Indian Concrete Journal

Strengthening of bridge-deck overhangs for sound wall addition using NSM FRP composites Anna Pridmore, Vistasp M. Karbhari

Increasing urban sprawl is resulting in buildings and inhabited areas being located closer to highways resulting in complaints regarding noise from traffic. Sound walls and noise barriers are often used to decrease noise. In the case of elevated bridges, the barriers have to be added to existing decks resulting in the need for substantial addition of overhang steel reinforcement to carry the additional load. In many cases related to older box-girder bridges, this either is not feasible structurally or requires substantial demolition of the existing structure with the consequent extensive disruption of traffic. The use of near surface mounted (NSM) fiber-reinforced composite (FRP) strips as additional reinforcement on the overhang region is shown to be an effective strategy enabling efficient and cost-effective rehabilitation of box-girder type bridge decks without extensive modification of the existing structure and much less disruption of traffic.

Sintered fly ash lightweight aggregate - its properties and performance in structural concrete P. N. Ojha, Brijesh Singh, Ashok Kumar Behera

The paper presents study conducted on sintered fly ash coarse aggregate produced indigenously. The sintered fly ash coarse aggregate [Low Density Aggregate (LDA) / Lightweight Aggregate (LWA)] is lower in density in comparison to normal weight aggregate. In the current study, class F fly ash has been used. The two fractions of sintered fly ash coarse aggregates (8-16 mm and 4-8 mm) were evaluated. Experimental programme evaluated the micro-structural, physical and chemical properties of sintered fly ash coarse aggregates for its suitability in making concrete for masonry units, hollow and solid lightweight concrete blocks, and structural lightweight concrete (SLC) for non-wearing surfaces. The paper also presents the experimental study on suitability of sintered fly ash lightweight aggregate in structural concrete. Concrete with sintered fly ash aggregate has been made at two watercement ratios (0.55 and 0.45). The various mechanical properties such as compressive strength, flexural strength, split tensile strength, drying shrinkage, modulus of elasticity, and Poisson’s ratio have been determined. The durability properties has also been investigated conducting rapid chloride ion penetration test (RCPT), electrical resistivity, chloride migration test, water permeability, and sorptivity (absorption) index. The mechanical and durability properties of LWAC have been compared with corresponding test results of normal weight aggregate concrete (NWAC) at same water-cement ratio of 0.55 and 0.45. The finding of the study has been useful for formulation of a new Indian Standard for production of structural lightweight concrete (SLC) using sintered fly ash lightweight coarse aggregate.

Novel textile-reinforced concrete-cold form steel cavity wall panel system for fast track construction V. Ramesh Kumar, Smitha Gopinath

Resilient infrastructure creation in a fast track manner is the need of the day. In this context, textile-reinforced concrete (TRC) is a highly promising construction material when integrated with cold form steel. This paper presents the development of a novel cavity wall panel system consisting of two prefabricated composite of TRC panels and profiled cold form steel sheet connected together using a spacer system. The novelty is hinged upon the spacer being used in this construction of cavity wall panel system facilitating an easy and efficient construction. Preliminary investigations were carried out on proposed wall panel system under axial compressive loading. Experimental results were examined with respect to response characteristics and failure modes for load-bearing wall panel applications.

Fracture studies on fiber-reinforced rubcrete Anand Raj, Praveen Nagarajan, A. P. Shashikala

This paper presents the details of studies carried out to investigate the fracture energy of fiber-reinforced rubcrete with an aim to assess the improvement in ductility. A three-point bend beam test was carried out using 18 mixes with compressive strength of 20 N/mm² as per RILEM TC-50 FMC. Experiments were carried out on four rubcrete mixes (with 5, 10, and 15% replacement of fine aggregates with crumb rubber), three polypropylene fiber-reinforced concrete mixes (with 0.1, 0.2, and 0.3% of polypropylene fibers occupying the total volume of concrete), and four steel fiber mixes (with 0.25, 0.5, 0.75, and 1% of steel fibers occupying the total volume of concrete). The fiberreinforced rubcrete mixes included rubcrete mixes with 15% of fine aggregate replacement with crumb rubber. Fracture energy obtained using the work of fracture method provides an insight into the ductility and toughness of concrete. The results of the study indicated that for rubcrete beams, the fracture energy was increased by 14% for rubcrete with 15% crumb rubber. The fracture energy of steel fiber-reinforced concrete beam with 1% steel fiber content was 56% higher than the fracture energy of ordinary concrete. The fracture energy of steel fiber-reinforced rubcrete beam with 1% steel fiber content and 15% crumb rubber content was 92% more than the fracture energy of the ordinary concrete beam. For polypropylene fiber-reinforced concrete beam with 0.3% polypropylene fiber content, the fracture energy was improved by 27%. In the polypropylene fiber-reinforced rubcrete beam with 15% crumb rubber content and 0.3% polypropylene fibers, the enhancement in fracture energy was 57%. Significant improvement in ductility was achieved using steel fiber-reinforced rubcrete mix with 1% steel fibers and 15% crumb rubber when compared to concrete.

Performance of polymer-modified fiber-reinforced high strength concrete Praphulla K. Deshpande, Keshav K. Sangle, Yuwaraj M. Ghugal

This paper presents the results of polymer-modified fiberreinforced concrete (PMFRC). The various strengths considered in this investigation are compressive, flexural, and shear strengths. The regimes of dry air curing are 28 days and 90 days. The M-40 grade of concrete is used as a reference mix. The fiber content was varied from 1% to 10% by weight of cement at the interval of 1% with 5% constant dosage of SBR (Styrene Butadiene Rubber) polymer. Cubes, prisms, and push-off specimens were prepared and tested subsequently at the ages of 28 days and 90 days. The significant improvement in compressive, flexural, and shear strengths, as well as ductility and toughness is observed due to synergistic effect of polymer and fibers. The results of effect of number and pull-out length of fibers on failure plane are presented.