New Repair Material for Ordinary Concrete Substrates: Investigating Self-Compacting Sand Concrete and Its Interaction with Roughness of the Substrate Surface

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.

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.