PERFORMANCE OF SUSTAINABLE GREEN CONCRETE INCORPORATED WITH FLY ASH, RICE HUSK ASH, AND STONE DUST

The performance of a sustainable green concrete with fly ash (FA), rice husk ash (RHA), and stone dust (SD) as a partial replacement of cement and sand was experimentally explored. FA and RHA have a high silica content, are highly pozzolanic in nature and have a high surface area without any treatment. These by-products show filler effects, which enhance concrete’s density. Results showed that the FA and RHA materials have good hydration behaviour and effectively develop strength at an early age of concrete. SD acts as a stress transferring medium within concrete, thereby allowing the concrete to be stronger in compression, and bending. Consequently, water absorption capacity of the sustainable concrete was lower than that of the ordinary one. However, a little reduction in strength was observed after the replacement of the binder and aggregate using the FA, RHA and SD, but the reduction was insignificant. The reinforced structure with sustainable concrete containing the FA, RHA, and SD generally fails in concrete crushing tests initiated by flexural cracking followed by shear cracks. The sustainable concrete could be categorized as a perfect material with no significant conciliation in strength properties and can be applied to design under-reinforced elements for a low-to-moderate service load

Properties and applications of FRP in strengthening RC structures: a review

In civil and structural engineering, building structures with robust stability and durability using sustainable materials is challenging. The current technological means and materials cannot decrease weight, enlarge spans, or construct slender structures, thus inspiring the exploration for valuable composite materials. Fiber reinforced polymer (FRP) features high-strength and lightweight properties. Using FRP motivates civil engineers to strengthen existing RC structures and repair any deterioration. With FRP, a system that can resist natural disasters, such as earthquakes, strong storms, and floods, can be developed. However, deterioration of structures has become a critical issue in modern construction industries worldwide. This paper reviews the FRP design, matrix, material properties, applications, and serviceability performance. This literature review also aims to provide a comprehensive insight into the integrated applications of FRP composite materials for improving the techniques of rehabilitation, comprising the applications toward the repair, strengthening, and retrofit of concrete structures in the construction industry today

Response of precast foamed concrete sandwich panels to flexural loading

This paper presents the results of an experimental and analytical investigation of a total of six precast foamed concrete sandwich panels (PFCSPs) as one-way acting slabs tested under flexural loads. Foamed concrete of 25.73 MPa was used to produce the PFCSP concrete wythes. The results obtained from the tests have been discussed in terms of ultimate flexural strength capacity, moment-vertical deflection profile, load–strain relationship, strain variation across the slab depth, influence of aspect ratio, cracking patterns, and ultimate flexural load at failure. An analytical study of finite element analysis (FEA) as a one-way slab model was then conducted. The increase in aspect ratio (L/d) from 18.33 to 26.67 shows a reduction of 50% and 69.6% on the ultimate flexural strength capacity as obtained experimentally and in FEA models, respectively. Theoretical analyses on the extremes of fully composite and non-composite actions were also determined. The experimental results showed that cracking patterns were observed in one direction only, similar to those reported on a reinforced concrete solid slab, as well as precast concrete sandwich panels, when both concrete wythes act in a single composite manner. The experimental results were compared with FEA model data, and a significant degree of accuracy was obtained. Therefore, the PFCSP slab can serve as an alternative to the normal concrete slab system in buildings

Structural behavior of axially loaded precast foamed concrete sandwich panels

This paper presents results from an experimental and analytical study of precast foamed concrete sandwich panels (PFCSPs). Full-scale experimental tests of six PFCSPs were conducted to study the behavior of the panels under axial loads. Foamed concrete (FC) was used to cast PFCSP concrete wythes. The axial load-bearing capacity, load–deflection profiles, load–strain relationships, slenderness ratio, load–displacement, load–deformation, failure and collapse modes, cracking patterns, and propagations under constant increments of axial loads were recorded and discussed. The properties and use of FC were briefly reviewed. Results of the experimental test and finite element analysis were compared with the theoretical values calculated based on the American Concrete Institute (ACI) design equation for a solid concrete wall and other empirical formulas developed by antecedent researchers which might be applicable to predict the ultimate load-bearing capacity of sandwich panels. A semi-empirical formula was proposed based on the laboratory test and finite element analysis results

Analytical mechanics solution for measuring the deflection of strengthened RC beams using FRP plates

Partial-interaction due to sliding between the steel bars, adhesively attached FRP plates and their bordering concrete surface, accompanied with the detachment of the FRP plates due to intermediate crack (IC) debonding make the deflection of strengthened RC beams difficult to anticipate. Previous research and design rules on determining the deflection of strengthened RC beams using FRP plates have opted for a full-interaction moment-curvature design technique where the deflection was measured by either deriving average effective moment of inertia and using elastic deflection equations or integrating the curvature along the beam’s length. Therefore, IC deboning of the plate and the slip resulting from the formation and broadening of new cracks were not directly considered. In this study, a partial-interaction moment-rotation analysis of an adhesively plated beam segment was used to derive analytical equations for the rotation of individual crack faces. The analytical expressions were used to compute the rotation at a crack for a given moment; subsequently, the influence of each crack to the midspan deflection of the RC beams was calculated. As for the uncracked region of the beam, the deflection contribution was measured by integrating the curvature over the uncracked span. The deflection results from the mechanics solution seem to compare well with experimental results. The analytical mechanics solution accounts for the partial-interaction between the steel bars, externally bonded FRP plate and their bordering concrete surface, and also the detachment of the external plate through IC debonding. Further, due to its generic nature and non-reliance on empirical data, the mechanics solution can be adopted to forecast the deflection of strengthened RC beams with novel types of reinforcement materials

