Cohesion is defined as the shear strength of material when compressive stress is zero. This article presents a new method for the experimental determination of cohesion at pre-set angles of shear deformation. Specially designed moulds are created to force deformation (close to τ-axis) at fixed pre-set values of angle with respect to normal stress σ. Testing is performed on series of concrete blocks of different strengths. From the compressive side, cohesion is determined from the extrapolation of the linear Mohr–Coulomb (MC) model, as the intercept on the shear stress axis. From the tensile stress side (from the left), cohesion is obtained using the Brazilian test results: first, indirect tensile strength of material σ_t^BT is measured, then Mohr circle diagram values are calculated and cohesion is determined as the value of shear stress τ^BT on the Mohr circle where normal stress (σ)t = 0. A hypothesis is made that cohesion is the common point between two tests. In the numerical part, a theory of ultimate load is applied to model Brazilian test using the angle of shear friction from the MC model. Matching experimental and numerical results confirm that the proposed procedure is applicable in numerical analysis.

Protecting the built cultural heritage is one of the most important tasks in architectural practice. The process of repair is time-consuming, weather-dependent, and sensitive to materials applied. Introducing new materials in historic building repair in order to decrease the time needed for repair, brings some risk in the preservation process. The most common material for masonry repair is lime mortar. Adding cement to lime mortar can improve the mechanical properties of mortar and speed up the repair process. The high amount of cement may increase the strength, but decrease ductility and permeability of mortar, causing damages to protected buildings. An increase in strength with the smallest amounts of cement demands optimization of water content in the mixture. Tests were performed to investigate the influence of the water/binder (w/b = water/(lime + cement) ratio on mortar strength and water permeability. An air-entraining agent (AEG) was introduced to improve permeability. Results confirmed that adding small amounts of cement to lime (20% by weight) and decreasing of w/b ratio, improves the strength, with almost negligible influence on water permeability. The addition of very small amounts of AEG did not decrease the strength, nor the permeability.

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Fashion and textile industry generate substantial volume of waste, during the production phase, as well as in the consumer phase. Textile waste is disposed in the landfills or incinerated, significantly affecting the environment. At the same time, construction industry faces demand to consider different approaches to the conventional formwork systems, which are resource intensive and disposed after the use. Feasibility of the usage of the cut-off knitted textile waste bonded with polymer-cement binder to create the composite formwork for casting concrete and mortar elements is presented in this paper. Experiments are designed with different types of cement-based mixtures to make the textile formwork composite and the polymer-cement mixture. Experimental research tested the bond between two pieces of textile bound by the selected polymer-cement binder and a proposal was given for determining the required overlap length. Obtained testing results for adequate and optimal samples, showed that the recycled textile waste may be used as efficient and low-cost alternative to traditional formwork, while providing flexible and non-prismatic geometrical shapes of the products and reducing the environmental impact.

This paper presents the assessment and reconstruction methods developed and adapted for the strengthening of the reinforced concrete office building structure in Libreville, Republic of Gabon. The office building reinforced concrete frame structure consists of a ground floor and eight upper floors (G+8). Upon completion of the construction, immediately prior to occupancy and during the furnishing phase, cracks appeared in the load-bearing elements of the structure – specifically in the beams and columns. Fearing catastrophic consequences and potential structural collapse, the client’s consultants recommended the total demolition of the building. However, the client opted for a structural expert assessment before making a final decision. The assessment revealed that the building was originally designed as a G+3 structure. During construction, the height was increased to G+8 without any documented changes of the original structural design. Structural assessment and analyses confirmed that the existing reinforced concrete structure could not support the increased load, but concluded that it was possible to strengthen the columns and beams to accommodate double increase of load. To verify the load-bearing capacity of the existing piles resting directly on bedrock, testing was conducted on soil samples, and the necessary reinforcements for the foundation structure were determined. Based on the conducted testing and the provided expert assessment, a reconstruction project was developed and successfully realized. The building was successfully rehabilitated and adapted for the designed use and occupancy.