Impregnated Cement Mixes

Ethylsilicate-32 is widely used in various spheres of economy, e.g. as a cementing and impregnating agent in the production of molds for precision molding, etc. For example, the cement obtained by mixing ethylsilicate with various fillers (quartz flour, cinder) solidifies in the cold. It is resistant to acids and weak alkali. Water only improves its mechanical properties. After baking at 300°C, the cement becomes resistant to concentrated alkali as well. 

For the selective absorption of Cs-Cg olefins a reactor (2.0 x0.4 cm) containing silica gel impregnated with concentrated sulphuric acid, was used. The adsorbent was prepared by mixing concentrated sulphuric acid and silica gel (fraction of 60-200 mesh) (3 2, w/w). Silica gel is a good filler for sulphuric acid, as it remains friable even on absorption of a larger amount of acid than its own weight. Other supports (cement, refractory brick) were found to be inefficient. The absorbent must be stored in hermetically sealed vessels as the olefins are no longer absorbed quantitatively if the content of water in the sulphuric acid is about 12% or above. 

PIC is a precast and cured portland cement concrete that has been impregnated with a monomer that is subsequently polymerized in situ. This type of cement composite is the most developed of polymer-concrete products. PCC, on the other hand, is a modified concrete in which a part (10%-15% by weight) of the cement binder is replaced by a synthetic organic polymer. It is produced by incorporating a monomer, prepolymer-monomer mixture, or a dispersed polymer (latex) into a cement-concrete mix. To effect the polymerization of the monomer or prepolymer-monomer, a catalyst (initiator) is added to the mixture. The process technology used is very similar to that of conventional concrete. So, unlike PIC which has to be used as a precast structure, PCC can be cast-in-place in field applications. PC can be described as a composite that contains polymer as a binder instead of the conventional portland cement. 

The technology of concrete soaking with monomeric substance and subsequent m situ" polymerization is relatively new. According to Worn [171], it was initiated by Steinberg in 1968. Beside of the polymer impregnated concretes, there are also the polymer concretes (resin concretes) without cement and the polymer-eement concretes in the latter case cement is mixed with monomer and water to produce the concrete mixture . This question will be discussed in Chap. 10. 

Systematic microscopical analyses of the clinker with its corresponding raw mix and cement are highly recommended. It is not uncommon for the writer to place a portion of the greater than 45-pm cement and raw mix in the same cup with the clinkers for epoxy impregnation and polished thin-section examination. 

Polymer concrete is a composite material formed by polymerising a monomer and aggregate mixture. There is no other cementitious material present in it. PPCC (or LMC) is a Portland cement concrete produced usually by replacing a specified portion of the mixing water with a latex (polymer emulsion). It can also be produced by adding a monomer to fresh concrete with subsequent in situ curing and polymerisation. PIC is a hardened Portland cement concrete with impregnated monomer which is polymerised in situ. 

Acid-resisting Cement. The principal types are as follows 1. Silicate an inert filler bonded with silica gel that has been precipitated in situ from Na- or K- silicate in the presence of Na2SiFg, or from silicon ester. 2. Rubber Latex essentially cement sand mixes impregnated with rubber. 3. Synthetic Resin with an inert filler. 4. Sulphur Cements usually with sand as filler. 5. Bituminous Cements. ASTM specifications for these materials are listed in Vol 4-05 of the Annual Book of ASTM Standards, and number some 25, including specifications for mortars and grouts. 

The cement-based matrices for ferrocement may be subjected to modifications, e.g. by admixtures of polymers and resins to the fresh mix or by impregnation of hardened ferrocement. The modifications are aimed at particular improvements of the final product, mainly an increase of strength or impermeability. 

Polymer concretes are those in which polymers are either impregnated in hardened concrete, incorporated in the mix, or replace portland cement. Impregnated polymers can double compressive strength and elastic modulus, decrease creep, and improve resistance to freezing and thawing. They are used in concrete road surfaces. Polymers added to the mix are used for resurfacing roads. They hasten cure time. Polymer concretes in which a... 

Combinations with polymers can be obtained by impregnation of the hardened composite (polymer impregnated concrete - PIC) or with a polymer latex which is added during mixing (latex modified cement - LMC) [137]. Both types of polymer incorporation would be expected to increase the matrix strength and the fibre-matrix bond. However, their influence on the other matrix properties is quite different. In PIC, the matrix has a higher modulus of elasticity and becomes more brittle, while in LMC the matrix will be more ductile with a lower modulus of elasticity. 

---