The by-products of wood sawdust and wood fiber are considered to be waste material. It is utilized in the construction of buildings in the form of sawdust concrete or wood fiber concrete. It is used to make lightweight concrete and possesses heat transfer of a long duration. In this study, wood concrete was made at eleven different mix proportions of cement to wood waste by weight, to produce a lightweight concrete aggregate that has the density 1508-2122 kg/m3. The experimental work consists of 330 concrete specimens as 99 cubes (150 * 150 * 150) mm, 165 cylinders (150 * 300) mm, 33 prisms (50 * 100 * 200) mm, and 33 prisms (100 * 100 * 500) mm. Mechanical and thermal properties such as stiffness, workability, compressive strength, static elasticity modulus, flexural forces, splitting tensile strength and density were examined in the specimens after 28 days of 20 oC curing. Also, compressive strength was investigated at 7 and 14 days of curing at 20 oC. The basic observation of the results shows the values with the limitations of ACI and ASTM. Moreover, it is the perfect way to reduce solid wood waste and produce lightweight concrete to be used in industrial construction. It was found that with the increase in the quantity of wood waste, the strength decreased; however, in terms of workability and concrete with a higher quantity of wood waste held very well. Lightweight concrete aggregate is around 25 percent lighter in dead load than standard concrete. Given all the physical and mechanical properties, the study finds that wood concrete can be used in the construction of buildings.

In the paper an alternative method for increasing punching shear resistance of the flat slabs from lightweight aggregate concrete by means of hidden steel fibre reinforced capital was presented. Previous experimental studies demonstrated that the addition of steel fibres to concrete allows for increase in the punching shear resistance of flat slab. Steel fibres modify the tensile strength of concrete, which translates into increased ductility of the material. The results of the experimental investigations were presented, the aim of which was to assess the effectiveness of the proposed solution. For economic and technological reasons, a hidden capital of a height equal to half of the slabs depth was made so that the top reinforcement could be installed later. It was found that presented solution allowed to increase the load carrying capacity by about 36% with respect to the control element, made entirely of lightweight aggregate concrete.

In the paper the results of experimental investigations concerning flat slabs made from reinforced lightweight concrete with sintered fly ash aggregate CERTYD were presented. In the research program 6 models made in a natural scale were included. The main variable parameter was slab longitudinal reinforcement ratio. The aim of investigation was the experimental verification of efficiency of double-headed studs as punching shear reinforcement. In the existing technical approvals such kind of reinforcement was allowed only in normal concrete slabs. It was demonstrated that double-headed studs can be an effective transverse reinforcement of lightweight aggregate concrete slabs. The use of double-headed studs resulted in increase in the ultimate load from 19% to 44%, depending on the slab reinforcement ratio which ranged from 0.5% to 1.2%. The comparative analysis showed that the Eurocode 2 provisions were conservative in relation to the experimental results, which were on average 42% higher than the theoretical ones however with a very low 7% coefficient of variation.

The paper discusses the principles of the Critical Shear Crack Theory (CSCT) in terms of the punching shear analysis of flat slabs made from lightweight aggregate concretes. The basic assumptions of the CSCT were discussed, explaining the differences with regard to the calculation of ordinary concrete flat slabs, relating mainly to the adopted failure criterion associated with ultimate slab rotation. Taking into account the observations and conclusions from the previous experimental investigations, it was confirmed, that contribution of lightweight aggregate particles in the aggregate interlock effect should be ignored, due to possibility of aggregate breaking. However, the analysis of the profile of failure surface confirmed, that particles of the natural fine aggregate increase the roughness of the surface and should be included by formulating failure criterion for LWAC slabs.
The theoretical load-rotation relationships were compared with the results of measurements, confirming good agreement in most cases. The theoretical ultimate rotations were lower on average by about 11% than the experimental ones. The analysis of 57 results of the experimental investigations on punching shear of LWAC slabs made from various types of artificial aggregates showed a very good agreement with predictions of the CSCT. The obtained ratio of the experimental to theoretical load was 1.06 with a coefficient of variation of 9.1%. The performed parametric study demonstrated a low sensitivity of the correctness of the CSCT predictions to a change in a fairly wide range of parameters such as: the longitudinal reinforcement ratio, concrete compressive strength and concrete density.