was applied for optimizing the mix proportions for the required performance by exploiting the relationship between the mix characteristics and the corresponding test results. A blend of 10% MK + 1% NS as part of cement replacement exhibited the highest mechanical properties and durability characteristics of concrete; concrete mix showed that the 28-days compressive strength (CS) was 103 MPa, which was 15% greater than the CS of the control mix without MK or NS. The same mix showed more than 40% higher flexural and split-tensile strength than the control mix; also it resulted in a reduction of 73% in the rapid chloride permeability value. ANOVA technique was used for optimizing the nano-silica and metakaolin content for achieving maximum compressive strength and minimum RCPT value. Statistical analysis using ANOVA technique showed that the maximum compressive strength and lowest RCPT value could be achieved with a blend of 10% MK and 1.55% NS.
Mass concrete has been commonly known for its thermal stresses which arise due to the entrapment of hydration temperature susceptible to thermal cracking. The utilization of mineral additives is a promising and widely adopted technique to mitigate such effects. This paper presents the thermal, physico-chemical, mechanical, and morphological behaviour of mass concrete with blends of bentonite (BT) and fly ash (FA). Apart from the rise in temperature due to hydration, the compressive strength, ultrasonic pulse velocity (UPV), differential thermal analysis (DTA), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD) analysis, and microstructure were studied. The results of this study revealed that the substitution of BT and FA significantly improved the compressive strength and development rate of UPV in the mass concrete samples. The FA concrete (FC) specimen presented the lowest temperature during the peak hours compared to all other concrete mixes studied in this research. Bentonite concrete (BC) was also found to be more effective in controlling the escalation of temperature in mass concrete. Scan electron microscopy (SEM) micrographs presented partially reacted FA particles in a mix. XRD and DTA analysis indicated that the concentration of calcium hydroxide (CH) declined by substituting FA and BT, specifically in ternary blends, which was due to the dilution effect and consumption of CH through the pozzolanic reaction.
Concrete is widely used construction material for the development of built environment which consumes huge amount of cement, around 4.3 billion metric ton all over the world. Reinforced concrete construction exposed to harsh environment such as chloride bound air causes deterioration in concrete through its pore structure by corroding the steel bar. The use of pozzolanic material i.e. metakaolin (MK), fly ash (FA), silica fume (SF), nano silica (NS) can be used as partially cement replacing material which not only reduces the pores in concrete but improves the mechanical, durability properties and microstructure of concrete. This paper reviews various transport mechanisms involved in ingress of deleterious material and incorporation of MK, FA and NS in concrete and their effects on concrete mechanical and durability properties. However, the research work provides an extended approach to evaluate combine effect using MK, FA, and NS and to produce a concrete with more refined pore structure for aggressive environment.
Sugarcane bagasse is an agricultural waste that can be transformed by incineration into a cement replacement material for various cementing purposes. This study investigated the role of finely ground bagasse ash (GBA) in producing engineered cementitious composites (ECCs) with the addition of polyvinyl alcohol (PVA) fibers. The main focus of this study was to develop a green ECC with higher strength capabilities (compressive, tensile, and flexural) and greater tensile ductility. To develop this composite, GBA was added into ECC mixes at different proportions, i.e., 10, 20, and 30%. The proportions of PVA fibers and the water-to-binder ratio were kept constant. The results revealed that the ECC mix containing 10% GBA exhibited higher compressive strength compared to that of a control and the other ECC mixes. The tensile and flexural strengths of the ECCs exhibited patterns almost similar to that of compressive strength. Moreover, the deflection in the control mix was higher compared to that of the GBA-ECC mixes at an initial curing age. The ECC mix containing 10% GBA exhibited better ductile behavior among all the ECC mixes used in this study.
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