Impact Resistance Of Concrete Research Articles

Improving the Impact Resistance of Reinforced Concrete

The strategic concrete structures are often required to resist impact loads arising from the projectile strike, falling weight, blast generated missile etc. The existing structures found deficient in resisting these loads are required to be retrofitted whereas the upcoming structures are required to be designed for expected impact loads. This paper explores the ways of strengthening existing reinforced concrete (RC) structures using externally bonded carbon fiber reinforced polymer (CFRP) sheets and improving the impact resistance of concrete by mixing hybrid fibers in its production. The impact response of concrete structures is assessed using experiments involving the impact of projectiles of different nose shapes on slab specimens. The material behavior at high strain rate is established using split Hopkinson pressure bar (SHPB) testing at varying strain rates. Analytical models are developed for predicting penetration depth, scabbing thickness, ballistic limit velocity and ejected mass. The experimental results were also validated through numerical modeling using LS-DYNA.

Effect of internal short fibers, steel reinforcement, and surface layer on impact and penetration resistance of concrete

This paper presents an experimental program to investigate the impact and penetration resistance of concrete. The research work is divided into two approaches. These approaches are effect of concrete constituents and effect of surface layer. Effect of concrete aggregate type, w/c ratio, fiber type, fiber shape, fiber volume fraction, and steel reinforcement is considered in the first approach. The second approach includes using fiber reinforced concrete and glass fiber reinforced polymer as surface layers. The evaluating tests include standard impact test according to ASTM D 1557 and suggested simulated penetration test to measure the impact and penetration resistance of concrete. The test results of plain and fibrous concrete from ASTM D 1557 method indicated that steel fiber with different configurations and using basalt have a great positive effect on impact resistance of concrete. Moreover, the simulated penetration test indicates that steel fibers are more effective than propylene fibers, type of coarse aggregate has negligible effect, and steel fiber volume fraction has a more significant influence than fiber shape for reinforced concrete test panels. Finally, as expectable, surface properties of tested concrete panels have a significant effect on impact and penetration resistance.

SHPB Dynamic Experiment on Silica Fume Concrete

Dynamic mechanical properties of silica fume concrete in a number of strain rate under the conditions of dynamic compression mechanical properties subjected to various strain rates were studied, and gained the stress versus strain curves, details of an experimental investigation using 74 mm-diameter split Hopkinson pressure bar(SHPB) apparatus were presented. The results showed that: The admixture of silica fume concrete impact resistance, especially under the impact of the performance of high-speed has a very important influence, with the impact velocity increased, the strain rate increase, and its impact more obvious.

Effects of Water-Borne Polyurethane on Calcium Silicate Hydrate and Toughness of Properties of Cementitious Composites

A novel kind of block polymer with characteristics of rod-like chain conformations-water-borne polyurethane (PUA) was synthesized by incorporate polyacrylate (PA) into the PU chain to prepare an aqueous polyurethane-polyacrylate (PUA) hybrid emulsion with core-shell structure. The interactions between Water-borne PUA and C-S-H nanostructure, which include intercalation and the polymerization degree of C-S-H silicate chains, were studied by small angle X-ray diffraction spectra and 29Si NMR spectra, respectly. The influences of water-borne PUA on mechanical performance of C-S-H were investigated experimentally. The small XRD results show that no evidence is observed for any fundamental size change in the C-S-H particles that have been formed in the presence of polymer. The NMR results indicate that there is a significant increase in the Q2/Q1 ratio ranging from 0.5 for pure C-S-H to 2.2 for PUA-C-S-H, respectively. The degree of silicate polymerization increases from 3.0 for pure C-S-H to 6.4 for PUA-C-S-H by calculation. PUA had minimal harmful effect on the compressive strength whereas the flexural strength was increased by 23.2% with dosage of 0.5% and 23.3% with dosage of 1.0%, respectively.The fracture energy ratios of concrete with a dosage of PUA less than 1% are greatly improved more than double with the decreasing of concrete strength less than 10%. The water-borne PUA also enhances the impact resistance of concrete. The impact energy consumption of samples with PUA increase nearly three times more than reference samples, also better than samples with PP fiber.

Toughness Properties of Concrete Modified with Water-Borne Polyurethane

A novel kind of block polymer with characteristics of rod-like chain conformations, water-borne polyurethane (PUA), was synthesized by incorporate polyacrylate (PA) into the PU chain to prepare an aqueous polyurethane-polyacrylate (PUA) hybrid emulsion with core-shell structure. The influence of water-borne PUA on workability and mechanical performance of concrete were investigated experimentally. PUA had minimal harmful effect on the compressive strength whereas the flexural strength was increased by 23.2% with dosage of 0.5% and 23.3% with dosage of 1.0%, respectively. The fracture energy ratios of concrete with a dosage of PUA less than 1% are greatly improved more than double with the decreasing of concrete strength less than 10%. The water-borne PUA also enhances the early plastic cracking resistance and the impact resistance of concrete. The impact energy consumption of samples with PUA increase nearly three times more than reference samples, also better than samples with PP fiber. And PUA can refine the crack from 2-4mm to 0.2-0.5mm of the main distribution, decreasing total area of crack greatly.

