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Concrete Mix Design
Published in M. Rashad Islam, Civil Engineering Materials, 2020
The water–cement (W/C) ratio is the ratio of the weight of water to the weight of cement used in a concrete mix. A lower water–cement ratio leads to higher strength and durability. However, a lower water–cement ratio makes the mix difficult to handle and place on the job site. Plasticizers or superplasticizers can be used to increase the ease of working with concrete without adding more water. If such is used, the ratio of water to cement plus pozzolan, W/(C+P) is used. Pozzolan is a fly ash or blast furnace slag. It includes many other materials, such as silica fume, rice husk, ash, or natural pozzolans. Pozzolans also strengthen concrete.
Effects on Roller Compacted Concrete of Isfahan slag
Published in L. Berga, J.M. Buil, C. Jofré, S. Chonggang, Roller Compacted Concrete Dams, 2018
Pozzolan is defined as a silicious or aluminum silicious substance which itself has a poor capability of cementation but it could have chemical reaction with calcium hydroxide and changes into a compound capable of cementation. Slag could also acts like other pozzolans. The fineness of slag particles is important to ensure satisfactory results.
Composition and properties of Portland cements
Published in Anjan Kumar Chatterjee, Cement Production Technology, 2018
In the USA, the granulated blast furnace slag is defined in ASTM C 989 and the test methods are specified in C1073. The granulated blast furnace slag is classified into three grades on the basis of a “slag reactivity index” at 28 days (viz., 80, 95, and 115 grades). According to ASTM C 595, pozzolans are required to meet the stipulation of fineness, pozzolanic activity, and expansion as shown below:
Surface application of multifunctional compound to prevent and control combined chloride and carbonation corrosion in concrete
Published in European Journal of Environmental and Civil Engineering, 2023
Ashish Kumar Tiwari, Shweta Goyal, Vijay Luxami
The use of pozzolanic cement in the construction industry is increasing from the past few years due to its sustainability and structural benefits. The incorporation of fly ash modifies the mechanical properties, permeation characteristics, and chemical composition of concrete. In corrosive environment, addition of fly ash improves the chloride diffusion coefficient, electrical resistivity and chloride binding capacity of concrete (Andrade & Buják, 2013; Angst, 2018; Florea & Brouwers, 2014; Hu & Poon, 2022; Jung et al., 2018; Thomas et al., 2012), but the rate of carbonation becomes 2–4 times higher in PPC concrete than OPC based concrete (Justnes et al., 2020; Lye et al., 2015, 2016; Morandeau et al., 2015; Stefanoni et al., 2018; Younsi et al., 2013). Thus, making the embedded rebar more vulnerable to corrosion (Aguirre-Guerrero et al., 2016; Hren et al., 2021). The severity of this problem increases when PPC concrete is exposed to combined environment as it decreases the steel resistivity (Aguirre-Guerrero et al., 2016) and increase the available chloride concentration (Montemor et al., 2002). The rate of corrosion is bound to increase in PPC based concrete after being subjected to combined environmental condition irrespective to their sequence of exposure (Hren et al., 2021; Ye et al., 2016).
Potential use of activated Algerian natural pozzolan powder as a cement replacement material
Published in European Journal of Environmental and Civil Engineering, 2021
Goufi Nourredine, Djamel Elddine Kerdal, Kaid Nouria, Idir Rachida
The effectiveness of the pozzolan calcination process was established, according to the evolution in compressive strength of the natural and calcined pozzolan pastes prepared with distilled water at 350°, 550°, 750° and 950 °C. Figure 7 depicts the increase in compressive strength for all samples using thermally treated pozzolan. At 7 days, calcination at 550° and 750 °C showed maximum compressive strength values, with 97% improvement over PZNE-20. Calcination at 350 °C led to the smallest increase (52%). This same trend was observed at 28 days with a slight improvement in strength for PZCE-750 samples, and the difference with PZCE-550 samples did not exceed 20%. The increase in short-term strength noted at the various calcinations temperatures could be correlated with the disorders created in the pozzolan crystal lattice by the pretreatment process and by the presence of more amorphous phases. Alexander (1960) and Hamidi et al. (2013) attributed the strength increase of calcined materials to the presence of a highly-reactive disturbed layer of material that forms on the surface of siliceous mineral particles, similar to the case of grinding that affects the reactivity of pozzolanic materials. This tendency favours additional consumption of the Portlandite by the newly created amorphous phases, which in turn improves the strength values.
Compressive strength and durability properties of pozzolan obtained from co-fired clay and rice husk
Published in Cogent Engineering, 2020
Mark Bediako, Albert A. Adjaottor, Simon K.Y Gawu, Eric Opoku Amankwah
Itim et al. (Itim et al., 2011) mentioned that shrinkage prediction is of very great essence for durability study and the inclination for long term functioning of concrete structures. Drying shrinkage is the loss of moisture (due to drying) from the concrete or mortar to the environment. Aside drying shrinkage, autogenous shrinkage is also a type of shrinkage that is widely gaining attention. Autogenous shrinkage is caused by a reduction in the pore relative humidity as a result of hydration products formation (Jensen & Hansen, 1996). Structural deformation due to shrinkage is well known to be the origin of cracks and even more rarely failure of concrete structures (Hua et al., 2017; Tam et al., 2012). Pozzolans are widely known as a material suitable for all cement-based products including concrete and mortar (Ballim & Graham, 2009; Bediako, Purohit et al., 2017; Fernandez et al., 2011). It has also been used successfully in refining pore structure and restraining shrinkage of cement-based products (Bao-guo et al., 2007; Khatib, 2004; Khatib & Hibbert, 2005).