求一篇土木工程工民建有关的英文文章，完整的，不要太多字，有没有中文翻译无所谓

The damage processes of ordinary concrete and high strength concrete,attacked by solutions of 2.5%,5.0% and 10%Na2SO4(mass fraction)are studied.And the effects of flexural loads with stress ratios of 25% and 50% of the initial flexural strength on the damage process of concrete are also investigated.The results show that the damage process of concrete attacked by sulfate salt exhibits an initial damaged stage,a performance improving stage and a performance worsening stage.When the concentration of Na2SO4 in a solution increases from 2.5% to 5.0%,the service time of the concrete decreases approximately 25%.Furthermore,it decreases to even 40% with an increase in a Na2SO4 concentration up to 10%.And the flexural load accelerates the deterioration rate of the concrete in the latter period.The stress ratio increases from 0 to 25%,the failure time of the concrete decreases 15%and the failure time decreases between 25% and 35% when the stress ratio increases from 25% to 50%.In addition,sulfate corrosion products of concrete are studied by SEM (scanning electron microscopy),EDS (energy disperse spectroscopy) and XRD(X-ray diffraction).

SEM是Search Engine Marketing的缩写，中文意思是搜索引擎营销。SEM是一种新的网络营销形式。SEM所做的就是全面而有效的利用搜索引擎来进行网络营销和推广。SEM追求最高的性价比，以最小的投入，在搜索引擎中获最大的访问量并产生商业价值。 现在随着互联网的深入生活，方便人们的生活，例如现在大家都普遍使用的B2C网站，还有网上缴费等等，很多都运用了SEM。 SEM可以在搜索引擎中进行品牌的维护，将品牌的负面信息尽可能少的呈现在搜索用户面前，可以预防竞争对手在网络上恶意的诬陷。同时可以在进行正面和商业信息的推广，进而达到品牌推广的目标。

---