Should i be concerned walking to my car from my building due to silica exposure from road work being done down the street from my building?

NO: It is very unlikely that you would develop a serious problem with such short exposure. Silicosis usually happens to workers exposed for a long time. If it is a construction, should be short term. However, some people with allergies might feel some effects. http://www.hse.gov.uk/construction/faq-dust.htm. I haven't found any evidence that masking is necessary for the public. I hope this helps