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Cement
Published in A. Bahurudeen, P.V.P. Moorthi, Testing of Construction Materials, 2020
[IES 2019] Which one of the following statements is not correct with respect to the properties of cement? Highly reactive pozzolanas enhance the early age strength of the composite cement.Pozzolanic activity refines pore structure, which decreases electrolytic resistance of concrete.The expansion due to alkali silica reaction can be controlled by the replacement of as high as 60% of OPC with high calcium pozzolana.Such high amounts of replacement cements result in higher accelerated carbonation depths compared to the pure use of OPC only.
The Effectiveness of Shrinkage Reducing Admixture and Fly Ash on Plastic Shrinkage of Concrete
Published in P. C. Thomas, Vishal John Mathai, Geevarghese Titus, Emerging Technologies for Sustainability, 2020
Jerison Scariah James, Elson John
In addition to SRA, supplementary cementitious materials can also improve the durability properties of concrete. The supplementary cementitious materials contribute to the properties of concrete through pozzolanic activity. Typical examples are fly ash, ground granulated blast-furnace slag or GGBS, silica fume, rice husk ash, and metakaolin. Among these, fly ash is the most commonly used material in the industry. Fly ash, which is the by-product of thermal power plants, is the most widely used pozzolanic material in the industry. It is available as a finely divided residue that results from the combustion of pulverized coal. Use of shrinkage reducing admixture is an effective way to reduce the shrinkage of concrete. However, the use of such admixtures can lead to secondary effects like reduction in strength, increase in workability, etc. Fly ash improves the compressive strength of concrete but the effect of these materials on shrinkage deformation behavior is not well defined, so there is the need for study in this area. The coupled interaction of fly ash and SRA on concrete is still miscellaneous.
Materials and RCC quality requirements
Published in L. Berga, J.M. Buil, C. Jofré, S. Chonggang, Roller Compacted Concrete Dams, 2018
Some mineral admixtures can show pozzolanic activity (fly ash, natural pozzolan and calcined clay-Figure 2), some others are cementitious (ground-granulated blast-furnace slag), whereas others are both cementitious and pozzolanic (high-lime fly ash)
Laboratory study and performance evaluation of cement treated base using chemical stabiliser
Published in Road Materials and Pavement Design, 2023
Supriya Marik, G. D. Ransinchung R. N., Aditya Singh, Lt. Prathmesh Khot
Moreover, on the addition of 4% stabiliser to these varying percentages of cement, the samples displayed an increase in strength. All samples depicted same trend of rising in strength with the increase in curing time. It has been also noticed that samples have attained sufficient strength within the first 7 days curing period. Though the strength gained by all samples later met the minimum standard of 4.5 MPa mentioned in IRC SP: 89:2018 (Part-II) (IRC: SP: 89 -, 2018). To make the construction economically viable and to curb the possibility of formation of thermal cracking, the mix with Soil + 4% cement + 4% Stabiliser was adopted to be the optimum content. Further on analysing SEM images of samples after UCS test, it was noticed that, incorporation of this stabiliser to the mix led to replacing CH bonds with the formation of stronger CSH gel compounds. These CSH bonds further led to progressive increment in the compressive strength. Pozzolanic activity is directly correlated to the surface area of the particles available in the mix. Higher the pozzolanic activity and larger will be the consumption of the produced calcium hydroxide (CH) during cement hydration process. This whole process leads to the formation of gelatinous compounds which form large interconnected networks between the soil particles and later enhances the strength of soil matrix (Currin et al., 1976; Sariosseiri & Muhunthan, 2009).
Cement-treated pavement layers incorporating construction and demolition waste and coconut fibres: a review
Published in International Journal of Pavement Engineering, 2022
João Crucho, Luís Picado-Santos, José Neves
With regard to the application of RA from CDW in cement bound granular mixtures (CBGM), whether in laboratory (Pasetto 2000, Xuan et al.2010, Ebrahim Abu El-Maaty Behiry 2013) or with experimental tracks (Agrela et al. 2012, Qamhia et al.2019, Stehlik et al.2016), the number of studies is still limited. Also, other industrial waste materials (e.g. steel slag, waste foundry sand, ladle furnace slag, glass wastes and coal ash) were already studied to be incorporated as aggregate in CBGM (Pasetto and Baldo 2013, 2015, 2016). In this case, the RA from CDW can be particularly interesting to use in CBGM, as the recycling process may release some of the residual not hydrated cement stored in the adhered mortar, thus enabling an additional cementation process (re-cementation). This re-cementation process may allow a reduction of the added cement required for the new CBGM. In addition, ceramic waste, such as clay brick and tiles, has potential for pozzolanic activity, which can enable savings in cement dosage (Ge et al. 2015, Wong et al. 2018, Zhu and Zhu 2020).
Effectiveness of using Metakaolin and fly ash as supplementary cementitious materials in pervious concrete
Published in European Journal of Environmental and Civil Engineering, 2022
Tarunbir Singh, Rafat Siddique, Shruti Sharma
Metakaolin which is a dehydroxylated form of kaolinite mineral is obtained by calcination of kaolinite clay from 500 °C and 800 °C. It contains a significant amount of silicon dioxide and aluminium oxide (about 99%) which reacts with the hydration products of cement to produce C-S-H and C-A-H products leading to strength enhancement. Also it leads to increased pozzolanic activity with pore structure refinement which provides strength to concrete. Various researchers have suggested replacing cement with MK to improve the microstructure, hydration, and nano-mechanical properties of concrete (Dinakar et al., 2013; Poon et al., 2001; Saboo et al., 2019). Replacing cement with MK reduced porosity and increased density in concrete and suggested 10% as the optimum replacement level of MK in concrete (Sata et al., 2016; Mineral Commodity Summaries (USGS), 2020). Poon et al. (2001) used MK at an early age to investigate the pozzolanic reaction in high-performance cement pastes utilizing FA. It was reported that pozzolanic reaction and CH consumption were higher in MK than in FA blended cement pastes. But after 28 days, the rate of pozzolanic reaction becomes slower. Use of MK also improves the carbonation resistance and sorptivity of concrete (Siddique & Khan, 2011). Gill and Siddique (2017) used MK in varying proportions to prepare Self Compacting Concrete (SCC) mixes and concluded that the use of MK significantly improved the strength and micro-structural properties of SCC. Güneyisi et al. (2012) investigated the effect of MK with different water-cementitious ratios on strength, permeability, and shrinkage cracking of concrete. They revealed that MK improved the strength and durability properties of concrete.