Terms Of Concrete Strength Research Articles

Structural properties of concrete reinforced with bamboo fibers: a review

Bamboo fibers show promising results in terms of concrete strength and avoid unavoidable brittle failure. However, an updated assessment is needed which collects all the relevant important information and provides an easy for the reader to judge the suitability of bamboo fibers. Therefore, this review is carried out on bamboo fiber-reinforced concrete to present past and recent research that was already done by another researcher. The fresh properties, structural properties, performance in elevated temperature, durability, and morphology structure are the main parameters of this review. Results indicate that bamboo fibers decreased the concrete flow like other types of fiber such as steel fiber etc. However, an increase in strength parameters was also detected with the addition of bamboo fibers. Furthermore, bamboo fibers increased the tensile strain which avoids undesirable brittle failure. The review also highlights the optimum addition proportion of bamboo fibers which varies from 1 to 1.5% by weight of cement. Finally, the study also recommends potential investigation for upcoming inventions.

Composite walls Composed of profiled steel skin and foam rubberized concrete subjected to eccentric compressions

This paper addresses the structural behaviour of profiled steel composite walls (PSCWs) infilled with foam rubberized concrete (FRC) under concentric, eccentric and flexural loads. FRC mechanical properties such as compressive strength, flexural strength, and splitting tensile strength are presented for different rubber contents; 0%, 50%, and 100% as sand replacement by volume. FRC with unit weight of 1000 kg/m3 and 50% rubber content was selected as the filler material. Three PSCWs were tested under concentric, eccentric compressive loads, and four-point bending loads. Finite element modelling (FEM) using ABAQUS software has been carried out to simulate the experimental behaviour of the PSCWs. Parametric study was carried out to investigate the effect of different concrete and steel strengths and steel sheet thicknesses. FEM results showed a good agreement with the experimental results. Practical formulas in terms of concrete strength, steel sheet buckling stress, wall geometry, and eccentricity are presented to predict interaction diagrams for PSCW structures.

Erratum to: “The truth about the geopolymers” S. Grzeszczyk, Cement Wapno Beton, 26(3) (2021), 101 – 108

In my article “The truth about geopolymers” by S. Grzeszczyk, Cement Wapno Beton, 26 (3) (2021), 101-108, there is an information I would like to rectify. There is a sentence: “Industrial application of geopolymers in Poland is limited to the activity of professor Maolepszy, who used this binder of blast furnace slag activated with NaOH addition to the construction of the students’ hotel, in Cracow.” It should be: “The activity of professor Małolepszy includes the use of a slag-alkali binder, in which the activator was sodium carbonate. This material was used for the manufacturing of precast concrete units of the” Żerań “type, of which a building was erected in the 1970s in the area of the “Prefabet” company in Kraków, Poland. This building was examined for twenty years in terms of concrete strength and durability. In practice, a total of about 100 thousand cubic meters of slag-alkali concrete has been used in Poland.”

Water impermeability of hydraulic concrete based with thermal power plant waste substrate

One of the main factors in ensuring the reliability of concrete used in the construction of hydraulic and reclamation facilities is their waterproofing and frost resistance, and the design of the optimal composition of concrete to ensure waterproofing is of great importance. The main goal of the study was to select the water/cement ratio of the concrete mix not only in terms of concrete strength but also in terms of concrete strength, to ensure the optimal concentration of aggregates for dense structural concrete and finally to increase the water permeability of hydraulic concrete using microfillers and chemical additives. In the study, industrial ash (Angren Thermal Power Plant) was used to modify technical lignosulfonates and prepared a plasticizer L-2 chemical additive. Studies have shown that if the size of pores and capillaries that occur in the concrete structure is less than 10-5 cm, they will not allow free water to pass through. But if these dimensions are larger than 10-5 cm, they will have the property of water permeability. The size of the pores formed in the cement gel, which is usually used in the preparation of concrete, is less than 10-5 cm, and they are impermeable to water. However, the sizes of capillaries and pores of different sizes formed in the concrete structure may vary depending on the factors listed above (10-6 - 0.2 cm). Based on the research, the technological factors affecting the waterproofing of hydraulic concrete were analyzed. It was argued that the use of L-2 plasticizer chemical additive in the amount of 0.25% of the cement mass in the preparation of hydraulic concrete can reduce the water-cement ratio by 18% and increase the waterproofing of hydraulic concrete by 3 times. In addition, it was considered that by waterproofing open pores and capillaries in freshly poured concrete, their waterproofing can be increased by 20. … 30 times.

