Polymers have been used as additives in cement mortars and concrete since the 1920s when natural rubber latex was added to road paving materials. Since then, there has been considerable development of polymer modification for cement and concrete. Commercial products, called cement admixtures, are used in many applications in the construction industry from sea walls to roads. A significant volume application for polymer modified Portland cement is adhesive and grout for attaching ceramic tiles to walls and flooring.
Often there is confusion with regard to the terminology associated with the production and application of these materials. Some of the more common terms that are used in the construction industry are defined in Table 1.
Portland Cement - Portland cements are based on calcium silicate, CaSiO3. Portland cement, the fundamental ingredient in mortar and concrete, is calcium silicate cement made from a combination of calcium, silicon, aluminum, and iron oxide minerals. Clinker is a fused mineral mixture of limestone, shells or chalk and shale, clay, sand, or iron ore, which is crushed into a fine powder to manufacture Portland cement. Portland cements harden by hydration of the calcium silicate via reaction with water. |
Mortar- Generally a combination of Portland cement, sand aggregate, and water. Certain grades of cements may contain additions of fine aggregates of fumed silica, fly ash or milled slag as well as chemical additives to improve strength, entrain air, reduce heat generation and cracking, or improve corrosion resistance. |
Concrete- Generally a combination of Portland cement mortar and larger aggregates such as stone. |
Polymer Modified Cement - Portland cement modified with polymer additions (usually polymer latexes) to improve plasticity, water resistance, adhesion, or allow use in cold or freezing weather conditions. |
Thin-Set or Dry-Set Mortar - A mixture containing Portland cement, sand, and chemical additives that imparts plasticity and water retention. Used as a bond coat for installing ceramic tile. |
Polymer Modified Thin-Set Mortar - Polymer modified cement with aggregate. It provides an adhesive or grout with extremely high bond strength, superior to cements that are mixed with water only. Generally used for application of exterior or frost proof tiles and in applications where tiles are subjected to physical shock, thermal shock, and / or frost. |
There are several different types of polymers that have been used as additives in cement and concrete. These can be broadly divided into four groups: polymer latex (or polymer dispersion) redispersible polymer powder, water-soluble polymer, and liquid polymer. There are many different families of polymers that are associated with each type as summarized in Table 2.
Table 2: Polymer Products Used to Modify Portland Cement |
The polymers interact with the components of Portland cement when it comes in contact with water. This interaction is due primarily to ionic bonding, causing crosslinks, which inhibit the film formation property of polymers and influence considerably the crystallization process during the hardening of the cement.
Polymer modification of cement mortar and concrete noticeably improves application and performance characteristics. Admixtures can improve the concrete properties, particularly in relation to water absorption reduction, toughness enhancement, vibration damping and increase of the bond strength of cement to reinforcements. These characteristics permit the use of mortar and concrete in applications and environments where construction projects have previously been difficult or altogether impractical.
Since polymers are more expensive than cement, polymer admixtures are used in niche applications where these properties
本站所有信息与内容，版权归原作者所有。网站中部分新闻、文章来源于网络或会员供稿，如读者对作品版权有疑议，请及时与我们联系，电话：025-85303363 QQ：2402955403。文章仅代表作者本人的观点，与本网站立场无关。转载本站的内容，请务必注明"来源：林中祥胶粘剂技术信息网（www.adhesive-lin.com）".
©2015 南京爱德福信息科技有限公司 苏ICP备10201337 | 技术支持：南京联众网络科技有限公司
加载中...
