Two factors are driving the growing trend to rehabilitate damaged concrete structures: one, a need to keep these structures operational, and two, a responsibility to prevent demolition’s negative environmental effects. Finding a material that is durable, resistant, and inexpensive is critical. The extensive body of research to date has identified polymeric or resinous materials as the preferred choice, as they are widely available and are able to create a good cohesive bond. Adhesion, or the bond between the substrate and the repair material, is literally the glue that keeps it all together. While adhesives for concrete have been studied at length, there has been little focus on usable repair materials for thin or narrow places with complex geometries.
Researchers Karim Belmokretar, Kada Ayed, Djamel-Eddine Kerdal, Nordine Leklou, and Mohamed Mouli propose the use of self-compacting sand concrete as a cementitious repair material in their recent work, “New Repair Material for Ordinary Concrete Substrates: Investigating Self-Compacting Sand Concrete and Its Interaction with Roughness of the Substrate Surface.” In this Journal of Materials in Civil Engineering paper, the authors formulated nine SCSC mixes and selected the best mix to use for their cementitious repair material. They evaluated the bond strength of the mixes using two different pour techniques, as well as a pull-off test. Learn more about their successful development of a fluid concrete repair material that demonstrates excellent compressive strength, acceptable bond strength, and low porosity at https://doi.org/10.1061/JMCEE7.MTENG-15348. The abstract is below.
Abstract
This experimental investigation studied the development and use of a new self-compacting sand concrete (SCSC) to perform repairs on ordinary concrete (OC) substrates. This type of concrete should have the following characteristics: excellent fluidity, optimum stability, and acceptable bond strength. In addition, a new pouring method was used for the application of the repair layers. For this, nine SCSC compositions were tested for slump flow using an Abrams cone, passing ability by the L-box test, segregation resistance by the screen stability test, and compressive strength. The results obtained from these tests were then employed for selecting the best composition to use as a repair material. In addition, the volume of permeable pore and water absorption was determined by immersion tests. The compressive strength tests were carried out at three different ages, i.e., 7, 28, and 90 days, for the purpose of determining the physical and mechanical characteristics of ordinary concrete (OC) and those of SCSC, separately. The bond strength between the substrate (OC) and the repair concrete (SCSC) was evaluated by performing two tests: a tensile splitting test (indirect tension test) and a concrete pull-off test (direct tensile test), which was also used for the evaluation of the tensile strength of the concrete substrate (OC) and that of the repair concrete (SCSC). The resulting bond strength values showed that it is indeed possible to use SCSC as a repair material in thin and narrow places, and even those having complex geometries.
Practical Applications
This research aims to develop a novel, highly fluid, self-compacting sand concrete (SCSC) that is intended to be used as a cementitious repair material for the rehabilitation or reinforcement of civil engineering structures. The high fluidity of this type of concrete makes it an exceptionally workable material that has the capacity to flow through tightly reinforced elements or circulate into sections having geometrically complex shapes. SCSC is exceptionally effective for repairing narrow areas, such as the intersection of reinforced concrete members where reinforcement is overlapped, and for fixing sections below horizontal surfaces, such as bridge decks and other similar structures. The results obtained are very encouraging, with more than 70 MPa for the compressive strength and more than 3 MPa for the tensile strength. In addition, the ingredients making up this concrete are readily available almost everywhere. They can be utilized without specific manufacturing efforts. Some of the constituents of self-compacting sand concrete are fine natural sand, recycled sand and aggregates, and sand recovered from limestone waste.
Get the details on how you can use SCSC in concrete repairs in the ASCE Library: https://doi.org/10.1061/JMCEE7.MTENG-15348.
