High early strength Portland cement

Concrete, Mortar, and Plaster. Citric acid and citrate salts are used as admixtures in concrete, mortar, and plaster formulations to retard setting times and reduce the amount of water requited to make a workable mixture (172—180). The citrate ion slows the hydration of Portland cement and acts as a dispersant, reducing the viscosity of the system (181). At levels below 0.1%, citrates accelerate the setting rate while at 0.2—0.4% the set rate is retarded. High early strength and improved frost resistance have been reported when adding citrate to concrete, mortar, and plaster. 

Type III High-early-strength (HES) cements are made from raw materials with a lime-to-silica ratio higher than that of Type I cement and are ground finer than Type I cements. They contain a higher proportion of calcium silicate than regular portland cements. 

High-early-strength portland cement as specified in JIS R 5210 (Portland Cement) was used in all the mortar mixes for artificial woods. 

Two types of pulp sand mortar were used as the core plate of sandwich specimens. Mortar of Type M was made by mixing high-early-strength Portland cement, silica fume and pulp sand. Mortar of Type P was made directly with pulp sand. Mix proportions of each type of mortar are shown in Table 1 and Table 2. Pressurized forming was used to produce mortar plates of each type, whose pressure was lOMPa. Then specimens were put in a moist room of 20 C for about one day. After steam curing at 50 C for 24 hours, they were autoclave-cured on condition of 180 C for 3 hours. Finally they were dried out in an electric oven of 110 C for 24 hours. The geometry of the specimen was 50x10x200 (mm). 

Portland cements are available commercially in many different forms, including varieties for high early strength and for sulfate resistance and very finely ground materials called microfines. 

There are four distinctly different types of Portland cement. Only types I and II are used for grouting, type I (often referred to as ordinary Portland cement), almost exclusively. Type II (high early strength cement) differs from type I primarily in its finer particle size. This provides more reactive surface area, and thus more rapid setting, often desirable in structural work. Grouters, however, are more interested in the finer particle size, which permits penetration into finer voids and cracks. Typical grading analysis of various cements are shown in Figure 9.1. 

When a high early strength is required, such as for post-tensioned structures or pre-tensioned precast elements, Portland cement with a strength class of 52.5 may be used. Blended cements are usually not suitable because of the slow rate of hydration, with the exception of Portland-silica fume cement and special (fast) slag cements. 

High-CjS chnkers are employed in the production of high early strength Portland cement (corresponding to ASTM Type HI cemerrt). To produce such cement, the clinker. 

The fineness of cement may be conveniently characterized by the Blaine method, even though the values obtained by this procedure are systematically lower than those found by the more accurate, but also more complicated, BET method. The specific surface area of ordinary Portland cement typically ranges between 280 and 350 m /kg (Blaine), whereas high early strength cement may be groimd up to a specific surface area of 450-500 m /kg (Blaine). This higher smface area contributes to an accelerated hydration of the cement, but also increases its water requirement. 

CIMENT FONDU HIGH EARLY-STRENGTH cement HYDRAULIC CEMENT KEENE S cement PORTLAND CEMENT RAPIDHARDENING PORTLAND cement REFRACTORY CEMENT, SILICATE... 

AljOj + Fe203) in a hydraulic cement. In Portland cement this modulus usually lies between 2 and 3. A cement with a low silica modulus can be expected to have high early strength, but if this modulus is high the final strength will be the greater. 

Only for cements with low heat of hydration and/or high sulphate resistance Portland cement, Eisen portland cement, Hochofen cement and trass cement with slow early hardening behaviour are additionally given the symbol L, while the symbol F is added to cements with high early strength... 

RHC Rapid-Hardening (or High Early Strength or High Initial Strength) Portland Cement / Portlandzement mit hoher Fruhfestigkeit/schnellerhartend... 

CEMENT, PORTLAND. While in the fluid state, Portland cement causes etching of aluminum alloys as indicated in laboratory tests and in service applications. After the cement has set, no further corrosion occurs as a result of a protective film forming on the aluminum. Galvanic corrosion will develop If aluminum is coupled to dissimilar metals in cement or concrete to which chlorides have been added for high early strength. Aluminum alloys have been used for freight cars, hopper cars, and tote bins handling cement. Aluminum has also been used successfully for racks and pallets in the concrete block industry, molds and forms, and terrazzo divider strips. See also Ref (Dp. 129, (2) p. 161, (3) p. 228. 

Although many Ca-rich fly ashes are self-cementing, strength gain is usually too slow for most practical applications. Moreover, aluminosilicate rich ashes are essentially unreactive with water. The most important application of fly ash is as a partial replacement for Portland cement. In this application, Portland cement furnishes much of the early strength, up to 1 month, while the high alkalinity of cement chemically activates the ash such that its slow reaction with cement components and water contribute increasingly to... 

Cement was chosen for the present study because of its low cost, simplicity of use, and stability in most environments. It is, however, rather porous. Also, in the presence of water, hydrolysis reactions promoted by the high pH of the cement can cause conversion reactions resulting in the release of iodine from many compounds. Type III Portland cement was chosen because of its early strength (curing time 8 days). 

The depth of carbonation as a function of concrete strength is shown in Fig. 6.71 [307]. There is a large ntunber of data indicating no special difference in carbonation process of Portland and other cements, as their strength is similar [301, 308, 309]. Only in the case of low quality concrete with high w/c ratio and porosity, these concretes produced from Portland cement show better resistance to carbonation. One can explain the difference by higher total porosity of concrete with mineral additiorrs at early age however, their permeability after longer period of time is markedly improved (Table 6.9) [310]. 

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