Experiment and Analysis of Mechanical Properties of Lightweight Concrete Prefabricated Building Structure Beams

Recent years have witnessed that the prefabricated concrete structure is in the widespread use of building structures. This structure, however, still has some weaknesses, such as excessive weight of components, high requirements for construction equipment, difficult alignment of nodes, and poor installation accuracy. In order to handle the problems mentioned above, the prefabricated component made of lightweight concrete is adopted. At the same time, this prefabricated component is beneficial to reducing the load of the building structure itself and improving the safety and economy of the building structure. Nevertheless, it is rarely found that the researches and applications of lightweight concrete for stressed members are conducted. In this context, this paper replaces ordinary coarse aggregate with lightweight ceramsite or foam based on the C60 concrete mix ratio so as to obtain a mix ratio of C40 lightweight concrete that meets the engineering standards. Besides, ceramsite concrete beams and foamed concrete beams are fabricated. Moreover, through three-point bending tests, this paper further explores the mechanical properties of lightweight concrete beams and plain concrete beams during normal use conditions. As demonstrated in the results, the mechanical properties of the foamed concrete beam are similar to those of the plain concrete beam. Compared to plain concrete beams, the density of foamed concrete beams was lower by 23.4%; moreover, the ductility and toughness of foamed concrete were higher by 13% and 3%, respectively. However, in comparison with the plain concrete beam, the mechanical properties of the ceramsite concrete beam have some differences, with relatively large dispersion and obvious brittle failure characteristics. Moreover, in consideration of the nonlinear deformation characteristics of reinforced concrete beams, the theoretical calculation value of beam deflection was given in this paper based on the assumption of flat section and the principle of virtual work. The theoretically calculated deflection values of ordinary concrete beams and foamed concrete beams are in good agreement with the experimental values under normal use conditions, verifying the rationality and effectiveness of the calculation method. The research results of this paper can be taken as a reference for similar engineering designs.

Water Sensitivity of Hemp-Foam Concrete

The necessity to build energy-efficient and low environmental impact buildings favors the development of biobased light-weight materials as hemp-foam concretes. In this context, experimental protocols were developed to study the effects of hemp shiv and the production methods on the water sensitivity of bio-based foamed concrete (BBFC). Foam concrete incorporates several materials and compounds: cement, protein-based foaming agent, ground granulated blast–furnace slag, metakaolin as a binder, and hemp shiv as bio-based aggregates. The study investigated first the effect of the incorporation of hemp shiv (from 0 to 15 vol%) and then the elaboration method, comparing direct method versus preformed method on the resulting physical properties, the isotherms sorption-desorption and the capillary water absorption of hemp-foam concretes. We observe an increasing porosity of the concrete with hemp shives content. Additionally, hemp shives increase the adsorption and the capillary absorption of water. Moreover, the preformed method produces concretes more sensitive to water than the direct methods since it increases its porosities.

Alkali-Silica. Reaction Of Foamed. Concrete Containing. Waste Glass as Aggregate

This research focused on examining Alkali-Silica. Reaction (ASR) of foamed concrete mixes containing1different1types of1crushed waste glass (CWG) with different chemical compositions. The reactivity was determined in sodium hydroxide solution by adopting mortar bar test. Four types of waste glass with different particle sizes and different percentages content were used. From the test results of recorded expansion of these mixes, it was noticed that the coarse glass resulted in more expansion than that of fine glass. Lead-silicate1glass (CR) exhibits the maximum expansion followed by1soda-lime1glass (SL) and boro-silicate glass (BS), while less expansion was recorded in mixes with green glass (GG). As compared to reference mix (FC), it was noted that the mixes with crushed waste glass (SL), (BS), and (CR) undergo notable expansion, while the expansion of the mixes with (GG) slightly increased compared to the reference mix (FC).

Experimental and Numerical Verification of the Railway Track Substructure with Innovative Thermal Insulation Materials

The article aims to present the modified structural composition of the sub-ballast layers of the railway substructure, in which a part of the natural materials for the establishment of sub-ballast or protective layers of crushed aggregate is replaced by thermal insulation and reinforcing material (layer of composite foamed concrete and extruded polystyrene board). In this purpose, the experimental field test was constructed and the bearing capacity of the modified sub-ballast layers’ structure and temperature parameters were analyzed. A significant increase in the original static modulus of deformation on the surface of composite foamed concrete was obtained (3.5 times and 18 times for weaker and strengthen subsoil, respectively). Based on real temperature measurement, it was determined the high consistency of the results of numerical analyses and experimental test (0.002 m for the maximum freezing depth of the railway line layers and maximum ±0.5 °C for temperature in the railway track substructure–subsoil system). Based on results of numerical analyses, modified railway substructure with built-in thermal insulating extruded materials (foamed concrete and extruded polystyrene) were considered. A nomogram for the implementation of the design of thicknesses of individual structural layers of a modified railway sub-ballast layers dependent on climate load, and a mathematical model suitable for the design of thicknesses of structural sub-ballast layers of railway line were created.

A Feasibility Study of Low Cement Content Foamed Concrete Using High Volume of Waste Lime Mud and Fly Ash for Road Embankment

This paper aims to study the feasibility of low cement content foamed concrete using waste lime mud (LM) and fly ash (FA) as mineral additives. The LM/FA ratio was first optimized based on the compressive strength. Isothermal calorimetry test, ESEM, and XRD were used to investigate the role of LM during hydration. Afterward, the optimized LM/FA ratio (1/5) was used to design foamed concrete with various wet densities (600, 700, 800 and 900 kg/m3) and LM–FA dosages (0%, 50%, 60%, 70% and 80%). Flowability measurements and mechanical measurements including compressive strength, flexural strength, splitting strength, elastic modulus, and California bearing ratio were conducted. The results show that the foamed concretes have excellent workability and stability with flowability within 170 and 190 mm. The high alkalinity of LM accelerated the hydration of FA, thereby increasing the early strength. The significant power functions were fitted for the relationships between flexural/splitting and compressive strength with all correlation coefficients (R2) larger with 0.95. The mechanical properties of the foamed concrete increased with the density increasing or LM–FA dosage decreasing. The compressive strength, tensile strength, CBR of all prepared foamed concretes were higher than the minimum requirements of 0.8 and 0.15 MPa and 8%, respectively in the standard.