Force-Deformation Study on Glass Fiber Reinforced Concrete Slab Incorporating Waste Paper

This study inspects the viability of engaging the discarded paper wastes in concrete by varying the volume proportions from 0%–20% with each 5% increment in replacement of the weight of cement. A physiomechanical study was conducted, and the results were presented. A glass fiber reinforced rectangular slab with a longer span (ly) to shorter span (lx) ratio of (ly: lx) 1.16 was cast with optimum replacement of waste-paper mass and compared the force-deformation characteristics with the conventional concrete slab without waste paper. The optimum percentage of discarded papers for the replacement of cement is 5%. Also, the results imply that the compressive strength at the age of 28 days is 30% improved for the optimum replacement. Based on the outcomes of the investigation, it can be inferred that the compressive strength gets progressively reduced if the volume of the discarded paper gets increases. The incorporation of glass fibers improves the split and flexural strength of the concrete specimens considerably. The ultimate load-carrying capacity of the glass fiber reinforced waste paper incorporated concrete slab measured 42% lower than that of the conventional slab. However, development of the new type of concrete incorporating waste papers is the new trend in ensuring the sustainability of construction materials.

CRACKING ANALYSIS OF PRECAST – IN SITU REINFORCED CONCRETE SLAB WITH PLASTIC VOID FORMERS

In this article results of experimental and numerical analysis of precast – in situ reinforced concrete slab with plastic void formers are discussed. Slab is composed of precast and in situ concrete layers. Voids are formed inside the slab using spherical plastic void formers. Slab cracking pattern is determined by numerical analysis. Cracking pattern acquired by numerical analysis is compared to cracking pattern determined by experimental study. Shear stiffness in the bond between precast and in situ concrete layers was specified when numerical model was built.

EXPERIMENTAL STUDIES OF DEFORMABILITY AND FRACTURE RESISTANCE OF AIRFIELD SLABS ON MODELS

The results of experimental studies of deformability and crack resistance of models of aerodrome slabs made of reinforced concrete and steel-fiber concrete, made on the basis of serial slab PAG-18 taking into account the scale factor, are presented. Two series of slabs were tested - two models of reinforced concrete and two models with one-percent dispersed reinforcement. The load was applied in steps, the instrument readings were recorded twice at each step and the crack opening width was measured starting from the moment of the first crack formation. Dial gauges, deflectometer and microscope MPB-3 were used as measuring instruments. In accordance with the normative documents acting in Ukraine, one of two possible loading schemes was considered - with the loading by the concentrated force applied in the span part of a plate which had a hinged support along its short sides. Plate models were tested on a specially made stand. Each load step ended with a five-minute dwell time, at the beginning and the end of which readings were taken on the measuring instruments. The deformations at the same levels were measured with dial gauges. The process of crack formation was observed with a Brinell tube in the places of the greatest crack opening. Breaking load for fiber concrete slab was 1.52 times higher than for reinforced concrete slab, and the moment of cracking initiation was 1.22 times higher. The process of cracking in the fiber concrete slab begins at higher loads than in the reinforced concrete slab. The initial crack opening width of the slabs is almost the same, and the final crack opening width of all the cracks in the fiber concrete slab is significantly lower than in the reinforced concrete slab. The deformations in steel-fiber concrete slabs when the load is applied in the span, both for compressed and stretched fibers, are higher than in reinforced concrete slabs. The experimental studies indicate that dispersed reinforcement of airfield slabs with steel fiber leads to their higher crack resistance.

Ductility and flexure of lightweight expanded clay basalt fiber reinforced concrete slab

Relevance. The load on a reinforced concrete slab with high strength lightweight aggregate concrete leads to increased brittleness and contributes to large deflection or flexure of slabs. The addition of fibers to the concrete mix can improve its mechanical properties including flexure, deformation, toughness, ductility, and cracks. The aims of this work are to investigate the flexure and ductility of lightweight expanded clay concrete slabs reinforced with basalt fiber polymers, and to check the effects of basalt fiber mesh on the ductility and flexure. Methods. The ductility and flexural/deflection tests were done on nine engineered cementitious composite (expanded clay concrete) slabs with dimensions length 1500 mm, width 500 mm, thickness 65 mm. These nine slabs are divided in three reinforcement methods types: three lightweight expanded clay concrete slab reinforced with basalt rebars 10 mm (first slab type); three lightweight expanded clay concrete slab reinforced with basalt rebars 10 mm plus dispersed chopped basalt fiber plus basalt fiber polymer (mesh) of cells 2525 mm (second slab type); three lightweight expanded clay concrete slab reinforced with basalt rebars 10 mm plus dispersed basalt fiber of length 20 mm, diameter 15 m (third slab type). The results obtained showed physical deflection of the three types of slab with cracks. The maximum flexural load for first slab type is 16.2 KN with 8,075 mm deflection, second slab type is 24.7 KN with 17,26 mm deflection and third slab type 3 is 32 KN with 15,29 mm deflection. The ductility of the concrete slab improved with the addition of dispersed chopped basalt fiber and basalt mesh.

