http://nopr.niscpr.res.in/handle/123456789/36 Tue, 11 Aug 2026 13:59:30 GMT 2026-08-11T13:59:30Z http://nopr.niscpr.res.in/handle/123456789/67720 Title: Challenges in production and placement of alkali activated concrete for in-situ applications Authors: Trivedi, Amit; Goel, Rajeev; Kumar, Rakesh; Ghatak, Arup; Singh, Brijesh; Kumar, Rohit Abstract: Despite the significant decarbonisation potential of alkali-activated concrete (AAC), its adoption for in-situ structural applications remains limited due to challenges related to workability retention, ambient curing, batching-plant compatibility, and safe handling of highly alkaline activators. This study has presented a comprehensive demonstration of the successful scale-up, production, placement, and structural application of a two-part AAC system in a conventional ready-mix concrete (RMC) plant. An optimised AAC mix incorporating locally available ground granulated blast furnace slag (GGBFS) and fly ash in a 70:30 ratio has been developed to achieve structural-grade performance under ambient curing conditions. The AAC has exhibited compressive strength, flexural strength, and drying shrinkage comparable to OPC-based M35 concrete, while achieving significantly higher early-age strength development. A critical operational barrier - heat generation during alkaline activator preparation (about 70 - 80 °C) has been addressed through targeted batching-plant modifications, including a water-circulation-based cooling system that has reduced activator temperatures to 35–40 °C, enabling safe handling and continuous production. Compatibility of a modified sulphonated naphthalene formaldehyde (SNF)-based admixture has ensured stable rheology and workability retention, with a slump of approximately 135 mm after 60 min, facilitating pumping and placement using a boom placer. Full-scale field casting has confirmed dense, homogeneous structural elements with sharp surfaces and no evidence of efflorescence or leaching. The results have demonstrated that, with minor plant modifications and robust safety protocols, two-part AAC can be reliably produced and placed in an RMC environment, providing a technically viable pathway for sustainable in-situ structural concrete construction. Page(s): 9-19 Sun, 01 Feb 2026 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/67720 2026-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/67719 Title: Experimental study on comparison of equivalent concrete compressive strength of cores and rebound hammer tests with in-place and standard cubes Authors: Pran Borah, Nibir; Raj Jesu Arul Raj, Leon; Chidambaram Rajendran, Siva; Deori, Sanjay; Basumatari, Dipak; Das, Rajib; Tamilarasu, Chockalingam Abstract: This study has presented a comprehensive test program that has compared the following, namely, the compressive strength of concrete cores extracted from the plinth beam (PB) of a substation, the compressive strength of both concrete cubes cast for the trial mix and those cast at the time of construction of the plinth beam, and the compressive strength of the plinth beam as assessed with a rebound hammer. Even though various techniques have been available for structural evaluation, there have been significant uncertainties in correlating the actual compressive strength of concrete. The standard procedures have been applied to a case study of a substation at Silapathar, Assam, owned by PowerGrid Corporation of India. To evaluate the quality of construction, different accepted methods suggested by various codes, such as the Indian Standard, the American Society for Testing and Materials Standard, the American Concrete Institute Standard, and the European Standard, have been employed. Experimental results have indicated that the equivalent compressive strength of concrete based on the rebound hammer has been 15.11% higher than the in-situ concrete strength. Similarly, the equivalent compressive strength of the concrete cube estimated using European and Indian codes has been 22% and 27% higher than the experimentally measured core compressive strength. The expressions proposed for estimating equivalent cylinder compressive strength have closely predicted the core compressive strength, compared with expressions for estimating cube compressive strength. This information has been useful for practising engineers not to reject concrete solely based on the acceptance criteria of the cube compressive strength of in-situ concrete, and to accept concrete based on non-destructive or semi-destructive tests. Page(s): 20-35 Sun, 01 Feb 2026 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/67719 2026-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/67718 Title: Enhanced MPPT for PV systems using a two-stage hybrid fuzzy logic and P&O algorithm Authors: Kumar, Rajesh; Bhattacharya, Ananyo; Singh S Vardhan, Aanchal Abstract: Photovoltaic (PV) systems have converted solar irradiance into electrical energy through PV cells that exhibit nonlinear voltage-current (V-I) characteristics. A key feature of these characteristics has been the maximum power point (MPP), where the product of voltage (V) and current (I) has reached its maximum, enabling optimal power extraction. The efficient operation of a PV system has required rapid and accurate Maximum Power Point Tracking (MPPT), especially in dynamically changing environmental conditions. This paper has presented a hybrid MPPT approach that has combined a Fuzzy Logic Controller (FLC) with the conventional Perturb and Observe (P&O) algorithm. The proposed two-stage control scheme has continuously identified and adjusted the MPP in response to variations in irradiance and temperature, including partial shading (PS) scenarios. In the first stage, the FLC has provided an intelligent initial estimate of the MPP region to improve the convergence speed of the P&O algorithm. In the second stage, another FLC has dynamically adjusted the step size of the P&O algorithm to improve response and reduce oscillations. The hybrid FLC-P&O algorithm has been validated through simulations under various conditions, including steady irradiance, sudden changes in sunlight, and partial shading of varying severity. The results have demonstrated that the proposed controller has achieved high tracking efficiency and has effectively overcome the limitations of the conventional P&O algorithm, particularly under non-uniform and rapidly changing environmental conditions. Page(s): 36-50 Sun, 01 Feb 2026 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/67718 2026-02-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/67717 Title: Developing fired bricks from drinking water sludge and fly ash using cow dung and rice husk biomass wastes as internal fuel Authors: Vachasiddha, Leena; A Tandon, Shalini; Kumar, Rakesh Abstract: The improper disposal of biomass waste has remained a persistent environmental and public health challenge due to inadequate disposal practices and governance gaps. This study has investigated a sustainable recycling approach by incorporating biomass waste with other industrial by-products, such as drinking water sludge and fly ash, in the production of fired bricks. This research has examined the utilization of cow dung and rice husk as internal fuels, combined with varying proportions of two main wastes—drinking water sludge and fly ash. The results have indicated that the highest compressive strength achieved has been 5.67 MPa, with bricks utilizing cow dung as an internal fuel having demonstrated marginally better performance compared to those using rice husk. The findings have highlighted the viability of producing non-load-bearing bricks using these waste materials, suitable for applications such as boundary walls, jogging tracks, temporary shelters, and similar structures. This study has underscored the potential for waste valorization in the brickmaking industry, thereby has contributed to waste management solutions and has promoted environmentally sustainable construction practices Page(s): 51-59 Sun, 01 Feb 2026 00:00:00 GMT http://nopr.niscpr.res.in/handle/123456789/67717 2026-02-01T00:00:00Z