China
Africa
Explore chapters and articles related to this topic
Portland Cements
Published in M. Rashad Islam, Civil Engineering Materials, 2020
The word cement describes a material which can bind two materials together. In civil and construction engineering, cement specifically means Portland cement, which can bind aggregate or stone pieces together and is used in binding civil engineering materials. Portland cement gets its name from the resemblance of the color of the hardened cement to Portland stone found in Dorset, England. The production of Portland cement broadly consists of heating crushed raw materials in a kiln at 1,480°C. The burned material, called the clinker, is cooled down, ground again, and different materials (such as gypsum) are added to obtain special properties. If water is mixed with cement, each component of cement reacts with water and hardens slowly. There are different types of cement, such as normal cement, normal-air entraining, moderate sulfate resistant, etc. These properties are gained by adding special materials with the clinker during production.
CERN (HL-LHC): New underground & surface structures at Point 1 & Point 5
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2019
A. Canzoneri, J. Amiot, F. Rozemberg, D. Merlini, F. Gianelli, G. Como, F. De Salvo, C. Helou, L.A. Lopez, P. Mattelaer
Four main rock types were identified within the Molasse as follows. Sandstone and marly sandstone vary from soft/poorly-cemented (UCS < 20 MPa) to very hard/cemented (UCS >35 MPa). They are composed of 40-70% Quartz, 5-10% Feldspar, 5-20% clay/mica and 5-45% calcareous cement. Stronger rocks are finer grained and more cemented.Sandy marls have these proportions: 20-45% of clay, 20-40% of quartz and 20-30% of calcite.Platy marls (also called marl “fissile”/“feuilletée” in French) can be assimilated to shales. They are composed of 45-60% clay, 15-30% of micro-crystalline quartz, and 20-30% calcareous minerals. The dominant clay is illite (swelling), but smectite (swelling) and chlorite (non-swelling) can also be present at up to 18%.“Grumeleuse” Marl is characterised by numerous closed, polished, discontinuous multidirectional, curved micro-fissures. It can sometimes be referred to as mudstone.
Guidelines of geomechanical and engineering-geological research on subsurface microbiota impact on hard rocks in the underground space of megalopolises
Published in Vladimir Litvinenko, EUROCK2018: Geomechanics and Geodynamics of Rock Masses, 2018
Experience gathered from microbiological investigations of underground space in megalopolises during its development and use is indicative of the fact that not only sandy-clayey soils are strongly vulnerable to the subsurface microbiota activity, but some types of hard rocks as well. These include many deposits of sedimentary genesis: calcareous rocks (limestone, dolomite rock, chalkstone), cemented clastic rocks (with various cement composition) – sandstone, conglomerate, breccia, argillite and siltstone. Under the action of active metabolites of subsurface microbiota (mineral and organic acids, soluble and slightly soluble gases, enzymes) carbonate rocks are transforming into some sort of residual deposits, or increases the rate of carbonates dissolution and leaching, which leads to the development of technogenic karst. The deterioration of cement in terrigenous rocks promotes the transition of hard rocks into different, loose types of sediments—sands, clayey sands, large detrital rocks.
Consolidated drained behaviour of PVA fibre reinforced cemented Toyoura Sand
Published in International Journal of Geotechnical Engineering, 2022
Muhammad Safdar, Tim Newson, Colin Schmidt, Kenichi Sato, Takuro Fujikawa
Overall, sand-cement-fibre composites have been observed to be more effective when specimens are cured for longer durations. These findings are likely to be due to a better contact between the sand-cement-fibre matrix bonding, and cement hydration due to a longer curing period. The cement not only bonds particles together (with some sand particles completely surrounded by the cement) but also fills some of the pores as inclusions. Specimens cured for only 3 days, show an absence of significant and noticeable peak. However, it has been shown that a larger well-defined peak is observed when specimens are cured for 7 to 56 days. The dilatancy behaviour increases due to the addition of fibres and cement. This dilative behaviour has been attributed to cemented particles forming highly interlocked clusters. The results presented here are generally in close agreement with the results presented by previous researchers (e.g. Coop and Atkinson 1993; Consoli, Prietto, and Ulbrich 1998; Consoli et al. 2009; Wang and Leung 2008).
Characteristics of cement-stabilized macadam containing surface-treated recycled aggregates
Published in Road Materials and Pavement Design, 2021
Lingyun You, Yufei Yue, Kezhen Yan, Yubo Zhou
Cement concrete is the most widely used for building materials in civil engineering, for example, the rigid pavement structures, the bridge structures, and the multi-layered buildings. It is estimated that worldwide concrete production amounts to about six billion tons per year (Marinković et al., 2010). Because of the ubiquity of cement in modern construction, massive consumption of natural aggregates, the major cement concrete component, is rapidly and continuously increasing in increasing utilisation and production of concrete (Belin et al., 2014; Marinković et al., 2010; Rahal, 2007). This trend raises the question about the natural supply of aggregates. Similarly, construction and demolition (C&D) waste is a relevant concern for environmental protection. Currently, the most common method of managing C&D waste is through landfill disposal, which creates large non-decomposable deposits. The cost of such deposits is twofold. Firstly, the deposits burden landfill capacity. Secondly, the deposits have the potential to leach into soil and water, polluting natural resources and ecosystems (Hu et al., 2013; Turatsinze et al., 2005). As shown in Figure 1, recycling is a possible way to reduce the amount of C&D waste and to save the natural aggregate sources.
An experimental study on the cyclic settlement of sand and cemented sand under different inclinations of the bedding angle and loading amplitudes
Published in European Journal of Environmental and Civil Engineering, 2019
Alaa H. J. Al-Rkaby, A. Chegenizadeh, H. R. Nikraz
Cementation occurs when cement particles gather around sand particles that are in contact with each other, resulting in parallel interparticle bonding (Lo, Lade, & Wardani, 2003; Wang & Leung, 2008). This phenomenon depends on many parameters, such as soil fabric, void ratio and the cement type and content. This cementation contributes to the stabilisation of the overall sand structure (Gao & Zho, 2012), making it more like a single block. The particles change from being loosely arranged to being cemented together and, as a consequence, the soil behaviour is less dependent on particle properties such as angularity, shape, orientation and alignment. Interparticle bonding creates a stable structure that can sustain applied stresses as a single mass and reduce the susceptibility to behave as a granulate, i.e. anisotropic, material. When cemented sand is subjected to loading, all particles in the bonded network contribute to carrying the applied stress, resulting in force chain that is distributed in a webbed pattern (Wang & Leung, 2008). This makes soil more stable and eliminates dependence on individual particles.