Evaluation of microscopic characteristics and repair effects of the flexible grouting material for cement-stabilized macadam

Cement-stabilized macadam (CSM) is prone to cracking and voids due to prolonged temperature variations, load, and hydration shrinkage, accelerating the deterioration of overall pavement performance. Grouting technology is commonly employed to repair CSM, with the properties of grouting materials significantly influencing the repair effect. This research proposed a flexible grouting material (FGM), revealed the underlying mechanisms through microanalysis, and evaluated the grouting repair effect and deformation characteristics using the semicircle bending (SCB) test combined with digital image correlation (DIC). The results indicate that the vinyl acetate- ethylene (VAE) latex in FGM reduces calcium hydroxide (CH) and ettringite (AFt) content between 3 and 7 days. With extended curing time, the characteristic peaks of Si-O bonds in calcium silicate hydrate (CSH) shift to higher wave numbers. The less harmful pores (27.32 %-*5.82 %) in FGM change to harmless pores (54.41 %-* 76.79 %), then the overall porosity of FGM decreases. The repair efficiency of CSM specimens improves as the grouting crack width increases, reaching a maximum repair effectiveness of 94.70 % at a width of 9 mm. The peak load of the repaired specimens occurs approximately later 10 seconds than that of CSM specimens and exhibits secondary loading peaks. The FGM might repair effectively inhibited crack initiation and propagation.