Evaluating the performance and durability of concrete paving blocks enhanced by bio-cement posttreatment

Concrete pavement often experiences accelerated deterioration due to water and chemical ingress through micro-cracks and surface voids. Particularly, the ingress of aggressive agents into the concrete matrix results in irreversible changes and deterioration on its endurance. Numerous studies unveiled that hydrophobic surface protection could be an inexpensive and effective way of enhancing the durability of concrete. This research work aims to assess the feasibility of bio-cement posttreatment for facilitating hydrophobic surface protection, thus enhancing the performance and durability of concrete blocks. Enzyme induced carbonate precipitation (EICP) is one of the promising bio-cement methods. Concrete blocks casted in four different grades were subjected to EICP treatment with different treatment schemes and recipes of cementation media. The treated blocks were tested for water absorption, ultrasonic pulse velocity (UPV) measurements, unconfined compressive strength (UCS), thermal performance, and scanning electron microscopy (SEM). The results indicated that the concrete blocks subjected to EICP posttreatment showed over a 55% reduction in water absorption, a 15% higher UCS and a 6.7% higher UPV when compared with control blocks. The SEM analysis suggested that the EICP posttreatment could enhance the durability of concrete paving blocks by enabling a layer of calcite on the surface and by plugging the transport pore channels of the concrete. Although most of the posttreatment strategies investigated herein were found to be operative, a better response was seen in the posttreatment by spraying scheme with 0.5 mol/L cementation media (CM). With the successful demonstration, the EICP treatment prior to the use of concrete blocks can be recommended to the pavement construction industry.