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Proportioning Concretes
Published in Avijit Chaubey, Practical Concrete Mix Design, 2020
Next, the water content is found and is based on Equations 2.3 or 2.4, whichever is applicable. Equation 2.4 is to be used only when the cement content (in the next step) is higher than 450 kg for 20 mm MSA and 500 kg for 10 mm MSA for any other case, eqn 2.3 is to be used. The water content calculated for the required workability is the water to be added into concrete, in addition to the water that will be required to bring the aggregates to saturated surface dry condition from its natural condition. Saturated-surface dry (SSD) is a condition in which all the pores of the aggregates are filled with water, but the surface of aggregate is fully dry. If the aggregates in natural condition are wetter than SSD condition, water has to be deducted from the values calculated, and if it is drier, then additional water should be added. The steps are thoroughly explained in Chapter 8. The formulas given for water content are based on a visual rating of aggregates of 3 as per Figure 2.1.
Composition
Published in J. Cliff Nicholls, Asphalt Mixture Specification and Testing, 2017
The European standard for bulk density, EN 12697-6 (CEN, 2012f), has four procedures: The dry procedure involves comparing the weight in air to the weight in water and assumes that all accessible voids are excluded and, as such, is suitable for mixtures with few voids.The saturated surface dry (SSD) procedure is similar but the weighing in air is after being submerged following which any water on the surface is removed by blotting, so that only internal voids in which water remains are excluded and, therefore, is suitable for mixtures with a few more voids than the dry procedure.The sealed specimen procedure again compares the weight in air and the weight in water but the specimen is sealed prior to both weighings so that all voids enclosed are included in the results and is suitable for mixtures with many voids. The weight of the sealing matter has to be allowed for in the calculation.The procedure by dimensions compares the weight in air with the volume by measurement and is suitable for very open mixtures like porous asphalt.
Concrete and Its Application in Concrete Gravity Dam
Published in Suchintya Kumar Sur, A Practical Guide to Construction of Hydropower Facilities, 2019
Physical properties of aggregates are also very important for the good performance and serviceability of concrete. Physical properties are as follows: Specific gravity of aggregate is essential for calculation in mix design.Porosity and absorption: Porosity has influence on the strength of concrete. Porosity of cement paste increases with the increase of the Water-Cement Ratio, and reduces the strength of concrete.Durability of concrete depend on permeability. Low permeability improves resistance to percolation of water which carries deleterious substances like chlorides, sulphates, alkali, and other substances that may affect the health of concrete.Water absorption is also a vital parameter for the performance of concrete. An aggregate is said to be saturated when all pores are filled with water.An aggregate is said to be in Saturated Surface Dry Condition (SSD) when only the surface is dry but the pores are filled with water.Moisture content of aggregates is the water content when water is in excess of set SSD conditions and total water content can be calculated by adding absorption and moisture.
Influence of the replacement of fine copper slag aggregate on physical properties and abrasion resistance of pervious concrete
Published in Road Materials and Pavement Design, 2021
Ali Rezaei Lori, Arash Bayat, Amirmokhtar Azimi
The basic mixture design of pervious concrete (PC) was selected based on ACI Committee 522 (2010) recommendation and the results of previous studies (Shirgir, Hasany, & Goodarzi, 2011). The natural fine dolomite aggregates were replaced with fine CS aggregate for all the concrete mixtures at 0%, 20%, 40%, 60%, 80%, and 100% levels by the volume of the aggregate. Details related to the concrete mix proportions are listed in Table 3. The water-to-cement ratio and the amount of cement content for all mixtures were 0.3 and 340 kg/m3, respectively. Further, the aggregates were used in the saturated surface dry (SSD) condition and an increase in CS led to a decrease in the water needed for the SSD condition. All the test mixtures were combined, compacted, and cured based on the procedure specified in ASTM C192 (2018). Initially, coarse aggregates and 5% cement were mixed for 60 s in order to coat the coarse aggregates. Next, sand, the remaining of cement, and water with superplasticizer was added and mixed for 180 s and then the mixture was rested for 180 s. Finally, the mixing process was continued for 120 s. Furthermore, the mechanical mixer was covered by polyethylene sheets during the mixing stages in order to avoid water evaporation. Then, the moulds were covered with plastic sheets and kept in a humidity cabinet at a temperature of 23 ± 2°C for 24 h. Eventually, the specimens were removed from the moulds and immersed in water in a container kept at a temperature of 23 ± 2°C for 27 days.