Properties of Hardened Cement Paste Depending on Silane Based Chemical Admixtures / Cheminiu Priedu Silanu Pagrindu Itaka Cementinio Akmens Savybems

The article focuses on the influence of water repellent, silane based concrete admixtures on the physical, mechanical and porosity properties of hardened cement paste. To obtain the expected results, six compositions of cement slurries were designed changing the amount and type of the silane based chemical admixture. In order to obtain technological, physical and mechanical properties of cement (slurry) stone, the following experiments, including a test on the flow characteristics of cement slurries, a test on compression and bending strength as well as the analysis of porosity and resistance to frost were accomplished. On the basis of the achieved results and using a different amount and type of silane based chemical admixtures, the flow characteristics of cement slurry has increased up to 1,47 times in respect to the control specimen. On the other hand, when using the above introduced silane based chemical admixtures, the obtained results show a decrease in the density and strength of compression and bending. By adding chemical admixture “WACKER BS 1701” 0,2% and taking into account the amount of cement, a decrease in density goes up to 2,4%. The most noticeable decrease in bending strength (26%) is obtained by using WACKER BS SMK 2101 (0,1% in respect to the amount of cement). In addition, the biggest decrease in compression strength (34,6%), considering the control specimen, can be noticed when using SILRES BS 290 (0,2%) as a silane based chemical admixture. Water absorption of the control specimen with no silane based chemical admixtures is very similar to those containing them (vary around 1). The properties of porosity (opened and closed) are also very close and vary around 2% at the maximum. The indicator of medium pore size-λ shows that the control specimen include large pores (λ = 7,92). In most cases, by using the silane based chemical admixture, minor pores are obtained (λ = 0,94 – 3,66). The results received following 100 cycles of freezing-thaw show that all specimens have passed the test. Their surfaces did not contain any cracking.