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maconwaterproofingblogspotcom blogChristos Strogilis (332)    http://www.macon.gr SBR latex for polymer cementitious mixes (3rd part)Posted Tuesday, April 14, 2009 (224 days 22 hours ago.) Viewed 14 times. Effects of SBR addition on the properties of cement mixes -1- Tensile, flexural and impact strength are generally improved. -2- Compressive strength will virtually remain unaltered. Bigger dosages and/or softer lattices may decrease it slightly. -3- Overall durability will be higher. -4- Setting time is generally reduced. -5- Bleeding is reduced due to air entrainment. -6- Creep will slightly increase due to the enhanced flexibility. -7- Abrasion resistance will increase due to the reduction of bleeding and crack formation. -8- Workability will increase for par W/C ratio. ACTION MECHANISMS OF SBR LATEX (1) SBR latex addition in the cement mix can reduce the ratio water/cement for par workability. Or it can increase workability for an unaltered W/C ratio. The polymer articles as well as the entrained air bubbles will have a ball bearing effect in the mix. In other words they will "lubricate" the mix particles by thus reducing the internal friction coefficient. The contained surfactants will additionally improve workability due their dispersion capabilities. (2) SBR latex will reduce bleeding due to its air entraining properties. This will in conjuction with the more favorable cracking profile make the hardened mix abrasion resistant. Antifoams are used as standard additives in most commercial lattices in an effort to control air-entrainment. Air entrainment will also increase with prolonged mixing duration. (3) SBR latex is used in cementitious, waterproofing brushable products to improve their water retention capabilities. These thinly applied products, when applied outdoors suffer from excessive moisture loss, especially if the climatic condition are adverse: high temperatures, strong winds, scorching sun etc. SBR latex addition will create a polymer network, that will help keep the water in the mixture for longer time and will thus lead to a more favorable hydration procedure. (4) SBR latex addition will increase the water resisting properties of modified concrete and mortarts. As water evaporates the coalescence of the latex globules will lead to the formation of an interconnected polymer network within the cementitious matrix. This flexible network will block the pores and help bridge microcracks making concretes and mortars less water permeable. (5) SBR latex addition will help enhance adhesion of the aggregates to the cement paste. The powerful bonding power of the polymer matrix will in a similar way improve the adhesion of the mix to smooth substrates: dense concrete, troweled mortars, steel reinforcement etc. End of 3 rd part Chris Strogilis Civ. Eng. MBA DipM 
Permalink Comments (0) Basements Waterproofing From the Negative Side :application Procedure(1st Part)Posted Monday, March 23, 2009 (246 days 22 hours ago.) Viewed 22 times. Waterproofing from the negative side has serious drawbacks which we have analytically cited in other articles on this website. We should use this type of waterproofing only as an emergency solution.
That said, there are countless occasions when the negative waterproofing emerges as the only option.
The objective of this article is to analyze completely the necessary steps for a successful waterproofing from the negative side.
SURFACE PREPARATION
Cementitious waterproofing products need a thorough preparation of the substrate and this is a serious drawback for these materials.
The surface - most usually concrete - must be structurally sound and clean.
Traces from dirt, formwork release agents, oils, efflorescence and other contaminants should be removed.
Laitance on the floors is a serious trap. It should be thoroughly removed by high pressure water blasting, abrasion blasting or a combination of both.
The final surface should be absorptive (having open pores).
Cracks, concrete honeycombs, bolt holes, construction joints etc. must be adequately cut out and filled with a high strength, non shrinking, waterproof, repair mortar.
Take care: The walls of the repair should be cut vertical or better in the shape of inverted V. This is critical for the right anchorage of the mortar.
All joints and cracks should be cut into at least a 2x2cm section and all holes to a 3x3x2cm opening.
PRE-WATERPROOFING
In the case of active water leaks a quite demanding pre-waterproofing procedure should be followed.
This is a task only for very experienced technicians. Actually when we are talking about waterproofing, there is no more demanding facet of the waterproofing than this.
end of 1st part
Chris Strogilis
Civ. Eng. - MBA - DipM
http://maconwaterproofing.blogspot.com
Permalink Comments (0) Resting( Minimum) Heart Rate:a Reliable Fitness Indicator?Posted Thursday, March 19, 2009 (250 days 17 hours ago.) Viewed 384 times. Resting or minimum heart rate can be a very reliable indicator of your fitness level.
