The basic objective of any cement composite is to achieve high strength and improve durability to withstand a longer life span. The present work discusses, the behavior of cement composite with the replacement of cement by an ultrafine material called Alccofine (1203) at 0, 5, 10, 15, 20 % and ground granulated blast-furnace slag (GGBS) at 30 % for M60 grade of concrete. A constant water cement ratio of 0.3 is adopted, to enrich workability a super plasticizer is used. For casting and curing normal procedures are followed as per IS code. To access the mechanical properties, strength and durability tests are conducted on concrete specimens. The strength aspect is maximum at 15 % Alccofine and 30 % GGBS replacement. From the water permeability test it is concluded that there is no seepage of water in all mixes. Hence the concrete is highly durable by the addition of Alccofine. As per ASTM C1202[1], the chloride permeability is very low in all the mixes.
Concrete is the core material of construction that has industrially made of calcareous mixture-cement as one of its core component. The use of large quantities of cement produces increasing CO2 emission, and as a consequence the green- house effect. A method to reduce the cement content in concrete mixes is to use mineral admixtures of various kinds which yields the desired results with lesser cement content, there are various admixtures for high strength concrete one of which is nanosilica that has been obtained from olivine of industrially produced by synthesis, these commercially available nanosilica (10 to 50 nm) attains a saturated yield state and decreases in yield strength on further increase in concentration of nanosilica. This research work aims to check the concrete with nanosilica dosage that has any effect on various mechanical and durability properties when compared to conventional concrete. Concrete samples were casted with incrementally varying dosage of nanosilica using M40 grade of concrete as per Indian standard design and M60 grade of concrete as per American standards. Casted specimens were tested for compressive, splitting tensile strengths for a curing period of 7 days and 28 days, and durability properties such a water absorption and acid test for a varying curing periods.
Chloride diffusion coefficient is determined in control concrete and with partial replacement of cement by fly ash, silica fume and slag in binary and ternary blended mixtures. Diffusion coefficients obtained from short and longer duration methods are compared, and the relationship between them is established. Binary/ternary blended concrete exhibits a chloride diffusion coefficient typically 6-7 times less than that for concrete without mineral admixtures. Rapid chloride ion permeability test (RCPT) gives the lowest value of the chloride diffusion coefficient whereas salt ponding test gives a substantially higher chloride diffusion coefficient among all the tests. An equation is proposed to predict chloride diffusion coefficient for binary/ ternary blended concrete from RCPT values. Nernst Plank, and Olek equations can be used for calculation of chloride diffusion coefficients from the values of Coulomb obtained in RCPT. Prediction of equivalent chloride diffusion coefficient of bulk diffusion test can be made from the rapid migration test result with highest level of confidence. Reinforced concrete structures containing binary/ternary blended concrete exhibit a service life double than that of concrete without a mineral admixture.
An experimental exploration was done to study the impact of recycled plastic waste granules as partial substitute for fine aggregate in normal-strength concrete. The volume of M-sand in conventional concrete proportioned for M30 grade was altered with 5, 10 and 15 percent plastics granules. Furthermore, 10 % by-weight of total aggregates in the plastic aggregate mixture was replaced with waste glass cullet was also investigated. The strength related properties of the plastic aggregate concrete showed decrease with increase in plastic replacement levels. A maximum of 13 % loss was observed in compressive strength and a 6.5 % loss in flexural strength. The modulus of elasticity property encountered a maximum loss of 4.5 % when compared to the control conventional mixture. The maximum slump loss of about 14 % was observed in the mixture with 15 % plastic aggregate concrete mixture. The dry unit weight of the plastic mixtures showed reduction in the range of 0.4 to 1.4 %. Whereas, the crushed glass incorporated plastic aggregate concrete mixtures performed in the acceptable range comparatively. The results validate the use of plastic granule aggregate as partial replacement for fine aggregate in the production of lower grade concretes for non-structural members.
The demand for construction is increasing with the rise in population. It is necessary to check the construction performance and economy of the project in a developing nation. Delays in planning and execution are a proven challenge for the construction industry for a long time. It directly affects the construction performance and economy of the project. The earlier studies focusing on construction delays provide various evidence on causes, classification, and mitigation of delay factors. Even with all the evidence, construction projects in India continue to suffer from delays. The objective of this article is to examine the trends and focus of research on construction delays over the last two decades and identify the research gaps. The preferred reporting items for systematic reviews and metaanalyses (PRISMA) technique is used to assess the literature on construction delays. Classification and analysis of studies are carried out based on journal representation, year of publication, type, nature of the study, sector of study, and mitigation tools adopted. Finally, this paper suggests areas for future research focus based on the findings of the literature review to further address the issue of construction delays. The identified research gaps are sector-specific delay factors, the study of delay factors and their respective impact, the lack of standardization of building information modelling (BIM), and the impact of delays on the environment. The paper adds value by facilitating researchers to decide the focus area in delay studies and the scope for their future research not only from conceptual but also from methodological points of view.