Structural performance of precast foamed concrete sandwich panel subjected to axial load

In this paper, experimental and simple analytical studies on the structural behavior of Precast Foamed Concrete Sandwich Panel (PFCSP) were reported. Full-scale tests on six PFCSP panels varying in thickness were performed under axial load applications. Axial load-bearing capacity, load-deflection profiles, load-strain relationships, slenderness ratio, load-displacement, load-deformation, typical modes of failure and cracking patterns under constantly increasing axial loads were discussed. Nonlinear Finite Element Analysis (FEA) using LUSAS software to investigate the structural behavior of PFCSP was contacted. The computed ultimate strength values using American Concrete Institute equation (ACI318) and other empirical formulas developed by pervious researchers which applicable to predict the ultimate strength capacity of sandwich panels were compared with the experimental test results and FEA data obtained; therefore, very conservative values resulted, a significant agreement with the FEA data that presented a high degree of accuracy with experiments and an increase in slenderness function

Structural behavior of laterally loaded precast foamed concrete sandwich panel

Experimental and analytical studies were carried out to investigate the structural behavior of precast foamed concrete sandwich panels (PFCSP) of total number (6) as one-way action slab tested under lateral load. The details of the test setup and procedures were illustrated. The results obtained from the experimental tests were discussed which include the observation of cracking patterns and influence of aspect ratio (L/b). Analytical study of finite element analysis was implemented and degree of composite action of the test panels was also examined in both experimental and analytical studies. Result shows that crack patterns appeared in only one-direction, similar to reports on solid slabs, particularly when both concrete wythes act in a composite manner. Foamed concrete was briefly reviewed and experimental results were compared with the finite element analyses data which gives a reasonable degree of accuracy. Therefore, based on the results obtained, PFCSP slab can be used as an alternative to conventional flooring system

Structural behavior of precast foamed concrete sandwich panel subjected vertical in-plane shear loading

Experimental and analytical studies were accomplished to examine the structural behavior of precast foamed concrete sandwich panel (PFCSP) under vertical in-plane shear load. PFCSP full-scale specimens with total number of six were developed with varying heights to study an important parameter slenderness ratio (H/t). The production technique of PFCSP and the procedure of test setup were described. The results obtained from the experimental tests were analysed in the context of in-plane shear strength capacity, load-deflection profile, load-strain relationship, slenderness ratio, shear cracking patterns and mode of failure. Analytical study of finite element analysis was implemented and the theoretical calculations of the ultimate in-plane shear strengths using the adopted ACI318 equation for reinforced concrete wall were determined aimed at predicting the in-plane shear strength of PFCSP. The decrease in slenderness ratio from 24 to 14 showed an increase of 26.51% and 21.91% on the ultimate in-plane shear strength capacity as obtained experimentally and in FEA models, respectively. The experimental test results, FEA models data and theoretical calculation values were compared and provided a significant agreement with high degree of accuracy. Therefore, on the basis of the results obtained, PFCSP wall has the potential use as an alternative to the conventional load-bearing wall system

Structural behavior of out-of-plane loaded precast lightweight EPS-foam concrete C-shaped slabs

This study aimed to develop optimum lightweight expanded polystyrene foam (LEPSF) concrete with a compressive strength of 35 MPa at a density of 1980 kg/m3, to produce precast LEPSF concrete C-shaped slabs with different parameters. LEPSF beads and quarry dust were used as partial replacements for coarse and fine aggregates at different percentages of (15%, 22.5%, and 30%) and (7.5%, 15%, and 22.5%), respectively. From the findings of this investigation, it was noticed that the use of LEPSF beads resulted in acceptable early age strength; however, a reduction in strength was observed at a mature age. Meanwhile, the use of quarry dust improved the compressive strength of LEPSF concrete by more than 30% compared to the mixtures with EPS alone. Totally, 256 samples were prepared to examine the physical and engineering properties of LEPSF concrete mixtures. Results revealed that the deflection of the full-scale LEPSF concrete C-shaped slabs was 31.5%–45.7% more than that recorded in comparable normal concrete slabs. Meanwhile, results have shown that the ductility of the precast LEPSF concrete C-shaped slabs improved in comparison to the normal concrete samples and they also exhibited 20% reduction in the self-weight. It was also seen that precast LEPSF concrete C-shaped slabs give more warning time before failure occurs. As such, it was concluded that the developed precast LEPSF concrete C-shaped slabs have a significant potential to be adopted in flooring systems of modern buildings today

RC beam strengthening using hinge and anchorage approach

Retrofitting of existing structures using adhesively bonded plates has been a major growth area in civil engineering and has gained well-deserved popularity over the past few years. This strengthening technique is in line with sustainable practices in construction and can be used to preserve eminent structures of historical or cultural values. This study aims to present an ideal design model for strengthening reinforced concrete elements using the hinge and anchorage design philosophies for retrofitting and plating existing structures. This includes a check on the intermediate crack (IC), critical diagonal crack (CDC), and plate end (PE) debonding mechanisms. The results of a theoretical model for an FRP plated reinforced concrete beam element were presented, and the findings showed that plating increased the shear at the datum point to cause a diagonal crack by 46.7%. The increase in moment capacity due to plating the hogging region was 64.3% while allowing for 30% moment redistribution from the sagging region to the hogging region. The accompanying increase in uniformly distributed load due to 30% moment redistribution was 42.8%. The results of the theoretical model were compared with previous design models for IC debonding to which it has been shown that following the anchorage approach, a higher strain in the plate may be allowed as compared to the hinge approach. In addition to the theoretical model presented, analysis on an FRP plated RC beam and slab were also presented to show the effect of different plate widths on the moment capacity and PE moment capacity