Resting heart rate or RHR is the number of your heart beats per minute measured when you are inactive.
The best time to calculate your RHR is when you are awake first thing in the morning.
You can place your index and middle fingers either on your carotid or on your radial arteries and count your pulse for 20". Multiply by 3 and you are OK.
I won't recommend this methodology. I prefer a heart rate monitor.
Relax and count your pulse for about 60". Your RHR is the lower number on the dial. For a more reliable measurement you can use the average indication of three consecutive days.
The RHR is dependent on various parameters. Some of the most important are:
- Age: A 20 years old man should have a RHR reduced by 3-4 beats/min from a 50 years old man (for the same fitness level).
- Sex: Women have RHRs higher by 3-5 beats/min when compared with men of the same age and fitness level.
- Stress: If you are stressed, your RHR will be higher up to 10%.
- Fitness level: The lower your RHR the more fit you are. Average, healthy men in their thirties have RHRs in the range of 70-75.
If their RHR is 85+ beats, they will have to do something because their heart overworks.
Conversely if their RHR is less than 60 beats/min, they are in an excellent form!
- Overtraining: Overtrained people can have their RHRs increased by 10% or even more compared to their normal measurements.
You can lower your RHR with systematic aerobic activities. This will make you heart a more efficient pump with a higher stroke volume. In other words it will be capable of sending more blood around the body with each beat.
Compare an athlete with a RHR of 50 beats to an unfit man, same age, with a RHR of 100 beats: The second man's heart has to do double job for the same result!
RHR is used to determine the training heart rate zones. This is an issue we will address very soon.
Chris Strogilis
Civ. Eng. - MBA - DipM http://totalfitness-christos.blogspot.com
Permalink Comments (0) Advantages and Disadvantages of Cement Based(cementitious) Waterproofing ProductsPosted Monday, March 16, 2009 (254 days 2 hours ago.) Viewed 325 times. Cement based waterproofing products are used massively all around the world for the waterproofing of projects as: - water tanks - swimming pools - basements - manholes - foundations etc. We will elaborate hereunder on the advantages and disadvantages of these well known and tested waterproofing materials. 1. ADVANTAGES 1.1 These products already have a long, proven track record. A considerable know-how has been developed round their use domain, and a lot of technicians are knowledgeable about their use. 1.2 Cement based waterproofing products are suitable for both negative and positive water pressures. Actually they are the only waterproofing products appropriate for projects with negative pressures. This means that many times they are the only available option. 1.3 Provided that one follows the manufacturer's instructions, they are generally easy to handle and apply. They don't need any sophisticated equipment except for the spray application. 1.4 They contain no solvents and are user and environment friendly. 1.5 They are suitable for contact with potable water. They are the mainstream product for the waterproofing of water tanks and reservoirs and can withstand very high positive pressures. 2. DISADVANTAGES 2.1 Conventional cement based waterproofing products are prone to cracking (following the substrate's cracks). Therefore they are not ideal for situations as the following: - vibrating substrates - when settlement is expected - when there is considerable movement of the substrate due to wide temperature fluctuations. 2.2 Cement based waterproofing products need a thorough, minute preparation of the substrate. Not even traces of laitance, dirt, grease, curing compounds etc. are acceptable! This is not an easy task to accomplish under the usual site conditions! 2.3 It is very difficult to provide idoneous curing conditions for these products and the problem is that perfect conditions are critical for their waterproofing behaviour. In Greece this is a major problem especially for the hot season and outdoor applications. 2.4 Cementitious waterproofing products are water vapor permeable. Though this might be considered as a distinctive advantage, there are a lot of applications where this property is mostly undesirable e.g. delamination problems of floor coverings etc. Please check on this website the articles on crystalline and flexible cementitious waterproofing. Chris Strogilis Civ. Eng. - MBA - DipM http:/imaconwaterproofing.blogspot.com http://monosimacon.blogspot.com/
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