The Stress–Strain State of Three-Layer Precast Flexural Concrete Enclosure Structures with the Contact Interlayers

Vu Tho,Elena Korol,Nikolai Vatin,Hoang Duc

doi:10.3390/buildings11030088

Abstract

The research object was three-layer reinforced precast concrete enclosure structures. The structures consist of heavy concrete B25 in the external layers and polystyrene concrete B1 in the internal layer. The stress–strain state of precast concrete structures during crack formation was studied by considering the influence of contact interlayers between different types of concretes. Stereoscopic microscopy and scanning electron microscopy were used in the experimental study of multilayer concrete blocks. Samples were made with a varied break time from 30 min to two hours between the previous and the next concrete layer placings. The experimental results showed that the contact interlayer with mutual penetration of aggregates into the adjacent concrete layers is formed in the successive layer-by-layer placing of various concretes. The thickness of the contact interlayer was up to 1 cm. The contact interlayer affects the solidity of the concrete layers’ connection and the structure’s stress–strain state. A model and method for calculating cracking in three-layer reinforced concrete structures with contact interlayers based on analytical and numerical calculations are proposed. Experimental data confirm the proposed calculation method. The results of three-layer reinforced concrete beams calculations show that: (i) the difference of the moment during crack formation in three-layer reinforced concrete beams schemes with and without taking into account the contact interlayer can reach 9.9%; (ii) the moment during crack formation obtained according to the proposed method is greater than that obtained according to the scheme of the cross-section conversion from 7.4% to 9.1%.

Highlights

Multilayer concrete structures with a middle layer of low thermal conductivity (Uvalue) concrete are widely used in enclosing structures of residential and public buildings [1,2,3]
This study aimed to develop a method for calculating precast multilayer reinforced concrete enclosing structures with a contact interlayer between layers of various concrete and taking into account the manufacturing technology of the structure
It was shown that the contact interlayers between the external and internal layers

Summary

Introduction

Multilayer concrete structures with a middle layer of low thermal conductivity (Uvalue) concrete are widely used in enclosing structures of residential and public buildings [1,2,3]. Typical three-layer reinforced concrete structure with a middle layer of light heat resistance concrete consists of: (i). The thickness of the external layer usually is not less than 40 mm, depending on the operating conditions of the structure and the thickness of the protective layer of the reinforcement; The internal layer of heat insulation and sound insulation is used by light concrete of low strength, such as foam concrete [11], coarse-pored concrete [12], arbolite concrete [13], polystyrene concrete [4,14,15], etc. The thickness of the middle layer is determined by the heat engineering calculation, depending on the regional location of the buildings and the purpose of the premises

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Results