Cement In Concrete Production Research Articles

INFLUENCE OF TECHNOLOGICAL FACTORS ON FOAM CEMENT CONCRETE FORMATION MIXTURES AND PRODUCT PROPERTIES

Summary In this paper, 250–500 kg/m3 density autoclave hardened foam cement concrete production technology influence on some of its properties made using Portland cement is discussed. Raw materials composition is given in Table 1. Foam for the production of good quality foam concrete products should meet the following requirements: 1) be stable and mechanically strong, because it should hold the foam concrete weight until the mixture hardens; 2) be temperature resistant, because due to binder hydration the mass temperature reaches 50–60 °C; 3) have a high recurrence, because the foam components slow down the binders hydration. The experiments have shown that the best foamier is Sulfonol and bone glue as a stabiliser for autoclave foam concrete. The formation of fixed density foam concrete products is very complicated problem. The foam cement concrete density dependence on its formation mixture density is derived by equation 4. When 1 dm3 foam cement concrete mixture is weighed, one can calculate the foam cement concrete density and immediately correct it, if necessary. We prepared foam with a recurrence of 20 and 50 and Sulfonol concentration of 1 and 2 % (Sulfonol and bone glue ratio 1: 0.2) to determine the foamier amount influence. The same amount of foam was used (3 dm3/kg per solids), when foam cement concrete mixtures were formed. The results given in Table 2 show that, when different amount of surface active materials are used, we get different foam and foam cement concrete mixtures as well as product density values. Foam cement concrete mass due to different foam concentrations and recurrence slow down the binding materials hydration and a mass temperature difference is observed (Fig 1). It was found that the block can be cut up in products when the mass plasticity strength reaches 0,0012 N/mm2. Product compression strength increases by 10—20 % (Table 2) when higher recurrence foam is used. A 2% Sulfonol foamier (Sulfonol: bone glue 1: 0.2 composition) was chosen for further experiments, using whipped foam recurrence of 50. Foam cement concrete densi-ty depends on the amount of foam used (Fig 2). Foam Reccurency influence on Foam cement concrete properties is given in Table 3. The use of larger V/K ratio, contrary to gaseous cement concrete, does not lower the foam cement concrete product density, because the same amount of foam is added to a larger volume. The most optimal way to produce foam cement concrete is when the V/K ratio changes from 0.6 to 0.7 (Fig 2). Foam cement concrete density dependence on technological operations regressive equation was derived. Closed pores dominate in the foam cement concrete structure and that is the reason why its heat conductivity is lower. Equal density gaseous silicate concrete, foam gaseous silicate concrete and foam cement concrete was made for comparison of results. The results (Table 4) show that foam cement concrete has the best heat conductivity and it is confirmed by the samples air resistance.

ポリエステルレジンコンクリートの強度に及ぼす影響

Generally, the steam curing method is adopted as an accelerated curing method of cement concrete products, but very few reports concerning the properties of steam-cured polyester resin concrete have appeared until now, in fear of hydrolysis of polyester resin by hot water or steam. In precast polyester resin concrete factories, the relatively expensive heat cure method by circulation of hot air is usually adopted for curing of products. The objective of this study is to examine the possibility of applying steam cure to polyester resin concrete in the same manner as cement concrete.Polyester resin concrete (polymer concrete) is mixed with variable catalyst or accelerator content for liquid resin in selected mix proportion, and the resin concrete specimens are prepared under various steam-curing conditions. The cured resin concrete specimens are tested for tensile and compressive strengths. The test results indicate that, in the catalytic system for ordinary temperature cure, the strength development of polyester resin concrete is accelerated by steam cure without noticeably harmful hydrolysis of polyester resin observed.

THE HYDRATION OF THE ALUMINATES OF CALCIUM: IV. HYDROTHERMAL REACTIONS OF TRICALCIUM ALUMINATE AND ITS HYDRATES

A study was made of the hydrothermal reactions of tricalcium aluminate and its hydrates between 120° and 350 °C. Homogeneous samples of the hexahydrate of tricalcium aluminate may be prepared by treatment of the aluminate or its hexagonal hydrate in saturated steam at temperatures up to 150 °C. At temperatures of 250 °C. and above, under conditions favouring rapid hydrolysis, such as the addition of water to the anhydrous aluminate or hydroaluminate before autoclaving and rapid elevation of the temperature of the autoclave, crystals of calcium hvdroxide and of a hydroaluminate of lower lime–alumina ratio appear, usually mixed with the isometric hexahydrate. The new hydroaluminate occurs as rectangular, elongated, prismatic plates of low birefringence, refractive index 1.627, and has a lime–alumina ratio probably lower than 1.5. The hexagonal hydrate of tricalcium aluminate gives on hydrothermal treatment a better yield of the low-limed hydroaluminate than does the anhydrous aluminate. Only partial hydrolysis of the hexahydrate was obtained under any of the conditions used, but the hexagonal hydrate, autoclaved for 12 hr. at 350 °C., gave products composed almost entirely of the rectangular plate hydroaluminate and calcium hydroxide. No free hydrated alumina was found in the hydrothermal products.The rectangular plate hydroaluminate of calcium may also be prepared by the action of calcium hydroxide on hydrated alumina in saturated steam at 350 °C. It is therefore a stable product under those conditions.At temperatures below 250 °C. birefringent crystalline material is also formed on autoclaving tricalcium aluminate or its hydrates under conditions favouring hydrolysis. The experimental evidence indicates that one of the products is the birefringent calcium hydroaluminate formed on autoclaving the lower calcium aluminates at temperatures of 105 to 150 °C. (5).Precast Portland cement concrete products, when subjected to steam-curing, normally contain an excess of water, and the conditions for the formation of these birefringent hydroaluminates of calcium are therefore present. The same applies to the commercial steam-curing of other materials containing free lime and hydrated alumina. The formation of these hydroaluminates may explain the peculiar effect on the tensile and compressive strength of mortar and concrete test pieces produced by hydrothermal treatment at temperatures above 150 °C. (9).