Influence of the Chemical Activation of Aggregates on the Properties of Lightweight Vibro-Centrifuged Fiber-Reinforced Concrete

Abstract

One of the most essential building materials for sustainable development is concrete. However, there is a problem with a lack of inexpensive, efficient ways to make it high-strength and ultra-dense. A promising direction is the additional processing or activation of the cheapest component of the concrete mixture—inert aggregate. The article is devoted to a promising method for the simultaneous activation of both large and small aggregates using vibro-centrifuge technology. It has been established that the activation of concrete aggregates with aqueous solutions of natural bischofite at a concentration of 6 g of dry matter per 1 L of water is the most rational and contributes the maximum increase in strength characteristics and the best values of strain characteristics. Strength characteristics increased up to 16% and ultimate strains increased to 31%, respectively, and the modulus of elasticity increased to 9%. A new improved lightweight fiber-reinforced concrete was created and an innovative technology is proposed that makes it possible to achieve savings in manufacturing due to a significant improvement in structural properties and reducing the working sections of reinforced concrete elements. Regularities between the fundamental chemical processes of the surface activation of aggregates and the physical processes of structure formation of compacted and hardened concrete were revealed. An improvement in the structure of concrete at the micro- and macro-levels was recorded due to a point decrease in crack formation at the interfaces of the “cement matrix-aggregate” and “cement matrix-fiber” phases, and a decrease in the number of micropore defects was also found. Economic efficiency reached 25–27%.

The Structure Features and Improvement of Concrete Properties with Dead Jellyfish Mass

“…The use of such a technological technique is more appropriate in regions where there is an environmental problem with the release of dead jellyfish from water bodies. The study of the addition of dead jellyfish mass in variotropic concrete is promising [47,55]. Dead jellyfish mass can be used for the manufacture of concrete and reinforced concrete structures operated in air-dry conditions, water, and aggressive solutions, as well as sea water, in order to improve the technological properties of concrete mixtures, increase the strength of concrete, and reduce cement consumption.…”

“…And at the fourth stage, crushed stone was added to the resulting cement-sand mortar, and the mixture was mixed until homogeneous. Next, the resulting concrete mixture was placed into metal molds with dimensions of 100 × 100 × 100 mm, which were then vibrated for 60 s. After 24 h, concrete samples of a control composition and with different contents of the DJM additive were removed from the molds and placed in a normal hardening chamber for 27 days at a temperature of 20 ± 2 • C and a relative humidity of 95% [47].…”

Analytical Review of the Current State of Technology, Structure Formation, and Properties of Variatropic Centrifugally Compacted Concrete

“…Such technologies include the production of concrete using vibration centrifugation. In accordance with this, when creating reinforced concrete structures, the concrete mixture is simultaneously affected by vibration and centrifugal force, "which leads to the formation of a heterogeneous structure, the peculiarity of which is an increase in density and strength with distance from the axis of symmetry of the element" [16,17,[25][26][27][28]. These structures were called improved variatropic structures and were investigated with different compositions of the concrete mixture.…”

Influence of Polymer Fibers on the Structure and Properties of Modified Variatropic Vibrocentrifuged Concrete

“…Considering the fact that more effective types of variatropic concretes have been previously established, specifically those obtained using vibration centrifugation technology, it will be interesting to study the structure, properties, and their mutual influence depending on the composition of vibrocentrifuged variatropic concretes based on polypropylene fiber. Given that we have previously established options for effective modification of vibrocentrifuged variatropic concretes with finely dispersed components [ 23 , 53 , 54 ], an even more interesting question is the study of polymer polypropylene fiber reinforcement of vibrocentrifuged variatropic concretes modified with various additives. Based on this, we formulate the purpose and objectives of this study.…”