Impact Resistance of Concrete with Partial Replacements of Sand and Cement by Waste Rubber

Effects of partial replacements of sand by waste crumb rubber and fine rubber, and cement by powder rubber, on the performance of concrete under low velocity impact loading were investigated. Specimens were prepared for 5%, 10% and 20% replacements by volume for both sand and cement. For each case, six beams of 100 mm × 100 mm × 500 mm were subjected to 5.15 kg hammer from 900 mm height. The number of blows of the hammer required to induce the first visible crack and ultimate failure of the beam were recorded. The results are presented in terms of impact energy required for the first crack and ultimate failure. The crumb and fine crumb rubbers increased the impact energy for both first crack and ultimate failure; the increase of impact resistance by crumb rubber was more than that by fine crumb rubber. However, the impact energy for both first crack and ultimate failure increased by the replacement of sand with fine crumb and crumb rubbers until 20%, while this energy increased with cement replacement by powder rubber until 10% replacements and then decreased, but is still higher than that of plain concrete.

Study on Performance of High-Performance Concrete Made with Fly Ash and Polypropylene Fiber

High-performance concrete was made with fly ash and polypropylene fiber, the study shows that when fly ash content was 20% and polypropylene fiber was 0.6~1.2kg/m3, it had no significant influence on the workability of concrete, however the changes of 28d compressive strength and drying shrinkage of concrete are within 10%, but it can reduce brittle and improve toughness, and impact resistance of concrete is improved obviously, when polypropylene fiber content was 0.9kg/m3, it can improve over three times.

The effects of silica fume and polypropylene fibers on the impact resistance and mechanical properties of concrete

Impact resistance and strength performance of concrete mixtures with 0.36 and 0.46 water–cement ratios made with polypropylene and silica fume are examined. Polypropylene fiber with 12-mm length and four volume fractions of 0%, 0.2%, 0.3% and 0.5% are used. In pre-determined mixtures, silica fume is used as cement replacement material at 8% weight of cement. The results show that incorporating polypropylene fibers improves mechanical properties. The addition of silica fume facilitates the dispersion of fibers and improves the strength properties, particularly the impact resistance of concretes. It is shown that using 0.5% polypropylene fiber in the silica fume mixture increases compressive split tensile, and flexural strength, and especially the performance of concrete under impact loading.

Flexural toughness and impact resistance of steel-fibre-reinforced lightweight concrete

This paper presents the flexural toughness, impact resistance, and other properties such as density, compressive and tensile strength, and modulus of elasticity, of both plain and fibre-reinforced lightweight aggregate concrete. It also discusses the effect of the density of coarse and fine aggregate on the flexural toughness and impact resistance. The impact resistance of the concrete was determined using instrumented drop-weight testing equipment. An expanded clay type of lightweight aggregate and steel fibres were used for the concrete. The compressive strength of the lightweight aggregate concrete ranged from approximately 40 MPa to 80 MPa. The results indicated that high compressive strength and density are desirable for good impact resistance of plain concrete, and the incorporation of the steel fibres improved the impact resistance substantially.

Flexural toughness and impact resistance of steel-fibre-reinforced lightweight concrete

This paper presents the flexural toughness, impact resistance, and other properties such as density, compressive and tensile strength, and modulus of elasticity, of both plain and fibre-reinforced lightweight aggregate concrete. It also discusses the effect of the density of coarse and fine aggregate on the flexural toughness and impact resistance. The impact resistance of the concrete was determined using instrumented drop-weight testing equipment. An expanded clay type of lightweight aggregate and steel fibres were used for the concrete. The compressive strength of the lightweight aggregate concrete ranged from approximately 40 MPa to 80 MPa. The results indicated that high compressive strength and density are desirable for good impact resistance of plain concrete, and the incorporation of the steel fibres improved the impact resistance substantially.

Impact Response of Plates Under Drop Weight Impact Testing

Concrete structures are often subjected to long term static and short term dynamic loads. Due to a relatively low tensile strength and energy dissipating characteristics, the impact resistance of concrete is poor. Research work carried out so far towards the development of concrete that exhibits improved impact resistance than conventional concrete showed that the steel fibre reinforced concrete has a good potential as a viable structural material for such applications. The overall objective of the study is to investigate the dynamic behaviour of steel fibre reinforced concrete plates under impact loading with respect to displacement, velocity and acceleration. In the drop weight test, eighteen plate specimens were tested with three different thicknesses of 20,25 and 30mm and with three different steel fibre contents of 0.5,0.75 and 1%.The edges of the plates were fixed on all sides. Displacement versus time, velocity versus time and acceleration versus time behaviour for all the plates tested were studied. It was found that when the aspect ratio of fibres is 50 and 75 there is a marginal increase in energy absorption for change in fibre content from 0.5 to 0.75%. There is a steep increase in energy absorption for a steel fibre content of 1% when the aspect ratio of fibre is 100.DOI: http://dx.doi.org/10.3329/diujst.v7i1.9580Daffodil International University Journal of Science and Technology Vol.7(1) 2012 1-11