Crumb rubber aggregate coatings/pre-treatments and their effects on interfacial bonding, air entrapment and fracture toughness in self-compacting rubberised concrete (SCRC)

Optimisation of rubberised concrete with high rubber content: An experimental investigation

“…100% sand replacement) [25]. The lower compressive strength of RuC can be attributed to the relatively high Poisson's ratio of rubber particles (nearly 0.5), the high porosity of the composite and the weak rubbercement paste bond (or Interfacial Transition Zone, ITZ) [26,27]. Other factors that reduce RuC strength include segregation, lower overall stiffness of the composite and casting and consolidation techniques [28].…”

“…To improve rubber-cement paste chemical/physical bonding [18], several rubber pre-treatments have been investigated such as washing with water [21,35,42], polyvinyl alcohol [43], NaOH [13,41,44,45], Ca(OH) 2 [46], silane coupling agents [47], organic sulphur compounds [48] or acid [40], as well as partial oxidation of the rubber surface [49], exposure to UV radiations [50] or pre-coating with cement [51], mortar [26], silica fume [39], limestone [52] or sand [45]. Despite some success in rubber pre-treatments (strength increase in the range of 3-40% [18,26,41,51,52]), results are often scattered and inconclusive, particularly when mixes with pre-treated rubber are not compared to mixes with as-received rubber [35,42]. The effects of the pre-treatments on the concrete hydration reaction and long term durability have not been investigated.…”

Mechanical Properties of Self-Consolidating Rubberized Concrete with Different Supplementary Cementing Materials

“…For example, Emiroglu et al [15] investigated the microstructure of the ITZ of rubberized concrete using Scanning Electron Microscopy (SEM) and found that the poor bonding between the rubber particles and mortar led to generate micro cracks started from and around the ITZ and affected negatively the mechanical properties. Also Najim and Hall [16] reported in their SEM investigation that a significant interfacial de-bonding and micro cracks were observed between the rubber particles and cement paste. The reduction of the compressive strength with higher percentages of CR may also be attributed to the significant difference between the modulus of elasticity of the rubber and the aggregate, as mentioned earlier [5].…”

Flexural fatigue performance and mechanical properties of rubberized concrete

“…The strength reduction in concrete cubes resulting from an increase in rubber content is due to two reasons. First, rubber particles have a greater air content compared to river sand, which leads to a lack of adhesion between rubber particles and other concrete materials [13,16]. Second, compared to aggregate, rubber has lower stiffness, and so a higher proportion of rubber particles in concrete reduces the mass stiffness and decreases its load bearing capacity [17].…”