NUMERICAL STUDY OF REINFORCED CONCRETE PLATES IN THE PRESSURE AREA

Here is the description of fi nite elementmodels of joints between reinforced concrete slab and column, made in the SIMULIA ABAQUS software package. The variable parameters were the ratio of the sides of the column cmax/cmin and the ratio of the side of the column to the eff ective depth c/h0. The calculation is performed in a non-linear formulation. Finite elementmodels showed realistic behavior: a punching shear pyramid was detected. It was found a signifi cant unevenness in the distribution of tangential deformations, as well as the main compressive deformations of the concrete slab near the column. The nature of the formation and development of the punching shear pyramid depends on the value of the ratio of the sides of the column cmax/cmin and the ratio of the side of the column to the eff ective depth slab c/h0.

Neural network-based formula for shear capacity prediction of one-way slabs under concentrated loads

<p>According to the current codes and guidelines, shear assessment of existing reinforced concrete slab bridges sometimes leads to the conclusion that the bridge under consideration has insufficient shear capacity. The calculated shear capacity, however, does not consider the transverse redistribution capacity of slabs, thus leading to overconservative values. This paper proposes an artificial neural network (ANN)-based formula to come up with estimates of the shear capacity of one-way reinforced concrete slabs under a concentrated load, based on 287 test results gathered from the literature. The proposed model yields maximum and mean relative errors of 0.0% for the 287 data points. Moreover, it was illustrated to clearly outperform (mean <i>V_test / V_ANN</i> =1.00) the Eurocode 2 provisions (mean <i>V_E,EC/ V_R,c</i>=1.59) for that dataset. A step-by-step assessment scheme for reinforced concrete slab bridges by means of the ANN-based model is also proposed, which results in an improvement of the current assessment procedures.<br></p>

Effect of concrete and reinforcement continuity on repairing mid-span zone in simply supported one-way slab

The flexural strength of slabs may be reduced due to accidents and environmental effects. This study focuses on the rehabilitation of the one-way reinforced concrete slab. Experimental works include five simply supported one-way reinforced concrete slabs with width, depth, and length of 400, 120, and 2200 mm, respectively. Different configurations of steel continuity between old and new concrete have been tested. Moreover, in the control specimen (steel is continued overall, the specimen and concrete are cast in one stage over the entire slab). In the other four specimens, the concrete is cast in two stages, the left and right parts representing the old concrete are cast first, and the middle part representing a new concrete is cast after that. In these four specimens, new steel is connected to old one by different configuration (original steel remain to continue, new steel connected to old one by weld, new steel connected to old one by making 90° hooks, and new steel bars is put inside bores using epoxy). After testing, the welding method of connecting new to old steel is the best one.

MUD-CONCRETE SLAB SYSTEM FOR SUSTAINABLE CONSTRUCTION

The urgency of global climate emergency has drawn significant attention to the building industry over the last few years. Today, the building sector is responsible for 38% of the world’s greenhouse gas emissions, according to UNEP. 60% -70% of embodied carbon in a conventional column-beam reinforced concrete building is in its floor system. This paper discusses the possibility of constructing an earthen slab system using mud-concrete. It investigates a doubly curved shell structure, working predominantly in compression, to fulfil both environmental and economical demands in the construction industry; reducing the cost and labour expenses nearly 50% compared with that of traditional reinforced concrete slab systems. A 1 m x 1 m prototype mud-concrete slab was constructed to check the potential for modular construction with a square footprint. Poured mud-concrete shell of 50 mm thickness is the primary structural component, while a non-structural mud-concrete filling to a horizontal level 50 mm from apex was used to create a usable floor surface. Masonry mould method was used as the formwork system for the construction considering its cost effectiveness and ease of construction.