Do you read Chinese? If yes, the following are the places of interest in Tianjin :
The following are in Tianjin city :
五大道-异国风情建筑 (you can take horse carriage from the football stadium to go one round, there are about 5 avenues), nothing fantastic
瓷房子 - a small house plastered with ceramics pieces. Was voted the top 10 best design museum in the world. Can take a look if you like China pottery, ceramics, furniture, etc.
古文化街- for China style curios, souvenirs, antiques, etc. So so.
南市食品街 - local products are 十八街麻花,耳朵饼,狗不理包子,小宝栗子 (personally I don't like all of them).
滨江道,和平区步行街 - shopping, nothing fantastic。 In China, most cities have 步行街 which are basically pedestrian street shopping.
The following are in Tianjin TEDA area, Tanggu area :
洋货市场 - fake bags, fake watches, fake belts, etc. The stalls anyhow quote prices, so have to bargain. Sian after a while. Close at 6 pm daily.
外滩 - riverside views, 步行街, eateries, nothing fantastic.
Further away :
佛罗伦萨小镇 - outlet mall. Prices are not really cheap. Italian ambiance.
Tianjin is much bigger than Singapore, but there are not much tourist attractions. Tourists mainly visit as a day trip from Beijing. From TEDA & Tanggu area to Tianjin city, it is about 1/2 hr by cab, or 1 hr by light rail + cab.
Nothing much to do in Tianjin really. You will get bored probably after 2 days. However, you can consider taking the bullet train to Beijing where you have more choices. Bullet train from Tianjin city to Beijing South Station takes only 1/2 hr, approx RMB58 (if I remember correctly). From TEDA/Tanggu, it will take 45 min. From Beijing South Station, take a cab or MRT about 1/2 hr to reach Beijing main area. You are more spoilt for choices in Beijing.