PREDICTING THE STRUCTURAL PERFORMANCE OF SANDWICH CONCRETE PANELS SUBJECTED TO BLAST LOAD CONSIDERING DYNAMIC INCREASE FACTOR

The safety of the civil structures could be significantly improved against shock waves and blast loads by using steel concrete steel (SCS) protective walls. A numerical study has been performed to simulate the response of SCS wall subjected to a near-field blast load. A conventional SCS panel subjected to near-field blast load and its structural performance is evaluated in terms of maximum damage and deformation. The simulations performed using ABAQUS\EXPLICIT finite element package and built-in concrete damage plasticity concrete constitutive formulation. The maximum deformation, plastic strain, and failure mode under different loading scenarios have been investigated. The aim of this study is predicting the structural response of the SCS panel with different blast charge and identification of optimum configuration in terms of concrete strength and plate thickness. In the second part of the study, two novel sandwich configurations consisting of a corrugated metal sheet and the concrete core are proposed and compared with the conventional protective walls. The optimum parameters for each structural component are identified using an optimization procedure. Based on this study, using the proposed wall configuration will results in superior performance compared to the conventional walls while the extra cost of fabrication is insignificant.

Interfacial Behavior of Glass Fiber-Reinforced Polymer Bars Embedded in Concrete with Internal Curing Agents

This paper presents an experimental investigation into the interfacial behavior of glass fiber-reinforced polymer (GFRP) bars embedded in concrete mixed with internal curing agents. Such an innovative concept to achieve high-performance concrete (HPC) structures has a number of advantages-for example, improved early-age cracking resistance and long-term sustainability. Of interest is the interaction between the noncorrosive GFRP and the internally cured concrete when mechanically loaded. Three types of presaturated internal curing agents-namely, microporous lightweight aggregate (LWA), crushed returned concrete aggregate (CCA), and superabsorbent polymer (SAP)-are employed to supply necessary moisture inside the concrete so that autogenous shrinkage is controlled, along with minimizing self-desiccation and expediting cement hydration. The effect of various replacement or addition ratios of the curing agents is examined in terms of concrete strength, surface friction, and interfacial stresses. A refined bondslip relationship is established in accordance with test observations and probability-based simulation. Simplified design equations are proposed to estimate the embedment length of GFRP bars for the application of internally cured concrete.

An investigation of the effectiveness of the utilization of biomass ashes as pozzolanic materials

Utilization of biomass ash from agro-industrial by-products (containing large amounts of silica in amorphous form) in cement manufacturing and/or concrete production can be an alternative solution to the incorporation of the traditionally used supplementary cementing materials (SCMs). An evaluation of biomass ashes, identified in the literature, with varying SiO2 contents in terms of concrete strength and performance in chloride exposure is the focus of this study. Results indicate that these materials are effective on concrete strength development and extremely efficient in reducing the concrete permeability. The dependency of this behavior on the level of SiO2 of the ash content was examined in depth and was concluded that it is affected by the composition of other components of the biomass ash.

Assessment of crack width estimation models for RC tension members

The objective of this study is to assess the crack width estimation equation suggested in CEB-FIP Model Code 1990 (1991) in terms of concrete strength. To evaluate the crack width estimation equation, a numerical model for a crack element is introduced by adopting detailed bond stress slip models. A remarkable advantage of the use of the model is that all significant internal variables within a crack element can be analysed, including average bond stress and tension stiffening effect, which are the vital parameters for the equation in CEB-FIP Model Code. Experimental results from literature were compared with those obtained by the estimation model equation in CEB-FIP Model Code and by the numerical analysis using the crack element model. The average bond stress and tension stiffening effect given in CEB-FIP Model seem to be overestimated and thus need to be reduced to properly reflect the effect of concrete strength.

Investigation of Concrete Haunched T‐Beams under Shear

Haunched beams are used in building construction for architectural and sometimes economical reasons. The American and British codes do not give any formulas for the design of haunched beams under shear. However, the German DIN code and some other European codes give a formula for calculating the equivalent shear stress. A formula is proposed by the writer, which gives the ultimate shear force of reinforced‐concrete haunched beams under shear in terms of concrete strength, stirrups contribution, and dowel action. The proposed formula is a modification of the American Concrete Institute (ACI) code expression for shear design. The modification takes into account the angle of haunch inclination and the dowel contribution. Ten beams of T‐cross section and different haunch inclinations were tested, and analyzed using the proposed formula to test its suitability for each beam. The correlation of results was satisfactory.