Experience of watertight construction joints in concrete / Ways of avoiding joints
Experience of watertight construction joints in concrete / Ways of avoiding joints
(OP)
Hi
Has anyone had experience of producing large continuous concrete structures that must be kept water tight?
My concerns are primarily with cracks caused by plastic shrinkage. If I wanted to produce a continuous concrete element 30m long (i.e. a wall) without any major cracking would precasting the element in smaller sections and joining them together by an insitu concrete pour over exposed reinforcement be a reliable way of avoiding plastic shrinkage issues?
Or has anyone had experience using admixtures to prevent cracking in large continuous elements?
Any advice / thoughts welcome
Has anyone had experience of producing large continuous concrete structures that must be kept water tight?
My concerns are primarily with cracks caused by plastic shrinkage. If I wanted to produce a continuous concrete element 30m long (i.e. a wall) without any major cracking would precasting the element in smaller sections and joining them together by an insitu concrete pour over exposed reinforcement be a reliable way of avoiding plastic shrinkage issues?
Or has anyone had experience using admixtures to prevent cracking in large continuous elements?
Any advice / thoughts welcome





RE: Experience of watertight construction joints in concrete / Ways of avoiding joints
As far as admixtures, there's no magic bullet for good techniques.
You need to get a copy of ACI 350 and follow its recommendations.
RE: Experience of watertight construction joints in concrete / Ways of avoiding joints
Wastewater tanks are commonly constructed to much larger dimensions. Follow the procedures listed by JedClampett and there should not be any problems.
RE: Experience of watertight construction joints in concrete / Ways of avoiding joints
RE: Experience of watertight construction joints in concrete / Ways of avoiding joints
It is important to get the terminology right. "Plastic shrinkage" occurs while the concrete is still plastic, i.e. before it hardens. I think drying shrinkage due to restraint is the main issue here. Cracks form vertically at about 10' centers if the base restrains the walls, and these cracks can't be avoided, but can be controlled by an adequate amount of reinforcement. My minimum for water retaining structures is 0.006Ag, and I like to add a few bars near the bottom to better control the restraint crack initiation.
There are successful specialist builders of water tanks who use precast panels and posttension them together. Not for the uninitiated.